JPS61239685A - Frequency and intensity stabilizing laser device - Google Patents

Abstract

PURPOSE:To stabilize oscillation frequency and oscillation intensity by utilizing the freedom of the setting of the intensity of an intensity setter and selecting a value close to the maximum value of oscillating beams as a set point. CONSTITUTION:One polarized light in oscillating beams from a gas laser 1 is selected by a polarizer 2, and intensity thereof is detected by a photoelectric detector 3. The intensity signal is transmitted over a first cavity length control system consisting of a preamplifier 5, a gain control amplifier 6, a bias control amplifier 7, a summing amplifier 8 and a temperature regulator 4, thus stabilizing oscillation frequency. On the other hand, oscillation intensity at a single longitudinal mode is set apart from the intensity adjusting point of the first cavity length control system by an intensity setter 13, a difference between the set value and said intensity adjusting point is detected by a comparator 9, and positive-negative or negative-positive constant voltage is generated in response to the positive or negative value of an error. The constant voltage is charged or discharged slowly to linear type integrators 11, 12 through a high resistor 10, and output voltage from an operational amplifier 12 is increased or decreased gradually. The voltage is added to the signal voltage of the first cavity length control system by employing the amplifier 8. Accordingly, both voltage coincide while being brought close to the set value of the setter 13.

Description

DETAILED DESCRIPTION OF THE INVENTION a) Field of Industrial Application The present invention relates to a laser device whose oscillation frequency and oscillation intensity are highly stabilized.

b) Conventional configuration and its problems The oscillation frequency of conventional gas lasers has been stabilized by using the Zeeman effect caused by a magnetic field, or by
This has been done by detecting the intensity of two polarized lights and utilizing the phenomenon that the intensity ratio of the two polarized lights changes depending on the length of the resonator.

However, the former method has the disadvantage that the plasma state of the laser discharge is biased due to the application of a magnetic field, which impairs the uniformity of cathode sputtering, resulting in a shortened laser life.

In addition, since the latter measures the intensity of two orthogonal polarized lights, it is necessary to control the resonator length so that the two polarized lights oscillate together. This made the laser extremely inefficient. Further, although the intensity ratio is controlled to be constant, there is a drawback that if the overall laser intensity fluctuates, the intensity itself cannot be avoided.

C) Purpose of the Invention The present invention aims to eliminate the above-mentioned drawbacks of conventional frequency-stabilized lasers and to provide a laser device that is efficient, has a long life, and has highly stabilized oscillation frequency and oscillation intensity. It is something.

d) Construction of the Invention In gas lasers with an internal cavity, the laser cavity length ° changes with temperature.

Therefore, as the temperature of the laser changes, the frequency of the oscillated light changes, and as the frequency changes, the intensity of the oscillated light changes according to the laser gain curve.

The longitudinal mode spacing of the laser is given by C721 hertz, where the laser cavity length is L, and the width of the gain curve is about 1 to 2 gigahertz, so when the cavity length is 10 to 20 cm, the interval is 1 as shown in Figure 1. It is considered that the longitudinal modes a and b of the ~2 tree are oscillating, and the oscillation lines a and b are moving according to the change in the resonator length.

Since the polarizations of adjacent longitudinal modes a and b are orthogonal,
In the conventional stabilized laser described above, longitudinal modes a and b
are detected by separating them using polarized light, and control is performed so that the intensity ratio of a and b is constant.

In contrast, the device of the present invention operates in one longitudinal mode, e.g.
Y0.8o,,ka,□U 414 dh kl
A G (7) Eyo1. □4,3 o. 1. By controlling the resonator length so that it oscillates, unnecessary oscillation mode b can be avoided.
This is to improve the oscillation efficiency and stabilize the oscillation intensity.

FIG. 2 shows an embodiment of the invention.

Polarized light having one polarization component is selected from the oscillation light of the gas laser 1 having an internal cavity by a polarizer 2, and the intensity of the polarized light is detected by a photoelectric detector 3.

Since the intensity of the polarized light changes as the resonator length changes as described above, the detected intensity signal is amplified by the preamplifier 5 and the gain of the control loop is adjusted by the gain adjustment amplifier 6.
Furthermore, after selecting the strength adjustment point of the control loop with the bias adjustment amplifier 7, the power is amplified with the summing amplifier 8, and the output is applied to the temperature controller 4 consisting of an electric fan or heater to keep the resonator length constant and adjust the frequency. Stabilization takes place. The above is the configuration and role of the first resonator length control system.

In the present invention, the object is achieved by using a second resonator control system described below in addition to the first resonator length control system described above. The second resonator control system is the intensity setting device 13
．． It is composed of a comparator 9 that outputs constant positive and negative voltages, a high resistance 10, an operational amplifier 12, and a large capacity capacitor 11.

The intensity setting unit 13 sets the oscillation intensity of the single longitudinal mode independently of the intensity adjustment point of the control loop of the first resonator length control system. A comparator 9 detects the difference between the set value and the intensity adjustment point, and creates a positive/negative or negative/positive constant voltage depending on the sign of the error. The positive/negative or negative/positive constant voltage created by the comparator 9 is slowly charged and discharged through a high resistance 10 to a linear integrator composed of a large capacity capacitor 11 and an operational amplifier 12, and the output voltage of the operational amplifier 12 is gradually increased. Or reduce it. This gradually increasing or decreasing voltage is added to the signal voltage of the first resonator length control system using a summing amplifier 8 by selecting a polarity such that the difference between the intensity adjustment point and the set value is small. By performing the above operations, the intensity adjustment point of the first resonator length control system is gradually moved, and the intensity setting device 13 of the second resonator length control system is moved.
If the value approaches the value set in and the two match, the movement will stop.

Since the setting value of the intensity setter 13 is selected regardless of the specifications of the first resonator length control system that constantly controls the resonator length, the first resonator, which is performing delicate operation, The adjustment point can be moved without causing any disturbance in the long control system, and the environment where the laser device is installed,
For example, when the temperature changes, in the case of only the first resonator length control system, the error signal level changes and therefore the adjustment point changes, and the frequency of the oscillated light and the oscillated light intensity change, but the intensity setting device 13 Since the set value of does not change depending on the environment, the stability is extremely high by using the second resonator length control system. In other words, the second resonance-length control system bears all the fluctuations in the error signal due to the environment, thereby preventing fluctuations in the set value.

By utilizing the arbitrariness of the intensity setting of the intensity setter 13 and selecting a set point close to the maximum value of the oscillated light, it becomes possible to use the oscillated light with high efficiency.

As described above, by using the first resonator length control system and the second resonator length control system in combination, laser oscillation with highly stabilized oscillation frequency and oscillation intensity and high oscillation efficiency can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram, and FIG. 2 is an embodiment of the present invention.

Claims (1)

[Claims] Among the oscillation light of a gas laser having an internal cavity, light having one polarization component is detected, and the gas laser is adjusted so that the intensity of the detected one polarization component becomes a certain intensity adjustment value. a first cavity length control system that controls the cavity length of the gas laser by controlling the temperature of the gas laser; a first cavity length control system that controls the cavity length of the gas laser; a light intensity electrical signal corresponding to the intensity adjustment value; The value of the light intensity electric signal is compared with the set electric signal generated by the means for generating the set electric signal corresponding to the other intensity set value set in the above, and the magnitude of the set electric signal and the light intensity electric signal is determined. A means for generating positive and negative voltages is used to generate positive and negative voltages, and the positive and negative voltages are converted into a long time constant integrating means consisting of an integrator made of a capacitor, etc., and an electric circuit having a function of gradually charging and discharging. and a second resonator length control system that adds the electric signal obtained by the long time constant integrating means to the signal of the first resonator length control system. A frequency and intensity stabilizing laser device characterized in that the intensity adjustment value is gradually corrected to approach the independently set intensity setting value.