Microwave excited gas laser oscillator

Details Microwave excited gas laser oscillator Microwave excited gas laser oscillator

1999-01-28

2001-07-10

Lee, John D. (Department: 2874)

Coherent light generators

Particular pumping means

Electrical

C372S055000, C372S073000, C372S084000

Reexamination Certificate

active

06259716

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a microwave excited gas laser oscillation control method for exciting by discharging, laser gas by microwave, and a microwave excited gas laser oscillator.
BACKGROUND OF THE INVENTION
Recently, gas laser oscillators are being reduced in size. To achieve this goal, the exciting frequency for a discharging gas laser has gradually reached higher frequencies. Hitherto, to supply the frequency for such gas laser oscillation, high frequency power sources of 100 kHz to scores of megahertz have been used. However, to reduce the size, problems of price and control performance occur. To solve these problems, various studies have been made on the microwave excited gas laser oscillator (herein after called MEGLO) for exciting by discharging laser gas by microwave.
FIG. 6
is a schematic diagram for explaining a constitution of a conventional MEGLO, and it is described below while referring to the drawing.
A microwave power source (hereinafter called power source)
4
is a switching power source of about 20 kHz, and a high voltage is applied so that a magnetron
1
may produce a microwave. The microwave emitted from the magnetron
1
is injected through a waveguide
2
into a discharge area
10
which is part of a discharge tube
3
in which laser gas flows. In the discharge area
10
, the laser gas is discharged and excited by the microwave. The excited and generated laser beam is amplified in a laser resonator composed of an output mirror
8
which is a partial reflector and a total reflector
9
. Part of the laser beam amplified in the laser resonator is delivered outside through the output mirror
8
.
As shown in
FIG. 6
, assuming that magnetron
1
, waveguide
2
and power source
4
to be one microwave generating unit (hereinafter called MGU)
200
, plural MGUs
200
are used in one discharge tube
3
. Further assuming the one discharge tube
3
and a plurality of MGUs
200
compose one microwave output unit (hereinafter called MOU)
300
, the number of MOUs used in one MEGLO is determined by the laser output of the MEGLO.
FIG. 7
shows an example of using four MGUs
200
in one discharge tube
3
, in which four microwave output timings are shown simultaneously. As shown in
FIG. 7
, each MGU
200
outputs intermittently so as to issue a microwave for a period of Ton
101
, and cut off for a period of Toff
102
. The microwave output timings from four MGUs
200
are nearly simultaneous. In order to stabilize the microwave output, pulse-width modulation (hereinafter called PWM) control of a specific off time is effected.
In the conventional MEGLO, the output of each magnetron
1
is controlled at a specific off time by the PWM control. However, when plural MGUs
200
composing one MOU
300
are disposed closely, the microwave output of each MGU
200
is issued at the same timing as shown in
FIG. 7
, and the discharges in the discharge area
10
may interfere with each other. In the event of such phenomenon, the continuous output of laser beam contains ripples, and the peak output of the laser beam in pulse operation fluctuates greatly, while at the same time, the laser beam output decreases. These problems are associated with the conventional MEGLO.
SUMMARY OF THE INVENTION
The present invention is devised to solve the above problems, and it is hence an object thereof to present a small-sized MEGLO capable of delivering a continuous output of stable laser beams and a high pulse peak output. The invention for solving the problems is described below.
The MEGLO of the invention comprises plural discharge tubes for passing laser gas inside, a magnetron for generating microwaves, a waveguide for coupling the microwaves generated from the magnetron to the discharge tubes; a power source for supplying electric power to the magnetron, and a controller for controlling the power source.
One discharge tube has plural discharge areas, and each discharge area has an MGU composed of a magnetron for supplying microwaves, a waveguide and a power source.
By one discharge tube and a plurality of MGUs, one MOU is composed, and the MEGLO of the invention usually comprises a plurality of MOUs.
The plural MGUs are disposed close to each other, and the controller drives by allowing a specific phase difference among adjacent power sources.
The controller also issues a reference clock for controlling the microwave switching phase of each discharge tube to the power source of each MGU.
In this constitution, the controller issues a reference clock in every power source of each MGU, and each power source drives the corresponding MGU on the basis of the entered reference clock. For example, in the case of two adjacent MGUs, while one is issuing microwaves, the other stops issuing microwaves. Next, at the timing when the busy MGU stops output of microwaves, the other MGU issues microwaves.
In this way, the reference clock controls the switching phase of the microwaves supplied to each discharge tube. Therefore, in the case of the MEGLO of the invention, if plural MGUs are closely disposed, mutual discharge interference can be decreased, and a stable laser beam being small in ripple content may be issued.


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