JPS5821385A - Method of regulating laser passage length - 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 The use of planar ring lasers as gyroscopes is known.

Typically, ring laser gyroscopes use a three or four sided laser path. The laser path consists of a laser operating chamber confined to a bore formed in the shape of the laser path in a laser housing that is typically removed from high stability glass.

A laser mirror is placed where the hole in the laser chamber and the laser path change direction. The holes extend from mirror to mirror and are large enough to prevent blurring of the laser light.

In order to excite the ring laser so as to produce two laser paths in opposite directions, at least one cathode is mounted somewhere in the laser housing and a quanode is connected to the laser hole in a geometry that connects the anode and cathode. It is customary to include a conduit in the laser housing so that the movement of ions and electrons between the cathode and the anode excites the laser phenomenon.

Typically, the laser gas within the hole is a helium-neon mixture at extremely low pressure. A sufficiently large voltage is applied between the cathode and the 7-node to ionize the gas between the cathode and the 7-node, causing the transfer of electrons from the cathode to the 7-node and from the 7-node to the cathode. Tuning is accomplished by creating positive ion movement within the gain hole of the laser gas to excite the laser gas and then adjusting the laser length to the specific laser frequency desired.

TEMoo, on-axis of oscillation
It is usually desirable for only modes to appear.

Therefore, one of the mirrors is located at the off-axis of the oscillation in the laser path (
The opening is opened to suppress the off-axis) mode.

If two laser oscillations occur simultaneously, one with light traveling in the laser path in a first direction and the other with light traveling in the laser path in the other direction, such a laser It is well known that scales are used as gyroscopes to detect the angular rotation of a laser housing about an axis perpendicular to the plane.

To tune the length of the laser path, it is customary to move one of the mirrors inwardly, such as by a screw mechanism, until the laser amplitude reaches its peak. The output of the laser through the partially transparent mirror can be used to servo control the position of the tuned bell.

Typically, the laser beam is also focused by a large radius mirror to produce a laser beam of substantially uniform cross-section.

This feature is illustrated in Umbrella Figures 2-4D of "Laser" by William Buie Smith and Peterpy Sorokin, McGraw-Hill, 1966.

A preferred embodiment of the invention concerns the modification of the laser by mounting a large radius concave mirror at the intersection of the two branches of the laser path and the tilting of the symmetrically arranged aperture mirror in the pyramidal angle. Typically, in a four-sided laser path, it is a plane mirror opposed to an apertured and tilted concave mirror. The tilted plane mirror and the concave mirror are moved up and down relative to each other until the appropriate laser action occurs. And they are fixed in position.

The slope is typically 1 to 3 are-minutes.
te), which depends on the wavelength of the laser beam, the diameter of the gain hole, and the amount of laser mode. The cavity length must be able to be varied by at least a half wavelength without affecting the mode quantity due to the gain hole so as to cause some substantial loss in laser gain. When one of the mirrors is tilted to change the length of the laser path, the plane of the laser path is tilted upward at the same angle as the mirror. Gyroscopes require that the sensing axis be perpendicular to the plane of the laser path.

To obtain a laser that can serve as a gyroscope,
The base of the gyroscope also needs to be tilted at the same angle of inclination so that the mounting base is parallel to the plane of the laser gas.

In the alignment improvement of the present invention, the ring laser gyroscope is made extremely small, with the length of each side of the laser path being substantially less than 1 inch (2.54 centimeters).

In such small lasers, the laser cathode is preferably of the same order of magnitude as the laser block itself. The cathode must be made large enough to generate sufficient current in the gain hole of the laser path to supply the necessary energy to the laser. A cathode block, having a hemispherical cathode coated on the surface of a hemispherical bowl formed in the cathode block, is typically attached to the bottom of the laser block. A passageway is created substantially from the center of the spherical surface defining the cathode surface upwardly into the laser block and from there directly outward into the laser ring. A pair of anodes are symmetrically arranged to split the electron and ion paths and travel in two directions through most of the gain of the laser path. The anode is placed outside the laser path and conduits are made in the laser block to connect the faces of the seven nodes with the laser path.

Application of a voltage between the cathode and the seventh node causes ionization of the gas in the cathode bowl, upwardly through a substantially vertical passage, thence outward into the laser path, and thence into the laser path. in different directions along the gain hole and to the surface of the 7 notes.

In order to align the laser with the detection axis perpendicular to the plane of the laser path, the plane of the bottom of the cathode housing is configured parallel to the plane of the laser path for easy alignment of the gyro.

It is therefore an object of the present invention to provide an improved optical resonator with a novel tuning mechanism.

A more particular object of the invention is to tune a ring laser.

A more particular object of the invention is to provide a ring laser configured to be used as a gyroscope.

Other objects will become apparent from the following description with reference to the drawings.

A preferred embodiment of a ring laser according to the invention used as a gyroscope is shown in the drawing. The ring laser has a laser block 10 and a cathode block 12, preferably made of glass ceramic. Typically, this glass-ceramic is trademarked CERVIT.

Known as ZERODUR and ULg. These materials have essentially zero expansion within the usable range of the laser. Laser block 10 carries the laser path. Cathode block 12 carries a cathode 16 and laser block 10 carries two anodes 52 and 54. The voltage between the cathode and the seventh node ionizes the laser gas to provide energy for the laser. Although the power supply for applying the voltage between the 7 nodes 52, 54 and the cathode 16 is not shown, any typical DC power supply can be used. A voltage is connected to cathode 16 . Shi-The Block 10 and Kando Block 12//'! They are held together by a sealant such as atmospheric pressure indium solder and K.

Good t siIt>Le+f'Route 14 a, 14 b,
14 c and 14 dFi square laser paths, more particularly substantially square as shown in the drawings. The laser block is typically a square laser block, but unused portions of the block can be arbitrarily cut away to minimize cost and manufacturing difficulties, and the resulting block is octagonal as shown. formatted into.

The four sides of the square laser block that are the intersections of the laser branches, or the non-adjacent alternate sides of the octagonal laser block, have mirror surfaces inside to reflect the laser beam.
Three mirror blocks 22, 24, 26 and 2B are installed. At least one mirror is partially transparent to emit the laser beam, at least one mirror is apertured to prevent generation of off-axio modes of oscillation, and one of the mirrors is partially transparent to emit the laser beam. It is a concave surface with a suitable radius of curvature to focus the beam.

Laser action in the laser path occurs in a helium-neon gas mixture at an extremely low pressure of 3.2 Torr. The gas mixture is typically 20 parts helium and 1 part neon.
And the ratio of neon 22 is 1. Four substantially coplanar conduits 30a130b, 30e and 30d are hollowed out in the laser block 1o connecting the mirrors to accommodate the laser gas in the laser working path. These are designed to allow for small angles, typically 3'-5'(3'-5'), without interference with the laser beam (to allow for translation and tilting of the plane of the laser beam in the D-axis). The diameter is as large as possible.

In the area circumferentially defined by the laser path, preferably in the center of the laser block 10, conduits 30m, 30
There are conduits perpendicular to planes b, 30c, and 30d. This conduit has two parts 32 and 34, part 32 leading to the top of the laser block 10 and part 34 leading to the cavity formed by the cathode surface 16. Conduits 32 and 34 are typically substantially conduits 30 m, 30 b, 3
Conduit 30 by conduit 36 in planes 0c and 30d
a, 30b.

30c and 30d.

There are four rooms 38 in the area of mirrors 22, 24, 26 and 28.
．． 40, 42 and 44, these chambers are branches 30a, 30b of the laser conduit.

This is the termination region for 30e and 30d, and is sufficiently large so as not to interfere with the laser beam. Cavity 40 is connected to conduits 32 and 34 by conduit 36.

Although the conduit 34 is preferably centered on the hemispherical cathode surface 16, the conduit 34 may not be so centered.

Further, the conduit 34 includes laser paths 14m and 14b.

Although shown perpendicular to planes 14c and 14d, conduit 34 can also be tilted. Conduit 34 extends to the outer surface of laser block 10 surrounded by a glass or metal stem sealed to the laser block. It is further to be understood that conduit 32 is an emptying conduit and its location in the center of the laser block is not critical. However, it is advantageous to form the conduits 32 and 34 in one line by machining with a suitable glass drill. It is further noted that although shown perpendicular to the paths of laser paths 14a, 14b, 14c and 14d, conduit 32 may be angled if desired. - Stem 50 is used to empty the system and refill it with the required gas at low pressure.

If stem 50 is metal, it can also be used as a 7 node. Conduit 32 connects conduit 3 to a region within cathode surface 16.
4, the laser conduits 30a, 30b, 3
It is connected via conduit 36 to Qc and 30d.

An evacuation pump (not shown) may be attached to stem 50 to remove all air from the system.

Additionally, a getter (not shown) may be placed in the conduit region attached to the stem 50 or to a stem (not shown) adjacent to the stem 50.

After the system is evacuated and gettered, the required laser gas is filled into the system at extremely low pressure and the stem is truncated to seal the system. Kan” 1 block 12
is held onto laser block 10 by both a low pressure vacuum within the chamber formed by cathode face 16 and a sealing material such as indium solder.

In the area of compartments 38 and 42 there are a pair of seven nodes 52 and 54 that are metallic conductors and extend from the outside of laser block 10 into chambers 38 and 42.

A positive voltage is applied to the anodes 52 and 54 and a negative voltage is applied to the cathode 1.
6, the electrons and ions are connected to the cathode 16
The cathode-to-7 node and anode-to-cathode lift begins in the passage defined by conduits 34 and 36 to the chamber and compartment 40 formed by. In section 40, the path splits and a portion of the ion-electron drift goes in one direction from section 40 to section 3B through the gain hole and from there to node 52. The movement of electrons and ions in the two directions within the gain hole of the laser path in opposite directions is
It excites the gas therein to a high energy state and descends from this high energy state to a lower energy state to produce light at a frequency to which the laser path is tuned. Energy is therefore provided to the laser from a power source coupled to cathode 16 and seven nodes 52 and 54.

Typically, the length of the laser cavity is tuned by moving curved and apertured mirrors. One of the two movable mirrors is tilted at a pyramidal angle so that vertical movement of the mirror moves the mirror inward and outward relative to the laser path to maximize the laser signal.

However, in a preferred embodiment of the invention, the aperture mirror is tilted inwardly at a small pyramidal angle, typically 3' to 5', and is concave to maintain an aperture open to the laser path. 2
2 to conduit 30 &, 30 bs 30 c and 30d
and move the laser 2 in a direction perpendicular to the aperture mirror 26.
The pyramidal angle between two planes is defined as 90° minus the dihedral angle between them. Diplanar angles are calculated by Van Nostrong
``Mathematics Dictionary (Mathematics Dictionary)'' by James & James, published by & Company
cs Dictionary) J 3rd edition. That is, "the union of a line with two half-planes having this line as one common edge. This line is the edge of a diplane angle, and the union of the line with one of the planes is one plane. A plane angle of a diplane angle is an angle formed by two lines that are the intersections of the plane of the diplane angle and a plane perpendicular to the edge. Any two plane angles are congruent.2
The magnitude of a plane angle is the magnitude of one of its plane angles. ”
Tilting mirrors and conduits 30a, 30b, 30c and 3
0d and the plane defined by mirror blocks 24 and 28 is slightly less than 90° but almost 90° and typically differs from 90° by only a very small pyramidal angle of the plane of the tilted mirror. . The pyramidal angle is determined by the laser wavelength, gain hole diameter, and laser mode amount. It must be possible to change the cavity length by at least one-half wavelength of the laser light without affecting the mode quantity by the gain hole in a way that causes some loss in laser gain. As the concave mirror is moved up and down, the laser path is also moved up and down so that it hits different parts of the tilted mirror, creating a shorter or longer path for the laser beam. By striking different parts of the tilting mirror, the on-axis beam will be quenched by the aperture diaphragm unless the tilting mirror also moves its aperture to realign with the laser beam.

All of the plane mirrors 24, 26 and 2'8 are connected to the conduits 3'Oa, 3
With the planes of the mirrors perpendicular to the same plane defined by the planes 0b, 30c and 30d, moving the concave mirror 22 up and down simply moves the laser beam up and down without changing the length of the laser path. However, with a mirror 26 having a plane tilted by a pyramidal angle, the entire plane of the laser path is tilted upward by that small pyramidal angle such that the incident and reflected laser beams on the tilted mirror are orthogonal to the plane of the bell. . As a result, the intersection of the laser beam and the concave portion of the concave mirror 22:' is moved on the concave surface. When the concave surface is a spherical surface, the amount of displacement is determined by the radius of the concave mirror and the inclination of the pyramidal angle of the plane mirror 26. □ Alternatively, the block carrying the concave mirror surface is simply tilted by a small pyramidal angle, so that the laser path length is lengthened by the movement of the block that does not move up and down but is tilted by a small pyramidal angle9. Na1Tarishi, Kagami 24.2
The intersection of the laser paths on 6 and 28 is moved. The mirror 26 also needs to be moved up and down to align the aperture with the new laser path. The conduit carrying the laser path is large enough to accommodate the vibrations in the position described above. .

With the structure described above, the smallest laser gyro can be constructed. 4 sides 14a114b, 14c and 14d
The sum of the lengths may be, for example, 6.8 centimeters long.

The cathode surface 16” is typically made of aluminum;
Indium solder is bonded to the aluminum and positioned at 60 and 62, and a negative voltage is applied to the aluminum cathode 1.
6.

The exhaust and fill stem 50 is typically made of a section of glass tubing with a flare at the bottom to accommodate the getter which is combusted with radio frequency heating. Alternatively, the stem may be smaller than shown. It may also be made from metal and can be used as a 7 node.

The mounting surface of the octagonal laser block 10 is typically only 1 centimeter in diameter and mirror blocks 22, 24.
26 and 28 are typically 0.8 centimeters or less in diameter. The mirror surface itself is typically 7.5 mm in diameter.
75 mm, with a typical thickness of 4 mm. The curved concave mirror surface of block 22 has a very long radius of curvature, on the order of 60 centimeters. Mirror 26 is apertured to ensure that off-axis mode operation is suppressed while allowing on-axis TEMoo mode. Laser operation is best performed when the aperture of tilted mirror 26 is aligned such that the rays normal to the outside of the aperture of mirror 26 are also on the radius of concave mirror 22. mirror block 2
2.24. Like 26 and 28, cathode block 12 is typically encapsulated with an indium-gold metal encapsulant. The body of laser block 10 is comprised of a glass-ceramic material with a very low or zero coefficient of expansion over the desired temperature range.

The reflectance of the mirror coating is typically on the order of 99.94 degrees. Transmission is typically less than 0.1% and scattering losses are typically on the order of 100 ppm. Typical minimum laser threshold anode-cathode currents are on the order of S~23A milliamps. Tuning is accomplished by attaching the mirror blocks with wax and moving mirror blocks 22 and 26. Then, after the laser is tuned, the position of the mirror block is measured, the mirror and wax are removed, and the mirror block is soldered exactly in place with an indium-all solder sealant.

The resonant frequency is typically an optical frequency on the order of 10" Hz. In normal use, the resonant frequency of the cavity may be tuned to the center of the gain curve, or to a fraction of a wavelength that lies close to this center. Desirably. In FIGS. 4, 5, 6, 7, and 8, the pyramidal angle is designated α. In FIG. 6, a two-Ω laser path is shown. , one is the number 1
4a, 14b, 14c and 14d, and the other by numerals 14e, 14f, 14g and 14h. The laser path is usually square, but
Due to the downward movement of the laser path, the path lengths are 14a and 14b.

There is a change from that shown by 14c and 14d to that shown by longer passages 14e, 14f, 14g and 14h. The relationship between the movement of the bell and the length of the aisle is diagrammatically shown in FIG. Here, the following two restrictions are given. First, the laser beam is inserted into the laser hole 30 a
, 30 b, 30 c and 30 d. Second, the beam must be within the mirror aperture on the mirror block 26. The vertical protrusion of FIG. 6 is shown in FIG.

For the first approximation, if we change the cavity length by a distance equal to the wavelength divided by the nominal path length (6 x 10 cm 16.8 cm or about 0.001%), then the displacement h (Fig. 4) is the distance de from the aperture of the inclined mirror 26
= h effectively moves inward by tanα. The desired movement in the direction shown in Figure 7 in rsJ is % of the wavelength of the laser beam.
It is of the order of. What can be seen from Figure 7 is that s −0,7
07d (assuming a square laser path), d is 6.33
It is the wavelength divided by 1.414, which is equal to x 10 centimeters.

Holes 30a, 30b, 30e and 30d typically have a diameter d2 at least equal to 0.1778 centimeters, although the laser beam diameter dB is less than or equal to 0.089 centimeters. The total allowable movement Δd for d is h=±
For G 1.0440 centimeters, it is 0.0"880 centimeters. From this, the angle α is calculated as the ratio α:h, or 1.017 X 10-" radians, which is about 3.49 AC minutes (3,49').

In FIG. 5, the curvature of the surface is exaggerated, with radius Ri
Not proportionate. Although the radius of the concave mirror on block 22 is shown to be quite short, it is actually on the order of 60 centimeters. The beam position on the one-sided mirror surface is from the dead center where α is zero to the point Δr from this dead center, Δr=aR=
(1-017X 1 0-3n (60)=0.0
611? cm. Beam radius is 0.0898 2
Or divided by 0.0449 centimeters.

For a beam displaced by a distance Δr=0.061 cm, the edge of the beam is at a distance of 0.1059 cm from the center of the circular mirror. A one-sided mirror typically has a diameter o,
4. Has an opening with a radius of 0.2 cm. Therefore, a margin variation of 0.2-0.11-0.09 centimeters is provided. This sets a limit on the allowable increase in the angle α and the allowable shift of the laser beam on the surface of the flat mirror 22 to 0.09/60=1.5×10 Fusians. Further, holes 30a, 30b, 30c and 3
0d limits the amount the mirror can shift. When the mirror 36 is tilted, the plane of the laser working path is also tilted by an angle α,
As shown, the base of the cathode block 12 needs to be tilted by the same angle so that the base is parallel to the laser plane. The base of the cathode block 12 is then mounted, for example, to a guidance system that recognizes that the angular measurement determined from the information provided by the ring laser is the angle perpendicular to both the laser path and the mounting surface and the measured angular velocity. sell.

Although a square laser path is shown, it is clear that the principles described herein could also be used with triangular and octagonal paths. The invention is applied to such passages by tilting at least one of the mirrors by a pyramidal angle.

It is also clear that a three-sided laser path can be used, and alternatively, a multi-sided laser path with more than four divisions allows the sliding of the concave mirror to shorten or lengthen the laser path. At least one of the mirrors has a small pyramidal angle such that
Can be used with apertures and concave mirror apertures.

The apparatus and method of the present invention comprises tilting one of the resonator pins such that movement of the tilting mirror in the tilting direction shortens or lengthens the path length of the resonator. It is clear that it can be used to tune other optical resonators.

The present invention includes linear as well as non-linear optical resonators.

It also includes tuning not only active resonators but also passive resonators.

Furthermore, it does not matter whether the optical resonator is stable or unstable.

Although the invention has been described in particular embodiments above, it is not intended to be limited by that description.

[Brief explanation of the drawing]

FIG. 1 is an external view of a typical laser block and cathode block coupled together, with an assembled view showing the truncated exhaust stem. FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. FIG. 4 is a simplified diagram illustrating a preferred embodiment of the concave mirror and opposing plane mirror of the device of FIG. FIG. 5 is a simplified diagram showing the relationship of the curvature of the concave mirror to the displacement of the laser plane. FIG. 6 is a simple diagram showing the displacement of the laser beam due to the displacement of the concave mirror and the inclined plane mirror. FIG. 7 is an enlarged schematic diagram of the cylinder taken at 7 in FIG. FIG. 8 illustrates bending the base of the cathode block to a contour parallel to the laser plane for use as a ring laser gyroscope. [Explanation of symbols of main parts] 10... Laser block 12... Cathode block 14... Laser path 16... Cathode 52, 54... ...Anode 22.24.26.28...Mirror 30a, 30b
, 30e, 30d ”...Laser conduit applicant Lydon Systems, Inc. 3I 匈, 3

Claims (1)

Claims: 1. At least a laser block having a laser conduit for accommodating a laser path for producing a ring laser beam, a laser gain medium in the conduit, and a mirror at the connection of the conduit. , a cathode and at least one anode are connected to the conduit by a passageway, the passageway between the cathode and at least one 7 node including at least a gain hole in the conduit in the opposite direction of the laser path, and at least one of the mirrors. A method of adjusting the laser path length of a ring laser in which one mirror is concave and has an aperture, the remaining mirrors are substantially planar, and at least one of the concave mirrors is tilted at a pyramidal angle with respect to the other mirrors. A method for adjusting a laser path length, comprising moving at least the concave mirror in the direction of the pyramidal angle with respect to the laser beam, and fixing the concave mirror at that position. 2. At least a laser block having four laser conduits for accommodating a laser path for producing a ring laser beam, a laser gain medium in the conduits, a mirror at the junction of the conduits, and a cathode and at least one 7 node are connected to said conduit by a passage, the passage between the leakage cathode and the at least one 7 node including at least a gain hole portion of said conduit in the opposite direction of the laser path; A method for adjusting the laser path length of a ring laser, wherein at least one mirror is concave, the remaining mirrors are substantially flat, and the plane mirrors not adjacent to the concave mirror are tilted at a pyramidal angle with respect to the other mirrors. □Moving the concave mirror to tune the laser beam and aligning the aperture to suppress off-axis modes of oscillation, moving the tilted mirror in the direction of the pyramidal angle; A method for adjusting a laser path length, characterized by fixing the position. 3 Adjusting the length of an optical resonator having at least two mirrors, at least one of which is concave, and support means for supporting at least one of the concave mirrors at an inclination of a pyramidal angle with respect to the other mirror. A method for adjusting an optical resonator length, characterized in that at least the inclined concave mirror is moved in the direction of the pyramidal angle with respect to the laser beam, and the position of the inclined concave mirror is fixed. 4 At least two mirrors, at least one of which is concave and the remaining mirrors are flat, and support means for supporting at least one of the flat mirrors at an inclination of a certain pyramidal angle with respect to the other mirror. adjusting the length of an optical resonator in which the tilted mirror is apertured to suppress off-axis modes of oscillation; A method for adjusting an optical resonator length, comprising moving the tilted mirror in the direction of the pyramidal angle so as to align the aperture and suppress an off-axis mode of oscillation, and fixing the position of the shifted mirror. .