JPS60218894A - Compact CO↑2 laser device with high frequency stability and wide band sweep capability - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention Technical Field The present invention relates to an OO laser device, which is most commonly used as a gas laser device, which is an important component in system configuration in fields such as optical measurement and spectroscopic analysis. In addition to stabilizing the frequency, it is also possible to sweep over a wide band while keeping the frequency stable.

Prior Art This type of OO8 laser device has conventionally been extremely large with a main valve oscillator over 1 meter in length, so various configurations have been proposed in the past in order to reduce its size. was. First, in order to shorten the optical resonator length, it was proposed to fill a ceramic waveguide with a gas such as 002 and place reflective mirrors at both ends. At the beginning of Vc, no frequency stabilization was performed. Next, in order to stabilize the frequency deposit, an organic gas cell similar to that described later in the present invention, which has a function of selecting all gas laser oscillation branches, is installed in parallel to generate all laser oscillations at the reference frequency. was proposed, but because the gas cell for frequency stabilization was placed outside the main valve oscillator, the frequency was stabilized, but the laser device had the disadvantage of being rather large. Moreover, when the frequency is stabilized by such means, there is also the disadvantage that the frequency is fixed at a selected predetermined value and cannot be changed even if necessary.

On the other hand, in a 00g laser, the oscillation frequency is approximately 1 OGHz, that is, there are so-called oscillation branches, each of which has a bandwidth of several hundred UHz to I GHz. In order to stabilize the oscillation frequency of the laser, it is necessary to provide means for selecting a desired oscillation branch.

C02 using a diffraction grating as such an oscillation branch selection means
Laser devices have been proposed in the past. However, since the diffraction grating used in a laser device diffracts and excludes unnecessary frequency components, in order to improve its frequency resolution and work effectively, it is necessary for the laser beam to spread over a wide range of diffraction gratings. . In order to expand the laser beam diameter, conventional OO and laser devices are constructed in the form of a folded resonator with a concave mirror interposed therebetween, which has the drawback of hindering miniaturization. Ta. Furthermore, if a desired oscillation branch is selected using such a configuration and the frequency is stabilized within that branch, it is almost impossible to stably sweep the oscillation frequency even within the band of the same branch. There were also drawbacks.

Summary of the Invention The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks at once;
Regarding OO and laser equipment widely used for chemical analysis, etc., we have created a completely new product that simultaneously satisfies eight conditions: miniaturization of the equipment, high stability of the oscillation frequency, and sweeping of the oscillation frequency over a wide band while maintaining high stability. The purpose of the present invention is to provide a CO laser device having the following configuration.

That is, the small OO laser device of the present invention has a ceramic waveguide filled with a gas containing 00°, a reflecting mirror is placed close to one end of the waveguide, and a diffraction grating is placed on the other end via a beam expansion lens. A Stark cell comprising two parallel plate electrodes sandwiching the optical path in the optical resonator and filled with an organic gas is arranged to form a main valve oscillator, and a Stark cell is arranged in which an organic gas is filled. The laser oscillation frequency is stabilized to a center frequency value of the eighth-order differential waveform of the saturated absorption signal exhibited by the organic gas, and the stabilized laser oscillation frequency is swept in accordance with the DC voltage applied to the parallel plate electrode. This is a characteristic of the heron.

EXAMPLES Below, the present invention will be described in detail by way of examples with reference to the drawings.

This invention small size 00. An example of the overall configuration of a laser device is shown in FIG. In the illustrated configuration example, a semi-transparent reflecting mirror 1 is provided in the main body of a laser device that performs laser oscillation, a waveguide 2 consisting of an airtight container with at least both ends completely transparent, and is arranged at an appropriate inclination with respect to the optical axis of the waveguide 2. Diffraction grating 8'J? and a lens 4 that enlarges the diameter of the original beam from the waveguide 2 and projects it onto the surface of the diffraction grating 8.

The waveguide 2 is made of a hollow airtight ceramic tube having a circular or rectangular cross section with a maximum width of several pairs, and contains 002 and He in its interior.

A mixed gas consisting of N, , Xe, Me, etc. is sealed at a total pressure of several lO to 100 Torr, and a high DC voltage is applied from a high voltage power supply 5 through a protective resistor R, and a current of about several mA is passed to discharge the gas. Let it all happen. Incidentally, the incoming mixed gas is, for example, Co, 't20~25%, Net
−601, N'io ~10%, Xe f 5%
The components are mixed at appropriate temperatures so that infrared light emission in the desired wavelength range is achieved at an appropriate temperature. A reflecting mirror 1 and a diffraction grating 8f are arranged at both ends of the waveguide 2 to constitute an optical resonator, and the oscillation branch in a desired wavelength range is selected by the diffraction grating 8. In order to increase the resolution and perform sufficient selection, it is necessary to enlarge the diameter of the laser beam on the surface of the diffraction grating 8, as described above. In order to increase the beam diameter,
In the device of the present invention, unlike the conventional device described above,
A lens 4 is interposed so that the required beam diameter can be expanded over a short distance.

Therefore, the CO2 laser device of the present invention having such a configuration,
A lens 4't is formed using a waveguide 2 with a length of about 1ocIrL.
- When interposed, the total length of the optical resonator from the reflecting mirror 1 to the diffraction grating 8 is kept below aocIIL, making it extremely compact compared to the conventional one, and the ability to select oscillation branches based on the action of the diffraction grating 8 Excellent 008. It becomes a laser device. Note that the power of the output laser beam can be varied over a wide range from many 10 mW to several W by appropriately adjusting the discharge current value or the mixture ratio of the filled gas or the filled gas pressure. The wave number of the oscillation branch that can be selected can be changed to 10 by rotating the diffraction grating 3 manually or automatically using a step motor or the like to change the inclination angle with respect to the original axis of the waveguide 2. Approximately several dozen bands can be obtained including both the .6 μm band and the 9.6 μm band.

In addition to the above-mentioned basic configuration, the compact CO2 laser device of the present invention has a diffraction grating 8 placed close to the optical resonator in order to stabilize the oscillation frequency in the selected frequency band of the desired oscillation branch. Then, arrange L1kg*L6. This Stark cell 6 has two parallel plate electrodes facing each other with an interval of several degrees between them, sandwiching the 20-element axis of the waveguide in an airtight container with at least both ends transparent. An organic gas anvil of a type that exhibits light absorption at m is sealed at a gas pressure of 9 Torr. This invention small size 00. In laser equipment,
This type of gas cell, which is added to the optical resonator to stabilize the oscillation frequency, is placed inside the optical resonator, which is the same position as in the conventional device described above, so there is no hindrance to the conversion of the C02 laser device into a shed. No, it's a small basic configuration! As described below, the stability of the oscillation frequency is significantly increased compared to the conventional one.

Therefore, the six-wire Stark cell configured as described above absorbs laser light with a strong energy level depending on the voltage value applied between the parallel plate electrodes, and produces a saturated absorption signal with a narrow spectrum width of several MFiz to several tens of MHz. to occur. Therefore, as will be described later, the oscillation output voltage of the sine wave oscillator 7 having an oscillation frequency of about IKl(z) corresponding to the highest response frequency of the electrostrictive element (PZT) 12 equipped with the diffraction grating 8 as a load is expressed by the Stark cell. The detection output signal of the photodetector 10 that receives the output laser light from the waveguide 2 when applied between the parallel plate electrodes in the synchronous detection amplifier 9
When synchronous detection amplification is performed by applying the third harmonic voltage from the harmonic generator 8 driven by the oscillation output of the sine wave oscillator 7, the amplified output is the Stark cell 6.
An eighth-order differential waveform of a saturated absorption signal with respect to the incident laser beam is obtained in a frequency band corresponding to the type of organic gas sealed in the chamber and the applied voltage. Therefore, in order to stabilize the laser oscillation frequency by using the steep slope of the 8th derivative waveform for frequency discrimination, the laser oscillation frequency can be controlled and stabilized so that the laser oscillation frequency always matches the center frequency of the 3rd derivative waveform. , the 8th order differential waveform signal, which is the amplified output of the synchronous detection amplifier 9, is sent to an electrostrictive element (PZT) via an electrostrictive element drive circuit ll.
12 to generate minute vibrations, thereby moving the position of the diffraction grating 3 in parallel with high precision, thereby finely adjusting the optical length of the optical resonator. Due to such fine adjustment of the optical length of the vanguard, the compact CO laser device of the present invention has a laser oscillation frequency stability of 10.0% compared to the conventional one.
This can be improved by approximately 00 times.

With the laser oscillation frequency stabilized with high precision as described above, the sine wave voltage from the sine wave oscillator 7 is applied between the parallel plate electrodes of the Stark cell 6 via the adder 14, and the high voltage power source When the DC high voltage from 18 is supplied to the adder 14, superimposed and added to the sine wave voltage, and superimposed and applied between the parallel plate electrodes in the Stark cell 6, the DC high voltage value is changed continuously, for example. As mentioned above, the laser oscillation frequency coincides with the center frequency position of the 8th derivative waveform of the saturated absorption signal and maintains stability about 10,000 times that of the conventional one, while maintaining the frequency range of each oscillation branch. Therefore, as the organic gas sealed in the Stark cell 6, NH, D,
0H8C1, 02Ti, C1.

0H8Br, 0H8F, Off, I, N)
I, , NF, , O,f(4F, .

If various organic gases such as 0, H, F, PF, etc. are appropriately selected and used, all oscillation branches within the entire frequency range that can occur in a C02 laser can be suppressed over the entire frequency band. Therefore, extremely stable and broadband sweeping of the laser oscillation frequency can be performed.

Effects As is clear from the above explanation, according to the present invention, using an extremely small original resonator with a length of 3QCm or less, for example,
The oscillation frequency stability has been improved by about 10,000 times compared to the conventional one, and therefore has an extremely high frequency stability of about 1o-11 to 1g-12, and in each wavelength range of 10.6μm and 9#6μm. Each of the tens of oscillation branches over the entire area has a frequency of several hundred MHz.
It is possible to realize a compact CO laser device with extremely excellent performance that can sweep the frequency over the entire frequency range of
A special effect can be obtained. As stated at the beginning, there is no example of a 002 laser device other than the device of the present invention that satisfies the eight conditions of small size, high frequency stability, and frequency sweepability.

In addition to the above explanation, in order to stabilize the laser oscillation in the compact 00 laser device of the present invention, the reflecting mirror l and the waveguide 2 are provided with a fine movement system using a combination of a bellows and a fine movement screw. It is also a remarkable effect of the present invention to realize a fine movement mechanism with high precision, which allows the base axes to be adjusted with high precision through a mechanism, and which are connected to each other.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the overall configuration of a compact CO and laser device according to the present invention. 1...Reflector, 2...Waveguide, 8...Diffraction grating,
4... Lens, 5, 18... High voltage power supply, 6...
・Stark cell, 7...Sine wave oscillator, 8...
Harmonic generator, 9... Synchronous detection amplifier, 10... Optical detector, 11... Electrostrictive element drive circuit, 1z... Electrostrictive element (PZT), 14... 7111 calculator .

Claims (1)

[Claims] L 00. A reflection #IA is placed close to one end of a ceramic waveguide filled with a gas containing Fe, and a diffraction grating is placed at the other end via a beam expansion lens to form a base resonator, and the optical resonator is A Stark cell completely filled with an organic gas is arranged with two parallel plate electrodes sandwiching the optical path in the inner plate, and the 8th derivative of the saturated absorption signal exhibited by the organic gas is determined according to the AC voltage applied to the parallel plate electrodes. A small 2U CO laser, characterized in that the laser oscillation frequency is stabilized at the center frequency value of the waveform, and the stabilized laser oscillation frequency is swept in accordance with the DC voltage applied to the parallel plate electrodes. Device. a In the laser device according to claim 1,
The diffraction grating is held by an electrostrictive element, and a detection output signal of the output laser beam of the main valve oscillator whose frequency changes according to the alternating current voltage applied to the parallel plate electrodes is detected by harmonics of the alternating current voltage. By applying synchronous amplification to the electrostrictive element, the diffraction grating is slightly moved in the optical axis direction of the base valve vibrator, thereby finely adjusting the base length of the base valve vibrator. A small CO and laser device.