JPH0618950A - Higher harmonic generator - Google Patents

Abstract

PURPOSE:To improve the output and efficiency of the second harmonic generator and to enable miniaturization and operation stable over a long period of time by providing a laser beam source which oscillates at a specific mode and a monolithic type resonator. CONSTITUTION:A laser beam of 860nm wavelength, a single mode or single transverse mode and decreased astigmatisms is emitted from a semiconductor laser diode(LD) 12. This laser beam is made incident as a basic wave 29 on the monolithic type resonator 15 provided in proximity at <=1.5mm distance. While the basic wave 29 may be a circular beam or elliptic beam, the basic wave having a small spreading angle is more preferable. The basic wave 29 is made incident on the inside of the monolithic type resonator 15 from the incident point A on a spherical mirror 15b and is amplified as resonance light 30 by ring resonation in the monolithic type resonator 15. The resonance light 30 is partly converted to a second higher harmonic wave 50 of 430nm wavelength when the light propagates toward the crystal axis (a) in the nonlinear optical crystal 15. This second higher harmonic wave 50 is emitted from a spherical mirror 15C on the exit side.

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 a fundamental wave emitted from a laser light source into a second or third harmonic within a monolithic resonator containing a non-linear optical material.

[0002]

2. Description of the Related Art In recent years, various devices have been proposed for obtaining a second harmonic wave or a third harmonic wave whose wavelength is converted by passing a fundamental wave emitted from a semiconductor laser or the like through a nonlinear optical material. In these devices, a nonlinear optical material is arranged in a resonator composed of a plurality of reflecting surfaces, and a fundamental wave is confined in the resonator to be amplified so that harmonics are efficiently generated.

As the resonator, a monolithic resonator in which an end surface of a non-linear optical material is processed into a spherical shape or the like, a reflection film is further provided, and a resonance is caused therein, and a resonator in which a plurality of mirrors are arranged are arranged. And an external resonator in which a nonlinear optical material is arranged in the resonator is known.

Recently, in order to miniaturize the device and improve the conversion efficiency to higher harmonics, the external resonator type is changed to the monolithic type in which the fundamental wave is resonated inside the nonlinear optical material. Mainstream is shifting.

FIG. 13 shows a second harmonic generation device 11 using a monolithic resonator 5 as an example of the prior art. The second harmonic generation device 11 includes a laser light source, a collimator lens 3, a mode matching lens 4, and a K.
The monolithic resonator 5 is made of a non-linear optical material such as NbO ₃ crystal. The monolithic resonator 5 has its end surface polished into a spherical shape, and is further provided with mirrors, and a spherical mirror 5b and a spherical mirror 5c are provided.
Have and. One spherical mirror 5b is used as an incident end face, and the remaining spherical mirrors 5c are used as emission end faces.

The laser light source emits a fundamental wave 28 having a wavelength of 860 nm, for example. The fundamental wave 28 is collimated by the collimator lens 3, passes through the mode matching lens 4, and becomes incident light 28a. The incident light 28a is incident on the incident end face at a predetermined incident angle θ so as to satisfy the resonance condition.

Inside the monolithic resonator 5, a ring-shaped path (a triangular reflection path connecting A, B and C) composed of two spherical mirrors 5b and 5c and a plane mirror 5a is formed. The light is amplified as the resonance light 30 while passing through in order. The spherical mirror 5c has a property of reflecting the resonance light 30 and transmitting the second harmonic wave 50.
It is used as an emitting end face of the harmonic wave 50. The plane mirror 5a totally reflects both the resonance light 30 and the second harmonic wave 50. In this case, the resonance light 30 must be phase-matched between the incident light 28a and the resonance light 30 when traveling parallel to the crystal axis a inside the monolithic resonator 5.

When the resonance light 30 passes through the inside of the monolithic resonator 5 in the direction of the crystal axis a of the nonlinear optical material, that is, in the direction A to B in the figure, a part of the resonance light 30 has a wavelength of 430 nm. It is converted into the second harmonic wave 50 and emitted from the point B of the spherical mirror 5c. In order to meet the phase matching condition and stabilize the harmonic conversion efficiency, a temperature control device is provided on the plane portion (for example, reference numerals 5d and 5a) of the monolithic resonator 5 to control the temperature by a Peltier element or the like.

In this conventional example, the distance from the laser light source to the monolithic resonator is about 50 mm to 200 mm.
Have a distance of about. It has been known that the beam spot on the incident end surface of the monolithic resonator is about 25 μm. In this way, since the optical path length to the monolithic resonator 5 is long and the optical lens system is used,
The phase of the incident light 28a on the incident end face that is resonantly coupled is disturbed as compared with the optimum condition, and the wave front is also disturbed in some cases.

Although not a second harmonic generator, a semiconductor laser device having a structure in which an optical coupling system between a light source and a solid-state laser medium is omitted is also known. For example, as in Japanese Patent Laid-Open No. 3-292784, there is also a structure in which a semiconductor laser as a light source is placed in close contact with or in the vicinity of a solid-state laser medium to prevent diffusion of the semiconductor laser light without using a condenser lens.

Similarly, there is JP-A-4-62880 as an example of a semiconductor laser device in which a lens is omitted. The characteristic is that a laser medium for exciting a laser is mixed with a material for generating a higher harmonic wave to generate a higher harmonic wave in addition to the function of laser oscillation.

However, these techniques utilize the direct absorption and stimulated emission of energy into the laser medium to excite laser light (laser oscillation). The physical positional accuracy between the laser light source and the solid-state laser medium has a wide tolerance. It was difficult to directly apply this to a monolithic oscillator for a harmonic generator that requires precise phase matching.

[0013]

In the above-described second harmonic generator, when a high-power laser light source is used, the laser emitted from the monolithic resonator 5 in order to satisfy the resonance condition at the incident end face thereof. The light (fundamental wave 28) had to be adjusted by an optical lens system. because,
This is because the fundamental wave 28 could not be directly incident due to various characteristics (for example, laser light aperture due to diffraction, phase disturbance, etc.).

For example, since the aperture of the fundamental wave 28 emitted from the laser light source and the aperture of the resonant light 30 are greatly different at the incident end face of the monolithic resonator 5, the optical lens system for coupling them is as follows. The length from the laser light source to the incident point A is as large as 50 mm to 200 mm.

Further, for phase matching at the incident point A,
The assembly of the optical lens system and the alignment with the monolithic resonator 5 required an accuracy of several μm. Therefore, it has been desired to solve these problems in order to make a practical harmonic generator.

[0016]

According to the present invention, there are provided two or more end faces through which resonance light passes, which are made of a non-linear optical material, and a resonance path of the resonance light passing through the two or more end faces is a reciprocating type. Alternatively, a circular type is provided, and one of the end faces includes a monolithic resonator having an incident end face on which incident light is incident, and a laser light source that oscillates in a single longitudinal mode or a single transverse mode. In the harmonic generation device in which the harmonic wave converted from is emitted from any one of the end faces, the laser light emitted from the laser light source becomes incident light without passing through the solid lens, and 1.
The incident light that is made incident with a beam spot having a size of 5 mm or less and that has entered the inside of the monolithic resonator is passed through the resonance path to become resonance light, and the light flux of the resonance light at the incident end face and the incident light Provided is a harmonic wave generating device characterized by being resonantly coupled to a beam spot.

Further, there are provided two or more end faces through which the resonance light passes, which is made of a non-linear optical material, and the resonance path of the resonance light passing through the two or more end faces is provided in a reciprocating type or a circulating type. One of the end faces includes a monolithic resonator having an incident end face on which incident light is incident, and a laser light source that oscillates in a plurality of modes, and harmonics converted from the resonant light are emitted from any of the end faces. In the harmonic generation device, the laser light emitted from the laser light source becomes incident light without passing through the solid lens and is incident on the incident end face with a beam spot having a size of 1.5 mm or less. The incident light that has entered the inside of the container is passed through the resonance path to become resonance light, and the luminous flux of the resonance light at the incident end face and the beam spot of the incident light are resonantly coupled. Because is it in, and part of the resonant light oscillation of the laser light source is fed back to the laser light source to provide a harmonic generator characterized by comprising been brought stably.

[0018]

The harmonic generator of the present invention eliminates the optical lens system such as the lens for focusing the laser light and the mode matching lens which have been used conventionally, and does not give a large convergence to the laser light of the laser light source. Is incident on the monolithic resonator.

Resonant light generated inside the monolithic resonator and incident light are resonantly coupled at the incident end face. Since there is no optical lens system, spherical aberration due to it,
Phase disturbance etc. does not occur in the incident light. Also, the matching of the wavefront of the incident light is improved.

Further, the loss of the laser light in the optical lens is naturally eliminated, and a larger power can be input. Further, the most difficult and important phase matching in the harmonic generator can be adjusted only by the positional relationship between the monolithic resonator and the laser light source. Especially, it suffices to just assemble it around the axis deviation at the incident point A.

Further, since the laser light source is arranged in the vicinity of the monolithic resonator and more preferably fixed integrally with the monolithic resonator, it can be expected to operate stably against mechanical vibration. . Mechanical displacement is unlikely to occur.

[0022]

【Example】

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention. The second harmonic generation device 1 is composed of a semiconductor laser diode 12 (hereinafter abbreviated as LD) and a monolithic resonator 15 as a laser light source.

In this embodiment, the LD 12 has a wavelength of 860n.
m, a single longitudinal mode or a single transverse mode, which emits laser light with little astigmatism is used. Here, the single longitudinal mode means that the frequency spectrum of the laser light has one remarkable peak, and the single transverse mode means that the spatial spread is unimodal. And the fundamental wave 2
It is incident on the monolithic resonator 15 as 9. The fundamental wave 29 may be a circular beam or an elliptical beam, but a beam with a small divergence angle is desirable. The LD 12 and the monolithic resonator 15 are provided close to each other at a distance of 1.5 mm or less. In this embodiment, they are provided at a distance of 1 mm.

In practice, in order to generate usable harmonics, the beam spot at the incident end face should be 10 μm or less. Desirably, a beam spot with a range of 5 to 10 μm is preferable, and a more efficient resonance condition can be satisfied in this range. The distance between the LD12 and the monolithic resonator 15 and the beam spot at the incident end face are LD1
It is related to the performance of 2. If the spread angle is small, the LD 12 can be provided at a relatively long distance.

If the beam spot size is 5 μm or less, it becomes difficult to match the resonance path at the incident end face of the monolithic resonator in manufacturing, and loss and phase disturbance in the nonlinear optical material cannot be ignored. It becomes difficult to satisfy the resonance condition. However, when a laser light source having a high beam spot convergence and a high output is used, it is slightly difficult to manufacture, but it becomes possible to resonate at a beam spot of less than 5 μm, and a harmonic of a narrow beam diameter is obtained. Output can be achieved. For example, a thickness of 2 μm is also possible.

The size of the beam spot usually indicates its radius, but the radius may be equivalently indicated. For example, even an elliptical beam has a size corresponding to the optical surface, that is, a size that fits into an effective curved surface of the incident optical surface, and can be effectively used if it can resonate.

The monolithic resonator 15 uses KNbO ₃ as a nonlinear optical crystal. At least a part of the one end face is processed into a spherical shape, and a reflection film that reflects 92% of the fundamental wave 29 and the resonance light 30 having the same frequency as the fundamental wave 29 is vapor-deposited to form the spherical mirror 15b. At least a part of the other end face is also processed into a spherical shape, reflects 99% or more of light in the same frequency band as the fundamental wave 29, and makes the second harmonic of the fundamental wave approximately 8%.
A spherical mirror 15c is formed by depositing a reflective film that transmits 0% or more.
Are formed. The material of the spherical mirror is basically the same as that of the conventional example.

Further, the lower surface of the monolithic resonator 15 which is ring-shaped and constitutes a part of the resonance path constituted by the circulation of the resonance light 30 is cut into a plane along the crystal axis a to obtain the fundamental wave and A plane mirror 15a that totally reflects the second harmonic is formed. In this case, total reflection of resonance light by crystals may be used.

The length of the monolithic resonator 15 in the direction of the crystal axis a (the distance between A and B in the figure) is 7 m.
m, the radius of curvature of the two spherical mirrors is 5 mm. With this size and shape, a resonance condition can be achieved by direct laser input from the LD 12. A temperature controller is provided on the plane 15d to perform phase matching by temperature control.
Phase control by temperature is generally used, but other methods may be used.

In the second harmonic generation device 1, L
The fundamental wave 29 having a wavelength of 860 nm is emitted from D12. Here, the fundamental wave 29 means that it is composed of a fundamental frequency component with respect to a target harmonic wave. Basic wave 2
Light 9 is incident on the monolithic resonator 15, and is incident on the inside of the monolithic resonator 15 from an incident point A on the spherical mirror 15b. Then, inside the monolithic resonator 15, the fundamental wave 29 becomes the resonant light 30 and is ring-resonated and amplified.

The resonant light 30 is the nonlinear optical crystal 15
When propagating in the crystal axis a direction, a part of the wavelength 43
Converted to 0 nm second harmonic 50. This second harmonic wave 50 is emitted from the spherical mirror 15c on the emission side.

(Embodiment 2) FIG. 2 shows a second embodiment.
The LD 12 and the monolithic resonator 15 are the same as in the first embodiment. The LD 12 and the monolithic resonator 15 are fixed with a transparent adhesive 13 such as an ultraviolet curable resin. L
Incident light having a fundamental frequency emitted from D12 passes through the transparent adhesive 13 and is incident on the monolithic resonator 15 (incident light is not shown). Between the laser light source and the monolithic resonator 15, a medium having a specific refractive index close to the refractive index of the nonlinear optical material and transparent to incident light that is laser light is provided.

The refractive index of an optically transparent resin material is
Various types from about 1.4 to 1.7 are known. Among them, a material having a refractive index close to that of the nonlinear optical material is selected. As a result, the LD 12 and the monolithic resonator 15
It was possible to obtain a higher output of the second harmonic as compared with the case where a gas (air or an inert gas such as nitrogen) was provided between the two (in the case of the first embodiment). The reason is shown below.

FIG. 3 shows a state where the laser light source and the monolithic resonator 15 are mismatched. The laser light emitted from the laser light source is widely opened as incident light and reaches the incident end face. On the other hand, the luminous flux at the incident end face of the resonance light 30 generated inside the monolithic resonator 15 is small. In this case, stable resonance is very difficult, and efficient oscillation cannot be expected. That is, the monolithic resonator 15 for generating harmonics
In order to efficiently resonate the laser light from the LD 12, the difference between these two light fluxes should be made as small as possible.

As an example for this purpose, there is a means for reducing the distance between the LD 12 and the monolithic resonator 15. However, although the difference between the light fluxes can be reduced, it is actually difficult to set the distance to 0.2 mm or less in terms of manufacturing accuracy. Unless highly accurate assembly technology and optical adjustment are performed, the luminous flux of the incident light emitted from the LD 12 will be much wider than the luminous flux of the resonance light 30.

FIG. 4 shows an LD 12 and a monolithic resonator 1.
This is the case where the space between 5 is filled with the transparent adhesive 13. Since the refractive index of the transparent adhesive 13 is larger than that of air (which is almost equal to the refractive index in a vacuum) (for example, n = 1.5), FIG.
The spread of the light flux of the fundamental wave 29 was smaller than that of the above, and the resonant light 30 could be efficiently resonated inside the monolithic resonator 15. The transparent adhesive 13 is LD1
2 and the monolithic resonator 15 are integrally fixed. The value of the refractive index is preferably in the range of 1.4 to 1.7. This is because if it is too large, the characteristics of the incident laser light change. Further, it is necessary that the refractive index of the nonlinear optical material is not exceeded.

Further, it becomes possible to match the size of the desired light flux. It has a function as a light guide up to the incident end surface (spherical mirror portion) of the fundamental wave 29 and also functions as a fixing member. In this case, the position of the transparent adhesive 13 can be adjusted by gradually hardening the transparent adhesive 13 while performing the harmonic generation operation. An optically homogeneous adhesive is desirable as the transparent adhesive.

Actually, refraction of the laser light occurs at the first interface between the emitting end of the LD 12 and the transparent adhesive 13 and at the second interface between the transparent adhesive 13 and the incident end face of the monolithic resonator 15. sell. In this case, the first interface and the second interface are surfaces through which the laser light always passes, and are the same as when a solid lens is used. Therefore, it can be said that the characteristics of the laser light are relatively not adversely affected in the case of the present invention by the influence of the laser light on these interfaces.

(Embodiment 3) FIG. 5 shows a third embodiment.
The monolithic resonator 25 is composed of two planes in which light is reflected and one spherical surface. One plane is the incident surface itself, and the other is the total internal reflection surface. The spherical surface is the exit surface of harmonics. The luminous flux of the resonance light 30 is shown in FIG. The illustration of the laser light emitted from the LD 12 is omitted. In this embodiment, the radius of curvature of the spherical surface is 5 mm, and the length of the monolithic resonator 25 in the crystal axis a direction is 4.5 mm (approximately the length from the incident point to the outgoing point). The LD 12 is provided close to the monolithic resonator 25 at a distance of approximately 0.5 mm. At this time, the diameter of the resonant light 30 on the incident end face is several μm.

General LD used for harmonic generator
In the case of No. 12, the diameter of the light flux of the laser light on the light emitting surface is about several μm, which is almost the same as the diameter of the resonance light 30 inside the monolithic resonator 25, so that the LD 12 and the monolithic resonator 25 are connected to each other. By providing them so close to each other, it is possible to make light enter very efficiently. Further, the wavefront of the emitted laser light can be matched with the resonance light 30 as it is.

FIG. 6 is shown as a comparative example. this is,
This is a case where a resonator having a standing type resonance mode is used. In this standing configuration,
In the monolithic resonator 35, one spherical surface is used as an emitting surface and one flat surface is used as an incident surface.
Is reciprocally reciprocated between the reflection surface inside the laser light source and the spherical surface (emission surface of higher harmonic wave) of the monolithic resonator 35 to be multiplied. In this case, it is difficult to make the resonant light a certain size or more.

(Embodiment 4) FIG. 7 shows a fourth embodiment.
The monolithic resonator 16 includes the spherical mirror 16b, the spherical mirror 16c, and the plane mirror 1 as in the first embodiment.
6a, but with a spherical surface having a radius of curvature of 5 mm and a length in the crystal axis a direction of 9.3 mm, the diameter of the light flux of the resonant light 30 on the incident surface is 1 m.
It spreads over m. Therefore, even if the distance between the incident surface and the LD 12 is widened to about 1 mm, high coupling efficiency between the fundamental wave 29 and the resonant light 30 as incident light was obtained. In this case,
A sufficient physical distance can be provided between the LD 12 and the monolithic resonator 16, which is advantageous in manufacturing.

(Embodiment 5) FIG. 8 shows a fifth embodiment.
The monolithic resonator 17 has a spherical mirror 17b, a spherical mirror 17c, and a plane mirror 1 as in the first embodiment.
7a has a similar shape, but has an entrance surface provided with a spherical mirror 17b or an exit surface provided with a spherical mirror 17c and a plane mirror in order to increase the reflection angle on the entrance surface and the exit surface. The distance from the total reflection surface provided with 17a is long.

Therefore, the light flux of the resonance light 30 is weakly focused between the spherical mirror and the total reflection plane mirror than between the spherical mirrors. In such a case, the efficiency of oscillation was improved by making the fundamental wave 29, which is the incident light from the LD 12, enter in the direction of the total reflection surface. In this embodiment, both the case where the LD 12 and the monolithic resonator 17 are close to each other (about 1 mm) and the case where they are closely contacted (0.2 mm or less) are possible.

(Embodiment 6) FIG. 9 shows a sixth embodiment.
The monolithic resonator 18 has an incident end face having a convex curved surface, and further has a planar shape, and has an end face that emits the harmonic wave 50 and reflects the resonant light 30 to the inside. LD1
The fundamental wave 29 emitted from No. 2 is incident on the incident end face. In this case, the incident angle is 0 degree. Therefore, a part of the resonant light 30 reaches the LD 12 as the return light 40. The resonance light 30 linearly reciprocates between the incident end face and the emitting end face. This type of harmonic generator has a simple structure and is easy to manufacture. In this embodiment, the LD12
And the distance between the monolithic resonator 18 and 1 mm,
The beam spot on the incident end face was 10 μm.

(Embodiment 7) FIG. 10 shows a seventh embodiment. The monolithic resonator 19 includes an incident end face having a convex curved surface, is flat, and has two end faces that emit the harmonic wave 50 and reflect the resonance light 30 to the inside.
The fundamental wave 29 emitted from the LD 12 is incident on the incident end face. In this case, the incident angle is set to a predetermined incident angle that satisfies the resonance condition.

The resonance path of the resonance light 30 is V-shaped. Resonance is achieved by the resonant light 30 linearly (V) passing through this V-shaped resonance path. This is also a non-ring type, that is, a reciprocating type resonance path. A part of the resonance light is converted into the harmonic wave 50 in relation to the crystal axis of the nonlinear optical material. Since this type of harmonic generator has only one convex curved surface, it is relatively easy to manufacture and is advantageous in that respect. Also, by combining with a non-linear optical material, it is possible to output two or more harmonics 50 at the same time.

In this example, the distance between the LD 12 and the monolithic resonator 19 was 0.8 mm, and the beam spot on the incident end face was 0.15 mm.

(Embodiment 8) FIG. 11 shows an eighth embodiment. The monolithic resonator 20 has two convex curved end faces. These are confocal
This is called the end face shape of the mold. In this case, the relationship between the radius of curvature R of both end faces and the length of the monolithic resonator 20, that is, the length L of the crystal axis length is L = R / 2. The resonance path is substantially V-shaped, as in the seventh embodiment.

Resonant coupling between the fundamental wave 29 which is the incident light and the resonant light 30 is stronger than that in the seventh embodiment because the end face opposite to the incident end face is similarly formed by the convex curved surface. . Further, the resonance light 30 can be narrowed to a narrower light flux. In this example, the distance between the LD 12 and the monolithic resonator 20 was 2 mm, and the beam spot on the incident end face was 1 mm.

(Ninth Embodiment) FIG. 12 shows a ninth embodiment. The monolithic resonator 21 has one convex curved end face and two planar end faces. In the present embodiment, resonance is established by the resonance light 30 circulating in a triangular ring-shaped resonance path. The other constituent features are the same as those in the above-described embodiment. In this example, the distance between the LD 12 and the monolithic resonator 21 was 0.5 mm, and the beam spot on the incident end face was 8 μm.

The L used in the embodiment described above
As the D12, a single longitudinal mode or a single transverse mode is exemplified, but using an LD that oscillates in a plurality of modes,
By feeding back a part of the resonant light from the monolithic resonator to the LD, the oscillation of the LD can be stabilized. Such a configuration is possible. This is because light having the same frequency as the fundamental wave can travel backward in the optical path from the LD as the light source to the incident end surface and further to the resonance path. The multiple modes include a plurality of vertical modes or a plurality of horizontal modes.

The shape of the resonance path will be described. It is generally known that a ring-shaped resonance path through which resonance light circulates has higher resonance stability than a reciprocating resonance path. In terms of manufacturing, the reciprocating type is advantageous. In terms of output power, it is determined by the characteristics of the LD 12 used and parameters such as phase matching conditions. Uniquely, it cannot be said that which type has high output.

However, a high output can be obtained by optimizing the incident light from the LD 12 and the resonant coupling at the incident end face. It is necessary to introduce the light into the monolithic resonator without causing the loss of the incident light and without causing the phase disturbance, and further to suppress the loss inside the resonator to a predetermined value or less.

Although KNbO ₃ is exemplified as the nonlinear optical material in the above embodiments, the present invention is not limited to this, and other materials such as LiNbO ₃ and β-BBO, A are used.
DP, CDA, RDP, RDA, KDP, KTP, LB
Non-linear optical materials such as O and MNA can be used.
Further, although the embodiment has been described with respect to the generation of the second harmonic, the present invention is not limited to the second harmonic generator, and may be applied to a second or higher order, for example, a third harmonic generator. You can also

[0056]

According to the present invention, an ultra-compact and highly efficient second device is provided.
A harmonic generator is obtained. It can be used as a laser light source of a short wavelength (blue to green wavelength band) of various electronic devices.

For example, when an information reading device for an optical recording medium is constructed by using the second harmonic generation device as a light source for information detection, recording is performed using the second harmonic output of high output and high efficiency. Not only can a high-density device be obtained, but an extremely small harmonic generator can be obtained. Further, since there is no intermediate optical system such as a lens for which fine adjustment of assembly is difficult, manufacturing is easy. It can be said that it has become more mechanically robust.

It has become possible to use it in a portable device or in an environment where long-term stable operation is desired. Further, since the oscillation efficiency is improved, it is possible to operate with a small power source or the like, and to provide an energy-saving device.

Further, the output of higher harmonics was increased. It is possible to generate the second harmonic of at least 1 mW or more, and preferably about 2 mW. By using such a second harmonic generation device, the fundamental wave can be efficiently converted into a harmonic wave.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment.

FIG. 2 is a block diagram showing a second embodiment (basic configuration).

FIG. 3 is a block diagram showing a comparative example (mismatch state).

FIG. 4 is a block diagram showing a second embodiment (operating state).

FIG. 5 is a block diagram showing a third embodiment.

FIG. 6 is a block diagram showing a comparative example (standing type resonator).

FIG. 7 is a block diagram showing a fourth embodiment.

FIG. 8 is a block diagram showing a fifth embodiment.

FIG. 9 is a block diagram showing a sixth embodiment.

FIG. 10 is a block diagram showing a seventh embodiment.

FIG. 11 is a block diagram showing an eighth embodiment.

FIG. 12 is a block diagram showing a ninth embodiment.

FIG. 13 is a block diagram showing a conventional example.

[Explanation of symbols]

 1: Second harmonic generation device 12: LD 15: Monolithic resonator 15b: Spherical mirror (incident end face side) 15c: Spherical mirror (emission end face side) 15a: Flat mirror (total reflection face) 29: Fundamental wave 30: Resonant light 50: Second harmonic

Claims (6)

[Claims] 1. A non-linear optical material is provided with two or more end faces through which resonance light passes, and a resonance path of the resonance light passing through the two or more end faces is provided in a reciprocating type or a circulating type. One of the end faces includes a monolithic resonator having an incident end face on which incident light is incident, and a laser light source that oscillates in a single longitudinal mode or a single transverse mode, and the harmonics converted from the resonant light are In the harmonic wave generating device emitted from any of the end faces, the laser light emitted from the laser light source becomes incident light without passing through a solid lens and becomes a beam spot with a size within 1.5 mm on the incident end face. The incident light that has been made incident and has entered the inside of the monolithic resonator is made to pass through the resonance path to become resonance light, and the luminous flux of the resonance light at the incident end face and the beam spot of the incident light are reflected. DOO harmonic generator, characterized in that are thus allowed to resonant coupling. 2. A non-linear optical material is provided with two or more end faces through which resonance light passes, and a resonance light resonance path passing through the two or more end faces is provided in a reciprocating type or a circulating type. One of the end faces includes a monolithic resonator having an incident end face on which incident light is incident, and a laser light source that oscillates in a plurality of modes, and harmonics converted from the resonant light are emitted from any of the end faces. In the harmonic generation device according to the first aspect, the laser light emitted from the laser light source becomes incident light without passing through the solid lens, and 1.
The incident light that is made incident with a beam spot having a size of 5 mm or less and that has entered the inside of the monolithic resonator is passed through the resonance path to become resonance light, and the light flux of the resonance light at the incident end face and the incident light A harmonic generation device characterized in that it is resonantly coupled with a beam spot, and part of the resonant light is fed back to the laser light source to stabilize the oscillation of the laser light source. 3. The harmonic generator according to claim 1, wherein the laser light source and the monolithic resonator are provided close to each other within 1.0 mm, and the size of the beam spot is A harmonic generation device characterized in that it is approximately 10 μm or less. 4. The harmonic generator according to claim 1, wherein the laser light source and the monolithic resonator are provided close to each other at a distance of 1 to 3 mm, and the beam spot has a size of , A harmonic generator having a range of approximately 0.1 to 1.5 mm. 5. An optically transparent medium for passing the laser beam is continuously provided between the laser light source and the monolithic resonator, and the relative refractive index of the medium is 1.4 to.
The harmonic generation device according to claim 1, wherein the harmonic generation device is 1.7. 6. The harmonic generator according to claim 5, wherein the medium is a laser light source and a monolithic resonator fixed to each other.