JPH08201863A - Higher harmonic generating apparatus - Google Patents

Abstract

PURPOSE: To prevent the stop of outputs of second higher harmonics owing to the occurrence of thermal expansion or shrinkage of a supporting substrate by alteration of ambient temperature and owing to the alteration of optical length by installing an electromagnetic coil actuator in at least either one of optical parts installed between a semiconductor laser and a resonator. CONSTITUTION: To control the optical length 20 between a semiconductor laser 1 and a resonator 4, a mirror 24 for reflection provided with an electromagnetic coil actuator 25 is inserted between collimator lens 2 and a focusing lens 3. A portion of second higher harmonics 18 separated by a beam splitter 26 comes in a photodiode 27 and are converted into electromagnetic signals and sent to a detector 29. The output signals of the detector 29 are sent to an actuator electric power source 30 as feedback signals 31 of the electromagnetic actuator 25. The electromagnetic coil actuator 25 carries out displacement reflecting the output of the feedback signals 31 and functions as to keep the output of the second higher harmonics 18 stable as a whole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a harmonic generator for converting fundamental wave light emitted from a semiconductor laser into a harmonic by a non-linear optical material.

[0002]

2. Description of the Related Art A plan view of an example of a conventional second harmonic generator is shown in FIG. 3 and a side view thereof is shown in FIG.

The fundamental wave light 16 having a wavelength of 860 nm emitted from the semiconductor laser 1 held by the support 8 enters the resonator 4 via the collimator lens 2 and the focus lens 3. The resonator 4 is composed of a pair of resonance mirrors 5 and 7 and a KNbO ₃ single crystal 6 which is a nonlinear optical material. The fundamental wave light 16 is resonated between the resonance mirrors 5 and 7, and a part of the resonance light 17 is KNbO _3. The single crystal 6 converts the second harmonic light 18 having a wavelength of 430 nm.

In order to generate the second harmonic light 18, it is necessary to control the temperatures of the semiconductor laser 1 and the KNbO ₃ single crystal 6 so as to satisfy the phase matching condition. The temperature of the semiconductor laser 1 is controlled by setting the thermistor 9 and the Peltier device 10 to KN.
The temperature control of the bO ₃ crystal 6 is performed by the driving power supply 15 using the thermistor 12 and the Peltier element 13. The semiconductor laser 1, KNbO ₃ crystal 6, thermistor 9, 1
2. The Peltier elements 10 and 13 are installed and fixed on the substrate 23.

As a technique for stabilizing the output of the second harmonic light 18, a part of the resonant light 17 from the resonator 4 is returned to the semiconductor laser 1 as the return light 19 so that the semiconductor laser 1
The optical feedback control of pulling the optical frequency of 1 to the resonant optical frequency of the resonator 4 is used.

In the case of the optical feedback control, the second harmonic generator is a composite resonator composed of the semiconductor laser 1 and the resonator 4, so that the optical length 20 between the semiconductor laser 1 and the resonator 4 is controlled to be constant. There is a need to. The optical length 2
The position control accuracy required for 0 is 16
Accuracy on the order of wavelength (accuracy of about 0.1 μm) is required.

In order to suppress the fluctuation of the optical length 20 due to the thermal expansion and thermal contraction of the supporting substrate 14, the temperature of the supporting substrate 14 is controlled by the driving power source 15 using the thermistor 21 and the Peltier element 22. The temperature control accuracy of the support substrate 14 at the thermistor position is 0.01 ° C., and copper is used as the material of the support substrate 14 because it has good thermal conductivity. However, the conventional second harmonic generation device has a drawback in that the output of the second harmonic light 18 is stopped by the fluctuation of the ambient temperature of ± 2 ° C.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art. That is, it is an object of the present invention to solve the problem that thermal expansion and contraction of the supporting substrate occur due to the environmental temperature fluctuation of ± 2 ° C., the optical length fluctuates, and the output of the second harmonic light is stopped.

[0009]

The present invention has been made to solve the above-mentioned problems, and is composed of a semiconductor laser as a fundamental wave light source and a plurality of resonance mirrors for resonating the fundamental wave light. A harmonic generator comprising a resonator and a nonlinear optical material provided on the optical axis of the fundamental wave light in the resonator, wherein the semiconductor laser, the resonator, and the semiconductor laser and the semiconductor laser are arranged between the resonator. There is provided a harmonic wave generation device in which an electromagnetic coil actuator is provided in at least one of the optical components.

Since the electromagnetic coil actuator of the present invention has a good responsiveness, it is suitable for position adjustment of a semiconductor laser or the like.

In the present invention, it is preferable that the optical component is a reflection mirror for the fundamental wave light, and an electromagnetic coil actuator is provided on the reflection mirror because the optical lengths of the semiconductor laser and the resonator can be easily adjusted.

As the non-linear optical material, KNbO is used.
₃ , β-BaB ₂ O ₄ , KTiOPO ₄ , KH ₂ PO
₄ , non-linear optical crystals such as LiNbO ₃ and other organic non-linear optical materials can be used, but KNbO ₃ single crystal is preferable in terms of high conversion efficiency to the second harmonic and easy handling of the crystal.

Further, the present invention can be applied not only to the second harmonic but also to a higher harmonic generator such as a third harmonic.

[0014]

The harmonic generator according to the present invention controls the electromagnetic coil actuator by feeding back the electric signal of the harmonic output detected by the light receiving section so that the harmonic output is always constant. It operates so as to adjust the optical lengths of the semiconductor laser and the resonator by the electromagnetic induction effect of.

[0015]

EXAMPLES Examples of the present invention will be described below. 1 is a plan view and FIG. 2 is a side view of a second harmonic generation device according to an embodiment of the present invention. Reference numerals 1 to 20 are the same as those in FIGS. 3 and 4 showing the conventional example.

Optical length 20 of semiconductor laser 1 and resonator 4
In order to control the above, a reflection mirror 24 having an electromagnetic coil actuator 25 added is inserted between the collimator lens 2 and the focus lens 3. Beam splitter 26
A part of the second harmonic light 18 separated by is incident on the photodiode 27, converted into an electric signal, and input to the detector 29. The output signal of the detector 29 is input to the actuator power supply 30 as the feedback signal 31 of the electromagnetic coil actuator 25. The electromagnetic coil actuator 25 performs a displacement corresponding to the output of the feedback signal 31, and functions so that the output of the second harmonic light 18 becomes constant as a whole.

The semiconductor laser 1 is a rated 100 mW single mode laser with a wavelength of 860 nm, and the non-linear optical material is a KNbO ₃ single crystal 6 having a length of 5 mm and an antireflection film having a fundamental wave reflectance of 1% or less. used. The resonance mirror 5 is provided with a reflection film having a radius of curvature of 10 mm and a reflectance of the fundamental wave of 95%, and the resonance mirror 7 is similarly provided with a radius of curvature of 10 mm and a reflectance of the fundamental wave of 99%.
The one provided with the reflective film of was used. As the photodiode 27, a Si photodiode is used.

From the above examples, an optical output of 6.2 mW at a wavelength of 430 nm was obtained as the output of the second harmonic light 18. As for output stability, as a result of changing the environmental temperature fluctuation from 25 ° C to 45 ° C at a rate rate of 1 ° C / min, the output of the second harmonic light 18 remained stable from 6.2mW to 5.9mW and fluctuated. The width was stable within 5%. Moreover, the stop of the output of the second harmonic light 18 was not recognized even in response to mechanical vibration.

[0019]

The second harmonic generator according to the present invention has the following effects.

(1) The output of the second harmonic light is more stable than that of the conventional second harmonic generator even when the ambient temperature changes and mechanical vibrations occur.

(2) Since it is not necessary to control the temperature of the supporting substrate in the second harmonic generator as in the conventional case, the temperature control system can be simplified.

(3) The starting time can be shortened as compared with the conventional second harmonic generator.

[Brief description of drawings]

FIG. 1 is a plan view of a second harmonic generation device according to an embodiment of the present invention.

FIG. 2 is a side view of a second harmonic generation device according to an embodiment of the present invention.

FIG. 3 is a plan view of a conventional second harmonic generator.

FIG. 4 is a side view of a conventional second harmonic generator.

[Explanation of symbols]

1: Semiconductor Laser 2: Collimating Lens 3: Focus Lens 4: Resonator 5: Resonant Mirror 6: Nonlinear Optical Material (KNbO ₃ Single Crystal) 7: Resonant Mirror 8: Support 9: Thermistor 10: Peltier Element 11 : Supporting tool 12: Thermistor 13: Peltier element 14: Support substrate 15: Driving power supply 16: Fundamental wave light 17: Resonance light 18: Second harmonic light 19: Return light 20: Optical length 21: Thermistor 22: Peltier element 23 : Substrate 24: Reflecting mirror 25: Electromagnetic coil actuator 26: Beam splitter 27: Photodiode 28: Photodiode power supply 29: Detector 30: Actuator power supply 31: Feedback signal

Claims (2)

[Claims] 1. A semiconductor laser which is a fundamental wave light source, a resonator comprising a plurality of resonance mirrors for resonating the fundamental wave light, and a non-linear optical material provided on the optical axis of the fundamental wave light in the resonator. In a higher harmonic wave generating device comprising: a semiconductor laser, the resonator, and at least one of the optical components arranged between the semiconductor laser and the resonator, an electromagnetic coil actuator is provided. Harmonic generator. 2. The harmonic generator according to claim 1, wherein the optical component is a reflection mirror for fundamental wave light, and the reflection mirror is provided with an electromagnetic coil actuator.