JPH0667236A - Wavelength conversion element - Google Patents

Abstract

PURPOSE:To provide the wavelength conversion element which is simple in construction and can be easily produced. CONSTITUTION:An n-Al0.36Ga0.64As clad layer 6, an SCHregion 7, an SQW active layer 8, an SCH- region 10, a P-Al0.36Ga0.64As clad layer 11 and a P-GaAs contact layer 12 are respectively grown and formed on the upper side of an n-GaAs substrate 5. The upper side of the element is formed to a mesa stripe shape. Both upper and lower sides of the element are provided with an N side electrode 13 and a P side electrode 14. Coatings 17 which allow the passage of the incident light of a basic wavelength on the element without reflection are applied on both end faces of the element. The SQW active layer 8 is formed as a gain medium waveguide having a crystal structure of a zinc blended type. The second harmonic wave to the incident light (the light of the basic wavelength) is generated within this SQW active layer 8 and is emitted from an exit end.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength conversion element for inputting a fundamental wave and generating and outputting a second harmonic of the fundamental wave.

[0002]

2. Description of the Related Art FIG. 3 shows the structure of a conventional general wavelength conversion element. In the figure, a plurality of Ti diffusion regions 2 having a width D of 3.2 μm are arranged on the front surface side of a substrate 1 made of LiN _b O ₃ using an electron beam exposure method and a thermal diffusion method while maintaining a periodic interval L ₀ of 6.4 μm. Has been formed. Then, in the center of the surface of the substrate 1, a proton exchange region having a width W of 3.0 μm and extending in the longitudinal direction so as to intersect these Ti diffusion regions 2 is formed as a waveguide region 3.

The waveguide region 3 thus constructed has the above-mentioned T
Since the intersection with the i-diffusion region 2 is a periodic domain-inverted region, the equivalent refractive index is the same for light of different wavelengths of 1.064 μm and 0.532 μm. The phase matching condition is satisfied between the lights of two different wavelengths. As a result, when the light of wavelength 1.064 μm is the fundamental wave and the light of wavelength 0.532 μm is the second harmonic,
Harmonics can be extracted at maximum output. That is,
The wavelength λ _W from the YAG laser is 1.06 at the entrance side of the waveguide region 3.
When light of 4 μm is incident as a fundamental wave, a second harmonic having a wavelength of ½ of the fundamental wave is generated while propagating in the waveguide region 3, and a wavelength λ from the emission end side of the waveguide region 3 is generated. _W is 1.06
By providing both a 4 μm fundamental wave light and a 2nd harmonic wave with a wavelength λ _2W of 0.532 μm, and providing a bandpass filter that passes the 2nd harmonic wave on the exit end side of this waveguide region 3. The second harmonic of the fundamental wave is extracted.

[0004]

However, the SHG (Second Harmoni) using the conventional substrate 1 of LiN _b O ₃ is used.
c Generation) element (second harmonic generation element) is used to obtain phase matching between the fundamental wave and the generated second harmonic wave.
Since the i-diffusion regions 2 are formed in a highly precise array at regular intervals, the device structure becomes very complicated, and it takes time to manufacture the device, and the device cost becomes high.

The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to provide a simple element structure,
It is to provide a wavelength conversion element that is easy to manufacture.

[0006]

In order to achieve the above object, the present invention is constructed as follows. That is, the present invention is a wavelength conversion element having a waveguide structure including a gain medium active layer, wherein the gain medium active layer is composed of a zinc blende type semiconductor crystal layer, and at least one of the semiconductor crystal layers. The edges are characterized in that they are provided with an antireflection coating for a wavelength which is twice as long as the wavelength to be obtained.

[0007]

When light of a fundamental wave having a wavelength of 1.48 μm is incident on the incident end side of the wavelength conversion element of the present invention, the light propagates through the zinc blende type semiconductor crystal layer and reaches the emission end. This zinc blende type semiconductor crystal layer generates a second harmonic of the fundamental wave. Then, this second harmonic is repeatedly reflected between the input and output ends of the zinc blende type semiconductor crystal layer (gain medium active layer) and positive feedback is applied to cause laser oscillation of the standing wave of the second harmonic. That is, both the second harmonic having a wavelength of 0.74 μm and the fundamental wave having a wavelength of 1.48 μm, which are laser oscillation lights, are emitted from the emission end side of the zinc blende type semiconductor crystal layer. By providing a bandpass filter that passes the second harmonic on the emission end side of this wavelength conversion element, the target second harmonic can be extracted.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an embodiment of the wavelength conversion element according to the present invention. In the figure, an n-Al _0.36 Ga _0.64 As cladding layer 6 and an Al _0.28 Ga _0.72 A layer having a layer thickness of 600 Å and having no dopant component are formed on an n-GaAs substrate 5.
SCH-region (light confinement layer) 7 composed of s and layer thickness
Al _0.20 Ga _0.80 As without 100Å dopant component
SQW consisting of (bandgap wavelength λg = 0.74 μm)
Active layer 8 and Al with a layer thickness of 600Å without dopant components
_An SCH-region (optical confinement layer) 10 made of _0.28 Ga _0.72 As, a P-Al _0.36 Ga _0.64 As clad layer 11,
A P-GaAs contact layer 12 is grown in order, and the left and right sides of the laminated semiconductor are removed by etching from the P-GaAs contact layer 12 on the surface to a part of the SCH-region 10 to form a mesa stripe shape having a width S of about 2 μm. An N-side electrode 13 is formed on the lower surface side of the substrate 1, and a P-side electrode 14 is formed on the upper surface side of the P-GaAs contact layer 12.

The front and rear end surfaces 15 and 16 of this element are cleaved surfaces, and SiN ₄ having a thickness of 2000 Å is formed on both end surfaces 15 and 16.
Membrane 17 is coated. The SiN ₄ film 17 functions as a non-reflective coating with respect to light having a wavelength of 1.48 μm and as a high-reflection coating with respect to light having a wavelength of 0.74 μm. With this configuration, the SQW active layer 8 as the gain medium active layer serves as an optical waveguide that transmits the fundamental wave with a wavelength of 1.48 μm in a non-reflective manner. It functions as a Fabry-Perot resonator for light having a wavelength of 0.74 μm, and the wavelength conversion element of this embodiment has a structure similar to that of a normal semiconductor laser.

The wavelength conversion element of this embodiment is constructed as described above, and its operation will be described below. First, a current having a magnitude 0.95 times the threshold current that causes the wavelength conversion element of this embodiment to oscillate as a Fabry-Perot type laser diode is applied as a bias current from the P-side electrode 14 to the N-side electrode 13. To be In this current applied state, the applied current does not reach the threshold current, so the SQW active layer 8
No internal laser oscillation occurred.

In this state, as shown in FIG. 2, when a fundamental laser beam having a wavelength of 1.48 μm is incident on the incident end side of the device, the SQW active layer 8 has a zinc blende type crystal structure. Therefore, when light is guided through the SQW active layer 8, a second harmonic wave is generated with respect to the guided light. In the example in this figure, SQ
Since the fundamental wave having a wavelength of 1.48 μm is guided to the W active layer 8, a second harmonic wave having a wavelength of 0.74 μm is generated.

Normally, the second harmonic generated in the semiconductor is very weak, but in the case of this embodiment, the second harmonic wave S
The QW active layer 8 has a zinc blende type crystal structure and serves as a gain medium.
The harmonics are amplified by stimulated emission. This second harmonic is reflected between the entrance and exit ends of the SQW active layer 8 to generate a standing wave, and if the intensity of incident light with a wavelength of 1.48 μm is made sufficiently strong, amplification of the standing wave with a wavelength of 0.74 μm is amplified. A positive feedback is applied to the laser to cause laser oscillation as a Fabry-Perot resonator, and this laser oscillation light, that is, the second harmonic of the fundamental wave having a wavelength of 0.74 μm, is emitted from the emission end of the SQW active layer 8.

On the other hand, since the SiN ₄ film 17 on both sides of the element functions as a non-reflective film with respect to laser light having a fundamental wavelength of 1.48 μm, the fundamental wave generates the second harmonic as described above. However, the light is emitted from the emission end of the SQW active layer 8 in a non-reflection state. That is, when the fundamental wave laser light having a wavelength of 1.48 μm is incident on the incident end side of the element, both the fundamental wave light and the second harmonic light are emitted from the exit end of the element. Therefore, by providing a bandpass filter 18 that passes only the second harmonic on the emission end side of this element,
It is possible to extract the 0.74 μm second harmonic laser light.

In this embodiment, the fundamental wave having a wavelength of 1.48 μm is S
Since it passes through the waveguide of the QW active layer 8 without reflection, it is not necessary to perform phase matching between the fundamental wave and the second harmonic, and therefore the structure of the conventional example in which this phase matching needs to be achieved. The element structure is much simpler than that of.

The present invention is not limited to the above-mentioned embodiments, and various embodiments can be adopted. For example, in the above embodiment, the wavelength conversion element having the ridge waveguide type element structure manufactured by using the AlGaAs material has a wavelength of 1.48 μm.
The case where the fundamental wave of m light is converted to the second harmonic of light having a wavelength of 0.74 μm has been described. However, the wavelength conversion element of the present invention has a material and an element structure other than that of the present embodiment and a wavelength other than that of the present embodiment. It is possible to perform wavelength conversion of a region. For example, the SQW active layer 8 is formed as a gain waveguide having a zinc blende type crystal structure by using a synthetic material of GaAlInP and GaInP, and antireflection coating for a wavelength of 1.3 μm is applied to both end faces thereof. , A fundamental wave having a wavelength of 1.3 μm can be incident and converted into a second harmonic of 0.65 μm for extraction. Further, as the SQW active layer 8, a gain waveguide similarly having a zinc blende type crystal structure is formed by using a synthetic material of ZnSe and ZnS, and antireflection coating for a wavelength of 0.98 μm is applied to both end faces thereof. Therefore, the 0.98 μm wavelength light is used as the fundamental wave,
It can be extracted by converting it to the second harmonic of 0.49 μm light.

Further, in the above-mentioned embodiment, the non-reflecting film of the fundamental wave is provided on both ends of the element, but it may be provided on one side.

[0017]

According to the present invention, the gain medium active layer of the device is composed of a zinc blende type semiconductor crystal layer, and at least one end side of the semiconductor crystal layer has a wavelength twice the wavelength to be obtained. Since the antireflection coating for the wavelength of the length is applied, the second wave for the fundamental wave can be generated by injecting the light of the fundamental wave of the wavelength of the antireflection coating.
Higher harmonics can be emitted from the element emission end. Moreover, in this wavelength conversion, the phase matching between the fundamental wave and the second harmonic generated in the gain medium active layer becomes unnecessary,
The element structure is also much simpler than that of the conventional example, and therefore, the element can be manufactured very easily, and the wavelength conversion element of the present invention can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a perspective configuration diagram showing an embodiment of a wavelength conversion element according to the present invention.

FIG. 2 is an explanatory diagram showing a wavelength conversion operation of the element of the example.

FIG. 3 is an explanatory diagram of a conventional wavelength conversion element.

[Explanation of symbols]

5 n-GaAs substrate 6 n-Al _0.36 Ga _0.64 As clad layer 7,10 SCH-region 8 SQW active layer 11 P-Al _0.36 Ga _0.64 As clad layer 12 P-GaAs contact layer 13 N-side electrode 14 P-side electrode 17 SiN ₄ film

Claims (1)

[Claims] 1. A wavelength conversion element having a waveguide structure including a gain medium active layer, wherein the gain medium active layer is composed of a zinc blende type semiconductor crystal layer, and at least one end of the semiconductor crystal layer. Is a wavelength conversion element coated with an antireflection coating for a wavelength twice as long as the wavelength to be obtained.