JP2007322695A - Wavelength conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength conversion element which hardly produces a loss due to absorption of fundamental wave laser and the second higher harmonic wave laser even when the fundamental wave laser of high power density is made incident, has high efficiency of wavelength conversion and is composed of a small number of components. <P>SOLUTION: The wavelength conversion element is provided with: a core made of a nonlinear optical material which converts wavelengths of the inputted fundamental wave laser and generates the second higher harmonic wave laser; a planar waveguide in which the fundamental wave laser is propagated in a free space in the horizontal direction, while being confined in the core in the thickness direction; a filter which is integrally formed on one reflection edge surface of the core, reflects the fundamental wave laser and transmits the second higher harmonic wave laser; and a mirror which is integrally formed on a part of the other side reflection edge surface facing one reflection edge surface of the core and reflects the fundamental wave laser, wherein the filter and the mirror are formed such that the fundamental wave laser inputted into the core is returned in the core by several times and is propagated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wavelength conversion element, and more particularly to a wavelength conversion element used for a light source such as a laser display device or an optical memory device in the field of optical information processing.

In recent years, a visible light laser that can be used as a light source of the three primary colors (blue, green, and red) of a laser display device has been demanded. As this visible light laser, a wavelength conversion laser device for converting the wavelength of a laser beam as a fundamental laser to a second harmonic laser having a half wavelength of the fundamental laser, that is, twice the frequency, by acting on a nonlinear optical material. Is used.
The conventional wavelength conversion laser device has an incident part on which the fundamental wave laser is incident, a reflection surface that reflects the fundamental wave laser and the second harmonic laser of the fundamental wave laser at a predetermined angle from the incident part. A pair of high-reflecting mirror portions that repeatedly reflect incident light rays a plurality of times, an emission portion that emits light rays that are repeatedly reflected between the high-reflecting mirror portions, and light rays that repeatedly reflect between the pair of high-reflection mirror portions Includes a wavelength conversion element that passes through and phase-matches.
A light beam incident at a predetermined incident angle from the incident part is repeatedly reflected a plurality of times between the pair of high reflection mirror parts, and the transmission optical path distance can be extended by passing through the wavelength conversion element in the meantime. Therefore, conversion efficiency can be improved (for example, refer patent document 1).

In addition, another conventional wavelength conversion laser device includes a plurality of wavelength conversion elements sequentially arranged in a beam path of an incident fundamental wave laser, a plurality of condensing means for converging lasers passing through the plurality of wavelength conversion elements, A plurality of beam splitters for changing the beam path of the laser wavelength-converted by the plurality of wavelength conversion elements and separating the laser beam from the fundamental wave laser beam are provided.
Since the fundamental wave laser is focused and incident on the plurality of wavelength conversion elements, a high beam power density of the fundamental wave laser can be obtained in the plurality of wavelength conversion elements, and the conversion efficiency in the plurality of wavelength conversion elements. (For example, refer to Patent Document 2).

JP-A-6-43514 Japanese Patent Laid-Open No. 11-44897

However, since the fundamental laser is repeatedly reflected between the pair of high-reflecting mirror parts and transmitted through the wavelength conversion element between them, the path through which the fundamental laser passes through the wavelength conversion element can be lengthened. Since the efficiency increases in proportion to the power density of the fundamental laser, there is a problem that the conversion efficiency is low when the power density of the incident light is low.
Further, when the laser beam passing through the wavelength conversion element is converged, the beam spot diameter must be adjusted. However, there is a problem that the conversion efficiency is lowered if the aperture angle of the beam is increased due to the phase matching condition.
In addition, since a plurality of wavelength conversion elements and a plurality of condensing means are provided, there is a problem that the number of parts increases and the apparatus is large and expensive.

  An object of the present invention is to provide a wavelength conversion element that has little loss due to absorption of the fundamental laser and second harmonic laser even when a fundamental laser having a high power density is incident, has high wavelength conversion efficiency, and has a small number of components. It is to be.

  The wavelength conversion element according to the present invention has a core made of a nonlinear optical material that converts the wavelength of an input fundamental wave laser to generate a second harmonic laser, and the fundamental wave laser is in a free space in the horizontal direction and has a thickness. A planar waveguide that is confined and propagated in the core in a direction, a filter that is integrally formed on one reflection end face of the core, reflects the fundamental laser, and transmits the second harmonic laser; and the core A mirror that is integrally formed on a part of the other reflection end surface opposite to the other reflection end surface and reflects the fundamental laser, and the filter and the mirror have a fundamental wave laser input to the core. It is formed so as to propagate in a plurality of times in the core.

In the wavelength conversion element according to the present invention, the second harmonic laser having a large power is transmitted to the outside through the filter at one reflection end face, and the action length of the second harmonic laser with the nonlinear optical material is short. Since the absorption of the second harmonic laser is small and the temperature rise of the nonlinear optical material is small, the phase matching can be maintained, and the decrease in wavelength conversion efficiency can be suppressed and stabilized.
Even if the power of the second harmonic laser is increased, the second harmonic laser having a large power is output to the outside through the filter at one reflection end face. The second harmonic laser, which is short and has high power, suppresses the GRIIRA phenomenon, which increases the absorption of the fundamental laser in the nonlinear optical material, reduces the absorption of the fundamental laser, reduces the temperature rise of the nonlinear optical material, and achieves phase matching. Is maintained, and a decrease in wavelength conversion efficiency can be suppressed and stabilized.

Embodiment 1 FIG.
FIG. 1 is a plan view of a wavelength conversion element according to Embodiment 1 of the present invention. FIG. 2 is a side view of the wavelength conversion element according to Embodiment 1 of the present invention.
As shown in FIGS. 1 and 2, the wavelength conversion element according to the first embodiment of the present invention includes a planar waveguide 1, a filter 2 that reflects the fundamental laser 11 and transmits the second harmonic laser 12, and a fundamental wave. A mirror 3 that reflects the laser 11, an antireflection coating (hereinafter referred to as “AR coating”) 4 that prevents reflection of the input fundamental wave laser 11, and a heat radiating plate 6 that exhausts heat generated in the planar waveguide 1. Is provided.
In the planar waveguide 1, the fundamental laser 11 propagates in free space in the horizontal direction and is confined and propagated in the planar waveguide 1 in the thickness direction, and is diffracted multiple times in the planar waveguide 1 by the filter 2 and the mirror 3. Propagate. Further, the second harmonic laser 12 in which a part of the fundamental laser 11 is converted in the planar waveguide 1 is output from a plurality of locations of the filter 2.

The planar waveguide 1 is a parallelogram flat plate and has two reflection end faces on which a filter 2 and a mirror 3 are formed. Further, the planar waveguide 1 has an incident end face that intersects at a right angle with the propagation direction of the fundamental wave laser 11 toward the filter 2 as an entrance of the fundamental wave laser 11 at one corner of the other reflection end face.
The core 7 of the planar waveguide 1 is a thin film made of a nonlinear optical material, and the thickness in the thickness direction is 3 μm. The nonlinear optical material is lithium niobate (hereinafter abbreviated as “LiNbO ₃ ”) to which 5 mol% of magnesium oxide (hereinafter abbreviated as “MgO”) is added. And the photorefractive effect and the optical damage are improved by adding MgO to LiNbO ₃ .

The clad 8 of the planar waveguide 1 is a thin film that contacts both surfaces of the core 7 in the thickness direction. The clad 8 is made of a material having a refractive index smaller than that of the nonlinear optical material constituting the core 7. For example, alumina (hereinafter abbreviated as “Al ₂ O ₃ ”) or silicon dioxide (hereinafter “SiO ₂ ”) is used. Abbreviated). The clad 8 is formed so that both the fundamental laser 11 and the second harmonic laser 12 can propagate in the thickness direction of the core 7 in a single mode (lowest order mode).
In the planar waveguide 1, the phase matching is performed in the propagation direction toward the filter 2 with respect to the fundamental laser 11.

The filter 2 is integrally formed on one reflection end face, and has a reflectivity of 99.5% with respect to the fundamental wave laser 11 traveling from the core 7 to the filter 2 and the second harmonic traveling from the core 7 to the filter 2. The dielectric multilayer film has a reflectance of 0.5% with respect to the laser 12.
The mirror 3 is a dielectric multilayer film that is integrally formed on the other reflection end face excluding the incident end face, and has a reflectivity of 99.5% with respect to the fundamental laser beam traveling from the core 7 to the mirror 3.
The AR coat 4 is a dielectric multilayer film which is integrally formed on the incident end face and has a reflectance of 0.5% with respect to the fundamental wave laser 11 incident from the outside.
The substrate 5 is bonded over the entire surface of one clad 8a, and the planar waveguide 1 is fixed to reinforce the rigidity of the planar waveguide 1.
The heat radiating plate 6 is bonded over the entire surface of the other clad 8b opposite to the one clad 8a and exhausts heat generated in the core 7. Therefore, the heat radiating plate 6 has a high thermal conductivity and a non-linear optical coefficient of thermal expansion. For example, a metal such as copper, a semiconductor such as silicon (Si), or a ceramic such as aluminum nitride (AlN) or silicon carbide (SiC) is used.

  In the planar waveguide 1, the optical path of the fundamental wave laser 11 extends from the incident end face to one of the reflection end faces, and is folded at one of the reflection end faces to be twice a predetermined angle from the propagation direction toward the filter 2 of the fundamental wave laser 11. It inclines and extends to the other reflection end surface, is folded at the other reflection end surface, and extends to one reflection end surface. This is repeated, and a plurality of reflections are made between one reflection end face and the other reflection end face. When the fundamental laser 11 propagates in the propagation direction toward the filter 2 of the fundamental laser 11, the nonlinear optical material acts to partially convert the wavelength to become the second harmonic laser 12.

Next, the operation of the wavelength conversion element according to the first embodiment will be described.
The fundamental laser 11 output from a light source (not shown) is focused only in the thickness direction by a cylindrical lens (not shown) or the like so that the spot diameter in the thickness direction is about 1 μm. Further, the spot diameter in the horizontal direction is about 50 μm, collimated in the horizontal direction, passes through the AR coat 4, and enters the core 7 of the planar waveguide 1. Since the AR coat 4 has a higher transmittance than the fundamental laser 11, the transmission loss of the fundamental laser 11 is small.

The fundamental laser 11 incident on the core 7 of the planar waveguide 1 propagates in free space in the horizontal direction and is confined in the waveguide mode defined by the core 7 and the clad 8 of the planar waveguide in the thickness direction. Propagate. Since the phase matching condition with the nonlinear optical material is met, a part of the fundamental laser 11 is wavelength-converted to become the second harmonic laser 12. In addition, since it collimates and injects in a horizontal direction, the phase matching conditions by an angle can be matched.
In addition, since the thickness direction propagates as a plane wave in the waveguide mode, the phase matching condition according to the angle can be matched.

The fundamental laser 11 that has propagated through the planar waveguide 1 to one reflection end face is folded back by the filter 2 at one reflection end face. One reflection end face is inclined at a predetermined angle from a right angle with respect to the propagation direction of the fundamental laser 11. On the other hand, the second harmonic laser 12 is transmitted through the filter 2 at one reflection end face and output. Note that the filter 2 has a high reflectance with respect to the fundamental laser 11 and a high transmittance with respect to the second harmonic laser 12, and thus the reflection loss of the fundamental laser 11 and the transmission loss of the second harmonic laser 12. There are few.
The fundamental laser 11 that is turned back at one reflection end face propagates through the planar waveguide 1 toward the other reflection end face, but the angle of the nonlinear optical material and the propagation direction of the fundamental laser 11 are shifted. Propagation is carried out with almost no wavelength conversion due to mismatch, and is reflected by the mirror 3 at the other reflection end face.

Since the other reflection end face is parallel to one of the opposing reflection end faces except for the incident end face on which the AR coat 4 is formed, the other reflection end face is parallel to the fundamental wave laser 11 incident from the incident end face. Propagate toward. Since the mirror 3 has a high reflectance with respect to the fundamental laser 11, the reflection loss of the fundamental laser 11 is small.
A part of the fundamental laser 11 propagated toward one reflection end face is converted into a second harmonic laser 12 by wavelength conversion. In this way, the fundamental wave laser 11 reciprocates between the filter 2 and the mirror 3 a plurality of times, and a part of the fundamental wave laser 11 that propagates toward one of the reflection end faces is wavelength-converted second harmonic laser 12. Is transmitted through the filter 2 at one reflection end face and output.

In such a wavelength conversion element, the fundamental wave laser 11 propagating in the planar waveguide 1 has a large collimated beam diameter in the horizontal direction, but propagates in the thickness direction in the mode of the planar waveguide 1 in the thickness direction. Since it is confined in a small beam diameter, the power density of the fundamental wave laser 11 is increased, so that the wavelength conversion efficiency is increased.
Further, since the fundamental wave laser 11 is diffracted a plurality of times within the core 7 made of a nonlinear optical material, the working length becomes longer and the wavelength conversion efficiency becomes higher.
In addition, when an astigmatic difference occurs in the fundamental laser 11, for example, the semiconductor laser diode (LD) has a beam focus position in the horizontal direction and the thickness direction due to a difference in the light confinement state inside the resonator. Astigmatism is slightly deviated, and in the planar waveguide 1 having no waveguide structure in the horizontal direction, the fundamental laser 11 can be efficiently coupled in the thickness direction, and since the horizontal direction is collimated, it is efficient. Wavelength conversion can be performed.
Thus, when the wavelength conversion efficiency is increased, the second harmonic laser 12 having a large power can be obtained.

However, since the light absorption of the second harmonic laser 12 is larger than the light absorption of the fundamental laser 11 in the nonlinear optical material, the second harmonic laser 12 having a large power is absorbed and heat generation is increased, and the nonlinear optics is increased. Since phase mismatch occurs due to a change in the temperature of the material, the wavelength conversion efficiency is conversely reduced.
Further, when the wavelength conversion efficiency is increased and the power of the second harmonic laser 12 is increased, the absorption of the fundamental laser 11 in the nonlinear optical material is increased, thereby causing a Green Induced IR Absorption (hereinafter referred to as “GRIIRA”) phenomenon. As a result, the absorption of the fundamental wave laser 11 is converted into heat, a temperature rise occurs, the phase becomes mismatched due to the temperature change of the nonlinear optical material, and the wavelength conversion efficiency is lowered.

However, in the wavelength conversion element according to the first embodiment, the second harmonic laser 12 having a large power transmitted through the filter 2 at one reflection end face is output to the outside, and the nonlinear optical material of the second harmonic laser 12 Since the second harmonic laser 12 absorbs less and the temperature rise of the nonlinear optical material is small, the phase matching can be maintained and the decrease in wavelength conversion efficiency can be suppressed and stabilized. it can.
Further, even if the power of the second harmonic laser 12 is increased, the second harmonic laser 12 having a high power is transmitted to the outside through the filter 2 at one reflection end face. Is short, the GRIIRA phenomenon is suppressed, the absorption of the fundamental laser 11 is small, and the temperature rise of the nonlinear optical material is small, so that the phase matching is maintained and the decrease in wavelength conversion efficiency is suppressed and stabilized. be able to.

  Further, since the fundamental wave laser 11 and the second harmonic laser 12 propagating through the planar waveguide 1 are close to the heat radiating plate 6, even if heat generation due to light absorption occurs in a relatively wide region, the heat radiating plate from the nonlinear optical material. Exhaust heat to 6 is preferred. Accordingly, heat generation is small due to absorption of the second harmonic laser 12, phase matching is easily maintained, a decrease in wavelength conversion efficiency can be suppressed, and stable acquisition can be achieved.

Further, since the filter 2 and the mirror 3 are integrally formed on the reflection end face of the planar waveguide 1, the fundamental wave laser 11 is reflected by the filter 2 or the mirror 3 and is folded back to the planar waveguide 1, and the propagation mode is maintained as it is. Is maintained, and the reflection loss of the fundamental laser 11 is reduced.
Further, since the filter 2 and the mirror 3 are integrally formed on the reflection end face of the planar waveguide 1, the number of components is small, and the cost can be reduced by downsizing.

In Embodiment 1, magnesium oxide-added lithium niobate (MgO: LiNbO ₃ , Mg: LN) is described as an example of the nonlinear optical material. However, lithium niobate (LiNbO ₃ , LN), lithium tantalate ( The same effect can be obtained even when LiTaO ₃ , LT) or magnesium oxide-added lithium tantalate (MgO: LiTaO ₃ , Mg: LT) is used as the nonlinear optical material.
The nonlinear optical material may be a congruent composition or a stoichiometric composition, and the same effect can be obtained.

Embodiment 2. FIG.
FIG. 3 is a plan view of a wavelength conversion element according to Embodiment 2 of the present invention. FIG. 4 is a side view of a wavelength conversion element according to Embodiment 2 of the present invention.
The wavelength conversion element according to the second embodiment of the present invention is different from the wavelength conversion element according to the first embodiment in the planar waveguide 1B, and the other parts are the same. Is omitted.
Since the planar waveguide 1B according to the second embodiment is different from the planar waveguide 1 according to the first embodiment except for the core 7B, the other parts are the same. To do.

  As shown in FIGS. 3 and 4, the core 7 </ b> B according to the second embodiment has a periodic polarization inversion structure in which the polarization regions 14 and the polarization inversion regions 15 are alternately arranged, and the fundamental wave laser 11. The direction of spontaneous polarization of the ferroelectric material as the nonlinear optical material is periodically reversed with the coherent length as a period in the propagation direction toward the filter 2. Moreover, this ferroelectric substance is a magnesium oxide addition lithium niobate, and is a Z cut board | substrate. The coherent length is 6.6 μm so that the fundamental laser 11 and the second harmonic laser 12 are quasi-phase matched. The polarization direction of the fundamental laser 11 is the thickness direction since the ferroelectric is a Z-cut substrate. Further, by using a Z-cut substrate, it is possible to form a periodically poled structure in a wide range in the horizontal direction.

The phase matching condition in the first embodiment, although the non-linear optical constant is d _13, since the non-linear optical constant is a pseudo phase matching according to the second embodiment is the largest d _33, is highly efficient wavelength conversion laser Realized.

  Then, by forming a comb-like electrode on the + Z cut surface on the ferroelectric Z-cut substrate and applying a strong electric field between the electrodes, the polarization region 14 and the polarization inversion region 15 have a period of coherent length. Alternating structures are formed.

Next, the operation of the wavelength conversion element according to the second embodiment will be described.
The fundamental laser 11 that passes through the tip of the polarization region 14 is partly wavelength-converted to become the second harmonic laser 12, and the second harmonic laser 12 is fundamental when propagating from the tip to the end of the polarization region 14. The phase difference with respect to the wave laser 11 is π. This is because the refractive index of the nonlinear optical material has wavelength dispersion, and the fundamental wave laser 11 and the second harmonic laser 12 have different phase velocities.
On the other hand, the fundamental wave laser 11 that passes through the tip of the domain-inverted region 15 disposed behind the polarization region 14 is partly wavelength-converted to become the second harmonic laser 12, but the second harmonic at this time The phase of the wave laser 12 is reversed so that the phase difference with respect to the fundamental laser 11 becomes π. Then, the wavelength is converted at the tip of the polarization region 14, and the wavelength is converted at the tip of the second harmonic laser 12 that propagates through the polarization region 14 and reaches the back polarization inversion region 15 and the back polarization inversion region 15. The second harmonic laser 12 has a phase difference of π with respect to the fundamental laser 11 at the tip of the domain-inverted region 15.

  When a part of the fundamental laser 11 that passes through the phase-matched planar waveguide 1 is wavelength-converted, the second harmonic laser 12 is different in phase difference by π between the polarization region 14 and the polarization inversion region 15. However, since the phase changes by π when propagating through the previous region, the phases coincide with each other and the second harmonic laser 12 is strengthened.

In such a wavelength conversion element according to the second embodiment, similarly to the wavelength conversion element according to the first embodiment, the fundamental wave laser 11 having a high power density propagates through the planar waveguide 1 a plurality of times to obtain a long working length. Therefore, the wavelength conversion efficiency to the second harmonic laser 12 is increased.
In addition, in the quasi-phase matching type in which the nonlinear optical material has a periodically poled structure, the phase is inverted for each coherent length that is a distance where the phase difference is π, so that the second harmonic laser 12 at each action point is overlapped. Then, the intensity increases additively, and the second harmonic laser 12 having a constant intensity can be transmitted through the filter 2 at one reflection end face and output.

  As in the wavelength conversion element according to the first embodiment, when the direction of spontaneous polarization is uniform, the second harmonic laser 12 generated at each action point propagates with the phase of each harmonic laser 12 shifted. When propagating beyond the coherent length, which is the distance at which the phase difference becomes π, the intensity of the synthesized second harmonic laser 12 decreases, and the increase / decrease is repeated in the period of the coherent length.

In Embodiment 2, magnesium oxide-added lithium niobate (MgO: LiNbO ₃ , Mg: LN) has been described as an example of the nonlinear optical material. However, lithium niobate (LiNbO ₃ , LN), lithium tantalate ( The same effect can be obtained even when LiTaO ₃ , LT) or magnesium oxide-added lithium tantalate (MgO: LiTaO ₃ , Mg: LT) is used as the nonlinear optical material.
The nonlinear optical material may be a congruent composition or a stoichiometric composition, and the same effect can be obtained.

Embodiment 3 FIG.
FIG. 5 is a plan view of a wavelength conversion element according to Embodiment 3 of the present invention. FIG. 6 is a side view of the wavelength conversion element according to Embodiment 3 of the present invention.
The wavelength conversion element according to the third embodiment of the present invention is different from the wavelength conversion element according to the second embodiment in the planar waveguide 1C, and is otherwise the same. Is omitted.
The planar waveguide 1C according to the third embodiment is the same as the planar waveguide 1B according to the second embodiment except for the core 7C, and the other parts are the same. To do.

As shown in FIGS. 5 and 6, the core 7C according to the third embodiment has a period in which the regions 16a, 16b, and 16c in which the polarization regions 14 and the polarization inversion regions 15 are alternately arranged are arranged in an array. It has a domain-inverted structure, and the direction of spontaneous polarization of the ferroelectric material as the nonlinear optical material is periodically reversed with the coherent length as a period in the propagation direction of the fundamental laser 11 toward the filter 2.
The periodic domain-inverted structures arranged in an array are arranged only on the propagation path of the fundamental laser 11 in the propagation direction toward the filter 2 of the fundamental laser 11. The ferroelectric is magnesium oxide-added lithium niobate and is an X-cut substrate. The coherent length is 6.6 μm so that the fundamental laser 11 and the second harmonic laser 12 are quasi-phase matched. In this manner, the fundamental laser 11 having a large aspect ratio in which the horizontal direction of the nonlinear optical material is the Z-axis direction and the polarization direction is the horizontal direction can be used.

Then, a comb-shaped electrode and a counter electrode are formed on a ferroelectric X-cut substrate, and a strong electric field is applied between the electrodes, whereby the polarization regions 14 and the polarization inversion regions 15 alternate with a period of a coherent length. A side-by-side structure is formed.
In particular, in the method of poling an X-cut off-cut substrate with an electric field using a comb-shaped electrode and a counter electrode, the region width of periodic polarization inversion is narrow. The same effect as in the second embodiment can be obtained.

  Further, since the nonlinear optical material is an X-cut substrate, the polarization direction of the fundamental wave laser 11 is the horizontal (Z-axis) direction, and the fundamental wave laser 11 having a large aspect ratio with the polarization direction as the horizontal direction should be used. it can. For example, a semiconductor laser (Laser Diode, LD) that oscillates in the 1 μm band has a planar waveguide structure, the polarization direction is horizontal by the TE mode, and the horizontal direction has a large beam diameter and a small expansion angle. In the thickness direction, the beam diameter is small and the divergence angle is large.

In this way, since the fundamental wave laser 11 has a large beam shape with a long aspect ratio in the horizontal direction by focusing with a cylindrical lens or the like only in the thickness direction, coupling with the planar waveguide 1 wide in the horizontal direction is suitable. Yes.
In addition, by using a wavelength conversion element using an X-cut substrate in which the polarization direction of the fundamental laser 11 is the horizontal (Z-axis) direction, the polarization direction of the wave plate or the like need not be rotated by 90 degrees and used as it is. And can be simplified.

  In the third embodiment, the X-cut substrate made of a nonlinear optical material has been described. However, the effects described in the third embodiment can be obtained even by using a Y-cut substrate made of a nonlinear optical material.

It is a top view of the wavelength conversion element concerning Embodiment 1 of this invention. It is a side view of the wavelength conversion element concerning Embodiment 1 of this invention. It is a top view of the wavelength conversion element concerning Embodiment 2 of this invention. It is a side view of the wavelength conversion element concerning Embodiment 2 of this invention. It is a top view of the wavelength conversion element concerning Embodiment 3 of this invention. It is a side view of the wavelength conversion element concerning Embodiment 3 of this invention.

Explanation of symbols

  1, 1B, 1C planar waveguide, 2 filter, 3 mirror, 4 AR coating, 5 substrate, 6 heat sink, 7, 7B, 7C core, 8a, 8b cladding, 11 fundamental wave laser, 12 second harmonic laser, 14 Polarization region, 15 Polarization inversion region, 16a, 16b, 16c A region in which a polarization region and a polarization inversion region are arranged.

Claims (6)

The core is composed of a nonlinear optical material that generates a second harmonic laser by converting the wavelength of the input fundamental wave laser, and the fundamental laser is confined in the core in the free space in the horizontal direction and in the thickness direction. A propagating planar waveguide;
A filter that is integrally formed on one reflection end surface of the core, reflects the fundamental laser, and transmits the second harmonic laser;
A mirror that is integrally formed on a part of the other reflection end surface facing the one reflection end surface of the core and reflects the fundamental laser;
The wavelength converter according to claim 1, wherein the filter and the mirror are formed such that a fundamental wave laser input to the core propagates by being diffracted a plurality of times in the core.   The wavelength conversion element according to claim 1, wherein the nonlinear optical material has a periodically poled structure.   The wavelength conversion element according to claim 2, wherein the nonlinear optical material is made of lithium niobate, magnesium oxide-added lithium niobate, lithium tantalate, or magnesium oxide-added lithium tantalate.   4. The wavelength conversion element according to claim 2, wherein the nonlinear optical material has a plurality of the periodically poled structures arranged in an array.   The wavelength conversion element according to claim 4, wherein the nonlinear optical material is an X-cut substrate or a Y-cut substrate. A substrate for fixing the planar waveguide;
A heat dissipation plate for exhausting heat generated in the planar waveguide,
The substrate is bonded at one horizontal plane of the planar waveguide,
6. The wavelength conversion element according to claim 1, wherein the heat radiating plate is joined to the other horizontal plane opposite to the one horizontal plane of the planar waveguide.

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