JP2002118317A - Wavelength selective optical device using etalon and diffraction grating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-precision wavelength-selective optical system in which the influence of an unavoidable manufacturing error of a wavelength-selective optical element is improved, and an application device configured using the same. I do. SOLUTION: When the diffracted light from the diffraction grating 103 has a wavelength distribution that changes almost monotonously along the dispersion direction, and two opposing planes of the etalon 104 have a C-shaped non-parallelism. , The diffraction grating 103 and the etalon 104,
By setting the direction of the wavelength distribution of the diffracted light and the direction of non-parallelism of the etalon 104 so as to be aligned with each other based on a preset rule, the influence of errors inevitable in manufacturing the wavelength selection optical element is improved. In addition, it is possible to obtain a wavelength selection optical device that achieves high-precision wavelength selectivity, and applied equipment configured using the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength selection optical device using an etalon and a diffraction grating as a wavelength selection element, and to an applied device such as a spectrophotometer or a laser device using the wavelength selection optical device. .

[0002]

2. Description of the Related Art In the field of spectroscopic analysis, a wavelength selecting optical system has been developed to improve the accuracy of analysis. Further, when a laser is used as a light source for high-precision analysis / measurement or a light source for processing, an optical system for selecting a wavelength is required for controlling the spectrum of the laser.

In particular, in an excimer laser used as a light source of a semiconductor exposure apparatus, in order to improve the influence of chromatic aberration of an exposure optical system on an exposure pattern, a band width of a spectrum which is originally several hundred picometers is narrowed to one picometer or less. There is a need to. The narrowing of the band is realized by incorporating a wavelength selection optical system in the laser resonator.

In such a wavelength selection optical system, a Fabry-Perot etalon (hereinafter, abbreviated as etalon) or a diffraction grating, which is a filter used in an optical region, is used.

[0005] First, an etalon is composed of two parallel flat plates having appropriate reflectances facing each other with an appropriate gap interval and being accurately parallel to each other. The etalon is determined by the multiple interference of light generated in this gap. It is an optical element that can selectively transmit only the wavelength. The wavelength to be transmitted is determined by the reflectance of the reflecting surface and the size of the gap interval. Usually, a gap having good parallelism is formed by sandwiching a plurality of spacers having the same thickness between two parallel flat plates.

Next, FIG. 3 shows a schematic diagram of the transmission characteristics of the etalon. The transmission characteristics of the etalon are in the free spectral range.
The peak is shown for each unique wavelength pitch determined by the etalon gap interval (FSR). Further, the shape of the spectrum of each peak is mainly determined by the reflectance, roughness, and parallelism of the parallel plate.

In an actual laser, a diffraction grating is used to select only one peak from such higher-order etalon peaks.

Conventionally, narrow band lasers have been disclosed in
No. 52667 is known.

Hereinafter, the configuration will be briefly described. FIG. 6 shows a configuration of a conventional narrow-band discharge excitation laser. A laser gas is sealed in a resonator composed of a total reflection mirror 605 and a semi-transmission mirror 604, and a discharge tube window 603 for transmitting light.
A discharge tube 601 having a and 603b is placed, and oscillates by discharge excitation. Etalons 606a and 606b, which are wavelength selection elements, and a prism 607 are provided in the optical resonator.
a, 607b are placed, and it becomes possible to selectively oscillate a laser only in a specific narrow band wavelength.

[0010]

However, in an actual etalon, a variation on the order of nanometers occurs due to the production of the spacer or the accuracy of the assembly. As a result of the evaluation of the characteristics of the etalon, it has been found that there is a tendency that two parallel flat plates have a C-shape in the variation of the gap interval. This is schematically shown in FIG.

In FIG. 4, the gap interval 401 is exaggerated so as to be widened downward in order to make the gap interval particularly easy to understand. In the case of FIG. 4, the gap interval increases from the top to the bottom of the etalon.

Now, the laser beams are respectively shown in FIG.
When passing through the position of the etalon, when a certain peak in the transmission characteristic of the etalon is seen, the gap spectrum 401 of the etalon is different at each beam transmission position, so that the transmission spectrum has a peak wavelength little by little as shown in FIG. Is shifted. If the gap interval 401 has a variation of several tens of nanometers, the peak wavelength shift is on the order of picometers, and the spectrum width of the entire beam exceeds 1 picometer. It is difficult to control the spacing.

Next, as a result of evaluating the diffraction grating, it has been found that the wavelength to be selected is shifted depending on the portion of the grating to be used. Further, the shift tends to monotonously shift from one end of the diffraction grating to the other end. Such characteristics cannot be considered in an ideal diffraction grating, and it is considered that the characteristics are due to manufacturing. However, it is difficult to maintain the groove pitch uniformity on the order of several tens of nanometers over a wide grating area.

Therefore, in an application field that requires precise wavelength selection accuracy, these manufacturing errors pose a problem.

An object of the present invention is to provide a high-precision wavelength selection optical system in which the influence of the unavoidable manufacturing error of such a wavelength selection optical element is improved, and an applied device constituted by using the same. And

[0016]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention provides an optical system for selecting a wavelength using at least a diffraction grating and an etalon. When the wavelength distribution has a substantially monotonous change, and the two opposing planes of the etalon have a C-shaped non-parallelism, the diffraction grating and the etalon are subjected to the wavelength distribution of the diffracted light. And the direction of non-parallelism of the etalon are arranged so as to be aligned with each other based on a preset rule.

As a result, it is possible to obtain a wavelength selecting optical device which can reduce the influence of errors which cannot be avoided in the production of the wavelength selecting optical element and realize high-precision wavelength selectivity, and an applied apparatus constructed using the same. Can be

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is directed to an optical system for performing wavelength selection using at least a diffraction grating and an etalon, and to diffract light from the diffraction grating substantially along a dispersion direction. Has a monotonically changing wavelength distribution,
And when the two opposing planes of the etalon have a C-shaped non-parallelism, the diffraction grating and the etalon are deflected by changing the direction of the wavelength distribution of the diffracted light and the direction of the non-parallelism of the etalon. It is a wavelength selection optical device installed so as to be aligned based on rules set in advance to each other, to improve the decrease in wavelength selectivity that is inevitable due to manufacturing errors,
This has the effect of realizing an optical system having higher-precision wavelength selectivity.

As described in the second aspect of the present invention, the direction of the wavelength distribution of the diffracted light and the direction of the non-parallelism of the etalon are set in advance as a rule, and the long wavelength shift side of the diffraction grating and the short wavelength of the etalon are set. It is preferable that the shift side has a corresponding positional relationship with respect to the optical axis of the diffracted light.

According to a third aspect of the present invention, there is provided means for tilting one or both of the diffraction grating and the etalon in accordance with a desired center wavelength. It is more preferable to use a wavelength selection optical device.

The invention according to claim 4 of the present invention is the invention according to claim 3.
It is a scanning spectrophotometer using the described wavelength selection optical device, and has an effect that a highly accurate spectrophotometer can be configured.

The fifth aspect of the present invention is the first aspect of the present invention.
4. A laser device, wherein the wavelength selection optical device according to any one of items 1 to 3 is used for a laser resonator for narrowing a wavelength spectrum, and a laser having a spectral width narrowed with high precision. This has the effect that a resonator and a laser device using the same can be configured.

Further, as in the invention according to claim 6, an excimer laser is used as the laser, and the laser apparatus according to claim 5 may be used.

According to the seventh aspect of the present invention, the fifth aspect is provided.
Or a laser processing process apparatus characterized in that processing is performed using the laser apparatus according to 6, wherein the effect of chromatic aberration in a projection optical system used in the present processing apparatus is reduced, and a more precise processing process can be realized. Has an action.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

(Embodiment 1) FIG. 1 is a schematic diagram showing a configuration of a wavelength selection optical device according to the present embodiment. The light 101 incident from the slit 102 is collimated by the collimation mirror 107 and is incident on the diffraction grating 103 at an appropriate angle according to the wavelength to be selected.

At this time, in the diffraction grating 103, the wavelength of light tangent to the direction of the diffracted optical axis 108 due to a manufacturing error is A
It is assumed that it is known in advance that the wavelength shifts to the longer wavelength side near the end and shifts to the shorter wavelength near the B end.

Next, when the diffracted light passes through the etalon 104, as shown in an exaggerated manner in FIG.
It is assumed that it is narrow at the end and wide at the D end. In such a case, as described above, the peak of the transmission spectrum shifts to the short wavelength side as the etalon approaches the C end, and conversely, shifts to the long wavelength as the etalon approaches the D end.

Therefore, the positional relationship between the A end and B end of the diffraction grating 103 and the C end and D end of the etalon 104 is shown in FIG.
When the light is arranged so as to have the relationship shown in FIG.
As for the light detected by the above, only the light that passes only near the center of the etalon 104 can pass through the etalon 104.

That is, the long wavelength shift end of the diffraction grating 103 and the short wavelength shift end of the etalon 104, the diffraction grating 103
The short wavelength shift end of the etalon 104 and the long wavelength shift end of the etalon 104 are arranged so as to correspond to each other with respect to the diffracted optical axis 108, so that the C and D ends of the etalon 104 are reversed or in other directions. Than if they were placed
The wavelength selectivity can be improved.

In such an optical system, by providing means for tilting either or both of the diffraction grating and the etalon in accordance with the center wavelength to be selected, the selected wavelength can be freely changed. Thereby, it is possible to realize a wavelength selection optical system having higher precision wavelength selectivity.

Further, by constructing the means for inclining the diffraction grating and / or the etalon as described above so that wavelength scanning can be performed by inclining, a high-precision scanning spectrophotometer can be realized. Can be.

(Embodiment 2) FIG. 2 is a schematic diagram showing a configuration of a laser resonator according to the present embodiment. In this laser resonator, a laser gas is sealed in a resonator using a diffraction grating 205 and a semi-transmissive mirror 204, and a discharge tube 201 having discharge tube windows 203a and 203b for transmitting light is placed. Causes laser oscillation.

In the optical resonator, a wavelength selection optical device using an etalon 206, prisms 207a and 207b, and a diffraction grating 205 is disposed as a wavelength selection element. By arranging such a wavelength selection optical system, it is possible to selectively oscillate only a wavelength in a specific narrow band.
However, the positional relationship between the etalon 206 and the diffraction grating 205 is the same as that described with reference to FIG. Install D-end.

With such an arrangement, it is possible to improve the wavelength selectivity of the laser resonator.

Further, in such a wavelength selection optical system, by providing means for tilting both or any one of the diffraction grating and the etalon in accordance with the center wavelength to be selected, it becomes possible to adjust the selected wavelength. This makes it possible to configure a laser device having a laser resonator whose wavelength is selected with higher accuracy.

When a laser processing apparatus is constructed using such a laser apparatus, the influence of chromatic aberration in the projection optical system used in the present processing apparatus can be reduced, and a more precise processing can be realized. can do.

If an excimer laser is used as such a laser device, for example, a laser processing device with good processing accuracy can be constructed.

[0039]

As described above, according to the present invention, at least in the wavelength selection optical system using the etalon and the diffraction grating, the C-shaped non-parallelism of the gap interval of the etalon caused by a manufacturing error and the diffraction grating The influence of the shift of the selected wavelength depending on the location can be improved, and a more accurate wavelength selection optical system can be realized.

Further, by using such a wavelength selection optical system, it is possible to realize applied devices such as a high-precision spectrophotometer and a high-performance laser processing device.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a wavelength selection optical device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of a wavelength selection optical device according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram of transmittance with respect to a wavelength of light transmitted through an etalon.

FIG. 4 is a side view showing the configuration of the etalon.

FIG. 5 is a characteristic diagram showing a transmission spectrum of an etalon.

FIG. 6 is a schematic diagram showing a configuration of a resonator of a conventional narrow-band laser device.

[Explanation of symbols]

 Reference Signs List 101 light 102 slit 103 diffraction grating 104 etalon 105 lens 106 photodetector 107 collimation mirror 108 diffracted optical axis 201 discharge tube 203a, 203b discharge tube window 204 semi-transmissive mirror 205 diffraction grating 206 etalon 207a, 207b prism

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 26/00 G02B 26/00 5F072 H01S 3/00 H01S 3/00 B 3/08 3/08 3/225 3/223 E (72) Inventor Nobuaki Furuya 1006 Kadoma, Kadoma, Osaka Prefecture F-term (reference) in Matsushita Electric Industrial Co., Ltd. AA50 AA58 AA64 AA68 5F071 AA06 DD04 JJ10 5F072 AA06 JJ13 KK01 KK06 KK08 KK18 YY08

Claims (7)

[Claims] 1. An optical system for selecting a wavelength using at least a diffraction grating and an etalon, wherein the etalon has a wavelength distribution in which diffracted light from the diffraction grating changes substantially monotonously along a dispersion direction. When two opposing planes have a C-shaped non-parallelism, the diffraction grating and the etalon are set in advance to the direction of the wavelength distribution of the diffracted light and the direction of the non-parallelism of the etalon. Wavelength-selective optics installed so as to be aligned based on the rules set forth above. 2. As a rule in which the direction of the wavelength distribution of the diffracted light and the direction of non-parallelism of the etalon are set in advance, the long wavelength shift side of the diffraction grating and the short wavelength shift side of the etalon are defined with respect to the optical axis of the diffracted light. 2. The wavelength selection optical device according to claim 1, wherein the wavelength selection optical device has a corresponding positional relationship. 3. The wavelength-selective optical device according to claim 1, further comprising means for tilting one or both of the diffraction grating and the etalon in accordance with a center wavelength to be selected. 4. A scanning spectrophotometer using the wavelength selection optical device according to claim 3. 5. A laser device, wherein the wavelength selection optical device according to claim 1 is used for a laser resonator for narrowing a wavelength spectrum. 6. The laser device according to claim 5, wherein an excimer laser is used as the laser. 7. A laser processing apparatus for performing processing using the laser apparatus according to claim 5. Description: