JPH0249486A - Dye laser oscillator - Google Patents

Abstract

PURPOSE:To prevent a laser beam from deteriorating in quality by a method wherein an effective velocity of light inside an optical resonator is made to change through the change of a refractive index due to the distortion inside an electrostrictive element by changing the voltage applied to the electrostrictive element and the wavelength of an oscillating beam of a dye laser oscillator is made to change continuously. CONSTITUTION:An etalon 2 executes a fine adjustment of the wavelength of oscillating laser rays on an optical axis of a diffractive grating 6 and an output mirror 5. A beam magnifier 3 magnifies a laser beam so as to use a large area of the diffractive grating 6 as effectively as possible. A light transmissive electrostrictive element 10 continuously and finely adjusts the wavelength of the oscillating laser beam taking advantage of the change of a refractive index through varying the applied voltage. A dye cell 4 makes a die solution, which serves as a laser medium, flow. A voltage is applied from a power source 14 to the element 10 through the intermediary of electrodes 11, and a laser oscillation frequency can be changed through the change of a refractive which follows the change of the applied voltage. By this setup, the wavelength of oscillating laser rays of a dye laser oscillator can be continuously changed, so that a laser beam can be prevented from deteriorating in quality.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Field of Industrial Application) The present invention relates to a dye laser oscillator, and particularly relates to a dye laser oscillator in which the oscillation wavelength is continuously variable or the continuous variable range is expanded. .

(Prior Art) Conventionally, as a dye laser oscillator, one shown in FIG. 4, for example, is known.

Reference numeral 1 in the figure is the oscillator body of the dye laser, and within this oscillator body 1, an output mirror 5 and a reflective diffraction grating 6 are provided at both ends, and these constitute an optical resonator. Furthermore, the diffraction grating 6 has wavelength selectivity, and the oscillation wavelength can be roughly selected by adjusting its inclination angle. Rough output mirror 5
On the optical axis between the and the diffraction grating 6, there is an etalon 21 that finely adjusts the oscillation wavelength, and a beam expander 3 that expands the laser beam to effectively utilize the wide surface of the diffraction grating 6 and improve wavelength selection performance. ．． A dye cell 4 is provided through which a dye solution, which is a laser oscillation medium, flows. Also, dye cell 4
is irradiated with excitation light 7 in order to pump the dye molecules and make them an active medium capable of laser oscillation.

(Problem to be solved by the invention) In such a dye laser oscillator, the output mirror 5
The wavelength of the output laser beam 8 emitted from is the optical cavity length,
That is, when the distance between the diffraction grating 6 and the output mirror 5 is L, the following formula holds: Δλ=zL (1) C.

From equation (1), the wavelength of the output laser light can only be oscillated at discrete wavelengths with a wavelength interval Δλ. Therefore, even if the wavelength is selected using the diffraction grating 6 and the etalon 2, the oscillation wavelength cannot be changed completely continuously.

Here, C is the effective speed of light within the optical resonator. In order to compensate for this drawback, as shown in FIG. 5, the conventional method is to seal the inside of the oscillator body 1 and change the gas pressure inside the optical resonator using a gas pressure regulator 9 to increase the effective light velocity within the optical resonator. Continuous variation of the oscillation wavelength was realized by changing C and changing Δλ. However, in this device, the gas pressure cannot be raised very high due to strength problems, and therefore the range in which the oscillation wavelength can be continuously varied is narrow. Furthermore, it was difficult to change the gas pressure in a short time, making it impossible to change the oscillation wavelength at high speed.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a dye laser oscillator in which the oscillation wavelength can be continuously varied and the oscillation wavelength can be changed in a short period of time, for example, on the order of one second.

[Structure of the Invention] (Means for Solving the Problems) The present invention comprises an oscillator body, a pair of diffraction gratings and an output mirror disposed facing each other in the oscillator body and forming an optical resonator; It is characterized by comprising an etalon, a light-transmitting electrostrictive element, and a dye cell, which are sequentially arranged on the optical axis between a diffraction grating and an output mirror, and a power source that applies a voltage to the electrostrictive element.

(Function) By changing the voltage applied to the electrostrictive element, the effective speed of light C in the optical resonator changes due to the change in refractive index caused by the strain within the electrostrictive element, so the oscillation wavelength of the dye laser oscillator can be continuously changed. It can be changed.

Furthermore, when the oscillation frequency of a dye laser oscillator is repeatedly changed at high speed, temperature distribution occurs within the electrostrictive element due to heat generation within the electrostrictive element. propagates through multiple reflections within the electrostrictive element. This can prevent the quality of the laser beam from deteriorating even if a refractive index distribution occurs due to temperature distribution. At the same time, multiple reflections of the laser beam within the electrostrictive element increase the optical path length of the laser beam, and the range of change in the effective light velocity within the optical resonator is expanded. Roughly making the area of the electrodes provided on the opposing surface of the electrostrictive element smaller than the area of the opposing surface causes non-uniformity in electric field distribution within the electrostrictive element when voltage is applied.

This changes the angle of the laser beam entrance/exit surface of the electrostrictive element, so it is possible to correct the deviation of the laser beam entrance/exit position due to a change in the refractive index within the electrostrictive element, and eliminate the optical axis deviation.

(Example) A first example of the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1, an output mirror 5 forming one end of the resonant mirror of the resonator and a reflective diffraction grating 6 forming the other end of the optical resonator are arranged as a pair in the oscillator main body 1. . The diffraction grating 6 also serves as a coarse selection of the oscillation wavelength. An etalon 2 that finely adjusts the oscillation wavelength on the optical axis of the diffraction grating 6 and the output mirror 5, a beam expander 3 that expands the laser beam to effectively utilize the widest possible surface of the diffraction grating 6, and an applied voltage. A light-transmissive electrostrictive element 10 that continuously and finely adjusts the oscillation wavelength by utilizing the refractive index change caused by the change, and a dye cell 4 through which a dye solution serving as a laser excavation medium flows are sequentially arranged. The electrostrictive element 10 is formed in the shape of a parallelogram or a trapezoid, and electrodes 11 are provided on both upper and lower surfaces thereof, and a voltage is applied to the electrodes 11 from a power source 12. Further, the dye cell 4 is irradiated with excitation light 7 . In addition, code 8
indicates the output laser.

In the dye laser oscillator having the above configuration, a voltage is applied to the electrostrictive element 10 from the power source 14 via the electrode 11, and the laser oscillation frequency can be changed by the resulting change in the refractive index. Furthermore, by adopting a structure in which the laser beam is multiple-reflected in the vertical direction within the electrostrictive element 10, the electrostrictive element 1
The optical characteristics are less likely to change due to temperature differences in the vertical direction within 0, and stable operation can be achieved for a long period of time. moreover,
If we consider the case where the electrode area is made smaller than the area of the facing surface of the electrostrictive element 10 and the electric field near the input/output ends of the laser beam is reduced, for example, when a voltage is applied, the electrode area contracts in the vertical direction, the peripheral area becomes smaller than the central area. deformation due to voltage application is reduced. Therefore, the electrostrictive element 10 is deformed so that the inclination of the laser light input/output surface becomes smaller. As a result, it is possible to suppress the deviation between the incident height and the output height of the electrostrictive element 10 due to an increase in the refractive index of the electrostrictive element 10 due to contraction in the vertical direction.

This situation is shown in FIG. Reference numeral 14 in FIG. 2 indicates a change in external shape.

FIG. 3 shows a second embodiment of the present invention, in which the beam expander 3 and electrostrictive element 10 in FIG. 1 are combined and integrated, and other parts are the same as in the first embodiment. Since it is similar to the example, its explanation will be omitted. In this embodiment, by using a light-transmitting electrostrictive element beam expander 13 that serves both as a light-transmitting electrostrictive element and a beam expander, an effect similar to that of the first embodiment can be obtained.

[Effects of the Invention] According to the present invention, the oscillation wavelength can be varied continuously, the wavelength tunable range is wide, and the oscillation wavelength can be changed at high speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of a dye laser oscillator according to the present invention, FIG. 2 is a longitudinal cross-sectional view showing a modification of the shape of the electrostrictive element in FIG. 1, and FIG. FIG. 4 is a block diagram showing a conventional dye laser oscillator, and FIG. 5 is a block diagram of a conventional device for continuously changing the oscillation wavelength. 1... Oscillator main body 2... Etalon 3... Beam expander 4... Dye cell 5... Output mirror 6... Reflective diffraction grating 7... Excitation light 8... Output laser Light 9...Gas pressure adjustment device 10...Light-transmitting electrostrictive element 11...Electrode 12...Power source 13...Electrostrictive element beam expander 14...Outline change Fig. 1 (8733 ) Agent Patent Attorney Yoshiaki Inomata (Baka
1 person) Figure 2

Claims (1)

[Claims] an oscillator body; a pair of diffraction gratings and an output mirror disposed facing each other in the oscillator body forming an optical resonator;
An etalon, a light-transmitting electrostrictive element, and a dye cell are sequentially arranged on the optical axis between the diffraction grating and the output mirror;
A dye laser oscillator comprising: a power source for applying a voltage to the electrostrictive element.