JPS584475B2 - ring laser - Google Patents

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 is a bore formed in the shape of the laser path in the laser housing, which is usually made from high stability glass.
Consists of a laser operating chamber confined to

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 an anode is connected to the laser hole in a geometry that connects the anode and the 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 to the cathode and anode to ionize the gas between the cathode and anode, causing the movement of electrons from the cathode to the anode and the movement of positive ions from the anode to the cathode within the gain hole of the laser gas. Tuning is accomplished by exciting the laser gas by generating a laser beam 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 transmitting mirror can be used to servo control the position of the tuned mirror.

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

This feature was developed by McGraw-Hill, published in 1966 by William Buoy Smith and Petterpy Sorokin.
2 to 4D of "Laser".

A preferred embodiment of the invention involves modifying the laser by mounting a large radius concave mirror at the intersection of the two branches of the laser path and tilting the symmetrically arranged aperture mirror in a 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 arc minutes.
te) 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 one-half wavelength without affecting the mode quantity due to the gain hole, resulting in 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 each side of the laser path length 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 the gain hole portion of the laser path.

The anode is placed outside the laser path and a conduit is made in the laser block to connect the face of the anode with the laser path.

Application of a voltage between the cathode and anode causes ionization of the gas within the cathode bowl upwardly through a substantially vertical path, thence outwardly into the laser path, and thence along the gain hole of the laser path. in different directions and to the surface of the anode.

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 for use 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 has the trademark CERVIT.
Known as ZERODUR and ULE.

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 anode ionizes the laser gas to energize the laser reservoir.

Although a power supply for applying a voltage between anodes 52, 54 and cathode 16 is not shown, any typical DC power supply can be used, with a positive voltage connected to anodes 52 and 54, while a negative voltage Connected to cathode 16.

Laser block 10 and cathode block 12 are held together by atmospheric pressure and a sealant such as indium solder.

The preferred laser paths 14a, 14b, 14c and 14d are rectangular laser paths, and more particularly are 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 28 are mounted.

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% helium and 2% neon.
The ratio is 0 to 1 and neon 22 to 1.

Four substantially coplanar conduits 30a, 30b, 30c and 30d for containing laser gas in the laser working path.
is hollowed out in the laser block 10 that connects the mirrors.

These should be of a diameter large enough to allow for translation and tilting of the plane of the laser beam at small angles, typically on the order of 3 to 5 arc minutes (3' to 5'), without interference with the laser beam. be.

In the area circumferentially defined by the laser path, preferably in the center of the laser block 10, conduits 30a, 30b are provided.
, 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 typically include substantially conduits 30a,
Conduits 36 in faces 30b, 30c and 30d connect conduits 30a, 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 the termination areas for the laser conduit branches 30a, 30b, 30c and 30d, and are large enough so as not to interfere with the laser light.

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.

Additionally, although conduit 34 is shown perpendicular to the plane of laser paths 14a, 14b, 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 should further be understood that conduit 32 is for 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 noteworthy that the laser paths 14a, 14b, 14
Conduit 32 is shown perpendicular to the passageways of c and 14d.
may be tilted 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 an anode.

Conduit 32 is connected via conduit 34 to a region within cathode surface 16 and to laser conduits 30a, 30b, 30c and 30d via conduit 36.

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

Additionally, a getter (not shown) may be located within 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 vented, the required laser gas is filled into the system at very low pressure and the stem is truncated to seal the system.

Cathode 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 anodes 52 and 54 that are metal conductors and extend from 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
begins to drift from cathode to anode and from anode to cathode in the passage defined by conduits 34 and 36 to chamber and compartment 40 formed by.

In compartment 40, the path splits and a portion of the ion-electron drift is passed through the gain hole from compartment 40 to compartment 38, and from there to the anode 52 in one direction and in the opposite direction in two directions within the gain hole of the laser path. The movement of electrons and ions excites the gas therein to a higher energy state, which drops from this higher energy state to a lower energy state producing 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 anodes 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';
concave mirror 22 to maintain an aperture open to the laser path;
are moved in a direction perpendicular to the conduits 30a, 30b, 30c and 30d and the aperture mirror 26 to lengthen or shorten the laser operating path.

The pyramidal angle between two planes is defined as 90° minus the dihedral angle between them.

The 2,000-sided angle is found in the Mathematics Dictionary (Mathematics Dictionary) by James & James, published by Van Nostrong & Company.
hematics Dictionary), 3rd edition.

That is, "the union of a line and two half-planes having this line as one common edge.

This line is the edge of a 2,000-hedral angle, and its union with one of the planes is one plane.

A 2,000-hedral plane angle is an angle formed by two lines that are the intersections of the 2,000-hedral plane and a plane perpendicular to the edge.

Any two plane angles are congruent. The magnitude of a diplane angle is the magnitude of one of its plane angles.

” The diplanar angle between the tilted mirror and the plane defined by the conduits 30a, 30b, 30c and 30d and the mirror blocks 24 and 28 is slightly less than 90°, but almost 90°.
, which typically differs from 90° by a very small pyramidal angle of the plane of the tilting 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 to hit different parts of the tilted mirror, creating a shorter or longer path for the laser beam.

By hitting different parts of the tilting mirror, the on-axis beam will be quenched by the aperture stop unless the tilting mirror also moves its aperture to realign with the laser beam.

All of the plane mirrors 24, 26 and 28 are conduits 30a, 30b.
, 30c and 30d, the concave mirrors 22
The vertical movement 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 mirror. .

This causes the intersection of the laser beam and the recess of the concave mirror 22 to be moved on its concavity.

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, such that the laser path length is lengthened or shortened by movement of the block that does not move up or down but is tilted by a small pyramidal angle. shi, mirror 24, 26
The intersection of the laser paths on and 28 is moved.

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 sufficiently thick to accommodate the vibrations at the locations described above.

With the structure described above, the smallest laser gyro can be constructed.

The sum of the lengths of the four sides 14a, 14b, 14c and 14d may be, for example, 6.8 centimeters long.

The cathode surface 16 is typically made of aluminum, with indium solder bonded to the aluminum at 60 and 6.
2 and a negative voltage is applied to the aluminum cathode 16
will be applied to

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 an anode.

The mounting surface of the octagonal laser block 10 is typically only one centimeter in diameter, and the mirror blocks 22, 24,
26 and 28 are typically 0.8 centimeters or less in diameter.

The mirror itself is typically 7.75 millimeters in diameter and has a typical thickness of 4 millimeters.

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.

Cathode block 12, as well as mirror blocks 22, 24, 26, and 28, are typically encapsulated with an indium-gold metal encapsulant.

The body of laser block 100 is comprised of a glass ceramic material that has a very low or zero coefficient of expansion over the desired temperature range.

The reflectance of mirror coatings is typically on the order of 99.94%.

Transmission is typically less than 0.1% and scattering losses are typically on the order of 100 ppm.

A typical minimum laser threshold anode-cathode current is 14
It is on the order of ~21/2 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-gold solder sealant.

The resonant frequency is typically an optical frequency on the order of 1014 Hz.

In normal use, the resonant frequency of the cavity is at the center of the gain curve,
Alternatively, it is desirable to be tuned to a fraction of the wavelength that is close to the center.

In FIGS. 4, 5, 6, 7, and 8, the pyramidal angle is indicated by the symbol α.

In FIG. 6 two laser paths are shown, one with the number 14
a, 14b, 14c and 14d, the other by numerals 14e, 14f, 14g and 14h.

The laser path is normally square, but due to the downward movement of the laser path, the path length increases from that shown by 14a, 14b, 14c and 14d to longer paths 14e, 14f, 14g.
and 14h.

The relationship between mirror movement and path length is illustrated diagrammatically in FIG.

Here, the following two restrictions are given.

First, the laser beam is transmitted through the laser holes 30a, 30b, 30
It must not be blurred by c and 30d, and secondly,
The beam must be within the mirror aperture on 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 x 16.8 cm or about 0.001%), then the displacement h( Fig. 4) shows the opening of the inclined mirror 26 at a distance d=
htanα effectively moves inward.

The desired movement in the direction indicated in FIG. 7 by "S" is on the order of one-half the wavelength of the laser light.

It can be seen from FIG. 7 that s = 0.707 d (assuming a square laser path), where d is the wavelength divided by 1.414, which is equal to 6.33 x 10 -5 centimeters.

Holes 30a, 30b, 30c and 30d typically have a diameter dg 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=±0.0440
In the case of centimeters, it is 0.0880 centimeters.

From this, the angle α is the ratio α:h or 1.017×1
Calculated as 0-3 radians, which is approximately 3.49 arc minutes (3.49').

In FIG. 5, the curvature of the surface is exaggerated and the radius R is not proportional.

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 curved mirror surface is from the dead center where α is zero to the point Δr from this dead center, Δr=aR=(1.017×10
-3) (60) = 0.061 cm.

The beam radius is 0.0898 divided by 2 or 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 curved mirror.

Curved mirrors typically have an aperture of 0.4 in diameter and 0.2 cm in radius.

Therefore, a margin of change of 0.2-0.11=0.09 cm is given.

This sets a limit on the allowable increase in angle α and the allowable shift of the laser beam on the plane of curved mirror 22 to 0.09/60=1.5×10 −3 radians.

Furthermore, holes 30a, 30b, 30c and 30d limit the amount that the mirror can shift.

If the mirror 36 is tilted, the plane of the laser working path will also be at an angle α
tilt the cathode block 1 as shown in FIG.
20 bases need to be tilted by the same angle so that the bases are parallel to the laser plane.

The cathode block 120 base can then be 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. .

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, or alternatively, a multi-sided laser path with more than four branches, such that the sliding of the concave mirror shortens or lengthens the laser path. at least one mirror having a small pyramidal angle
Can be used with apertures and concave mirror apertures.

The apparatus and method of the present invention provides a method for tilting one of the resonator mirrors 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 a resonator.

The present invention includes linear as well as non-linear optical resonant paths.

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. 4 is a simplified diagram illustrating a preferred embodiment of the concave mirror and opposing plane mirror of the apparatus of FIG. 1; FIG. FIG. 5 is a simplified diagram showing the relationship between the curvature of the concave mirror and the displacement of the laser plane. FIG. 6 is a simplified 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 simplified view taken at 7 in FIG. FIG. 8 shows bending the base of the canned 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, 22,
24, 26, 28... Laser conduit, 52, 54... Anode.

Claims (1)

Claims: 1. A laser block comprising a laser conduit containing a laser gain medium for accommodating a laser path for producing a ring laser beam, a mirror at the junction of said conduit, and a mirror connected to said conduit by a passage. a ring laser comprising a cathode and at least one anode, wherein a passage between the power sword and the anode includes a gain hole that is at least part of the conduit in an opposite direction of the laser path; A ring laser, wherein one of the mirrors is concave, the remaining mirrors are substantially planar, and at least one of the mirrors is tilted at a pyramidal angle with respect to the other mirrors. 2. The ring laser according to claim 1, wherein the tilted mirror has an aperture for suppressing an off-axis mode of oscillation. 3. The ring laser according to claim 1, wherein the laser paths are substantially in the same plane and the concave mirror is inclined at a certain pyramidal angle with respect to the other mirrors. . 4. The ring laser according to claim 3, wherein the concave mirror has an opening so as to suppress an off-axis mode of oscillation. 5. The ring laser according to claim 2, wherein the laser path has four branches, and the mirror is connected to a substantially planar mirror at the junction of three of the branches of the laser path. a concave mirror at a fourth junction of the branch, said concave mirror being inclined at a pyramidal angle with respect to the plane of said laser path such that movement of said concave mirror adjusts the length of said laser path. A ring laser characterized by: 6. The ring laser according to claim 5, wherein the concave mirror has an opening so as to suppress an off-axis mode of oscillation. 7. In the ring laser according to claim 5, two of the plane mirrors are substantially parallel to each other, and the other plane mirror is opened so as to suppress an off-axis mode of oscillation. Features a ring laser. 8. The ring laser according to claim 1, wherein the laser path is substantially coplanar, and one of the plane mirrors
A ring laser, wherein one of the mirrors is tilted at a certain pyramidal angle with respect to the other mirror, and the tilted mirror has an aperture so as to suppress an off-axis mode of oscillation. 9. A ring laser according to claim 8, wherein the laser path has four branches, the mirrors being parallel substantially planar mirrors at two non-adjacent junctions of the laser path; A ring characterized in that it comprises a concave mirror at a third junction of the laser path and a plane mirror at a fourth junction of the laser path and inclined at a pyramidal angle with respect to the other mirrors. laser. 10. The ring laser according to claim 9, wherein the laser path is substantially square, and includes a cathode block attached to the base of the laser block and a substantially canned block at the interface between the blocks. further comprising a cathode consisting of a substantially hemispherical metal coating on a hemispherical recess, said anode being a pair of anodes each disposed adjacent to a different one of said parallel plane mirrors; A passage formed in the laser block with the anode extends from substantially the center of the hemispherical cathode to the region of the tilted mirror and from there in opposite directions along two gain hole branches of the laser path. A ring laser, characterized in that the ring laser extends to the parallel mirrors and the anode. 11. A ring laser according to claim 10, characterized in that the base of the cathode and laser block combination is inclined such that the plane of the passageway is substantially parallel to the base. ring laser.