Interference multibeam light filter (versions)

FIELD: physics.

SUBSTANCE: light filter has on a flat surface a planar optical waveguide and prisms for inputting and outputting radiation into the waveguide that are optically insulated from the waveguide by uniform air gaps or by a uniform thin layer of a transparent dielectric with a refraction index less than that of the prisms and the waveguide. In the first version, said surface is the totally-reflecting face of the radiation output prism and the totally-reflecting face of the radiation input prism, which occupies part of the face of the radiation output prism, is attached to the waveguide on top of the optically insulating layer, having a thickness smaller than that of the optically insulating layer under the waveguide. The second version employs the surface of a flat plate. The face of the radiation input prism adjacent to the waveguide is much smaller than the face of the radiation output prism adjacent to the waveguide and lies from the waveguide at a shorter optical distance than the face of the radiation output prism.

EFFECT: designing a light filter having high resolution, large dispersion region and high optical power.

4 cl, 4 dwg

 

The invention relates to optics, optical devices, based on the use of the phenomena of total internal reflection and interference of light beams, including, devices, optical filters used in scientific research and technology for spectral analysis and monochromatization of light.

Solved the problem of creating filters with high resolution, i.e. a narrow bandwidth, while ensuring a wide free spectral range.

As taken similar known device type standards Fabry-Perot [Skokov IV Multibeam interferometers in measurement technology. - M.: Mashinostroenie, 1989], which contains a transparent flat plate, on the opposing surfaces of which are deposited semitransparent mirror coating. In principle, the standards are optical resonators with standing light wave. When passing through the Etalon collimated optical radiation between the mirror surfaces due to the multiple reflection occurs multibeam interference pattern, the radiation is standard only on the wavelengths of the spectrum, in between the plates which resonance occurs, i.e. fit an integer number of half-waves. Width generated by the reference spectrum band transmitted radiation determine aetsa largely a reflection coefficient of the mirror coatings; when using metallic coatings this coefficient is about 0.9 and less.

The advantage of the Fabry-Perot interferometers over the color filters of other types, for example, diffraction, is their large aperture; lack of counterpart are significant losses of light energy on the mirrors, resulting in a significant width of spectral bandwidth at low orders of interference, that is, the lack of a high resolution device when using it as a filter, and at large orders of interference, in which the filter has a consummate big resolution, dramatically decreases the dispersion region (free spectral range).

As the prototype was taken multibeam interference filter (optical resonator) [Johansen L.V. Theory of resonant electromagnetic systems with total internal reflection. / L.V., Johansen // ZH - 1962, 32., 4 - S-418], where instead of the reflection of light from the film mirrors, as in the standard Fabry-Perot is used the effect of total internal reflection at the boundary between dielectrics with different refractive indices. For I / o radiation in the prototype uses one or two optical prisms, mirrors - layers of transparent dielectric between the plastic is Oh and prism; the layers have a refractive index less than that of the plate and prism. The layer thicknesses of the order of the wavelength of the used light. When the direction of the collimated light flux on the input face of the prism input light wave is refracted and falls inside the prism layer with a lower refractive index at an acute angle, and, under certain conditions, an effect of total internal reflection: the wave returns to the prism input, but partially penetrates the plate and can spread it like distribution in the fiber. Coming from the filter radiation is formed from the past in the optical tunneling through the surface with the total internal reflection of rays and their interference with each other. The phenomenon of total internal reflection takes place only in transparent layers, and therefore, optical loss due to light absorption is practically eliminated. However, due to the oblique incidence of sun rays on the inner plate, the rays in it when multiple reflections are distributed, as in the fiber along the plate to the edge, and the part of the electromagnetic wave is lost at the edge of the plate, without leaving to the outside through the input / output radiation.

Thus, the filter prototype has insufficient resolution, although its reflective surface can have MSE of the ü anything small optical loss due to the effect of total internal reflection.

The problem solved by the present invention is the creation of an optical filter having a narrow spectral bandwidth and a wide free spectral region.

The task is solved in that in multibeam interference optical filter containing on a flat surface of the planar optical waveguide and prism input waveguide and the output radiation is optically isolated from the waveguide uniform air gap or a uniform thin layer of a transparent dielectric with a refractive index lower than that of the prism and the waveguide, in accordance with the invention, the said surface is Panaorama face of the prism output radiation, and on top of the waveguide optically insulating layer having a smaller thickness than the optical insulating layer under a waveguide attached Panaorama face of the prism input radiation, which occupies part of the face of the prism output.

It is also proposed adjacent to the input prism surface faces the output prism apply a thin film absorbing mask, acting along the beam in the waveguide at the edge of the input prism.

A variant multipath interference filter, containing on the surface of the flat plate of the planar optical waveguide and prism input waveguide and output radiation, the location the data over the waveguide in series along the radiation, moreover, the waveguide is optically isolated from the plates and prisms air gap or a thin layer of transparent dielectric with a refractive index lower than that of the prism and the waveguide, which in accordance with the invention, adjacent to the waveguide facet prism input radiation is much less adjacent to the waveguide facets of the prism output radiation and is positioned from the waveguide on a smaller optical distance than the face of the prism output radiation.

It is also proposed that the sections of the waveguide, designed for input and output radiation are not the same.

The invention is illustrated using figure 1-4.

Figure 1 - diagram of the multipath interference filter based on the effect of total internal reflection, as shown in two projections (a) and (b). Here 1 - prism input radiation in the planar light guide 3, 2 - prism output radiation from a fiber, 4 and 5 of the transparent dielectric film, the insulating fiber and having a refractive index less than that of the light guide and the prism, n icon at the bottom of the refractive indices corresponding to the number of icon elements of the device, 6 and 7 faces of prisms input and output radiation. Arrows indicate flows of radiation at the input to the filter and exit.

2 is a diagram of multipath interference filter based on the effect on the aqueous internal reflection. Here 8 - opaque mask, the remaining symbols correspond to figure 1.

Figure 3 - scheme variant multipath interference filter based on the effect of total internal reflection. Here 9 is a planar light guide, 10 - prism input radiation in planar waveguides 11 - prism of the output radiation from a fiber, 12 - transparent insulating, the prism input radiation, a layer with a refractive index lower than that of the waveguide and the prism 1, 13 - transparent insulating, the prism output radiation, a layer with a refractive index lower than that of the waveguide and the prism 11, 14 - base transparent flat plate, n icon at the bottom of the refractive indices corresponding to the number of icon elements of the device, l is the length of a section of waveguide with spatially unsteady regime of passage radiation, lI- length of the waveguide adjacent to adjacent to the waveguide facet prism input radiation, lO- length of the waveguide adjacent to adjacent to the waveguide facet prism output radiation. Arrows indicate flows of radiation at the input to the filter and exit.

4 is a diagram of a design of the monochromator based on the use of multibeam interference filter. Here 15 - emitter 16 - lens. 17 is adjustable slit with adjustable position in the focal plosko and, f is the focal length of the lens.

In accordance with figure 1, the incoming collimated radiation falls on the face 6 of the prism, passes through the prism of the first input radiation and tunnels in the light guide 3 through the thin transparent film 4 having a refractive index less than that of the prism and the optical fiber and the thickness less than the wavelength. The film may be replaced by an air gap. The radiation in the waveguide has a modal character and extends zigzag. Each time the ray falls on the side of the waveguide adjacent to the prism 2, the portion of the radiation passing due to the tunneling layer 5 with a refractive index of n5less than refractive indices of the waveguide and prism 2, enters the prism 2 and apply it at an angle φ to its face adjacent to the waveguide. The angle of incidence of the radiation from the inside of the prism input radiation on its surface adjacent to the light guide, more angle of total internal reflection (air defense) on this surface, which is caused by the ratio of the indices of refraction of the contact in this field environments.

Rays, released from the neighbouring places of incidence of radiation from the inside of the light guide at its border, adjacent to the prism must differ in phase by an integer number of 2π radians, in this case, these rays and all other rays, emitted from the optical fiber can interfere with each other with the formation of maximum interference.

The wave excitation fiber, having a form isolated from the substrate film, requires incident beam angle of incidence on the base (adjacent to the waveguide) face of the prism 1, equal to:

φ'=arcsin(γm/n1),(1)

where γm=n3sinθm- slow waves in the waveguide, θm- the angle of incidence of the beam fashion m in the waveguide on its surface.

The angle of fashion is determined by the wavelength, refractive index and thickness of the light guide. If the incident collimated light flux of radiation of different wavelengths propagating in one direction, with fashion waveguide coincide only radiation with a single wavelength light with other wavelengths due to interference as distribution in the waveguide damped. For selection of radiation with a different wavelength, change the angle of radiation incidence on the prism so that the radiation is trapped in the waveguide, corresponded to the picture mode waveguide (corner fashion θmfor this wavelength.

After the prism of the output radiation, the radiation is focused in the focal plane is the plane of the lens set aperture with a slit. Missed slit radiation falls on the photodetector; a slit cut from the spectrum of the last of the light flux of the radiation in one fashion waveguide.

The required ratio between the values of the refractive indices of the waveguide and adjacent environments for a symmetric waveguide the following:

n1=n2γmn4=n5,(2)

The figures shows the structure of a symmetric waveguide. The refractive indices of the prisms are equal refractive indices of the layers 4 and 5 also are equal and less than that of the prisms.

Included in the prism 2, the radiation is distributed in it at an angle φ to its basic faces:

φ=arcsin(γm/(n2=n1)).(3)

The number of beams N, which is cleaved during movement in each waveguide included in the beam and emitted from the prism 2, will bring the flax is equal to the number of drops of the beam in the waveguide at its adjacent prism side:

NL2htgθm(4)

where L is the length of the waveguide, h is its thickness.

The fact that prism with a larger face is from the surface of the waveguide at a greater optical distance than a small prism (film 5 is thicker film 4), increases the number N of rays emerging from a large prism, since each beam has a smaller share of energy due to increasing attenuation when tunneling through a thicker film.

Part of the radiation propagating in the waveguide, due to tunneling penetrates into the layer 4 with a refractive index n4=n5, but, due to the fact that it borders on the outside of the structure with air, radiation returns to the waveguide.

Dispersion region in the proposed interference device can be defined by analogy with the Fabry-Perot interferometer expression:

Δλ=λ/m,(5)

where m is the order of interference with the formation of the interference pattern is consistent the surrounding room fashion spread of the light beam in the waveguide.

Resolution proposed interference device, also similar to the Fabry-Perot interferometer is determined by the expression:

A=Nm(6)

Here N is the number of interfering beams equal to the number released from the prism 2 rays.

Here is a numerical calculation based on the book [guided wave optoelectronics: TRANS. from English. Ed. So tamira. - M.: Mir, 1991 - 575 S.], pp.28-30. We assume that the waveguide is distributed fashion m=2, n3=1,7. n4=n5or =1.5, h=1,25 µm, λ=1 µm. Get the value of the angle of fashion θ2=62°. If the refractive indices of the prisms is equal to the index of the waveguide, the corners propagating inside the waveguide beam relative to the normal to the base faces of the prisms is equal to θ2=62°. The calculation in (3) also shows that φ=θ2. Knowledge of φ allows us to calculate the geometric dimensions of the prisms. When the size of the base face output prism along the waveguide L=5 cm in accordance with (4) find the number of rays emerging from the prism: N=104. Finally, we obtain: resolution of the interference filter A=Nm=2·104the dispersion region Δλ=λ/m=0.5 µm. The aperture ratio of the filter is approximately determined by the area of the entrance face of the input prism and proportional the optional size of the face in the plane of the drawing l=0.5 cm

Compare the result of the above design parameters of the proposed interference filter with typical parameters common optical filters:

on the basis of the diffraction grating:

- m=2, λ=0.5 µm, Δλ=0.25 μm in the first order spectrum, A=104the luminosity is proportional to the width of the entrance slit illuminator grid (of the order of 0.001 to 0.01 cm);

based on the Fabry-Perot interferometer:

- h=2.5 cm, λ=0.5 µm, m=105, A=3·106, Δλ=0,5·10-5um.

The comparison shows that the present invention in a filter similar spectral characteristics to the diffraction filter, but surpasses it in 50-500 times the aperture, inferior to the Fabry-Perot interferometer resolution when working in the last mode, the use of large orders of interference, but surpasses it by 5 orders of magnitude across the width of the area variance.

Figure 2 illustrates the method of removing from the work area of the waveguide resulting from the waveguide light fluxes in the formation in space-steady-state mode mode. Refrigera rays emitted from the waveguide is absorbed by the mask 8, the mask length along the beam must be greater adjacent to the waveguide facets of the prism input radiation. The resulting destruction of the prism input radiation from the working sections of the waveguide and the prism of radiation output forming the output aperture is asego radiation beam (figure 2 arrows facing rays) is also necessary for the interference removal is not repairbuy rays, whose direction in the fiber does not correspond to the directions of the modes at the wavelength of these rays.

Depicted schematically in figure 3 variant multipath interference filter also uses a symmetric waveguide, but the location of prisms on one side of the waveguide required to enter into the design of the interferometer transparent base plate - base 14 on which is located the planar waveguide, the insulating layer and the prism. Radiation enters the prism 10, is experiencing on the base face of the prism total internal reflection and partially tunnels through the transparent film 12 having a refractive index less than that of the waveguide and prism, in the waveguide. In the waveguide radiation extends zigzag at an angle of incidence corresponding to a mode of the waveguide. On the border of the plate 14 is total internal reflection of the radiation propagating in the waveguide, the radiation due to tunneling penetrates to some depth in the plate, but, due to its large thickness, returns to the waveguide. Lots transparent layers 12 and 13 have the same plate, the refractive indexes smaller indicators prisms 10 and 11 and the waveguide, the radiation tunnels through a layer of prism 10 in the waveguide and the waveguide in the prism P. the radiation Intensity in the tunneling of the prism 10 d which should be more than that of the waveguide in the prism 11, which is provided by the greater thickness of section 13 (under the prism 11) layer than under input prism 10. When performing the latter increases the number of "zigzags" beam in the waveguide and the number of rays that have passed the output prism 11 and interfering with each other, as shown above, increases the resolution of the interference filter.

With the passage of the radiation in the waveguide section of length l (figure 3) of the light flux eliminated refrigera rays arising in the surrounding waveguide space, and passes the interference dissociation of rays in waveguide whose direction does not coincide with the modes of the waveguide for wavelengths of these rays. This area is located between the edges of the sections lIand lOwaveguide designed for input and output radiation.

All calculations performed for the optical filter according to claim 1 of the formula, valid for the variant according to claim 3 of the formula.

Figure 4 shows, as an example of possible application of the optical filter according to the invention the optical system monochromator-based use as dispersing element multibeam interference filter. As the emitter 15 is used a light source with a "white" spectrum, and a luminous flux having transverse and angular dimensions, overlapping linear and angular and ercury the input prism. Coming out of the prism 2 monochromatization radiation is focused by lens 16; in the focal plane of the lens forms a picture of the optical spectrum; in this plane, place the diaphragm with adjustable width and location transparent slit 17. Moving the slit in the focal plane, rebuild the monochromator wavelength of transmitted radiation; the gap also allows you to eliminate from the spectrum of light flows almost all the modes of the waveguide, in addition to one fashion. Thus, the device divides the radiation into a spectrum by wavelength, like a diffraction grating.

At the direction of the light parallel beam nemonokhromaticheskogo collimated radiation to achieve the effect of scanning the wavelengths passed by the filter, it is necessary, as in the case of bars, turn the device relative to the direction of incident radiation, as the rays with different wavelengths have different angles of the modes in the waveguide. The center of rotation should be a place of contact beams from the input prism light guide.

For manufacturing the device according to the invention uses materials and technology used in the optical industry. For prisms can be used sapphire (n=1,75) or glass TF (n=1.7 to 1.9)for insulating films and plates of fused quartz. Important is the manufacture of optical surfaces prize and plates with a high degree of flatness.

The above explanations show that the task can be achieved is described technical solutions.

The technical result of the invention is to provide a filter having a high resolution, large area variance and a high aperture ratio.

The invention can be used in optics and optoelectronics as a narrowband optical filter, as a dispersing device monochromators and spectrometers.

1. The interference of multipath filter containing on a flat surface of the planar optical waveguide and prism input waveguide and the output radiation is optically isolated from the waveguide uniform air gap or a uniform thin layer of a transparent dielectric with a refractive index lower than that of the prism and the waveguide, characterized in that the said surface is Panaorama face of the prism output radiation, and on top of the waveguide optically insulating layer having a smaller thickness than the optical insulating layer under a waveguide attached Panaorama face of the prism input radiation, which occupies part of the face of the prism output.

2. The device according to claim 1, characterized in that adjacent to the input prism surface faces the output prism deposited thin film absorbs the second mask, acting along the beam in the waveguide at the edge of the input prism.

3. The interference of multipath filter containing on the surface of the flat plate of the planar optical waveguide and prism input waveguide and output radiation, located above the waveguide in series along the radiation, the waveguide is optically isolated from the plates and prisms air gap or a thin layer of transparent dielectric with a refractive index lower than that of the prism and the waveguide, characterized in that adjacent to the waveguide facet prism input radiation is much less adjacent to the waveguide facets of the prism output radiation and is positioned from the waveguide on a smaller optical distance than the face of the prism output radiation.

4. The device according to claim 3, characterized in that the adjacent edges of the sections of the waveguide input and output radiation are not the same.



 

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2 dwg

FIELD: physics.

SUBSTANCE: method involves investigating residual stress on a section within the investigated area of an object using speckle interferometry technology. Irradiation of a weld point with a heat-affected zone using a speckle interferometer and collection of fringe patterns are carried out during formation of the weld joint, using pressure drop during the period of cooling the weld point after obtaining said weld point, by twofold exposure in one cycle of making the next point of the weld joint. The apparatus has a radiation source - a single-frequency laser, a speckle interferometer, a device for contact welding and a recording device with a control panel. The speckle interferometer and the radiation source are in form of a module which operates in concert with contact welding electrodes in a cycle of making weld points.

EFFECT: wider technological capabilities, improved quality and shorter time for conducting nondestructive rapid inspection and low power consumption during said inspection.

2 cl, 1 dwg

FIELD: physics.

SUBSTANCE: apparatus for measuring the surface form of a three-dimensional object in coordinates X, Y, Z has an array of probes, in the bottom part of which a detecting head is rigidly mounted, and in the top part there is a light-reflecting element, placed in a holder with multiple guides lying in nodes of a two-dimensional grid with known coordinates of the points of contact of detecting heads of each probe relative the centre of the holder, which enable each probe to freely move along the axis Z, wherein the two-dimensional grid can have an arbitrary geometric form. The apparatus also includes a mechanism for moving the three-dimensional object and the holder in order to calculate the surface form of the original object based on data on coordinates X, Y, Z, a computer, a flat support optical element, an optical device in form of an interferometer for measuring distance in the Z direction between the reflecting surface of the probes and the flat support optical element, having a coherent light source, an optical system which forms a wide parallel light beam whose diameter is larger than the size of the region of the two-dimensional grid, a beam splitter, a photodetector array on which an image of the light-reflecting elements from the array of probes is formed using a lens.

EFFECT: enabling measurement of the surface form of three-dimensional objects in motion and high measurement accuracy.

36 cl, 4 dwg

FIELD: physics.

SUBSTANCE: device has an optical radiation source, a photodetector, a first optical beam splitter, a mode filter based on a polarising light guide with high linear birefringence, a polariser, a second optical beam splitter, a phase modulator and a multi-turn fibre sensitive coil made from a polarising light guide.

EFFECT: high accuracy of the fibre-optic gyroscope by reducing parasitic phase difference in the interferometer.

3 dwg

FIELD: methods of phase modulation.

SUBSTANCE: method is based upon applying step sawtooth voltage to wideband phase modulator. Sawtooth voltage is specified with of numbers of m, n and k. Duration of each step equals to path time of light beam along light-guide of sensitive coil of gyro used to perform modulation of phase difference of beams of ringular interferometer. It is presented in form of pulse sequence with period of T0. During first half-period of the sequence the phase difference pulses have like number of alternating pulses with amplitudes of -(π-Δ) radians and +(π+Δ) radians. During second half-period the pulses have like number of alternating pulses with amplitudes of -(π+Δ) and +(π-Δ) radians correspondingly. Values of m and n are chosen from set of any positive integer non-zero numbers. Value of Δ is chosen within range of values from 0,05π radians≤ Δ ≤0,95π radians.

EFFECT: improved sensitivity of fiber-optic gyro; improved stability of scale factor.

5 dwg

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