JPH06102553A - Optical wavelength conversion element and short wavelength laser beam source - Google Patents

Abstract

PURPOSE:To stably output and modulate the higher harmonic waves emitted from the optical wavelength conversion element constituted by using a nonlinear optical effect. CONSTITUTION:Electrodes 15 are formed on an optical waveguide 2 of the optical wavelength conversion element constituted by forming polarization inversion layers 3 and the optical waveguide 2 on an LiTaO3 substrate 1. The output light of an SHG (second harmonic wave generating element) is stabilized by impressing the electric field by the electrodes 15 to the above-mentioned optical wavelength conversion element. The output of the SHG is modulated to multiple stages by dividing the electrodes and controlling the respective voltages. Then the stable operation is executed by changing the voltage to be impressed to the optical wavelength conversion element even if the environmental temp. changes and the wavelength of a semiconductor laser changes. The phase matching states under the respective electrodes are controlled by dividing the electrodes and, therefore, the high-speed modulation of the output in multiple stages is possible. In addition, the integration of the modulating mechanisms on the optical wavelength conversion element is possible and, therefore, the small-sized light source is constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength conversion device and a short wavelength laser light source used in the field of optical information processing utilizing coherent light or in the field of optical measurement control.

[0002]

2. Description of the Related Art Polarization reversal for forcibly reversing the polarization of a ferroelectric substance is performed by forming a periodic polarization reversal layer in the ferroelectric substance, and using an optical frequency modulator utilizing surface acoustic waves or a nonlinear polarization. It is used for an optical wavelength conversion element that uses polarization inversion. In particular, if it becomes possible to periodically invert the nonlinear polarization of the nonlinear optical material, it is possible to manufacture a second harmonic generation element (hereinafter referred to as an SHG element) having a very high conversion efficiency. Thus, by converting light from a semiconductor laser or the like, a compact short-wavelength light source can be realized, and it can be applied to the fields of printing, optical information processing, optical application measurement control, and the like, and thus is actively studied. The polarization inversion type SHG element is capable of highly efficient wavelength conversion, and can also perform arbitrary wavelength conversion by changing the periodic structure. However, since it is based on the periodic structure, the wavelength dependence is high and the output fluctuation with respect to the wavelength fluctuation of the fundamental light is very large.

As an example showing this, there is a report of wavelength conversion of a semiconductor laser using a quasi-phase matching (hereinafter referred to as QPM) type polarization inversion optical waveguide as an optical wavelength conversion element. (Yamamoto et al., Optics Letters Optics L
etters Vol.16, No.15, 1156 (1991)). FIG. 12 shows a schematic configuration diagram of a short wavelength light source using a semiconductor laser and a QPM light wavelength conversion element. The light emitted from the semiconductor laser 101 is converted into a parallel beam by the collimator lens 102, and the deflection direction is rotated by the λ / 2 plate 103 to change the NA.
The light is focused on the incident end surface 5 of the optical waveguide by the focusing lens 104 of = 0.6. Then, wavelength-converted blue light is obtained. The incident end face 105 is provided with a non-reflective coating in order to avoid returning light to the semiconductor laser.
From 05, about 1% of return light is generated. As a result, 1.1 mW of blue light was obtained for an incident light intensity of 35 mW entering the optical waveguide of the semiconductor laser. Since the nonlinear optical effect is used, the output light is proportional to the square of the input light intensity. However, the wavelength tolerance of the QPM light wavelength conversion element was only 0.2 nm.

On the other hand, in order to apply the short wavelength laser light source to an optical disk, a laser printer, etc., it is necessary to modulate the output intensity of the light source. In particular, modulation of output intensity at several 100 MHz is indispensable for recording on an optical disc. Conventionally, the modulation of the output intensity of a short wavelength laser light source is
The SHG output modulation is performed by modulating the output of the semiconductor laser of the fundamental wave.

Another method for modulating the intensity of light is an AO modulator using surface acoustic waves. This can be used to modulate the intensity of the light output from the light wavelength conversion element.

[0006]

In the conventional light wavelength conversion element, since there is no mechanism for modulating the output light intensity in the element, the output light intensity is modulated by the fundamental wave semiconductor laser intensity modulation. . The output of the semiconductor laser of the fundamental wave was modulated by modulating the driving current of the semiconductor laser. However, when the output is modulated, the output wavelength fluctuates at the same time, and the output wavelength fluctuates significantly by 1 nm or more. Was there.

However, the conversion efficiency of SHG has a large wavelength dependence of the fundamental wave, and when the wavelength of the fundamental wave changes by several angstroms, the conversion efficiency changes by 50% or more. Therefore, there is a problem in that the output of the SHG light fluctuates with the fluctuation of the wavelength, and stable intensity modulation is difficult.

Further, since the SHG output is proportional to the square of the input light intensity, there is a problem that the input light intensity needs to be adjusted in a complicated manner in order to linearly modulate the output light intensity in several steps. It was

Further, if an output modulation from the optical wavelength conversion element is attempted by using the AO modulator, the output is output via the AO modulator, so that the output decreases. High cost. However, the module becomes complicated and it is difficult to reduce the size of the light source.

Therefore, an object of the present invention is to provide an optical wavelength conversion element and a short wavelength laser light source for stably modulating a harmonic wave.

[0011]

In order to solve the above-mentioned problems, the present invention adds a new device to an optical wavelength conversion element based on a domain-inverted structure so as to maintain a stable output intensity and The present invention provides an optical wavelength conversion element that can be modulated in stages.

That is, the present invention has a substrate made of a non-linear material having an optical waveguide, a domain inversion layer, an incident portion and an emitting portion, and n (n ≧ 2) electrodes formed on the substrate, and In the optical wavelength conversion element, the electrodes are arranged in the propagation direction of the optical waveguide.

Further, the thin film heater has a substrate made of a non-linear material having an optical waveguide, a polarization inversion layer, an incident part and an emission part, and n (n ≧ 2) thin film heaters formed on the substrate. Are optical wavelength conversion elements arranged in the propagation direction of the optical waveguide.

[0014]

In the optical wavelength conversion device of the present invention, the SHG output is controlled by controlling the phase matching condition in the polarization inversion layer by the electrodes formed in the propagation direction of the waveguide, and the phase matching is performed even if the wavelength of the semiconductor laser changes. Since the highest harmonic output is always obtained by changing the state, a very stable output can be obtained. Moreover, since the phase matching state under each electrode can be controlled by the plurality of electrodes, the SHG output intensity can be modulated in multiple stages, and an optical wavelength conversion element capable of output intensity modulation can be configured. Moreover, since the output modulator can be integrated on the optical wavelength conversion element, a small element can be constructed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As one of the embodiments, the structure of the optical wavelength conversion device of the present invention will be described with reference to the drawings.

(Embodiment 1) First, FIG. 1 shows a structural diagram of a first embodiment of an optical wavelength conversion device according to the present invention. In this embodiment, as a polarization inversion type optical wavelength conversion element, a LiTaO ₃ substrate 1 is used.
The optical waveguide 2 manufactured by using proton exchange is used therein. In FIG. 1, 1 is a -C plate (-side of a substrate cut out perpendicular to the C axis), a LiTaO ₃ substrate, 2 is an optical waveguide formed, 3 is a polarization inversion layer, 10 is an incident portion of a fundamental wave P1, 12
Is an emission part of the harmonic P2, and 15 is a comb-shaped electrode formed on the optical waveguide.

The steps of the method for manufacturing the light wavelength conversion element will be described with reference to FIG. (A) A Ta film 13 having a thickness of 30 nm is formed on the LiTaO ₃ substrate 1 of the -C plate by a sputtering method. (B) After applying a photoresist on the Ta film 13, a stripe having a width W is formed for 10 mm in every cycle Λ in the Y propagation direction of the substrate by a normal photolithography method, and then dried in a CF ₄ atmosphere. The resist pattern is transferred to the Ta mask 13 by etching. (C) Heat treatment in pyrophosphoric acid at 260 ° C. for 20 minutes to form a proton exchange layer. (D) The LiTaO ₃ substrate is heated in a heating furnace with a high temperature rise. (E) 410 ° C. of this substrate
Is annealed for 4 hours to diffuse the proton exchange layer and reduce the refractive index difference between the polarization inversion layer and the non-inversion layer.
(F) A Ta film is formed on the LiTaO ₃ substrate 1 by the sputtering method. After coating a resist on the Ta film, an optical waveguide stripe having a width of 4 μm is formed in the X propagation direction of the substrate by a photolithography method, and then dry etching is performed in a CF ₄ atmosphere to form a Ta mask 13.
(G) This substrate is heat-treated with pyrophosphoric acid at 230 ° C. for 20 minutes, and the unmasked portion of LiTaO ₃ is subjected to proton exchange treatment to form the proton exchange optical waveguide 6. (H) After removing the Ta mask, the surface perpendicular to the optical waveguide 2 is optically polished to make the incident portion 10
And the emission part 12 was formed. The polarization inversion layer period of the manufactured element was 3.6 μm, the inversion layer width was 1.8 μm, and the depth was 1.8.
The optical waveguide had a width of 4 μm and a depth of 1.9 μm.
An aluminum comb-shaped electrode was formed on the manufactured light wavelength conversion element by the same photolithography process. An optical wavelength conversion device with a comb-shaped electrode could be manufactured by the above steps.

Next, the operation principle of the manufactured light wavelength conversion element will be described. The fundamental wave P1 entering the optical waveguide 2 is converted into a harmonic wave P2 by a polarization inversion layer having a phase matching length Λ / 2 by a polarization inversion layer having a period Λ, and the following
The harmonic power is increased by the non-polarization inversion layer having the length of / 2. The higher harmonic wave P2 thus increased in power in the optical waveguide 2 is emitted from the emitting portion 12.

Now, the period .LAMBDA. Of the polarization inversion layer is about 3.6 .mu.m for the fundamental wave P1 having a wavelength of 0.86 .mu.m, and the wavelength-converted light P2 having a wavelength of 0.43 .mu.m can be obtained. FIG. 3 shows the relationship between the distance of the optical waveguide and the SHG output at this time. As the wave propagates through the optical waveguide, the fundamental wave is converted into a harmonic by the polarization inversion layer, and the intensity P2 of the harmonic increases in proportion to the square of the distance. The output P2 is proportional to the square of the incident light intensity P1.

Next, the control of the output light intensity by the electrodes will be described. A method of modulating the phase matching state of the light wavelength conversion element by the comb-shaped electrodes will be described with reference to the cross-sectional view of the light wavelength conversion element. In FIG. 4A, 1 is a LiTaO ₃ substrate of a −C plate (the − side of the substrate cut out perpendicular to the C axis), 2 is an optical waveguide formed, 3 is a polarization inversion layer, and 10 is a fundamental wave P1.
Is an incident part, 12 is an output part of the harmonic P2, and 15 is a comb-shaped electrode formed on the optical waveguide. The period of the domain inversion layer is Λ
Is. When the comb-shaped electrodes are formed according to the period of the domain inversion layer, the electric field in the LiTaO ₃ crystal is generated as shown in FIG. 4 (b). LiTaO ₃ has a large electro-optical constant in the C-axis direction, and when a voltage is applied in the C-axis direction, the refractive index changes due to the electro-optical effect (FIG. 4 (b)). In the polarization inversion type optical wavelength conversion element, it is necessary to satisfy the phase matching condition for efficient wavelength conversion. This condition is Λ = λ / 2 (N2ω-Nω), Λ is the period of the polarization inversion layer, λ is the wavelength of the fundamental wave, N2ω is the effective refractive index of the harmonic in the optical waveguide, and Nω is the optical waveguide. Is the effective refractive index of the fundamental wave at. When an electric field is applied by the comb-shaped electrodes, the polarization direction and the electric field direction have the same relationship in both the polarization inversion layer and the non-polarization inversion layer, so that the refractive index changes in the same direction in both parts. For example, if the refractive index increases by Δn in the polarization inversion layer, Δn also increases in the non-inversion layer. Therefore, the total refractive index increases by Δn. When the refractive index in the optical waveguide is changed, the value of N2ω-Nω is changed, so that the phase matching condition can be controlled and the conversion efficiency of the optical wavelength conversion element can be modulated by the electric field. FIG. 4C shows a case where a flat electrode is used instead of the comb-shaped electrode. The electric field is applied in the same direction. In this case, if the refractive index change in the polarization inversion layer is Δn, the refractive index change in the non-inversion layer having different polarization directions is −Δn, and as shown in FIG. It becomes 0, the refractive index cannot be controlled by the electric field, and the phase matching state cannot be controlled.

The electro-optic effect is a phenomenon in which the refractive index changes when an electric field is applied, and the refractive index changes depending on the direction and magnitude of the electric field. LiTaO _{3 A} material having a large electro-optical effect, and particularly has a large electro-optical constant of r _{33 in the} C-axis direction. This is because the refractive index in the C-axis direction changes due to the electric field in the C-axis direction, and the refractive index change Δn also takes a value of ± depending on the direction of the electric field. For example, when an electric field is applied in the + C direction, the refractive index change −Δn indicates the value where the polarization is inverted, and the refractive index change + Δn indicates the value in the other portions. Therefore, when the electric field in the opposite direction is applied between the polarization inversion layer portion and the non-inversion layer portion by using the comb-shaped electrode, the entire refractive index can be changed by Δn.

FIG. 5 shows the relationship between the voltage applied to the comb electrodes and the SHG output. It can be seen that the SHG output changes depending on the applied voltage. A stable optical wavelength conversion element can be constructed by adjusting the applied voltage so that the SHG output is always maximized even when the environment changes or the wavelength of the fundamental wave changes.

Next, the output light intensity was modulated by this element. If the comb-shaped electrodes are divided, the phase matching state can be controlled independently in each part. As shown in FIG. 3, the propagation distance of the optical waveguide and the SHG output have a squared characteristic. Therefore, in order to change the output linearly, the length of the electrode is
L0, L0 (2 ^1/2 -1 ^1/2 ) and L0 (3 ^1/2 -2 ^1/2 ) were used. As can be seen from FIG. 6, when the output is P0 when the phase matching condition of the portion of length L0 is satisfied and the phase matching of the other portion is not established, L0, L0 (2 ^1/2 −1 ^{1 / When} the phase matching condition of ² ) is satisfied and the other parts are not matched, the output is 2P0, L0, L0 (2 ^1/2 -1 ^1/2 ), L0
The output 3P0 is obtained when the phase matching condition of (3 ^1/2 -2 ^1/2 ) is satisfied, and the SHG output can be linearly modulated in three stages.

The element actually manufactured had an element length of 20 mm and a wavelength tolerance of 0.8 nm. The wavelength variation of the semiconductor laser is corrected by changing the voltage of the comb-shaped electrode formed on the optical wavelength conversion element so that the harmonic wave is stably output. FIG. 7 shows the relationship between the wavelength change of the semiconductor laser and the optimum voltage of the light wavelength conversion element. Even if the wavelength is deviated by 0.3 nm, the harmonic output becomes maximum when the voltage is changed by 10V. The stability of the harmonic output is greatly improved compared to the conventional optical wavelength conversion element, and its practicality is increased. The semiconductor laser obtained a stable harmonic output even when it was changed by about 20 ° C. The electrodes formed on the device have lengths L1 = 11.5 mm, L2 = 4.8 mm, and L3 = 3.7 from the entrance to the exit.
mm comb electrodes were formed. Electrode 1, electrode 2,
The electrode 3 is used. 40mW for optical waveguide by semiconductor laser
I input the fundamental wave of. When a voltage of 10 V was applied to the electrodes, the phase matching condition was satisfied at the electrodes. Therefore, the relationship between the voltage applied to each electrode and the SHG output was measured.

[0025]

[Table 1]

As described above, by forming the electrodes for controlling the phase matching state of the device in the polarization inversion layer and dividing the electrodes, a stable SHG output can be obtained and the output is intensity-modulated to another stage. We were able to. Furthermore, a high-speed modulation experiment was conducted on the manufactured device. When applied voltage ± 5V and modulation frequency 200MHz, S / N = 30d
A good modulation characteristic of B or more was obtained.

The produced device has a waveguide loss of 0.2 dB / c.
Since the length is very small as m, the electrode length could be produced without considering the waveguide loss. However, in the case of an element with a large waveguide loss, it is necessary to consider the loss due to the waveguide loss in the length of the electrode of the element. For example, when the waveguide loss is adB / cm, the electrode length is L1 = L0 × 10E (-10aL0), L2
= L0 (2 ^1/2 -1 ^1/2 ) × 10E (-10aL0√2), L3 =
It becomes L0 (3 ^1/2 -2 ^1/2 ) x 10E (-10aL0√3), and it is necessary to correct the electrode length to the value calculated from the waveguide loss.

Next, the operation principle of another optical wavelength conversion device according to the embodiment of the present invention will be described. The method of controlling the phase matching state of the light wavelength conversion element can be realized by an electrode structure other than the comb electrode. Here, a case where a planar electrode having a simple structure and easy to manufacture is used will be described with reference to FIG. In FIG. 8 (a), 1 is -C plate (C axis of the substrate cut out in vertical - side) LiTaO ₃ substrate, an optical waveguide formed in 2, 3 the polarization inversion layer, 16 is a flat electrode is there. When an electric field is applied to the polarization inversion layer, the refractive index changes due to the electro-optic effect. Electrode 1 is placed on the part where the polarization direction is periodically reversed.
When 6 is produced and a voltage is applied, an electric field in the z direction is applied. The electric field causes a difference in refractive index between the polarization inversion layer and the non-inversion layer to form a grating. Let the grating period be Λ. Letting Δn be the change in the refractive index due to application of a voltage, W the width of the inversion layer, and Λ the period, the average change in the refractive index under the electrode Δ
N = (ΔnW−Δn (Λ−W)) / Λ, and W ≠ 0.
When 5Λ, ΔN can be changed by the refractive index Δn that changes depending on the applied electric field. As a result, it is possible to control the phase matching condition of the fundamental wave and the higher harmonic wave propagating through the optical waveguide by using the planar electrode which can be easily manufactured as in the previous embodiment.

Next, an embodiment in which wavelength stabilization of a semiconductor laser and output modulation of an optical wavelength conversion element are combined using a grating will be described. As shown in FIG. 9 of this embodiment, an optical waveguide 2 is formed on a LiTaO ₃ substrate 1, and a layer 3 (polarization inversion layer) in which the polarization is periodically inverted is further formed on the optical waveguide 2. By compensating the mismatch between the propagation constants of the fundamental wave and the generated harmonic by the periodic structure of the polarization inversion layer 3, the harmonic can be generated with high efficiency. When the fundamental wave P1 is incident on the incident surface of the optical waveguide 2, the harmonic P2 is efficiently generated from the optical waveguide 2 and operates as an optical wavelength conversion element. Bragg reflection grating 18 (Distributed Bragg Reflector or less DBR manufactured near the emission part
By using a grating), the wavelength of the semiconductor laser which makes the basic light incident on the device is fixed. When the wavelength of the semiconductor laser is fixed, the output of the optical wavelength conversion element operates very stably without depending on changes in the environment.

The DBR is a reflector having wavelength selectivity and reflects only a specific wavelength. When a specific wavelength is fed back to the semiconductor laser by the DBR grating, the wavelength of the semiconductor laser is fixed to the reflection wavelength of the DBR. If the phase matching wavelength by QPM and the reflection wavelength of DBR are matched, stable wavelength conversion can be performed using a semiconductor laser. In the conventional example, the polarization inversion layer was formed in the optical waveguide, and this was also used as the DBR grating. Therefore, the light emitted from the semiconductor laser is coupled to the optical waveguide through the fiber, but it is partially reflected by the DBR grating and the oscillation wavelength of the semiconductor laser can be fixed.

In the present embodiment, the polarization inversion layer is produced in the Y propagation direction, but the same element can be produced in the X propagation direction.

In this embodiment, the -c plate is used as the substrate, but the same device can be manufactured also by applying the electric field direction by the electrodes to the c direction also with the x plate and the y plate. .

In this embodiment, a LiTaO ₃ substrate was used as the substrate, but a LiTaO ₃ substrate doped with MgO, Nb, Nd or the like can be used to produce a similar device.

In this embodiment, pyrophosphoric acid was used for ion exchange, but orthophosphoric acid, benzoic acid, sulfuric acid, etc. can also be used.

In this embodiment, an ionization-resistant mask is used.
Then, the Ta film was used, but₂O _FiveAcid resistance such as Pt, Au, etc.
Any film having a property can be used.

Although the proton exchange waveguide is used as the optical waveguide in the present embodiment, other optical waveguides such as Ti diffusion waveguide, Nb diffusion waveguide and ion implantation waveguide can also be used.

(Embodiment 2) Here, the control of the phase matching condition by temperature will be described.

Instead of the modulation of the output light intensity of the light wavelength conversion element by the comb-shaped electrode described in the first embodiment, the control is performed by the thin film heater.

First, a method of forming a thin film heater on the light wavelength conversion element will be described. The light wavelength conversion element is similar to that of the first embodiment. The fabricated optical wavelength conversion element was vapor-deposited with SiO ₂
After adding 300 nm, a Ni-Cr layer having a thickness of 200 nm was formed. This Ni—Cr layer becomes the thin film heater 15.

The thin film heater 15 is manufactured by the above-mentioned steps.
The attached optical waveguide is manufactured, and the optical wavelength conversion element shown in FIG. 10 can be manufactured. The length of this element is 20 mm.
In FIG. 10, the semiconductor laser light (wavelength 0.8
6 μm) is guided from the incident part 10 and propagates in a single mode, and a harmonic wave P2 having a wavelength of 0.43 μm is emitted from the emitting part 1.
2 was taken out of the substrate. The propagation loss of the optical waveguide 2 was as small as 0.2 dB / cm, and the harmonic P2 was effectively extracted. One of the causes of low loss is that phosphoric acid forms a uniform optical waveguide. The thin film heater 17 was used for heating to control the temperature of the light wavelength conversion element to 30 ° C. Harmonics of 3mW (wavelength 0.43μ with input of 40mW of fundamental wave)
m) was obtained. The conversion efficiency in this case is 7.5%. The tolerance for the wavelength of the light wavelength conversion element is 0.8 nm. The wavelength variation of the semiconductor laser is corrected by changing the temperature of the light wavelength conversion element so that the harmonic wave is stably output. FIG. 9 shows the relationship between the wavelength change of the semiconductor laser and the optimum temperature of the light wavelength conversion element. Even if the wavelength is shifted by 0.8 nm, the harmonic output becomes maximum when the temperature is changed by 2 ° C. The stability of the harmonic output is greatly improved compared to the conventional optical wavelength conversion element, and its practicality is increased. 2 semiconductor lasers
Harmonic output was stably obtained even when the temperature changed by about 0 ° C. Since the thin film heater consumes less power and can respond at a speed of about μs, it is effective in tracking wavelength fluctuations.

Next, in the same manner as in Example 1, the thin film heater was divided, and the phase matching condition in each heater was controlled. As a result, similarly to Example 1, the output could be intensity-modulated in three stages.

In the multimode propagation with respect to the fundamental wave, the output of the harmonic wave is unstable, which is not practical and the single mode is effective.

Next, a second embodiment of the short wavelength laser light source of the present invention will be described. FIG. 12 shows a configuration diagram of the short wavelength laser light source of FIG. 11. The short wavelength laser light source is basically a semiconductor laser 31.
And the light wavelength conversion element 1. The fundamental wave P1 emitted from the semiconductor laser 31 fixed to the Al frame 30 is collimated by the collimator lens 34, and then introduced into the optical waveguide 2 of the optical wavelength conversion element 1 by the focus lens 35 to become the harmonic P2. To be converted. Further, 33 is a quartz plate for heat insulation. Here, the configuration of the light wavelength conversion element is similar to that of the first embodiment. In this example, a short wavelength laser light source was manufactured by combining this optical wavelength conversion element and a semiconductor laser. The output harmonic output is split by the beam splitter 36, detected by the Si detector 27, and fed back by electrical processing to keep the voltage of the electrode constant at the maximum point of the harmonic output. In this state,
By modulating the voltage applied to the electrode 28, the output of the short wavelength laser light source can be modulated in multiple stages.

In the embodiment, LiNb is used as the nonlinear optical crystal.
O ₃ and LiTaO ₃ were used, but ferroelectrics such as KNbO ₃ and KTP, M
It is also applicable to organic materials such as NA.

[0045]

As described above, according to the optical wavelength conversion element of the present invention, on the optical wavelength conversion element having the polarization inversion layer,
By providing multiple electrodes in the propagation direction of the optical waveguide,
The output of the light wavelength conversion element can be linearly changed in multiple stages. Moreover, since the output of the optical wavelength conversion element can be stabilized at the same time by the electrode, stable output can be obtained at the same time.

Further, by the short wavelength laser light source of the present invention,
Since a light source having a short wavelength and capable of output modulation can be realized, and the output modulator is integrated in the element, a small light source can be configured. As a result, it becomes possible to apply to applications such as optical disks and laser printers, and the practical effects are extremely large.

[Brief description of drawings]

FIG. 1 is a structural diagram of a first embodiment of an optical wavelength conversion device of the present invention.

FIG. 2 is a manufacturing process diagram of the optical wavelength conversion element of the optical wavelength conversion element of the present invention.

FIG. 3 is a characteristic diagram showing the output of the second harmonic of an optical wavelength conversion device with polarization inversion.

4A is a cross-sectional view of a light wavelength conversion element with a comb-shaped electrode, and FIG. 4B is a characteristic diagram showing electric field distribution, electro-optical constant, and refractive index change in the light wavelength conversion element with a comb-shaped electrode. Is a cross-sectional view of a light wavelength conversion element with a planar electrode. (D) is a characteristic diagram showing the electric field distribution, electro-optic constant, and refractive index change in the light wavelength conversion element with a flat surface.

FIG. 5 is a characteristic diagram showing a relationship between an applied electric field and SHG output.

FIG. 6 is a characteristic diagram showing the relationship between the length of the light wavelength conversion element and the SHG output.

FIG. 7 is a characteristic diagram showing the relationship between applied voltage and phase matching wavelength.

FIG. 8A is a cross-sectional view of a light wavelength conversion element with a planar electrode, and FIG. 8B is a characteristic diagram showing an electric field distribution, an electro-optic constant, and a refractive index change in the light wavelength conversion element.

FIG. 9 is a configuration diagram of an optical wavelength conversion element according to another embodiment.

FIG. 10 is a configuration diagram of an optical wavelength conversion device according to another embodiment of the present invention.

FIG. 11 is a block diagram of a short wavelength laser light source of the present invention.

FIG. 12 is a configuration diagram of a conventional optical wavelength conversion element.

[Explanation of symbols]

1 LiNbO ₃ substrate 2 optical waveguide 3 polarization inversion layer 10 incidence part 12 emission part 13 Ta mask 14 proton exchange layer 15 comb-shaped electrode 16 planar electrode 17 thin film heater 18 grating P1 fundamental wave P2 harmonic 27 Si detector 28 electrode 30 Al frame 31 Semiconductor laser 33 Quartz plate 34 Collimator lens 35 Focus lens 36 Beam splitter 101 Semiconductor laser 102 Collimator lens 103 λ / 2 plate 104 Focus lens 105 End surface

Claims (9)

[Claims] 1. A substrate made of a non-linear material having an optical waveguide, a domain inversion layer, an incident part and an emission part, and n (n ≧ 2) electrodes formed on the substrate, wherein the electrodes are the An optical wavelength conversion element characterized by being arranged in the propagation direction of an optical waveguide. 2. A thin film heater comprising: a substrate made of a non-linear material having an optical waveguide, a polarization inversion layer, an incident part and an emission part, and n (n ≧ 2) thin film heaters formed on the substrate. Are arranged in the propagation direction of the optical waveguide. 3. The lengths of the electrodes are L0 and L0 in order from the vicinity of the incident portion.
(2 ^1/2 -1 ^1/2 ), L0 (3 ^1/2 -2 ^1/2 ), ..., L0
The optical wavelength conversion device according to claim 1, wherein the relationship of (n 1 ^/2- (n-1) ^1/2 ) is satisfied. 4. The length of the thin film heater is L0, L0 (2 ^1/2 -1 ^1/2 ), L0 (3 ^1/2 -2 ^1/2 ), in order from the vicinity of the incident portion.
The light wavelength conversion element according to claim 2, wherein the relationship of L0 (n1 ^/ 2- (n-1) ^1/2 ) is satisfied. 5. A short wavelength laser light source comprising the light wavelength conversion element according to claim 1 and a semiconductor laser. 6. A substrate made of a non-linear material is LiNb _x Ta.
The optical wavelength conversion device according to claim 1, which is a _1-x O ₃ (0 ≦ X ≦ 1) substrate. 7. The light wavelength conversion element according to claim 1, wherein the electrode is a comb-shaped electrode. 8. The electrode is a parallel electrode, and the period Λ of the domain inversion layer and the width W of the domain inversion layer below the electrode are W ≠ Λ / 2.
The optical wavelength conversion element according to claim 1, wherein 9. The light wavelength conversion device according to claim 1, wherein the electrodes are parallel electrodes, and the depth Da of the domain-inverted layer below the electrodes and the depth Dw of the optical waveguide are Dw> Da. element.