JPH01183871A - Laser device - Google Patents

Abstract

PURPOSE:To prevent the yield of distortion in a gap, by providing O rings between a tightly sealed container and the outer surfaces of Fabry-Perot etalons (FP), filling the spaces between the O rings with elastic resin, and providing springs in the device. CONSTITUTION:FPs 7 are contained in a tightly sealed container 8 with specified parallel gap being kept. A flange 30, which holds a window 8a, is fixed to one side of the tightly sealed container 8. A flange 30, which holds a window 8a, is fixed to the other side through a spring shoes 31. The O rings 33 are coupled at the outer surfaces of the FPs 7 with specified intervals being provided. Spaces formed between the O rings 33 and the tightly sealed container 8 are filled with elastic resin 34. The O rings 33 serve the following roles: the role, which elastically holds the FPs 7 together with the resin 34; and the role, which prevents the outflow of the resin to the side of the window 8a and to the side of a pipe 9a for pressure fluctuation before the resin is hardened when the resin is charged through injecting holes 35. Springs 37, which are provided between the other FP 7 and the spring shoes 31, are adjusted to suitable forces so that a gap with the FP 7 becomes parallel. In this way, the regular gap is kept without distortion, and the FPs 7 are stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applicability] The present invention relates to a laser device, and in particular to the holding of a -y appripérot etalon for wavelength tuning.

[Conventional technology]

Figure 2 shows, for example, the magazine r IEEE Journal Q.
uantumEleetronies QE-14(”
78) is a schematic configuration diagram showing the conventional wavelength stabilized laser shown in No. 17J.

In the figure, 1 is a laser oscillator 1 and 2 each having a structure for changing the wavelength inside, a Fabry-Perot etalon, 3 is a photodetector, and 4 is a servo mechanism for changing the wavelength.

Next, the operation will be explained. The wavelength of the laser beam emitted from the laser oscillator 1 changes depending on the state of the optical resonator. In this example, selection can be made by changing the spacing between vanguards. However, it is difficult to stabilize the selected wavelength with high precision due to thermal deformation and vibration of the resonance wave. Therefore, the laser beam obtained from oscillation@1 is separated into spectra by a Fabry-Perot etalon (hereinafter referred to as FP) 2, which is a high-resolution spectrometer, and the intensity of the beam transmitted through the FP is measured by a photodetector 3. The example shown in this figure is an attempt to stabilize the wavelength. FP consists of two mirrors with high flatness facing each other with a gap d, and the center wavelength of the light that passes through the mirror surface at an angle of θ is 2nd ooso λ knee □ (1) It becomes a specific wavelength that causes a hailstorm. n is the refractive index between the gaps, and m is an integer. If an FP with high resolution is used, the intensity in the λ range of the laser's oscillation wavelength distribution can be found.

Generally, a laser beam has a certain divergence angle, so only the beam component that satisfies the above equation passes through the FP, forming a coaxial fringe (ring-shaped interference 1i4) centered on the optical axis of the beam. Therefore, after the FP, the photodetector 3
When λ changes, the position of the fringe changes,
It passes over the photodetector.

Now, FIG. 3 shows the change in the intensity of the beam appearing on the photodetector when the fringe crosses.

In the figure, (A) shows that the resonance interval is changed, and at the same time, the wavelength λ of the beam changes monotonically.

At the same time, the fringes generated by the FP move and the intensity of light entering the photodetector changes, resulting in the curve shown in (A) in the figure. This temporal S(a) indicates the spectral distribution of the oscillator 1. The depression near the maximum strength is called the lamb dip. Now, as the resonator spacing is slightly increased in section R (quadrature) in the figure, the beam intensity passing through the FP initially decreases and then increases from the center frequency λ0 of the lamb dip. Therefore, the servo mechanism 4 changes the resonance interval, simultaneously measures the direction of change in the beam intensity passing through the FP, and applies a servo so that the wavelength converges where the direction of change changes. The oscillation wavelength λ, r
The center wavelength λI of tFP can be fixed.

FIG. 4 shows a specific example of the seed laser device of B. In the figure, 5 is a total reflection mirror, 6 is a partial reflection mirror disposed opposite to the total reflection mirror 5 via the laser oscillator 1, Reference numeral 7 denotes a Fabry-Perot etalon (FP) for wavelength tuning, which is arranged between the laser oscillator 1 and the partial reflecting mirror 6. 8 is a sealed container containing the FP 7, a window 8a is fitted in the opposite position, and the inside is filled with gas. 9 is a container expansion/contraction means consisting of a bellows, and a pipe 9
It is connected to the sealed container 8 via a. 10 is a drive mechanism for the volume expansion/contraction means 9; 11 is a wavelength tuning frame that accommodates the sealed container 8 and is directly attached to the tank wall of the laser oscillator 1; 12 is a window that confines gas within the laser oscillation system 1; 13 is a It is a fan that circulates gas within the oscillator, and one end of its rotating shaft 14 is connected to a motor 16 via a coupling mechanism 15.

17 is a laser oscillation I#1, a total reflection mirror 5, a partial reflection mirror 6,
Laser light oscillated by FP7, 18 is this laser light 1
A beam extraction mirror 19 takes out a part of the laser beam 7, and a wavelength motor mechanism separates the extracted laser beam.
, a filter 21 for adjusting light intensity, an integrator 22 for diffusing the laser beam 17, a sealed container 1#24 containing a monitor FP 23 having a gap structure, and a lens 2.
It consists of 5.

24a is a window fitted into the sealed container 24;
2B is an image sensor for observing the fringes generated by the FP 23, and is, for example, a -dimensional image sensor. Reference numeral 27 is a light shielding box that accommodates 20 to 26 and blocks external light, and is arranged such that the interference filter 20 allows the laser light from the beam extraction mirror 18 to enter therein. 28 is a temperature adjustment means for keeping the temperature of the FP 23 constant;
29 is an image processing means for analyzing fringes, and drive mechanism 1
Output to 0.

Next, the operation will be explained. The wavelength of the laser beam emitted from the laser oscillator 1 is selected by various elements in the oscillator. For example, in an excimer laser, the original oscillation wavelength width is several angstroms, but the wavelength width is narrowed by inserting a spectroscopic element such as a prism, grating, or FP into the resonator. Moreover, by adjusting these spectroscopic elements, the wavelength can be set to any wavelength within the original oscillation wavelength width.

Now, a part of the laser beam 17 thus obtained is guided to a wavelength monitoring mechanism 19. Wavelength monitor mechanism 19 uses F P 23 to determine wavelength.

Since the inside of the sealed container 24 is always maintained at a predetermined temperature by the temperature adjusting means 28, the FP 23 is not affected by changes in temperature and atmospheric pressure.

In the above embodiment, a circular fringe that appears when light passes through the FP 23 is used. The diameter of the fringe is related to θ, and by determining θ, the wavelength λ■ is determined from equation (1) shown above.

The wavelength monitor mechanism 19 includes an integrator 22, an FP 23, and a lens 2 that weaken or diffuse the laser beam.
It consists of 5. Among the divergent components generated by the integrator 22, only the light having θ that satisfies the above equation is transmitted to the FP2.
3 and reaches the lens 25. The focal length of the lens is f
If so, the light having the component θ will gather at the focal position at a point farther away from the axis of the lens. Therefore, by observing the position where the light gathers using the image sensor 26, θ can be determined and λ can be calculated.

By the way, the intensity distribution of light on the image sensor 2B is as shown in FIG. 5, where the vertical axis shows the output and the horizontal axis shows the distance siX from the center of the fringe. Each corresponds to a different order m of FP. Each interval is called a free spectral range, and the wavelength can be uniquely determined within this range.

Moreover, since the free spectral range can be determined by the design of the FP, it is designed to be wider than the expected wavelength shift.

Furthermore, since each of them has a light intensity distribution corresponding to the wavelength distribution of the laser beam, an image processing means 23 is required to process this and obtain θ. Further, here, the current wavelength λ is calculated, and the drive mechanism 10 operates the volume expansion/contraction means 9 according to the result to adjust the pressure inside the sealed container 8, thereby adjusting the wavelength of the oscillator.

[Problem to be solved by the invention]

Conventional laser devices such as those described above lack consideration for holding the FP, and therefore the FP cannot be stabilized by slight external forces (heat input from the laser and propagation of vibration from the laser oscillator). There was a problem that distortion occurred in the gap that was obstructed and parallel.

The present invention was made to solve these problems, and an object of the present invention is to obtain a laser device that can elastically hold an FP in a sealed container and maintain parallelism of the gap.

[Means to solve the problem]

In the laser device according to the present invention, an O-ring is interposed between a sealed container and the outer periphery of a Fabry-Perot etalon housed therein, and an elastic resin is filled between each O-ring, and a spring is used to make the gap between the etalons parallel. It is decorated with interior decoration.

[Effect]

In this invention, since the elastic resin is used to solidify the space between the FP and the sealed container, the FP is held with a small external force, and the heat is dissipated through the resin covering the outer periphery of the FP, so there is little distortion. Further, the gap between the FPs is kept parallel by the spring.

〔Example〕

FIG. 1 is a sectional view showing an embodiment of the present invention, and 7 is a FP housed in a sealed container 8 with a predetermined parallel gap.
At one second, there is a window 8a on one side of the sealed container WIr8.
A flange 30 that holds the window 8a is fixed, and a 7 flange 3 that holds the window 8a via a spring receiver 31 on the other side.
2 is fixed. Reference numeral 33 denotes an O-ring fitted around the outer periphery of each of the above-mentioned FP7 at a required interval.
The space formed between the ring 33 and the sealed container 8 is filled with elastic '84M834. In other words, the above O
The ring 33 serves to elastically hold the FP 7 together with the resin 34, and also to prevent the resin from flowing out to the window side and the pressure fluctuation piping 9a side before it hardens when filling the resin from the injection hole 35. . 36 is one FP
A Teflon plate 37 supports the FP 7, and 37 are several springs interposed between the other FP and the spring receiver 31, and the springs 37 are adjusted to an appropriate force so that the gap between the FPs 7 is parallel. .

〔Effect of the invention〕

As I have not explained above, this invention houses a Fabry-Perot etalon in a sealed container, interposes an O-ring between the outer periphery of the etalon and the container, and fills each O-ring with an elastic resin. It is equipped with a spring that makes the mutual gap parallel, and the etalon has the effect of maintaining a regular gap and being stable without being distorted at all.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing a conventional wavelength stabilized laser, FIG. 3 is a graph showing changes in beam intensity appearing on the photodetection plate, and FIG. The figure is a configuration diagram showing a specific example of a laser device, and FIG. 5 is a diagram of the intensity distribution of light on an image sensor. In the figure, 7 is a Fabry-Perot etalon, 8 is a sealed container, 8m is a window, 30.32 is a flange, 31 is a spring receiver, 33 is an O-ring, 34 is a resin, and 37 is a spring. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] A Fabry-Perot etalon that tunes the wavelength emitted from a laser oscillator and a Fabry-Perot etalon that spectrally separates laser light within a monitor are housed in a sealed container, and an O-ring is interposed between the outer periphery of the etalon and the sealed container. A laser device characterized in that an elastic resin is filled between O-rings and a spring is installed to make the etalon gap parallel.