JPH07122802A - Ring laser gyro - Google Patents

Abstract

PURPOSE:To manufacture a multilayer film reflection mirror which is smoother and has less loss than one manufactured by ion beam sputtering. CONSTITUTION:Ion 43 is generated by discharging gas between an anode 38 and a filament 35 by an ion source 25, and is accelerated by a grid 46 to make cations 43 incident on a neutralization processing part 48. A number of thermions are emitted into the processing part 48 from a filament 49, made neutral atoms by bonding with the cations 43. The atoms passes through an ion blocking grit 54, becomes an atomic beam 56 and is incident on a target 26, and a substance 58 which outs from the target is attached to a substrate and formed into a film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention constructs a closed optical path with a plurality of reflecting mirrors in a laser block, oscillates a laser rotating clockwise and counterclockwise in the closed optical path, and generates a clockwise light and a counterclockwise light. Of the ring laser gyro that detects the laser oscillation frequency difference and detects the angular velocity input to the closed optical path around its axis.

[0002]

2. Description of the Related Art FIG. 3 shows a general structure of a ring laser gyro. The laser block 11 is a hermetically sealed container, and includes a concave reflecting mirror 12 and a flat reflecting mirror 13 inside the laser block 11.
And the movable reflecting mirror 14 are arranged at the apex position of an equilateral triangle, and the reflecting surfaces face each other at an angle of about 60 degrees, and the closed optical path 15 is formed by these three reflecting mirrors 12, 13, 14. It is configured. An anode 16 is provided near one side of the triangle, and cathodes 17 and 18 are provided near each of the other sides, and a gas such as He or Ne is sealed in the sealed container 11, and a clockwise light is emitted to the closed optical path 15. A counterclockwise light laser is oscillated. The movable reflecting mirror 14 is mounted on the piezoelectric actuator 19 and is moved back and forth to control the actuator 19 so that the closed optical path 15, that is, the optical path length of the ring laser is held constant. A part of each of the clockwise light and the counterclockwise light is transmitted from the concave reflecting mirror 12, and one of them is returned to the concave reflecting mirror 12 by the corner cube 21, and the reflected light,
The other of the transmitted light is incident on the light receiving element 22 and converted into an electric signal, and this electric signal is used for detecting the difference in laser oscillation frequency between the clockwise light and the counterclockwise light. The angular velocity input to the closed optical path 15 around its axis is detected. A dither mechanism 23 is provided to apply a bias for operating the ring laser while avoiding a region where the both-direction light is locked in, which is an obnoxious zone.

The reflecting mirrors 12, 13 and 14 use a multilayer film in which substances having different optical refractive indexes are alternately laminated. Conventionally, a vacuum deposition method, an ion assisted vacuum deposition method, an RF sputtering method, an ion beam sputtering method and the like are known for forming an optical multilayer film. Each method has advantages and disadvantages, and it is said that the ion assisted vacuum deposition method or the ion beam sputtering method is suitable for forming a high quality multilayer film required for a ring laser gyro.

A method of forming a multilayer film by the ion beam sputtering method, which is close to the present invention, will be described. In order to carry out the ion beam sputtering method, as shown in FIG. 4, a large-capacity ion source (usually Kauffman type) 25 and a target (usually two kinds) 2 made of a material forming a multilayer film 2
6, 27, a target holder 28 for holding these targets, an extremely smooth substrate 29, a substrate holder 31 for holding it, a vacuum container 32 for containing them, and pumps for evacuation. A device composed of the above is used. In particular, when a film such as an oxide film is to be formed and the stoichiometric value of the film grown on the substrate 29 is to be controlled correctly, oxygen gas may be introduced into the vacuum container 32. When an insulating material such as an oxide is used for the targets 26 and 27, in order to prevent the targets 26 and 27 from being charged due to the rush of ions and being unable to enter or disturb the ions thereafter. For the purpose of neutralizing the charge by supplying electrons to the surfaces of the targets 26 and 27, an electron supply system usually composed of a hot filament 33 is added in front of the ion source 25, that is, at a position where the emitted ions pass.

The mechanism of film formation is 1 from the ion source 25.
Inert gas ions such as argon accelerated to about KeV are rushed into the targets 26 and 27, and the kinetic energy of the incident argon ions causes the substance of the targets 26 and 27 to decompose and scatter into atoms, that is, spatter out.
A film is formed by re-depositing the target constituent atoms jumping out of the targets 26, 27 in a film form on the substrate 29 arranged so as to face the targets 26, (27). The film thus formed has a higher density than a film formed by ordinary vacuum vapor deposition, and a smooth and high-quality reflective film is required as a film having a smooth composition close to the stoichiometric value. It has been considered suitable for the construction of a resonator for a ring laser gyro. Therefore, as the reflecting mirrors 12, 13, 14 of the conventional ring laser gyro,
A multilayer film formed by the in-on-beam sputtering method has been mainly used.

[0006]

As described in the previous section, the ring laser gyro lowers the lock-in threshold value between two laser beams excited in the same laser resonator and propagating in the same direction. Therefore, it is necessary to use a reflecting mirror having extremely small light scattering, and in order to reduce the light scattering, it is necessary to form a reflective multilayer film having an extremely smooth surface and a different surface. Further, it is naturally required for the reflective multilayer film as a basic characteristic of the laser that other loss, for example, light absorption loss, is small in order to perform favorable laser oscillation.

On the other hand, in the process of film formation, generally, in order to obtain a smooth film, it is necessary to form the film at a low temperature to form an amorphous and isotropic structure. Further, in order to reduce the absorption loss of light, etc., it is necessary to make the composition of the film a correct stoichiometric value, and when forming the film by ordinary vacuum vapor deposition,
It is necessary to keep the temperature of the substrate high to enhance the chemical activity of the film forming substance. However, when the film is formed while the substrate is kept at a high temperature as described above, the film structure is crystallized and usually becomes a polycrystal, and it tends to be difficult to obtain a smooth and isotropic structure.

The ion beam sputtering method is one of the methods for solving this problem. Although the atomic substance sputtered out from the target by the kinetic energy of the incident ions can be obtained by a usual vacuum vapor deposition method, Uses energy that is several tens of times greater than the energy incident on the substrate, making it easy to obtain a stoichiometrically correct composition and an amorphous isotropic structure without heating the substrate. Are using. However, if a similar oxide is used for the target when forming a multilayer film such as an oxide used for a ring laser gyro, the target surface is positively charged by sputtering because it is electrically insulating. However, it works so as to prevent the incidence of ions generated from the ion source, and the sputtering cannot be maintained well. Therefore, as described above, the hot filament 33 is installed between the normal ion source 25 and the targets 26 and 27, thermal electrons are emitted into the space, and the electrons are attracted by the electric field based on the charge to neutralize the positive charge. The method is called.

However, this has a contradiction that the effect of heating, which goes against the effect of the original low temperature treatment, enters into the film forming process. Particularly in the case of an ultra-high precision reflecting mirror, since quartz or low thermal expansion ceramic glass is used for the substrate 29 and the thermal conductivity is remarkably low, there is a problem that it is difficult to lower the temperature of the front surface even if it is cooled from the back surface.
Although some ions combine with thermoelectrons to become neutral atoms before entering the target 26, the thermoelectrons are scattered in space and are attracted to the positively charged target, so that the neutral atom is generated. There are very few atoms.

In order to improve the performance of the ring laser gyro and improve the non-defective product rate, the present invention eliminates the problem and uses a reflecting mirror formed by a film forming mechanism making the most of the effect of low temperature treatment in the ring laser gyro. To do.

[0011]

According to the present invention, in each of the reflecting mirrors forming the closed optical path in the ring laser gyro, the substances having different optical refractive indexes on the polished substrate are the target substances by the atomic beam. It is characterized in that they are alternately laminated by sputtering.

[0012]

As described above, the problem of the ion beam sputtering method is that the material for sputtering the target is ionized. The atomic beam is accelerated by the ion source,
Ions having an energy suitable for sputtering are neutralized to form a neutral fast atom beam. Therefore, the target material can be sputtered out regardless of whether or not the target is charged, and it becomes unnecessary to insert an electron emission mechanism such as a hot filament between the ion source and the target, and the effect of the low temperature treatment can be obtained. Lossless, ready-to-use, smooth, and correct stoichiometric multilayer mirrors are formed, thus providing low scattering and low loss mirrors, lowering the lock-in threshold of ring laser gyros. Therefore, the performance of the ring laser gyro is improved, and the yield rate is improved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a multilayer film reflecting mirror formed by sputtering a target material by an atomic beam is used. First, the principle of the atomic beam sputtering method for forming this highly accurate reflective multilayer film is shown in FIG. It will be described with reference to FIG.
In the ion source 25, the filament 35 is heated by the output of the AC power supply 36 and emits thermoelectrons. A discharge gas (usually Ar) is introduced into the ion source 25 through the inlet 37,
A discharge occurs between the anode 38 and the filament 35, trapping the glow discharge in the discharge chamber 39. At this time, in order to generate a good discharge, the magnet 34
May be placed. The bias power sources 41 and 42 are adjusted to appropriate values in consideration of gas pressure and the like in order to maintain good discharge. Plasma is generated in the discharge chamber 39, and positive ions 43 and negative electrons 44 are generated. A grit 45 that reflects electrons is provided on the emission side of the positive ions 43 of the discharge chamber 39, and the grit 45 is grounded. A negative high voltage is generated between the grit 45 and the grit 46 that accelerates the ions outside the grit 45.
The positive ions 43 applied by the plasma generator 7 are accelerated at a high speed and extracted into the neutralization processing unit 48.

The neutralization processing unit 48 has a filament 49, which is heated by the output of the AC power supply 51, and a large amount of thermoelectrons 52 are generated in the neutralization processing unit 48. A negative bias power source 53 is attached to the filament 49, and the electron 5
2 is efficiently sent into the neutralization processing unit 48. When the positive ions 43 pass through the neutralization processing unit 48 at high speed, they combine with a large amount of electrons 52 and are neutralized to become high-speed neutral atoms, which pass through the grit 54 of the neutralization processing unit 48. The positive ions 43 that have not been combined with the electrons 52 are reflected by the grit 54 and returned to the neutralization processing unit 48 because a positive voltage is applied to the grit 54 by the power supply 55.
Only neutral, fast atoms can pass through the grit 54. The opening ratio of the grit 54 is, for example, 50 to 6
It is set to 0%. The applied voltage of the grid 54 is the grid 46.
The applied acceleration voltage is almost the same as the applied acceleration voltage and has a reverse polarity, for example, about 1 KV. The high-speed neutral atoms that have passed through the grit 54 become an atomic beam 56 and enter the target 26 held by the target holder 28. The incident high-speed atom 57 and the target material 58 sputtered out by this atom 57 are shown.

In the atomic beam generation source 61 shown in FIG. 1, an atomic beam 56 is generated in the vacuum chamber 32 and is incident on the target 26 as shown in FIG. 2A. Target 26
The atomic substance 58 sputtered out from is usually deposited on the substrate 29 placed at a position facing the target 26 and grows into a film. The inert gas introduced from the gas inflow port 37 (and the gas forming the film such as oxygen may be mixed) becomes the high-speed atomic beam 56 by the above-mentioned method in the atomic beam generation source 61, and is applied to the target 26. When incident, the same substance is sputtered out. At this time, when the target 26 is insulative, the target 26 is charged, but the incident atoms are electrically neutral, so that the sputtering can be continued.
The target material sputtered out is deposited on the substrate 29 to form a film. At this time, the hot filament etc.
The temperature of the substrate 29 can be kept lower than that of the ion beam sputtering method because it is not present in the second step, and film formation with a smooth film surface can be performed. When the film is an oxide or the like, its constituent substance can be supplied as a gas from the gas supply port 62 or as a radical (which is not ionized by activated atoms) from the supply unit 63.

FIG. 2B shows a ring laser gyro according to the present invention, and parts corresponding to those in FIG. 3 are designated by the same reference numerals. In the present invention, the concave reflecting mirror 12 and the flat reflecting mirror 1
3. The movable reflecting mirror 14 is formed by alternately laminating two material layers having different optical refractive indexes by the above-described atomic beam sputtering method.
The reference numerals 3 and 14 are attached at their peripheral portions by, for example, optical contacts so as to close the holes formed at the apexes of the triangle of the sealed container 11. The movable reflecting mirror 14 is made so that its central portion can move back and forth.

[0017]

According to the present invention, a multilayer film reflecting mirror is formed by an atomic beam sputtering method. In this case, since a hot filament is not provided between a high-speed particle generation source and a target which cause sputtering, a vacuum container is used. The internal temperature can be kept low, a reflective film having a smooth surface with little loss is formed, the lock-in threshold of the ring laser gyro is reduced, and the performance of the ring laser gyro is improved. It should be noted that the atomic beam sputtering method can improve the smoothness about twice as much as the conventional ion beam sputtering method under the same substrate conditions.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an atomic beam generation source of an atomic beam sputtering apparatus for making a reflecting mirror of a ring laser gyro of the present invention.

2A is a diagram showing an atomic beam sputtering apparatus, and FIG. 2B is a diagram showing an embodiment of the present invention.

FIG. 3A is a diagram showing a conventional ring laser gyro, B
FIG. 3 is a diagram showing an ion sputtering apparatus.

FIG. 4 is a diagram showing an ion beam sputtering apparatus.

Claims (1)

[Claims] 1. A plurality of reflecting mirrors form a closed optical path in a laser block, oscillate each of the lasers rotating counterclockwise and clockwise in the closed optical path, and generate laser oscillation frequencies of the counterclockwise light and the clockwise light. In the ring laser gyro that detects the difference between the reflection mirrors, each of the reflection mirrors is formed by alternately laminating substances having different optical refractive indices on the polished substrate by sputtering a target substance by an atomic beam. A ring laser gyro that is characterized.