JPS5917868B2 - Wavelength stabilized laser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wavelength stabilized laser, and particularly to a wavelength stabilized laser that utilizes saturated absorption of methane gas, iodine gas, etc.

In order to use a laser for precision measurements such as length measurement, the first condition is to stabilize the oscillation wavelength of the laser.

For this reason, many studies have been conducted to suppress the causes of various fluctuations as much as possible and to stabilize the wavelength by servo control.As one method, many studies have been conducted on methods that utilize the saturated absorption of molecules. . An external mirror type iodine stabilized He-Ne laser using an absorption cell filled with iodine gas has been put into practical use as a laser device that utilizes such saturated absorption. o, the resonator spacing is 30 (V7l or more), which is large.Also, in the external mirror type, the whole is made airtight to eliminate the influence of air fluctuations, but due to the structure of the laser tube, there is no airtight mechanism. Furthermore, since air at 1 atm is kept in an airtight state, fluctuations in the output of the laser tube caused by fluctuations in the air are extremely large.
An internal mirror type iodine stabilized laser has also been announced, but the iodine absorption cell part is an optical contact and requires special technology. Lifespan is short.

Furthermore, in the conventional iodine-stabilized He--Ne laser, the single mode region is narrow due to the large resonator spacing, and in order to enlarge the single mode region, it is necessary to reduce the output j5.

In many cases, the laser output is about 401tw to 601tw, which is too small for practical purposes such as length measurement. The present invention eliminates the above-mentioned drawbacks, and provides an internal mirror that uses saturated absorption to reduce the resonator spacing, thereby widening the single mode region i0, and increasing the output more than twice that of the conventional one. The purpose of the present invention is to provide a type of wavelength-stabilized laser.

In addition, the absorption cell is sealed between the internal mirror vibrators to maintain mechanical stability, eliminate the influence of air fluctuations, and significantly reduce noise.It is also small, lightweight, and stable. The object of the present invention is to provide an internal mirror type wavelength stabilized laser that utilizes saturated absorption to remove heat generated from the laser.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a plan view of the wavelength stabilized laser of the present invention with the laser tube in cross section, FIG. 2 is a front view of the laser of the present invention with part of the laser tube in cross section, and FIG. 3 is a partially cross sectional view of the laser of the present invention. FIG. 3 is a right side view of the laser of the present invention. 1 is a laser tube, and a cylindrical tube 2 constituting the side wall of the laser 1 is divided into two chambers by a partition wall 3, and a thin tube 4 is sealed so as to be held by the partition wall 3 on the oscillation optical axis of the laser beam. It is worn.

A disk 5 having a hole on the optical axis is welded to both ends of the cylindrical tube 2, and a reflector mount 6 is provided in the hole, and a resonator reflector 7 is mounted on the mount 6. It is provided. Bulkhead 3
An anode terminal 8 is sealed in one chamber of the cylindrical tube 2 separated by 2, and a cathode terminal 9 is sealed in the other chamber. 10
is provided and connected to the cathode terminal 9 with a metal wire. An absorption cell is provided in one of the chambers, and in this embodiment, the absorption cell 11 is arranged in the chamber containing the cathode 10 so that the oscillation optical axis and the axis of the absorption cell 11 coincide with each other. Both ends 12 and 13 of the absorption cell 11 are hemispherical,
Each pre-use star window 14 is welded. A side arm protrudes from one hemispherical end 13 for encapsulating iodine in this embodiment. This side arm 15 is extended to form a protrusion 16 from the cylindrical tube 2.
At this point, the laser beams are welded together via the disk 17 and the like, and then led out of the laser tube 1 . This side arm 1 led out to the outside
5 has its end sealed, and this side arm 15 is inserted into a dewar bottle 50 kept at constant temperature. In addition, in the case of this embodiment, He and Ne are inside the laser tube 1.
An inlet pipe to the getter 18 protrudes from the side wall of the cylindrical tube 2 facing the cylindrical tube protrusion 16 .

The laser tube 1 as described above is housed in a storage cylindrical tube 20, and the laser tube 1 is inserted from the right side in FIG. Grooves 21 and 22 are provided for the introduction pipe to the storage cylindrical pipe 20, and are positioned by an abutment part 23 provided on the left inner surface of the storage cylindrical pipe 20.

A flow channel 24 for cooling the laser tube 1 is provided on the inner surface of the storage cylindrical tube 20 at a position corresponding to the side wall of the laser tube. The inner surface protrusions 25 and 26 of the storage cylindrical tube 20 are formed at the front and rear of the flow channel 24 so as to have an inner diameter slightly larger than the outer diameter of the laser tube 1. O-rings 27 and 28 are provided. Furthermore, an intake port 29 for introducing cooling water into the flow channel 24 and an exit port 30 for discharging cooled water are provided on the side wall of the storage cylindrical tube 20. Further, both electrode terminals 8 and 9 of the laser tube 1 are provided on the side wall of the storage cylindrical tube 20.
Connecting terminals 31 and 32 to which a current is applied from an external power source are sealed by connecting terminal holders 33 and 34 so that they correspond to both electrode terminals when the laser tube 1 is stored. The mounting portions of both electrode terminals 8 and 9 of the cylindrical tube 2 are recessed to facilitate storage of the laser tube 1 into the storage cylindrical tube 20, so that the electrode terminals do not protrude beyond the outer diameter of the cylindrical tube 2. It is formed like this. A reflecting mirror drive unit 36 for vibrating the resonator reflecting mirror 7 along the oscillation optical axis is housed in the openings 35 at both ends of the housing cylindrical tube 20, and the holding ring 3
It is fixed by 7. This reflector drive unit 36 creates a radial magnetic field with an inner core 38, a permanent magnet 39, and a yoke core 40, and a gap 4 is provided between the inner core 38 and the yoke core 40.
A movable coil 4 is provided concentrically within the gap 41.
2 is inserted, and by passing a current through the coil 42, the coil 42 vibrates in the optical axis direction.

The end of the coil 42 opposite to the part inserted into the gap 41 is attached to a center holder 43 provided on the reflector mount 6.
As the coil 42 vibrates in the optical axis direction, the disc 5 is deflected to vibrate the reflecting mirror 7 in the optical axis direction, thereby changing the resonator spacing. The inner core 38 has a hole 44 on the optical axis, through which the laser light generated in the laser tube 1 is taken out. This laser light is received by a light receiving element and a signal for wavelength stabilization is extracted.
In this embodiment, the light-receiving element 45 is attached to a light-receiving element attachment part 46 and fixed to the rear end of the retainer ring 37 of the reflector drive part 36 by another retainer ring 47. In this embodiment, both reflecting mirrors 7 are configured to be vibrated along the optical axis by the reflecting mirror driving section 36, but by causing one of the reflecting mirrors 7 to vibrate minutely at a constant frequency, the absorption cell 1
An error signal is generated based on the saturated absorption of iodine in 1. This error signal is received by the light receiving element 45 and converted into a control signal by the processing device to control the other reflecting mirror 7 by the drive unit 3.
6 to change the resonator spacing and stabilize the wavelength. The side arm 15 from the absorption cell 11 is inserted into the Deyuwa bottle 50 to maintain a constant temperature, but the Deyuwa bottle 50 is equipped with a constant temperature bath (not shown).
Cooling water at a constant temperature is led from the intake port 52 through a pipe 51 or the like, and maintains the iodine gas in the absorption cell 11 at a constant temperature.

The dewar bottle 50 is provided with a cooling water outlet 53, and the outlet 53 is connected to the intake 29 to the flow channel 24 of the storage cylindrical tube 20 with a pipe 54 or the like to allow the cooling water to flow into the outlet. Cooling water is circulated from 30 through a pipe 55 or the like to return to the constant temperature bath. Furthermore, a storage cylindrical tube 2 housing the laser tube 1 is provided.
0 is fixed on a base 60, a storage cylindrical tube holding ring 63 is provided via a vibration isolating rubber 62 with a support 61 erected on the base 60, and the storage cylindrical tube 20 is placed in the holding ring 63.
is inserted and fixed onto the base 60 by fixing with screws or the like.

FIG. 4 is a diagram showing another embodiment of an inlet and an outlet for allowing cooling water to flow into the flow channel 24.

In this embodiment, the cooling water from the intake port 29 flows into the flow channel 24.
A donut-shaped small chamber 70 is provided in the front storage cylindrical pipe 20 into which the water flows. From this chamber 70 to the flow channel 24
A large number of nozzle-shaped small holes 71 are provided at equal intervals on the walls of the small chamber 70 and the flow channel 24 in order to allow cooling water to flow into the small chamber 70 and the flow channel 24. In order to provide such a small chamber 70, the laser tube abutment part 23 and the protruding part 25 are separated, and the small chamber forming ring 72 is inserted into a predetermined position from the left opening 35 of the storage cylindrical tube 20 and fixed. The small chamber forming ring 72 has a contact portion 23 formed inside thereof, and a small hole 71 is provided in the wall separating it from the flow channel 24.
0 links 73 and 74 to prevent water leakage. Similarly, on the outflow side, small holes and small chambers are provided to allow the cooling water to flow out. When the cooling water circulation path is formed in this manner, the flow of cooling water in the flow path for cooling the laser tube 1 is smooth and constant in the direction of the outlet, and uneven cooling does not occur. According to the present invention as described above, since the absorption cell 11 is formed separately from the laser tube 1 and is sealed between the resonator reflectors 7 of the internal mirror type laser tube, the resonator spacing is reduced. can be made smaller than the external mirror type and is mechanically stable.

Furthermore, since the resonator spacing can be narrowed, the single mode region can be widened and the output can be increased. Furthermore, He
Since the absorption cell 11 is sealed in the -Ne gas, there is no influence of air fluctuations, and the S/N ratio is greatly improved.
That is, when the gas pressure of He--Ne gas is 3 t0rr, the influence of fluctuation is 1/250 or less when compared with an external mirror type iodine stabilized gas laser. In addition, since the absorption cell is formed separately and sealed in the laser tube, and is welded at the protrusion 16 of the laser tube, there is no need for special techniques such as optical contact as in the past, and it can be used with ordinary glass. Laser tubes can be manufactured using crafting techniques, and manufacturing is relatively simple.

Furthermore, the laser tube is small, lightweight, and stable, and a flow path is formed on the inner surface of the storage tube 20.
Since the reflection pin drive unit 36 is housed in the openings 35 at both ends of the laser beam, it is durable and compact as a stabilized laser with a cooling mechanism.

Furthermore, since the heat generated from the laser tube is removed by flowing water, the main body of the measuring instrument etc. is not affected by the heat from the laser tube.

Therefore, the normally very large errors due to heat can be eliminated. It should be noted that the present invention is not limited to the embodiments described above, and it goes without saying that many modifications can be made.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the wavelength stabilized laser of the present invention with the laser tube in cross section, FIG. 2 is a front view of the wavelength stabilized laser of the present invention with a portion of the laser tube in cross section, and FIG. FIG. 4 is a right side view of the wavelength stabilized laser of the present invention taken in cross section, and FIG. 4 is a diagram showing another embodiment of the cooling water intake port. 1... Laser tube, 2... Cylindrical tube, 3
... septum, 4 ... tubule, 7 ...
・Resonator reflector, 8... Anode terminal, 9...
... Cathode terminal, 10 ... Aluminum pipe for cathode, 11 ... Absorption cell, 15 ... Side arm, 20 ... Storage cylindrical tube, 24・・・・・・
・Flow channel, 29...Intake, 30...
Outlet, 31, 32... Connection terminal, 35...
...Storage pipe opening, 36...Reflector drive section,
38...Inner core, 39...Permanent magnet,
40... Yoke core, 42... Moving coil,
43...Center holder, 45...Light receiving element, 50...Duwa bottle, 60...
Base, 61... Support, 62... Anti-vibration rubber, 63... Storage cylindrical tube holding ring, 70...
...small room, 71...small hole.

Claims (1)

[Claims] 1. A cylindrical tube, a thin tube sealed to partition the inside of the cylindrical tube, an anode provided on the side wall of the cylindrical tube that forms one chamber separated by the sealed portion of the thin tube, and the other chamber. a cathode provided on the side wall of the cylindrical tube to be formed; a resonator reflecting mirror provided on both end surfaces of the cylindrical tube; It is characterized by comprising an absorption cell having a Brewster window between which a space is isolated via the cylindrical tube space, and a side arm connecting the absorption cell and a constant temperature section disposed outside the cylindrical tube. wavelength stabilized laser.