JPS63239994A - Frequency tunable laser device - Google Patents

Abstract

PURPOSE:To make laser output frequency continuously variable by cancelling variation of the direction of outgoing light of a light frequency shifter by a phase-conjugatemirror while composing so as to make a frequency-shifted light to go out always in a fixed direction. CONSTITUTION:Outgoing light from a semiconductor laser light source 2 is made into parallel lights by a collimator lens 3 for being incident on a polarizing prism 5 through an optical isolator 4. This incident light is wholly made to go out of the polarizing prism 5 for being incident on a-ultrasonic modulator 6. Primary diffraction light diffracted by the ultrasonic modulator 6 operating as a frequency shifter of light passes through a 1/4 wavelength plate 8 to become circular polarization to be incident on a BaTiO3 single crystal 9. In the single crystal 9, the light refracted on the incident surface is used as pump light for generating a phase-conjugate wave. This phase-conjugate wave returns reversedly on the same path with the incident light as reflected light. According to such a laser device, modulation frequency omegas is electrically changed in order to obtain outgoing light having the frequency of omegao+2omegas always at a fixed outgoing angle and with a fixed output.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a device that continuously varies the frequency of output light from a semiconductor laser.

(Prior art) Conventionally, as a device for continuously changing the frequency of the output light of a laser, there is a device that can continuously change the frequency using an optical parametric incubator, as shown in YAG laser 1A, etc. There is.

(Problems to be Solved by the Invention) However, since a semiconductor laser has a lower output than a YAG laser+f, etc., optical parametric oscillation cannot be realized. Conventional semiconductor lasers that can continuously change the frequency of their emitted light are semi-nine semiconductor lasers. There were problems with speed, etc.

The present invention was developed in order to solve these problems, and it is possible to electrically control the output frequency of a semiconductor laser to continuously vary it, thereby realizing a variable frequency laser device with excellent controllability and response speed. The purpose is to

(Means for Solving the Problems) The present invention relates to a variable frequency laser device that continuously varies the laser output frequency, and its features include a laser light source and an input light source for emitted light from the laser light source. and a phase conjugate mirror that reflects light related to the light emitted from the optical frequency shifter, and the direction of the light emitted from the optical frequency shifter. The structure is configured so that the frequency-shifted light is always emitted in a constant direction by canceling the change in the frequency with a phase conjugate mirror.

(Example) The present invention will be explained in detail below using the drawings.

FIG. 1 is a block diagram showing an embodiment of a variable frequency laser device according to the present invention. 1 is a control circuit consisting of a drive circuit and an oscillation frequency stabilization circuit; 2 is a semiconductor laser light source such as a semiconductor laser with an external resonator that emits narrow frequency width laser light; 3;
numeral 4 is a collimator lens into which the emitted light from the semiconductor laser light source 2 is incident; numeral 4 is an optical isolator for preventing return light into which the emitted light from the collimator lens 3 is incident; 5 is an optical isolator into which the emitted light from the optical isolator 4 is incident; a polarizing prism arranged to emit all the light; 6 constitutes an optical frequency shifter and an ultrasonic modulator into which the light emitted from the polarizing prism 5 enters;
7 is a drive circuit that electrically controls the driving frequency of this ultrasonic modulator 6; 8 is a quarter-wave plate that receives the output light from the ultrasonic modulator 6; and 9 is a phase conjugate mirror; 1/
It is a BaTtO1 single crystal into which the light emitted from the four-wavelength plate 8 is incident. Here, the BaT, 03 single crystal is a nonlinear optical crystal for generating phase conjugate waves. Here, the phase conjugate wave refers to the complex conjugate E1 of the incident light E. 8
In the case of a tO3 single-crystal product, phase) (wave generation is performed by a process called degenerate four-photon mixing.

The operation of the v4 device configured as described above will be explained below. The emitted light from the semiconductor laser light source 2 becomes parallel light by the collimator lens 3, passes through the optical isolator 4, and enters the polarizing prism 5. All of this incident light is emitted from the polarizing prism 5 and enters the ultrasonic modulator 6 as described above. The ultrasonic modulator 6 operates as an optical frequency shifter. That is, if the frequency of the emitted light from the semiconductor laser 2 is ωo1 and the modulation frequency of the ultrasonic modulator 6 is ωS, then the frequency of the first-order diffracted light is ω. +ωS (by appropriately selecting the relationship between the traveling direction of the light and the ultrasound, the arrangement can be made so that ω0−ωS).

The first-order diffracted light diffracted by the ultrasonic modulator 6 passes through a quarter-wave plate 8 to become circularly polarized light and enters a BaTtOs single crystal 9. In the 8aTiOz single crystal 9, a phase conjugate wave is generated by using the light refracted at the cleavage plane as pump light.

This phase conjugate wave returns as reflected light along the same optical path as the incident light.

This light passes through the quarter-wave plate 8 and becomes linearly polarized light with a plane of polarization perpendicular to the incident light, so the ultrasonic modifier WA21
6 and has a frequency of ωo+2ωS, and is reflected by the polarizing prism 5 in the right angle direction to become output light. The direction of the first-order diffracted light of the ultrasonic modulator 6 changes depending on its modulation frequency, but due to its nature, the phase conjugate wave always returns in the opposite direction along the same optical path as the incident light. The exit angle of does not change.

According to the variable frequency laser device having such a configuration, ωS
By electrically changing , it is possible to obtain output light with a frequency of ω0+2ωS at a constant output angle and a constant output.

In the above example, instead of BaT (Ox single crystal), B
One in which an electric field is applied to SO single crystal, and L.

Any material capable of generating phase conjugate waves, such as NbO3 single crystal or Na gas, can be used.

Furthermore, if higher-order diffracted light other than the first-order diffracted light is used as the emitted light from the ultrasonic modulator 6, the amount of frequency shift can be increased.

In addition, light diffraction can be performed by B l agcx diffraction or Raman-
Either Nath scattering may be used.

Further, as the optical frequency shifter, something other than the ultrasonic transducer 5i may be used.

FIG. 2 is a block diagram illustrating a modification of the variable frequency laser device according to the present invention, in which a bomb beam 14 is added to a BaT+03 single crystal 9 from the outside. Reference numeral 10 denotes an external pump light source using a helium laser or the like, and reference numeral 11 denotes a mirror that reflects the light emitted from the external pump light ff110 that has passed through the BaT703 single crystal 9. 1/4 wavelength plate 8 to B
When the incident light 12 that has entered the aTjO31t1 crystal 9 collides with the external pump light 14, it generates a phase conjugate wave 13 and returns again along the same optical path as the incident light.

According to the variable frequency laser device having such a configuration, the loss of pump light is small, so that the reflectance as a phase conjugate mirror can be improved.

In the above modification, a part of the output of the semiconductor laser light source 2 shown in FIG. 1 may be guided by an optical system to be used as external pump light.

(Effects of the Invention) As described above, according to the present invention, the output frequency of a semiconductor laser can be electrically controlled and continuously varied, and a variable frequency laser device with excellent controllability and response speed can be realized with a simple configuration. can do. Also, due to the action of the phase conjugate mirror,
Output light can always be obtained at a constant output angle.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a variable frequency laser device according to the present invention, and FIG. 2 is a block diagram showing a modification of the variable frequency laser device according to the present invention. 2... Laser light source, 6... Optical frequency shifter, 9...
・Phase conjugate mirror.

Claims (2)

[Claims] (1) A variable frequency laser device that continuously varies the laser output frequency includes a laser light source and an optical frequency shifter that can input the emitted light of the laser light source and shift its frequency continuously under electrical control. , and a phase conjugate mirror that reflects light related to the light emitted from the optical frequency shifter, and by canceling changes in the direction of the light emitted from the optical frequency shifter with the phase conjugate mirror, the frequency-shifted light is always reflected. A variable frequency laser device characterized by being configured to emit light in a fixed direction. (2) The variable frequency laser device according to claim 1, which uses an ultrasonic optical modulator as the optical frequency shifter and a nonlinear optical effect element as the phase conjugate mirror.