JP2000012930A - Laser resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser resonator which can oscillate in a single mode, can be reduced in size and number of item parts, can be simplified in structure, and can make wavelength selection over a wide range. SOLUTION: A laser oscillator consists of a rear mirror 11 and an output mirror 16 respectively having reflecting surfaces S1 and S6 faced to each other and first and second transmitting members 12 and 14, which are arranged between the mirrors 11 and 16 with a fixed interval D inbetween and transmit light. At least either one the members 12 and 14 is formed as a laser medium, and the end faces S3 and S4 of the members 12 and 14 facing the interval D are formed as partially reflecting surfaces between which an etalon is constituted. The laser resonator is provided with an interval adjusting device 18, which changes the interval D by moving at least either one of the members 12 and 14 in the direction of the optical axis, so as to have the oscillation wavelength of the resonator changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laser resonator that oscillates in a single mode.

[0002]

2. Description of the Related Art FIG. 2 is a schematic configuration diagram of a conventional laser resonator, and FIG. 3 is a characteristic diagram thereof. As shown in FIG. 2, a basic laser resonator includes a laser medium 1 and mirrors 2 and 3 and oscillates at a plurality of wavelengths simultaneously. This multispectral radiation provides a high power output, but may require a higher degree of monochromaticity. Therefore, in order to increase the single mode output, in a conventional laser resonator, a fixed-space Fabry-Perot resonator 4 (referred to as an etalon) usually has a laser cavity (mirrors 2, 3).
During).

The etalon 4 is made of a special pair of glass plates, and the two surfaces 4a and 4b are polished highly parallel. The etalon space (between the two planes) differs from the laser cavity in two ways. First, the reflectivity of the etalon surface is very low, so that the cavity resonance of the etalon is wider than that of the laser (B) as shown in FIG. Second
In addition, the etalon cavity is much shorter than the laser cavity,
The spacing between resonance frequencies of the etalon (c / 2D) is much greater than the spacing between the resonance frequencies of the laser (c / 2L).
Thus, some cavity resonances will have higher losses than others, and the laser will operate in a single mode with minimal loss, as shown schematically in FIG. 3 (E). Note that the Q value in the figure is an index indicating how small the loss in the resonator is, that is, how easily the resonator oscillates, and is represented by the following equation (Equation 1). It can be said that the larger the Q value, the smaller the loss of the resonator and the easier the oscillation.

(Equation 1)

Further, when the etalon is tilted with respect to the optical axis,
The resonance frequency of the etalon moves within the laser transition spectral width, the different laser cavity modes have high Q values, and laser operation occurs at the corresponding new frequency. By simply tilting the etalon in this manner, the laser frequency can be tuned within a narrow frequency range.

[0005]

As described above, in a conventional laser resonator that oscillates in a single mode, if the laser resonator is composed of a laser medium and a mirror, the resonator is located within the gain wavelength range of the laser medium. Oscillation occurs at a wavelength that satisfies the resonance condition of
Since oscillation occurs at a plurality of wavelengths, a wavelength selection element (for example, etalon 4) for selecting only a specific wavelength is inserted,
Single wavelength oscillation was performed. However, in such a conventional technique, since the wavelength selection element is configured as a single unit, there is a problem in that a reduction in size is restricted, and the number of parts increases. That is, etalon 4 is usually number 1
Since it is composed of glass blocks spaced at intervals of 00 μm, miniaturization has been difficult. Further, since the distance between the two surfaces 4a and 4b constituting the etalon space is fixed, there is a problem that the wavelength can be selected only in a narrow range.

The present invention has been made to solve such a problem. That is, an object of the present invention is to provide a laser resonator which can oscillate in a single mode, can be downsized, simplify the structure, reduce the number of parts, and can select a wavelength in a wide range. It is in.

[0007]

According to the present invention, a rear mirror (1) forming reflection surfaces S1 and S6 opposed to each other is provided.
1) and an output mirror (16), and a first transmitting member (1) disposed between the output mirror and the output mirror at a predetermined interval D to transmit light.
2) and a second transmission member (14), at least one of the first transmission member and the second transmission member is a laser medium, and each end face facing the distance D between the first transmission member and the second transmission member. S3 and S4 are partial reflection surfaces, and an etalon is formed between the reflection surfaces. A laser resonator is provided.

With this configuration, the partially reflected light of the end face S3 of the first transmitting member (12) and the end face S of the second transmitting member (14) are formed.
The partially reflected light at 4 causes an interaction (interference), and as a result, the end faces S3, S4 and the space therebetween act as an etalon that transmits only a specific wavelength. Since the wavelength transmission characteristics of this etalon are determined by the reflectance of S3 and S4, the distance D between both surfaces, and the angle with respect to the optical axis, by optimizing these, a single wavelength within the gain wavelength range of the laser crystal is obtained. Oscillation is possible. Further, by finely adjusting the distance D between the surfaces S3 and S4, single-wavelength oscillation at an arbitrary wavelength in the gain wavelength region becomes possible. Therefore, with this configuration, it is possible to reduce the size, simplify the structure, reduce the number of parts, and to reduce the distance D as compared with the case where the resonator is configured by separately using the laser crystal and the wavelength selection element (conventional example). Can be fine-tuned, so that the wavelength can be selected in a wide range and oscillation can be performed in a single mode.

According to a preferred embodiment of the present invention, the first
An interval adjusting device (18) that changes the interval D by moving at least one of the transmission member and the second transmission member in the optical axis direction. This interval adjusting device can be composed of, for example, a piezo element, and is finely adjusted to several μm or less.
Wavelength selection can be variably performed. Further, the end face S
3, S4 is preferably a plane that is not perpendicular to the partially reflective coated optical axis. With this configuration, it is possible to prevent the partially reflected light from returning to the laser cavity and eliminate its adverse effect.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In the drawings, common portions are denoted by the same reference numerals, and redundant description is omitted.
FIG. 1 is an overall configuration diagram of a laser resonator according to the present invention. In this figure, a laser resonator according to the present invention includes a rear mirror 11 and an output mirror 16 each having reflecting surfaces S1 and S6 facing each other, and a first transmission through which light is transmitted and disposed at a certain interval D therebetween. It comprises a member 12 and a second transmission member 14. In FIG. 1, the first transmission member 12 is formed of a laser medium, and the second transmission member 14 is formed of a transparent member such as fluorite or quartz glass. In addition,
By constructing both transmission members 12 and 14 from a laser medium, the laser output can be increased.

Further, the first transmitting member 12 and the second transmitting member 1
Each of the end faces S3 and S4 facing the interval D of 4 is a partially reflecting surface with a partially reflecting coating. Further, as shown in this figure, the end faces S3 and S4 are preferably planes that are not perpendicular to the optical axis. With this configuration, the end face S3,
The light reflected by S4 is prevented from re-entering the laser cavity between the reflection surfaces S1 and S6, and oscillation of a single wavelength can be efficiently performed.

According to the present invention, the first transmission member 12 and the second transmission member
An etalon (that is, a Fabry-Perot resonator) is formed between the intervals D between the transmission members 14. Further, there is provided an interval adjusting device 18 that changes the interval D by moving at least one of the first transmission member 12 and the second transmission member 14 (the second transmission member 14 in FIG. 1) in the optical axis direction. The spacing adjusting device 18 includes, for example, a crystal holder 18a (for example, a tightening ring) that holds the second transmission member 14, a mount 18b fixed to an apparatus body (not shown), and a ring sandwiched therebetween. The piezo element 18c has a shape, and the axial length is changed by the voltage applied to the piezo element 18c to move the second transmission member 14 in the optical axis direction.

With the above-described configuration, the partially reflected light on the end face S3 of the first transmitting member 12 and the partially reflected light on the end face S4 of the second transmitting member 14 interact (interference), and as a result, the end faces S3, S4 and The space in between acts as an etalon that transmits only specific wavelengths. Since the wavelength transmission characteristics of this etalon are determined by the reflectance of S3 and S4, the distance D between both surfaces, and the angle with respect to the optical axis, by optimizing these, a single wavelength within the gain wavelength range of the laser crystal is obtained. Oscillation is possible. Further, the distance D between the surfaces S3 and S4
By fine-tuning, single-wavelength oscillation at an arbitrary wavelength in the gain wavelength range is possible. Also, the interval adjusting device 18
By changing the interval D using a piezo element, for example, fine adjustment of several μm or less can be performed, and wavelength selection can be variably performed. Therefore, with this configuration, it is possible to reduce the size, simplify the structure, reduce the number of parts, and to reduce the distance D as compared with the case where the resonator is configured by separately using the laser crystal and the wavelength selection element (conventional example). Can be fine-tuned, so that the wavelength can be selected in a wide range and oscillation can be performed in a single mode.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various changes can be made without departing from the spirit of the present invention.

[0015]

As described above, the laser resonator of the present invention can oscillate in a single mode, and can be downsized, simplified in structure, reduced in the number of parts, and can be used in a wide range. It has excellent effects such as wavelength selection.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a laser resonator according to the present invention.

FIG. 2 is a configuration diagram of a conventional laser resonator.

FIG. 3 is a characteristic diagram of a conventional laser resonator.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser medium 2, 3 mirror 4 fixed-space Fabry-Perot resonator (etalon) 11 rear mirror 12 first transmission member (laser medium) 14 second transmission member 16 output mirror 18 interval adjusting device D first transmission member and second transmission Spacing of members S1 Total reflection surface S2 Non-reflection surface S3, S4 Partial reflection surface S5 Non-reflection surface S6 Partial reflection surface

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayoshi Hirano 20-1, Kitakanyama, Odaka-cho, Midori-ku, Nagoya-shi, Aichi, Japan. No. 1 Shin-Nakahara-cho, Isogo-ku Ishi Kawashima-Harima Heavy Industries Co., Ltd. (72) Inventor Masataka Ohara 1 Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Ishikawajima-Harima Heavy Industries Co., Ltd. F-term (reference) 5F072 JJ01 JJ08 JJ12 KK06 KK08 KK26 KK30 SS01

Claims (3)

[Claims] A rear mirror (11) and an output mirror (16) forming reflection surfaces S1 and S6 opposed to each other, and a first transmission member (12) disposed therebetween at a predetermined interval D and transmitting light. ) And a second transmitting member (14), at least one of the first transmitting member and the second transmitting member is a laser medium, and each end face S3 facing the distance D between the first transmitting member and the second transmitting member. , S4 are partial reflection surfaces, between which an etalon is formed. 2. An apparatus according to claim 1, further comprising an interval adjusting device for changing at least one of the first transmitting member and the second transmitting member in the optical axis direction to change the interval D.
3. The laser resonator according to claim 1. 3. The laser resonator according to claim 1, wherein the end faces S3 and S4 are planes that are non-perpendicular to the optical axis of the partially reflective coating.