Narrow-band thin-film fabry-perot interferometer

 

(57) Abstract:

Usage: to create a structurally stable narrow-band filters, logical optical elements and picosecond keys UV, visible and IR frequency range. The inventive in narrow-band thin-film Fabry-Perot interferometer containing a substrate, two thin-film mirror and located between the intermediate layer, this layer is made from a material with low refractive index, in which microcrystals are formed from a material with high refractive index and having a size d determined from the ratio of 0.2 aB<d<e- the Bohr radius of an exciton and a free path length of an electron with high refraction material. 4 C.p. f-crystals, 5 Il.

The invention relates to optoelectronics and integrated optics and can be used to create a structurally stable narrow-band interference filters, logical optical elements and picosecond optical keys UV, visible and IR range of frequencies.

Known bulk Fabry-Perot interferometer (IFP). It consists of two glass or quartz plate, located on ncaor, fill in any environment. On facing each other in the plane of the applied reflective mirror coating with a high reflection coefficient R as a mirror was used as the metal layers and multilayer dielectric coatings. IFP is a multi spectral instrument with the two-dimensional dispersion and high resolution. When passing through IFP continuous radiation is its spatial decomposition in range, and when you reach a nonlinear mode IFP changing the optical parameters of the intermediate layer leads to a change in light intensity at a given wavelength (A. Szoke, V. Danev, J. Goldhar, and N. A. Kurnit. Appl.Phys.Lett.1969, Vol.15, N 11, P. 376-378). Since 1979 known IFP is used as a logical optical elements (H. M. Gibbs. Optical Bistability: Controlling Light with Light. N. Y. 1985).

Known IFP, consisting of plane-parallel single-crystal plate and the reflecting mirrors, which can be both external and sprayed directly on the polished surface of the plate. Known IFP were implemented on the basis of the crystal InSb (L 0.5 mm), cooled to 5 K, using natural Fresnel reflection (R 36%) from its surface. When falling on the interferometer capacity of the previous radiation. Nonlinear refraction is known IFP is caused by saturation of absorption at interband transition with a characteristic switching timesw500 NS when the incident radiation power P 8 mW (D. A. B. Miller, M. H. Mozolowski, A. Miller, S. D. Smith. Opt. Commun. 1978. V. 27, N. 1, P. 133-136). Known IFP, containing as an intermediate layer, a GaAs single crystal, and as mirrors of thin-film dielectric coatings with R 90% more complex in design. The intermediate layer of GaAs of thickness L 4.1 μm grown by metacom molecular epitaxy between two layers of Al0.42Ga0.58As a thickness of 1 to 0.2 μm each, located on a 150-micrometer substrate of GaAs. In the latter for the passage of a light beam etched hole with a diameter of 1-2 mm, after which the system napylyaetsya reflective coatings. IPP uses the change in the refractive index due to saturation of absorption of free excitons, which has a shorter switching times, but a higher energy threshold (sw40 NS and P 200 mW, respectively) (H. M. Gibbs, T. N. C. Vencatesan, S. L. McCall et al. Appl. Phys.Lett. 1979, V. 34, N. 8, P. 511-514).

The disadvantages of the known ISP of this species can be attributed to the greater weight and, as a consequence, the impossibility of applications in integrated optics. Known IFN IFP also, in which the intermediate layer is a superlattice consisting of 61 pairs of alternating microlayers of GaAs (1 33.6 nm) and Al0.21Ga0.79As (L 40.1 nm) (with a total thickness L 12 μm), the boundaries of which play the role of potential barriers, greatly increases the binding energy of free excitons (H. M. Gibbs, S. S. Tarng, J. L. Jewell et al. Appl. Phys. Lett. 1982, Vol.41, N. 3, P. 221-222). Device-based superlattices in GaAs remains the best of the implemented optical elements of logic. When the thickness L of 3 μm and the diameter of the working area 10 microns, energy and switching times at room temperature are, respectively, E 0.6 PJ (I 500 W/cm2andsw200 PS (L. L. Jewell, S. L. McCall, A. Scherer et al. Appl. Phys.Lett. 1989. Vol.5, N. 1, P. 55-57).

In known devices for large durations of exposure to the input radiation causes heating of the IFP, destroying exciton nonlinearity, thereby to hold the device in a state of high bandwidth is possible only in a few microseconds.

Also known volumetric IFP, in which the intermediate layer is made in the form casinolinea structure with three-dimensional spatial restriction of the movement of carriers (in superlattices this restriction is one-dimensional). Design investsoglashenij L 600 μm external plane-parallel mirrors with R 90% the Main disadvantage has long been the slow thermal nonlinearity, used for logical switching ( when the excitation power P 18 mW switching timesw1ms) (S. L. McCall, H. M. Gibbs. - J. Opt.Soc.Amer.A. 1978, Vol. 68, N 10, P 1378-1381). Bistable response IFP due to picosecond electronic nonlinearity, due to the dimensional quantization of the motion of electron-hole subsystem was registered J. Yumoto, S. Fukushima, K. Kubodera. Opt.Lett. 1987, Vol.12, N 10, P. 832-834. When the diameter of the working area 10 microns, energy and switching times are known IFP are E 10 PJ (I 6 kW/cm2andsw25 PS, work at room temperature).

The known device for the reason that the technology of synthesis of colored glasses is not possible to raise the volume concentration of microcrystals higher percentage units and limits the choice of starting materials (matrix and microcrystals), is limited in the spectral range of operating frequencies and cannot be made in the form of a thin-film element of the Fabry-Perot.

The closest in technical essence of the claimed invention is a multilayer thin-film Fabry-Perot interferometer (TPI) based with high refraction and viscoplasic materials, such as compounds A2B6, A3B5and their solutions, representing the night dielectric mirrors, made of alternating layers of two materials with high nBand low nHthe refractive index having an optical thickness equal to a quarter wavelength, at which the calculated transmittance of the interferometer, and the geometrical thickness lBand lHspecified value

linnin= lnnn=m/4,

wheremthe peak wavelength of the transmittance of the interferometer, and an intermediate layer of a material with refractive index n having the optical thickness, which fits m half of the working wavelength of the interferometermand geometrical thickness l, defined by the relation

ln=mm/2,

where m is the order of interference between them.

As an intermediate layer in known TPI applied one film arbitrary patterns. Spectral and nonlinear performance characteristics known to the TPI set of optical thickness and material of the intermediate layer.

Were made of narrow-band interference filters, the TPI switches and logic gates based on a whole series with high refraction and viscoplasic materials. Extremely great interest to the TPI-switches capilene interference structures (R. J. Campbell, J. G. H. Mathew, S. D. Smith and A. C. Walker. J. Modern Optics. 1989. Vol. 36, N. 3, P. 323-336).

Design of thin-film narrow-band Fabry-Perot interferometer is usually described by the formula

< / BR>
where P substrate;

B, H quarter-wave layers of materials with high and low refractive index;

k1and k2determine the rate of recurrence groups (EXT) and (HB) and characterize the thickness (as geometric and optical) and the reflection coefficient viscoplasic mirrors of the interferometer: the input and output

Typically used in interference systems mirror symmetric(k1k2k), and the optimal number of layers ranges from 6(k3) to 8(k 4). The reectivities of the mirrors in this range 85.95% W2mdescribes intermediate (separation) layer of the interferometer, the thickness of which fits m half of the working wavelength. When this layer is made of a material with a low index of refraction, the generalized formula for the design of the interferometer is

P(VL)kNR2m(HB)k.

In a static state thin-film narrow-band interferometer (TPI) (m 2) is characterized by a spectrum of bandwidth preveden is efficient transmittance at the maximum of Tmax, bandwidth0,5for values of bandwidth equal to half of the maximum Tmax/2 (usually referred to as ), bandwidtha 0.1for values of bandwidth equal to 0.1 Tmaxbackground transmittance Tmin.

High reflectance (low transmittance)on both sides of the Tmaxmarked on relatively small portions of the spectrumk=2-1andd=5-6(kshortwave, dthe long-wave region of the spectrum). Next, to the left of the1and right from6,the transmittance increases (reflected decreases), resulting in wide bands of high bandwidth, reducing the quality of the TPI as narrowband filtering devices. The latter is usually removed selectively absorbing filters (colored glass and other), and selectively reflecting interference mirrors. The main characteristics of narrowband TPI, defining its good quality, are high levels of light approaching 100% low bandwidth , lack of background (Tmin0 in the spectral range up tokandd).

The impact on the maximum transmission TPI Tmaxdetermined the expression of the e in the reflective coating, A. Transmission TPI decreases rapidly with increasing A, even in the absence of absorption in the intermediate layer.

A considerable effect on Tmaxand the difference of the reflectivities of the mirrors, which is especially pronounced at high values of reflectivity R. for example, in the absence of absorption in the mirror coating and the intermediate layer when the reflectivity of the mirror coating R199% and R297% of the maximum value of transmittance of the TPI is reduced to 75% At lower values of reflectivity of the mirror coating of the difference affects less. For example, if R190% and R295% Tmax88%

An important characteristic of the narrowband TPI is bandwidth, which is mainly determined by the reflectivity of the mirror coating. As the characteristic bandwidth and usually use a value of0,5(Fig. 1,a):

< / BR>
Shows the dependence shows that the bandwidth of the TPI same time, the higher the reflectivity mirror coatings R, higher order k, the greater the dispersion phase with the reflection from the mirror coatings /.. Last linearly depends on the order k. As noted above, the maximum constriction band may Yu lower the bandwidth is the use of coatings, reflecting a narrower spectral region and consisting of layers of optical thickness k/4 (k is an odd number). Such mirrors with high reflectance narrower than conventional mirrors of layers of optical thickness /4, have k times greater dispersion phase. However, to make such TPI technologically difficult, as you must apply to 50.100 layers.

The position on the spectrum bandwidth mand the value of the transmittance in the interference peak Tmaxnarrowband TPI respectively define the working range of wavelengths and contrast the TPI-element as a narrowband filter and as a logical device.

In the manufacture of the TPI widely used methods of evaporation and sputtering, and in the case of transparent conductive coatings chemical vapour deposition. Methods plasma polymerization and ion sputtering until used. Sputtering and evaporation rather complex processes, including sputtering or evaporation of individual atoms or molecules of the original volume of the target material, the transportation of the gas phase and condensation on the surface of the substrate. Due to a number of law enforcement physical processes that change this state of matter (melting, evaporation, and so is prohibited. One should choose only those within a particular technology ensures the reproducibility of the stoichiometric composition of the source materials in film coatings, which limits the spectral range of operating wavelengths, which can be made known to the TPI.

From 1930 known narrowband TPI-based viscoplasic and with high refraction materials are used as spectral filters (A. F. Perveen, Y. C. Gudkov, A. A. Poplavsky, R. S. Sokolova, E. I. Fadeev, M. N. Cherepanova, H. C. Tiroxina. Optical journal. 1993. N. 2. C. 4 14 Krylov I.e. Interference coatings. Optical properties and methods. - HP engineering, 1973), and in 1977 as nonlinear optical devices for optical signal processing (H. M. Gibbs Optical Bistability: Controlling Light with Light. N. Y. 1985).

As an optical filter device narrowband TPI work quite simply. They are used in the technique of physical experiment and optical instrumentation in those cases when a solid (or line) spectrum of the source you want to select radiation of a fixed wavelengthm. Of course, that filter must ensure consistency of the wavelength of the maximum intensity is introw in harsh climatic conditions is very limited (see for example, the work of Zakharov B. M. Christmas Century. N. Opto-mechanical industry here. 1975. N. 11. S. 79-80; Levin, M. D., Furman, W. A. Optical-mechanical industry here. 1973. N 4 S. 63 64). The work of the TPI as a nonlinear (switching) device is described in the article Abraham A. Seaton K. T. Smith D. In the world of science. 1983. # 4. C. 15 25. Is based on the dependence of the transmittance of the TPI

< / BR>
and averaged over the thickness of the field intensity in its intermediate layer

< / BR>
from the attack phase of the interfering light waves with the passage of the intermediate layer

< / BR>
where n is the refractive index;

a coefficient of absorption;

1 geometric thickness of the intermediate layer,

values of R, q and v, respectively, the reflectivity of the mirrors, the angle between the direction of propagation of rays in the intermediate layer and the normal to it and the jump in phase with the reflection from the mirrors.

In the case where an intermediate layer is used the film medium exhibiting optical nonlinearity of the refractive index, phenomenologically described by the expression

< / BR>
where n2the parameter of this nonlinearity,

n0the refractive index of the material of the intermediate layer in the weak light field,

the presence of all precisley as optical switching and bistable devices (Fig. 1,b).

Known optical switches (keys) (regardless of the complexity of the design) are elements that can be located in two different States characterized by high (open state) and low (closed) transmission T at a given wavelength vasb. In an ideal key in an open condition T=1, and in the closed T=0, the transition from one state to another is instantaneous. The main optical parameters are key contrast key M=Tabout/TCwhere To, TCthe transmission key in the open and closed States, respectively; performance, characterized at times of switching on and off and switching frequency; the energy E0hold the key in the closed state; the energy E1, above which the key is always in the open state; the energy EB=E1E0spent on the switch.

Known optical keys can be divided into the keys with hysteresis and without it. They have their applications in as the element base systems, optical information processing.

Work narrowband TPI as a nonlinear (switching) device has the following description ( TPI-element (Fig. 1,b, curve 1, with the sign of the detuning is opposite to the sign of the nonlinearity coefficient of the index of primaline), the increase in the input intensity shifts the loop bandwidth TPI element in the direction ofvasbdue svetoindutsirovannoi refraction (Fig. 1,b, curve 2). This shift leads to an increase in the density field within the intermediate layer TPI-element (due to the interference increase ), thereby pushing the loop bandwidth of the TPI-item even closer tovasb. Under certain conditions this process becomes self-sustaining, acquiring the avalanche-like character, and the contour of the TPI-element surge enters the state of maximum transmittance at the wavelength of excitation (open state). Here the density of the light field inside the interferometer is especially great, because the loop bandwidth of the TPI-element continues to move for Tmaxat the wavelength of excitation as long as the reduction due to the departure from resonance will not stop the device in the new steady state (Fig. 1,b, curve 3). Since in this state the TPI-element is characterized by high transmission, then to hold it at this point requires less input intensity due to almost maximum SUB> beam and the power density of the light field inside the nonlinear layer TPI on the intensity of the incident light beam Io(H. M. Gibbs, S. L. McCall, And T. N. C. Venkatesan, Optical Engineering. 1980. Vol. 19, N 4. P. 463 468). Off the TPI-element occurs due to the reduction of the intensity of the incident signal. Switching time swis determined by the relaxation time of the nonlinearity.

Consideration narrowband TPI as a real switching device assumes temporal reproducibility of its loop bandwidth as in the absence of light exposure, and after exposure to high peak intensities Io.

The main disadvantage of the known narrowband TPI element is a temporary instability of its spectral and amplitude characteristics, and thermal inertia of the mechanism of the nonlinearity of the intermediate layer (R. J. Campbell, J. G. H. Mathew, S. D. Smith, A. C. Walker. Appl. Opt. 1990. Vol. 29, n 5. P. 638 643; G. Ankelhold, F. Mitschke, D. Frerking et al. Appl. Phys. B. 1989. Vcl. 48, N. 1. P. 101 104)

The present invention is the problem of increasing the stability of the microstructure of the intermediate layer to the action of the laser radiation, thermal heat and moisture, extending the spectral range of operating wavelengths, increasing the maximum is when the relaxation of the nonlinear regime in the TPI in light.

The problem is solved in that in the thin-film Fabry-Perot interferometer, which is a multilayered system formed on the substrate, and consisting of two thin-film dielectric mirror made of alternating layers of two materials with high ninand low nnthe refractive index having an optical thickness equal to a quarter wavelength, at which the calculated transmittance of the interferometer, wheremthe peak wavelength of the transmittance of the interferometer, and an intermediate layer of a material with refractive index n having an optical thickness that is a multiple of half the wavelength of maximum transmittance of the interferometermand between them according to the invention the intermediate layer is formed by physical capacity of the layer of material with a low refractive index of nnand vkraplennykh it microcrystals formed from a material with a high refractive index of ninand having a dimension d, which is determined from the relation:

0.2 aB< d <enm,

where aB,ethe Bohr radius of an exciton and a free path length of the electron source with high refraction material, resulting in the position of the peak proposin/BR> where Iin, Ingeometric thickness with high refraction and nizkoroslogo material.

The best parameters of narrow-band thin-film Fabry-Perot interferometer can be obtained if the substrate is to use a metal with a dielectric coating or insulator with high thermal conductivity, such as SiO2, Al2O3CaF2, AlN, BN, and polymers.

To improve the reliability of the device as nizkoroslogo material of the intermediate layer also use materials for a number of: SiO2, Al2O3CaF2, AlN, BN and polymers.

With this purpose it is expedient as a quarter-wave layers with high refraction mirrors to use a polycrystalline film with a high packing density of microcrystals or two-component films formed of microcrystals with high refraction material and discopremiya matrix when applied by evaporation with high refraction material is hygroscopic or not possible to obtain sufficient density packaging, and as viscoplasic quarter-wave layers of mirrors to use the close-Packed microcrystallites the material of the substrate, viscoplasic layers of the mirrors and the intermediate layer is also achieved a reduction in the mechanical stresses on the boundaries of the individual layers and the increase of the coefficients of adhesion.

Introduction as an intermediate two-layer consisting of nizkoroslogo (matrix) material, do not modify the optical properties of the intermediate layer, and disseminated it microcrystals with high refraction (working) material with a size d determined from the relation:

0.2 aB< d <enm,

makes thin-film narrow-band Fabry-Perot interferometer device with adjustable (by choosing the size of the microcrystals) the magnitude of the transmission in the interference peak at a given wavelength, energy, achieve non-linear mode of operation and a time of relaxation, and also resistant to laser radiation, temperature and moisture due to the exclusion of the processes of recrystallization and chemical degradation microcrystals when used as a matrix material compounds, characterized by a high hardness, nephroscopes, achievement in film coating packing density of not less than 0.9 1, stechiometrically stood the rates of mechanical stresses and linear expansion relative to the material of the microcrystals. These can serve as dielectric materials commonly used for sealing optical coatings, in particular, SiO2, Al2O3CaF2, AlN, BN and polymers.

The size of the microcrystals of the intermediate layer should range

0.2 aB< d <enm,

for the following reasons:

for microcrystals size 3aB< d <ea significant role in the formation of the nonlinear properties of the TPI play size effects, leading in particular to the reduction of the transmittance of the TPI at a given wavelength and to the possibility of implementing non-linear switching TPI condition dimmable with picosecond relaxation times (O. C. Goncharov, G. C. Sinitsyn. Russian Academy of Sciences, 1990, No. 6, S. 21-28);

for microcrystals smaller, namely, d 3aBcharacteristic of quantum-size effects, manifested in the short wavelength absorption edge shift, expansion SpectraLink areas of photosensitivity and transparency TPI, as well as in the implementation of switching the TPI in the state of enlightenment with picosecond relaxation times. The conductivity of the TPI-elements with the same size of the microcrystals is controlled by a fast-response mechanisms e-tunneled is.2aB< d <enm,

allows you to produce a narrow-band filter with adjustable (by choosing the size of the microcrystals) the magnitude of the transmission in the interference peak at a given wavelength, which in turn allows you to increase the contrast of the TPI as the filter and the switching element. Use as the substrate material and nizkoroslogo material of the intermediate layer of fluorides of alkali halide metals, solid oxide compounds, nitrides of aluminum and boron, as well as polymeric compounds create additional benefits for improving the mechanical strength, wet strength, TPI, resistance to thermal shocks and repeated laser exposure, and to reduce thermal component at higher clock frequency TPI-element, since the above materials have coefficients of thermal expansion.

Accommodation microcrystals with high refraction (nonlinear) material with a size d determined from the relation

0.2 aB< d <enm,

in volume nizkoroslogo (matrix) material does not exhibit non-linear properties, allows to optimize the proposed TPI for the manifestation of specific mview laser radiation, temperature and moisture) due to the exclusion of the processes of recrystallization and chemical degradation microcrystals when used as a matrix material compounds, characterized by a high hardness, nephroscopes, achievement in film coating packing density of not less than 0.9-1, stechiometrically composition, chemical neutrality, predetermined thermal conductivity, and the opposite sign of the coefficients of mechanical stresses and linear expansion relative to the material of microcrystals). These can serve as dielectric materials commonly used for sealing optical coatings, in particular BaF2CaF2, SiO2, Al2O3, AlN, BN and polymeric compounds.

The proposed element is the choice of material and size of the microcrystals of the intermediate layer defines the spectral characteristics and the parameters of the nonlinearity, and thin-film matrix guarantees the preservation of microcrystals in relation to external influences and avoid recrystallization and the occurrence of mechanical stresses, thereby providing a high radiation resistance of the TPI system.

Job spectrotel microcrystals of the intermediate layer, and optimization of parameters of nonlinearity even at the expense of the choice of thermal conductivity of the matrix and the substrate relative to the microcrystals. This simply avoids the problems associated with the dissipation of heat in the intermediate layer, namely, as the material of the mirrors, the matrix and the substrate can be applied to compounds with higher than microcrystals, the coefficients of thermal conductivity. As with high refraction of the material of the mirrors in particular used ZnS.

Due to all these factors, narrowband interference system as filtering and logical device will not only meet the demanding awareness to the quality of such systems:

the refractive index (defined, homogeneous, reproducible) that is provided by stechiometrically, homogeneity, reproducibility and time stability used in this case, thin film structures;

high transparency, guaranteed high uniformity and density packaging film structures;

small scattering characteristic of close-Packed crystalline and amorphous materials;

geometric thickness (defined, reproducible), illustrates the
voltage (low defined, reproducible) by choosing the materials of the composition and use as the substrate material viscoplasic layers of the mirrors and the matrix films the same connection;

high coefficients of adhesion and hardness close to that of glass, also guaranteed by the choice of materials;

temperature stability and resistance to laser exposure, due to chemical and structural stability.

But will have a new spectral and optical properties, namely:

the expanded area of photosensitivity, transparency and optical nonlinearity;

picosecond switching mechanisms;

temporal stability of spectral-amplitude characteristics of the TPI effect of structural and chemical stability of the components of his film coating. The formation of the intermediate layer TPI with high refraction of microcrystals with size d determined from the relation

0.2 aB< d <enm,

where aB,ethe Bohr radius of an exciton and a free path length of the electron source with high refraction material and the dielectric matrix were produced by two methods:

the follower is as arbitrary structure and with high refraction of the material of the crystal structure with the size of the microcrystals d, determined from the relation:

0.2 aB< d <enm,

evaporation of multicomponent targets specified phase composition with high refraction and nizkoroslogo materials. The first method of physical cultivation of the intermediate layer TPI with high refraction of microcrystals with dimension d and discopremiya matrix technologically complex and provides an implementation casinoline heterosystems type microcrystalline with high refraction layer/nizkoplotnye layer, which by its structural characteristics, only a relatively resemble the composition of the microcrystals in the volume of the matrix. As the source materials are used specifically non-alloy plates with high refraction and nizkoroslogo material.

The second method is technologically simpler, but requires a specially prepared multi-component targets with the phase composition, adjusted in accordance with the conditions of deposition and the required parameters of the intermediate layer. The modes of formation of the intermediate layer TPI was chosen empirically by parallel analysis of the nature and magnitude of the shift of the absorption spectra of experimental samples relative to spec togami electron microscopy and diffraction on the light.

Due to the complexity of the spectral and structural diagnostics of the intermediate layer TPI, for this analysis due to the control shift witnesses (10 pieces) in one process simultaneously deposited samples experimental TPI, samples of mirrors and the intermediate layer without the mirror coatings. Last, due to the technological features of vacuum deposition, is a complete analog of the intermediate layer TPI, i.e., its "passport" in the study of structural and optical properties.

Initially, the physical capacity of the multilayer interference system is performed in the modes of formation of film coatings stoichiometric composition of the original work materials. In further technological parameters of physical capacity TPI can be further adjusted (in accordance with the results of microstructural and spectral analysis of the intermediate layer) in order to achieve the necessary size of the microcrystals d. With continuous deposition method, the size of the microcrystals d is set to its energy and temperature parameters (temperature and rate of evaporation, the temperature of the substrate, and when the discrete - even and thick ADNOC the P> Raw materials are selected so that the matrix material of the intermediate layer and the material of a quarter-wave layers of mirrors practically influence on the spectral and nonlinear properties of the resulting interference system i.e. were more wide gap, with high refraction than the material of the intermediate layer.

As targets were used specially undoped single crystals of raw materials and specially prepared multi-component target (MM) of the specified phase composition.

In the following the invention is explained in the detailed description of embodiments thereof with reference to the accompanying drawing, on which:

Fig.2 depicts schematically a General view of the narrow-band thin-film Fabry-Perot interferometer of the invention.

The proposed TPI element includes: a substrate (1), intermediate layer (2), two dielectric mirrors of alternating quarter-wave layers with high refraction (3) and nizkoroslogo (4) materials.

Declare the TPI includes a substrate (1) any of nizkoroslogo material either with high refraction material (including metal) with a dielectric coating. Next, go che the surrounding dielectric mirror. Discopremiya layers (4) are close-Packed microcrystalline or amorphous film obtained, in particular by evaporation nizkoroslogo the substrate material. And with high refraction (3) close-Packed microcrystalline or two-component film, if necessary: the first is used when with high refraction material of the mirrors allows you to get close-Packed, stoichiometric proof, non-hygroscopic film coating; and the latter in the opposite case. For the implementation of the component with high refraction layers are used for this source with high refraction material and nizkoplotnye sealing material of a quarter-wave layers of mirrors. As the result of a quarter-wave layer is formed in the form of microcrystals with high refraction material, located in the volume nizkoroslogo. On the dielectric mirror further methods of physical capacity is applied to the intermediate layer of the interferometer (2), specifies its spectral and nonlinear features such as filtering and switching device. The structure of the intermediate layer consists of microcrystals with high refraction material of size d, which is determined from the relation

Alaudin material of the intermediate layer can serve a variety of compounds depending on the purpose of the practical use of the TPI. In the case of narrow-band filters is a dielectric and semiconductor compounds. And in the case of logical devices with high refraction nonlinear materials (metals, dielectrics and semiconductors to organic dyes). As discopremiya matrix and in this case should be used sealing material and, in particular compounds of the series: SiO2, Al2O3CaF2, Aln, Bn, and polymers. On top of the intermediate layer is further applied to the second symmetric dielectric mirror with a quarter-wave layers (3) and (4).

At low intensities the impact of the proposed narrowband TPI cuts out a bar or a continuous spectrum of radiation of a given wavelength, the correspondingmits loop bandwidth (Fig.1,a).

With increasing intensity I0incident radiation (nonlinear mode) the proposed TPI-element switches to a state of maximum bandwidth (or darkening) at the wavelength of excitation at the expense of short-wave enlightenment and shear (0.2 andB<d 3AB) (or dark, 3aB< d <enm) its contour. Typical switching time is determined by the relaxation time of carriers, n is th characteristics of the proposed switching device is interpreted as follows. If photogeneration media microcrystals with high refraction material of size d, which is determined from the relation:

0.2 andB<d <3Anm,

and the subsequent filling of the levels of dimensional quantization of the probability of light absorption in pritravoy region of the spectrum is reduced, what are the observable effects of the enlightenment and the dynamic shift of the absorption edge. If photogeneration media microcrystals with high refraction material of size d, which is determined from the relation

3aB< d <enm,

and subsequent filling level of localization below the absorption edge is observed induced light absorption in this spectral region, which introduces observed this effect picosecond dimming circuit bandwidth TPI.

Experimental verification of the proposed narrow-band interference filters and nonlinear TPI elements was performed on sample devices formed according to the invention, substrates of nizkoroslogo material corresponding to the material discopremiya components of the nonlinear layer. The toggle signal was used for excitation (t 3 PS) laser naiteki narrowband TPI filters in which the intermediate layer according to the invention formed by the method of the physical capacity of the lamellae ZnSe/SiO2(neolentinus substrate SiO2(Fig.3) and ZnSe+SiO2(SiO2substrate) (Fig.4) with the size of the microcrystals with high refraction ZnSe material d, which is determined from the relation.

0.2 aB< d <enm,

where aB,e- the Bohr radius of an exciton and a free path length of the electron source with high refraction material.

Choice with high refraction material in this case is due to the fact that the micro-crystals of ZnSe in the volume of the matrix previously has not been implemented, and the TPI-based microcrystalline films of ZnSe most often used as a thermal switching device. Zinc selenide allows to obtain a soft hygroscopic film coating, which, as noted above, the TPI with an intermediate layer of ZnSe are characterized by instability in time

In Fig. 3,a,b and 4 a,b (for comparison) shows a micrograph of the structure of the intermediate layer narrowband interference filters made according to the invention, using as with high refraction material zinc selenide (ZnSe), and as the aqueous layer known TPI, made by the same methods of physical cultivation (by vacuum deposition), but using the same material (ZnSe) and without control d (Fig.3 b and 4 b).

It is seen that the physical capacity of the intermediate layer in the form of a layer of a material with a low refractive index of nNand disseminated it microcrystals formed from a material with a high refractive index of ninand having a dimension d, which is determined from the relation

0.2 aB< d <enm,

where aB,

ethe Bohr radius of an exciton and a free path length of the electron source with high refraction material, increases the transparency of the TPI at a predetermined wavelength and substantially expands the scope of its optical nonlinearity.

Indeed, Fig.3,and curve 1 in Fig.3,correspond to the composite film ZnSe + SiO2(note that shown in Fig.3 significant wavelength shift of a transmission spectrum of the intermediate layer for micro-crystals ZnSe registered for the first time and is in good agreement with the microstructure of the composite film, represents the microcrystals with ZnSe d 3 nm (for ZnSe (aB1.5 nm), embedded in SiO2matrix. As curve 3 in Fig.3 transmittance spectra of Peltry with high transmittance (80%) even in the region of strong absorption of the original single crystals of ZnSe.

Similarly, Fig. 4, a and curve 1 in Fig.4,correspond to the film heterosystem ZnSe/SiO2(note that the decrease in the magnitude of the wavelength shift is correlated with the size of the microcrystals d 4.5 nm, i.e., d 3AB). And spectrum 3 in Fig.4,the spectra of transmittance TPI (Tm30% = 6 nm). Not so high transmission proposed TPI in this case is obviously associated with a lower edge shift transmission of the respective intermediate layer.

Fig. 3, b, 4, b and curves 2 in Fig.3, 4,correspond to polycrystalline ZnSe films obtained under the same conditions of deposition. And curves 4 in Fig. 3, 4,spectrum bandwidth, best known TPI made in the usual method based on ZnSe (Tm=20% = 3,8 nm).

Shown in Fig.3 and 4 the results indicate the possibility of expanding the spectral region of transparency and photosensitivity TPI as filtering devices, due to the effects of dimensional quantization of microcrystals of the intermediate layer. Note that similar results were obtained for the interference of systems based on other materials, namely, CdS and CdSe, which is not practically used for the manufacture of the TPI visible range, because they have absorption edge, in the best with the transmission at wavelengthm530 and 650 nm.

In terms of stability to heat and moisture investigated narrowband MgO/SiO2and ZnSe/SiO2-TPI made in accordance with this invention. The first of them, made for filtering optical radiation, was used as with high refraction layers of the mirrors and the intermediate layer of the composite film consisting of MgO microcrystals (d= 12 nm) in amorphous SiO2the matrix, as well as material viscoplasic layers of amorphous quartz. And the second, made with the purpose of the study of nonlinear effects on the wavelength of the harmonic laser phosphate glass with neodymium (vasb= 528 nm), as layers of mirrors used close-Packed crystalline films of ZnS and cryolite, and as an intermediate layer micro-crystals ZnSe given grain size d3aBnamely, d 3 nm, discopremiya matrix. As substrates in both cases was used plane-parallel disks 20 and 2 mm quartz glass marks KU and KI. The filters contained from 9 to 15 layers, and the width of the peaks was 18 and 3 nm when the transmittance Tmaxrespectively, 65 and 40%

The optical characteristics of the ZnSe/SiO2filters the em. And the TPI-based oxide systems showed the presence of the spectral shift of the peak transmittance at a value less than 2 nm. Conventional oxide system ZrO2/SiO2manufactured by ELI sputtering in vacuum, had a shift of about 35 nm.

The reasons for this difference are seen in the different structures. The structure of the conventional ELI porous systems. For ZrO2. The packing density in the best case may be 0.7, and the evaporation out of the atmosphere of oxygen does not guarantee stoichiometric coatings. The structure of the systems produced according to the invention, more dense, because the microcrystals of the working environment housed in a thin-film matrix compounds with a packing density of about 0.99-1. So changes in the spectral characteristics of the TPI in this case can only happen if nestekhiometricheskie themselves microcrystals, namely when the processes nedookislennye. This, in particular, explains the best stability of ZnSe/SiO2-TPI with respect to MgO/SiO2-TPI manufactured by the same method of physical capacity. Analysis of the microstructure was performed by the method of electron microscopy with a resolution up to 1 nm, confirms this conclusion, allowing to consider the structure of the intermediate layer of each and the matrix and microcrystals. The presence of micropores is not registered.

The study of stability of the proposed device to intense laser exposure conducted using ZnSe/SiO2-TPI and trekhpotochnogo pulsed excitation with a repetition rate of 0.5 Hz when the excitation bandwidth of the filter, i.e., the area of transparency ZnSe (lvasb= 528 nmg470 nm), as well as at excitation in the region of strong absorption of ZnSe (vasb= 352 nm), did not reveal irreversible changes of a transmission spectrum of the TPI up to the peak power of the excitation 0.6 0.8 GW/cm2.

Studies of the proposed device as a logical element were carried out using a ZnSe/SiO2and CdS+SiO2-TPI. (Micro-structural and spectral characteristics of the last shown in Fig.5).

Characteristics of ZnSe/SiO2-switch shown in Fig.4,, the Well is logged dimming effect, correlating with the size of the microcrystals d3aB. Relaxation times = 10 ...25 PS.

The analysis of electron microscopic data of the intermediate layer CdS+SiO2element (Fig. 5, and shows that this two-part film, which consists of a combination of the cubic CdS microcrystals and AMO the definition properties. Indeed, from Fig.5,b, describing the spectral characteristics of the TPI (curve 3) and intermediate layer (curve 2) shows that in this case the spectra of transmittance is observed wavelength shift of the absorption edge, the value of which is consistent with the size of the microcrystals d= 15 nm. Curve 1 in Fig.5 b corresponds to the range of transmission close-Packed polycrystalline CdS film, the refractive index of which corresponds to a single crystal, as a result it was used as a reference sample, allowing to evaluate the magnitude and nature of changes in the absorption edge of the composite intermediate layers of equal optical thickness with high refraction material CdS.

The analysis of the spectral and structural characteristics of the intermediate layer allows to establish the existence of dimensional quantization of a nonlinear medium CdS+SiO-TPI, causing the possibility of obtaining picosecond switching times of the device in a state with a large deletion (due to the short wavelength of the enlightenment and the shift circuit bandwidth).

In Fig. 5 shows the results of a study of the amplitude and kinetic characteristics of the optical switch TPI state Bolshaya induced shift of the spectrum transmittance is Tmax3 nm, which not only guarantees a sufficient switching contrast of the device, but also the possibility of implementing a dispersive optical bistability, provided that the width of the loop bandwidth of the proposed TPI will be 6 nm.

The switching time of the proposed TPI amounted to 300 psec, and the relaxation time of 25 PS.. Moreover, as shown in a parallel study of nonlinear-optical properties of the intermediate layer TPI, the relaxation time of the system media with levels of size quantization does not exceed 5 PS, and the second 25-picosecond component of relaxation curve is responsible for radiative recombination of carriers.

Note also that the effect of shear and enlightenment loop bandwidth critical intensity, namely, is shown in Fig.5,the result corresponds to the upper threshold capacity Evasb0.17 µj, above which the short-wave dynamic shift circuit bandwidth can be significantly reduced, and the effect of the enlightenment replaced the dimming effect (Fig.5,g). Thus, the proposed TPI switch may be turned off not only reset, but also increase the intensity of the excitation.

Switching device on the basis of narrow-band inter is passed. When the thickness l of 1 μm and the diameter of the working area 10 μm, the turn-on time 300 FSEC, time off from 25 to 5 PS, the energy on one switch E2.7 PJ, work at room temperature.

The proposed device is intended for filtering optical signals and their logical processing in the UV, visible, near infrared wavelengths. The scope of experimental optics, including analog and digital optical logic. The high uniformity of the optical parameters on the substrate surface allows you to get the TPI in the form of discrete elements, and in the form of multiple lines and matrices. The device may vary in functionality and performance.

The proposed device operates as

narrowband filter with extended spectral range of operating wavelengths and increased the maximum transmission in the interference peak (Fig. 3, curve 3).

nonlinear switching element with picosecond switching times (Fig.5,b, d).

The proposed narrow-band thin-film Fabry-Perot interferometer has several properties that are unique from the point of view of creation on its basis of the elemental base optical digital the rum materials from metals, semiconductors and dielectrics to organic dyes and polymer compounds;

the integrity and integration of performance;

optimisation of the mechanism of nonlinearity and certification of properties TPI due to the parallel production of the intermediate layer without the mirror coatings and study of optical properties of the latter with respect to monocrystalline standards;

a wide range of operating wavelengths;

work at room temperatures;

the use of picosecond mechanisms of nonlinearity in conjunction with the effects of feedback and amplification of the internal field, which is characteristic for the TPI;

low thresholds of the optical switch;

the possibility of excluding thermal contribution of the substrate in such devices;

high radiation resistance and stability of the structure.

Below are the operating parameters of the inventive thin-film Fabry-Perot interferometer fabricated according to the invention by the methods of the physical capacity of the intermediate layer in the form of CdS microcrystals (d nm) in thin SiO2matrix.

The working spectral range of the Green-red region of the spectrum

The work pace is clucene E 0.2 PJ/mm2< / BR>
Switching time (on/off)sw0.3/25 nc

Contrast 2.5

The size of the two-dimensional matrix of elements sm2< / BR>
The use of solid compounds with high thermal conductivity as the substrate material and the matrix creates additional benefits for improving the mechanical strength, wet strength, TPI, resistance to thermal shocks and repeated laser exposure, and to reduce thermal component at high frequency operation.

1. Narrow-band thin-film Fabry-Perot interferometer containing a substrate, two thin-film mirror made of alternating layers of two materials with high and low refractive index having an optical thickness equal to a quarter wavelength of the maximum transmittance of the interferometer, and is located between the mirrors of the intermediate layer having an optical thickness that is a multiple of half the wavelength of maximum transmittance of the interferometer, wherein the intermediate layer is made from a material with low refractive index, in which microcrystals are formed from a material with high refractive index and imbong mileage electron with high refraction material.

2. The interferometer under item 1, characterized in that the substrate is made of dielectric material with a low refractive index or metal with a coating of dielectric material, the dielectric material is one of the following series: SiO2, Al2O3CaF2, BaF2, AlN, BN, polymers.

3. The interferometer under item 1 or 2, characterized in that the material with a low refractive index of the intermediate layer and dielectric mirrors used material from the following range: SiO2, Al2O3CaF2, BaF2, AlN, BN, polymers.

4. The interferometer according to any one of paragraphs. 1 to 3, characterized in that the material with high refractive index of the intermediate layer is used, or semiconductor, or dielectric, or metal.

5. The interferometer according to any one of paragraphs. 1 to 4, characterized in that the material with high refractive index dielectric mirrors used material from the following range: ZrO2, ZnS, MgO, ZnSe.

 

Same patents:

Ar coating // 2057351
The invention relates to the technology of optical coatings and can be used in an optical instrument for enlightenment parts

The invention relates to the treatment of hard surfaces, in particular for the application of coatings on optical parts, and can be used in laser technology

The invention relates to laser technology, namely the polarization of the laser mirrors
The invention relates to a method for producing multilayers on solid surfaces and can be used in the technology of electronic materials, optics, biology

FIELD: optical engineering.

SUBSTANCE: at least two dielectric layers are produced with preset thickness. Layers are disposed one onto the other to form pack of layers. Thickness of layer packs is subject to reduction and thicknesses of separate layers are similarly reduced by means of deforming layer packs to keep relation of thicknesses or relation of thicknesses of layers. Layer pack is disposed between two carrying layers before subjecting the layers to deformation. At least one carrying layer is formed from several separate layers, which are supposed to be disposed subsequently at the end of process of partial deformation at any previous layer of carrying layer. Separate layers of carrying layer can be overlayed onto previous separate layers of carrying layer.

EFFECT: simplified process of manufacture; improved reflection factor.

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Reflecting surface // 2256942

FIELD: optical instrument engineering.

SUBSTANCE: invention can be used for wide-band light reflecting. Reflecting surface has dielectric layers A, B and C. A layer is made of material having low refractivity, B layer is made of material with average refractivity and C layer is made of material having high reflectivity. Optical thickness of layers equals to λr/4, where λr is wavelength of middle part of interval having high refractivity. Sequence of layer alternation looks like (CDCABA)KCBC, where K>=and has to be integer. Spectrum range with high reflectivity is widened due to shift in adjacent bandwidths at opposite sides along wavelength scale.

EFFECT: widened spectrum range with higher refractivity.

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FIELD: optical engineering.

SUBSTANCE: device can be used for getting image from space, including surface of Earth, from space and from different sorts of air carriers. Device has at least one information channel which channel has objective, filter and multi-element receiver. Filter is made of two lenses, which lenses form flat-parallel plate. Lenses are made of the same material with equal radiuses of curvature of their spherical surfaces. Interference coatings are applied onto spherical surfaces, which coatings form, together with material of lenses, spectral range of device. Filter can be installed between objective and radiation receiver. In this case the first lens is made flat convex, the second one is flat concave. Center of radius of curvature of spherical surface of flat-convex lens is brought into coincidence with center of exit pupil of objective. Filter can be installed in front of objective.

EFFECT: constancy of borders of spectral sensitivity and of level of transmission within total area of angle of view; improved precision of measurement.

7 cl, 3 dwg

FIELD: optical instrument engineering.

SUBSTANCE: optical filtering device can be used for building devices for spectral filtration of optical images, for example, for wavelength re-tune optical filters, IR imagers working within specified narrow spectral ranges. Filtering device being capable of re-tuning within preset wavelength range is based upon interferometers. Interferometers are disposed along path of filtered radiation flow at different angles to axis of flow. Reflecting surfaces of plates of any interferometer, which plates are turned to meet one another, are optically polished and they don't have metal or interference mirror coatings. To filter selected wavelength of λm; the following distances among reflecting faces of interferometers: d1=(λm/2)k, k=1 or k=2, dn=(n-1)d1 or nd1. Filtering device is equipped with different filters which cutoff radiation outside borders of range to be filtered, including filters which are made of optical materials being transparent within band of spectral characteristic of sensitivity of consumer's receiver, which receiver registers filtered radiation. Filter cutting off short wavelength radiation is made of materials, which form border with positive derivative of dependence total internal reflection angle depending on wavelength. Filter cutting off long wavelength radiation is made of materials which form border with negative derivative of angle of total internal reflection depending on wavelength.

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SUBSTANCE: narrowband filtration cover contains two systems of alternating dielectric layers with different refraction coefficients and equal optical thickness λ0/4, in the form of high reflection mirrors, and a dielectric layer dividing them. In accordance to the invention, structure of high reflection mirrors additionally features dielectric layers with intermediate value of refraction coefficient and dividing layer has optical thickness λ0 or one divisible by it, and sequence of layer alternation has form (CBCABA)KD(ABACBC)K with nA<nB<nC, where refraction coefficient of dividing layer nD is not equal to nA (for example, nD=nC) and k≥1 is an integer number, where: λ0 - maximal filtration cover throughput wave length; A, B and C - dielectric layers with values of refraction coefficient nA, nB and nC respectively, and D - dividing layer.

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EFFECT: widened area of application.

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EFFECT: reduction of signal distortion to preset magnitude in a wide frequency range of the filter attenuation in the preset bandwidth and increase in attenuation to the preset magnitude that allows wider application of the aforesaid filters.

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FIELD: physics.

SUBSTANCE: invention concerns area of optical thin-film coatings. The spectral divider contains the optical interference system with alternating quarter wave layers; part of them has an optical thickness not multiple to quarter of length of an emission wave. The spectral divider design allows obtaining the optimised spectral characteristics having small fluctuations of the transmittance factor in a working range of transparency.

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FIELD: physics.

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EFFECT: reduced power loss, expanded performances.

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