Waveguide co2high-pressure laser with high frequency excitation

 

The invention relates to laser technology and can be used in the development of tunable radiation waveguide lasers used in medicine, monitoring of the atmosphere, optical radar, the sights and devices precision material processing. Waveguide CO2the laser includes a resonator, waveguide including a discharge cell, two mirrors and diffraction grating, and a device for moving one of the mirrors along its axis. The diffraction grating is a first reflector of the resonator, and the second reflector resonator consists of two interference mirrors with reflection coefficients that are selected based on the requirements of the field of continuous tuning of the frequency of radiation at specific laser transition. The device for moving the mirror is made of magnetostrictive. Ensured the expansion of generation and the field of continuous tuning of the frequency of radiation while maintaining the high selectivity of the resonator in relation to the allocated frequency radiation. 1 Il.

The invention relates to tunable radiation waveguide CO2lasers with tunable radiation. Lasers Tacoli and so on), technology precision machining of materials and research.

The first working models of the waveguide CO2lasers [1, 2] is excited by a DC discharge. The optical resonator of such lasers was formed waveguide gas discharge tube and the external mirrors, at least one of which is partially transmissive. For adjustment of the frequency of radiation one of the mirrors was replaced by a diffraction grating or prism, working on reflection (for example, a scheme Littrow).

The disadvantages of these structures can be attributed to the fact that at high pressure of the active medium (> 100 mm RT.CT.) applying a direct-current discharge was limited to the temperature and ionization instability characteristic of this type of discharge. To reduce the influence of temperature and ionization instability has allowed the use of high-frequency capacitive discharge [3, 4]. In this way, the pump waveguide CO2laser frequency selection of the exciting field can be achieved mode "electrodeless" discharge and reduce the impact of plasma-chemical processes at the electrodes and, consequently, their interaction with the electronic component gas-discharge plasma of a high pressure. Prima/sub> lasers and, accordingly, to extend the scope of the continuous tuning of the frequency of radiation at the expense of impact broadening of the contours of amplification lines of the individual vibrational-rotational laser transitions in the molecule of CO2.

However, smooth frequency radiation can be performed only if the waveguide resonator has sufficient selectivity and allows you to avoid competition in the generation of the longitudinal waveguide modes.

To increase the selectivity of the waveguide resonator WITH2laser allows the use of selective intracavity elements. A known design of a waveguide CO2laser [5] with high pressure active mixture of CO2Not (~ 450 Torr), selected as a prototype containing gas discharge waveguide cell with high frequency excitation, two partially transmissive mirror and a diffraction grating operating in reflection scheme Littrow. One of the mirrors mounted on piezoelectric structure could be moved along the axis of the resonator of the laser. The distance between the mirrors was a magnitude 9.5 see Both mirrors form a frequency-selective filter in the cavity laser with dispersion region of ~ 1500 GHz wavelength, the tion between the mirrors and therefore the offset curve of the transmittance of the filter using piezoelectric structure when applying for her control voltage.

A disadvantage of the known designs is a small length of the discharge of the waveguide channel, which, given the level of non-selective losses in the cavity prevents the threshold condition generation for laser transitions with low gain, limiting the spectral range and the area smooth frequency tuning of the laser radiation. In addition, the piezoelectric structure attached to him a mirror, may be unstable dependence of the displacement of the mirror from the values fed to it, the voltage due to parasitic leakage of electric current from the surface of a piezoelectric material. Such instability reduces selective properties of the optical cavity.

Also known gas laser [6] in which to increase the selectivity of the optical cavity and expanding the range of generation used magnetostrictive device for moving the mirror along its axis. However, the disadvantage of this device is the lack of selective elements in the resonator of the laser with dispersion region, exceeding miodowy interval of the resonator, which is the main limitation of the field of continuous tuning of the frequency of radiation.

Technolologies CO2laser high pressure while maintaining the high selectivity of its resonator in relation to the allocated frequency radiation.

The technical result is achieved by the fact that the waveguide CO2the high-pressure laser with high frequency excitation, containing the resonator, the waveguide including a discharge cell, two mirrors and diffraction grating, and a device for moving one of the mirrors along its axis, what is new is that the diffraction grating is a first reflector of the resonator, and the second reflector resonator consists of two interference mirrors for the reflection coefficients that are selected based on the requirements of the field of continuous tuning of the frequency of radiation at specific laser transition, the device for moving the mirror is made of magnetostrictive.

The increase in the threshold gain of the active medium of the waveguide CO2laser for weak lines generation is carried out by increasing the waveguide length of the discharge cell. The length of the cell L is selected as the threshold generation

where g0i- gain small signal allocated line (cm-1),

whereL- width at half-height of the loop gain of the laser transition, caused by the collision of molecules of the gas mixture (MHz). The value of the

L(MHz) can be estimated from the condition [7]

where ni- the share of gas components in the mixture, P is the pressure of the gas mixture (kPa), T is the absolute temperature in K.

Discrete frequency radiation by using a diffraction grating (r1) 150 l/mm with a reflectivity of 0.95% in the first order diffraction is configured autocollimating circuit at the center of the allocated line of the corresponding laser transition. Smooth the frequency of radiation from the center of allocated lines in the rangeis the interference reflector (r2) formed by two mirrors (andand. The value of d is chosen from the condition

When the change of the distance d, by moving the mirror g along the optical axis changes the reflection coefficient r2suppressing undesirable for the generation of longitudinal resonator mode laser, miodowy interval (L) is determined by the expression

Moving mirrorsis the magnetostrictive device consisting of three rods and mount for mirrors. The rod is made of magnetostrictive material (type Invar). To create a rod of technical magnetization them fixed induction coil. From a diffraction grating (r1) rod rigidly attached to the housing of the laser. By the interference reflector (r2) rod passed through a fixed to the body of the laser sleeve. At the ends of the rods, converted to (r2), is the mount mirrors. By passing an electric current through the induction coil from the stabilized source PI is I'm moving mirrors () along the optical axis of the resonator of the laser.

The excitation waveguide CO2laser high pressure (P ~ 200-300 mm RT.art., the composition of the mixture CO2:N2:He) is carried out using high frequency (~ 100 MHz) low-voltage discharge in a hollow, metal (Al, EEO) waveguide with cross-section 11 mm2and a length of 450 mm

Comparative analysis of the prototype shows that the inventive waveguide CO2high-pressure laser with high frequency excitation is characterized by the fact that for continuous tuning of the frequency of radiation used magnetostrictive device, consisting of three rods and mount for a mirror in the composition of the interference reflector.

Thus, the inventive waveguide CO2high-pressure laser with high frequency excitation corresponds to the criteria of the invention of "novelty."

The comparison of the proposed solutions not only prototype, but also with other technical solutions in this field of technology, has allowed to reveal in them the features distinguishing the claimed solution to the prototype that allows to conclude that the criterion of "inventive step".

The invention is illustrated by the drawing, which shows: the th pressure of the high-frequency excitation of the waveguide contains a discharge cell 1, formed water-cooled RF electrodes 2 and 3 and ceramic (EEO) unit 4 and is manufactured by hot pressing using vacuum technology. The cross-section of the cell has a value of 11 mm2. The length of the cell - 450 mm With one side of the cuvette is joined with evacuated unit 5, which is placed diffraction grating r1(150 gr./mm, r1=0.95) and node alignment diffraction grating 6. On the other hand cuvette vacuumized through the adapter 7 using plates made from ZnSe, located at the Brewster angle to the optical axis. The fixing unit 4 to the base of the laser structure 8 using rack mounting 9 and 10. Rack mounting the cylindrical rods 11 of magnetostrictive material (Invar). From block 5 ends of the rods are rigidly mounted in the rack mounting 9. The other ends of the rods 11 is fixed through the slide bushing in the rack 10. To create technical magnetization in the cores 11 at them fixed induction coil 12. At the ends of the rods facing the adapter 7, is the site of attachment and alignment 13 mirrors. At a distance d from the mirrorandform an interference reflector r2forming together with the waveguide cuvette 1 and the diffraction grating r1the optical resonator of the laser. The distance between the reflectors of the resonator r1and r2is the value of L=500 mm the Selection of the coefficients of reflectionandreflector r2on the basis of formulas (1-6) based on the requirements of the field of continuous tuning of the frequency of radiation at specific laser transition. High-frequency discharge between the electrodes 2 and 3 in the gas mixture of CO2:N2:No=1:1:6, at a pressure of ~ 200-300 mm RT.art., made using high-frequency power supply 15 (~ 100 MHz) with a power of 250 watts.

The configuration process on the allocated frequency radiation is carried out as follows. After the inflow of the gas mixture in the waveguide cell it is sealed. Then using the power supply unit 15 in a ditch lights high-frequency capacitive discharge. After this pre-setting of the laser emitted laser transition using the alignment of the diffraction grating and mirrors. Next on the mount and alignment 12 the particular generation in the center of the line radiation emitted laser transition, then from the stabilized power source voltage is applied to the induction coil 12, in excitatory terminals 11 technical magnetization. Due to the magnetostrictive effect, the rods change their length by moving the mirroralong the optical axis of the resonator of the laser, which allows you to change miodowy the interval of the interference reflector (see expression (6)), thereby making a smooth frequency radiation (see expression (4)).

The use of magnetostrictive device in the configuration of the optical resonator waveguide CO2laser will allow more stability (not less than 50%), compared with the piezoelectric devices of this kind to move and fix the position of the optical interference reflective elements for implementation of the continuous tuning of the frequency of radiation. This solution will allow us to expand the scope of tunable radiation waveguide CO2lasers for use in spectroscopy of polyatomic molecules, environmental monitoring, ambient air, in the creation of high-tech equipment in various fields NAU 3/00, Waveguide Gas Laser Devices. / P. W. Smith. 1971.

2. Bridges T. I. a.o. CO2Waveguide Lasers./ T. I. Bridges, E. G. Burkhardt, P. W. Smith, Appl. Phys. Letters. Vol.20, No. 10, 1972. P. 403-405.

3. Patent 4169251 USA, Ál. H 01 S 3/097. Waveguide Gas Laser with High Frequency Transvers Discharge Exitation /K. D. Laakman. 1978.

4. R. L. Abrams. Gigahertz Tunable Waveguide CO2The Laser. Appl. Phys. Letters. 25, 304 (1974).

5. Patent 46776 USA, Ál. H 01 S 3/22, Ál. H 01 S 3/10. RF-Excitted CO2Waveguide Laser with extended tuning range. Hans C. Marcinak, Frank E. Goodwin. 1987 (prototype).

6. Patent 1055613 UK Μl. N 03 B 304 N 03 J 106H 01 s Freqency Stabilisation of Gas Masers./ Kouchi Shimoda and Kasuo Ito. 1967.

7. Abrams R. L. Apll. Phys. Lett. - 1974, vol. 25, p.609.

Claims

Waveguide CO2high-pressure laser with high frequency excitation, containing the resonator, the waveguide including a discharge cell, two mirrors and diffraction grating, and a device for moving one of the mirrors along its axis, characterized in that the diffraction grating is a first reflector of the resonator, and the second reflector resonator consists of two interference mirrors with reflection coefficients that are selected based on the requirements to the field of continuous tuning of the frequency of radiation at specific laser transition, the device for moving the mirror is made of magnetostrictive.

 

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