JPH11243246A - External resonator semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser which is due to stabilize its operation by providing a beam converting function thereto. SOLUTION: A semiconductor laser 7, including a beam converter 6 of a beam conversion function having an anti-reflective film formed thereon, is formed on a relatively low level surface of a silicon substrate 1. Furthermore, a comb-like electrode 2, having a micro-mirror 5 fixed thereto as well as two anchors 4 having a center beam 3 straddled as fixed therebetween, are formed on a relatively high level surface of the substrate 1. These constituent elements are integrally formed on the substrate 1 so that interconnection between the micro-mirror 5 and electrode 2 is carried on the substrate 1 by the beam 3 which is spaced from the substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an external cavity semiconductor laser, and more particularly, to an external cavity semiconductor laser having a simple structure and capable of stabilizing operation.

[0002]

2. Description of the Related Art An external cavity semiconductor laser is provided with an optical device such as a plane mirror, a concave mirror, or a diffraction grating as an external reflector outside a semiconductor laser, and oscillates light from the semiconductor laser by the external reflector. This is a laser device that causes light oscillation by using the end faces of the external reflecting mirror and the semiconductor laser as resonators by returning to the above.

The laser oscillation wavelength characteristics and optical output characteristics of this external cavity semiconductor laser greatly depend on the distance and displacement between the semiconductor laser and the external reflection mirror and the set angle of the diffraction grating. In order to stabilize the laser oscillation operation without changing the distance from the mirror or the like, a large-scale apparatus configuration is used, and the cost is very high.

Therefore, conventionally, for example, Japanese Patent Application No.
As in the technique described in Japanese Patent Application Laid-Open No. 335825, an external cavity semiconductor laser has been proposed which stabilizes the operation by hybrid-integrating a semiconductor laser, an external reflector and a microactuator on the same substrate.

[0005]

However, in the external cavity semiconductor laser device described in Japanese Patent Application No. 4-335825, the spread of the light emitted from the stripe-type semiconductor laser increases. There has been a problem that the amount of reflected light returning from the external reflector to the semiconductor laser greatly changes even with a minute displacement of the external reflector, causing a wavelength shift due to internal carrier fluctuation.

Although it is conceivable to retrofit a selfoc lens or the like so as to perform beam conversion, alignment adjustment when retrofitting an optical device such as a lens is troublesome, so that the manufacturing process becomes complicated and cost increases. There was also a problem of inviting.

The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide an external cavity semiconductor laser in which a semiconductor laser has a beam conversion function to stabilize the operation. The point is to provide.

[0008]

According to a first aspect of the present invention, there is provided a semiconductor laser capable of controlling the length of a resonator, the reflector being moved in a predetermined direction by moving a reflecting mirror. A drive mechanism capable of controlling the length, and a semiconductor laser having an anti-reflection portion, and a laser beam output from the anti-reflection portion are integrally formed on a substrate so that the laser light is incident on the movable reflecting mirror. An external cavity semiconductor laser, characterized in that the semiconductor laser is provided with a beam converter for performing beam conversion of laser light emitted from the semiconductor laser.

According to a second aspect of the present invention, in the first aspect, the beam conversion section is constituted by a tapered waveguide connected to an active layer of the semiconductor laser.

According to the first and second aspects of the present invention, the beam conversion unit performs beam conversion for condensing the oscillation light from the semiconductor laser and narrowing the spread angle of the emitted light, and transmits the light to the reflecting mirror. Since the light is incident, the amount of light reflected back to the semiconductor laser hardly depends on the displacement of the reflecting mirror, and the operation can be stabilized.

Further, the invention according to claim 3 is based on claim 1.
In any one of (2) and (2), the antireflection section is formed by processing the end face of the beam conversion section so that the direction in which the end face exists is oblique to the optical axis direction of the semiconductor laser.

According to this, since the end face of the beam conversion section has an antireflection effect, the antireflection section can be realized with a simple configuration without particularly providing a dielectric multilayer film or the like.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an external configuration diagram of an external cavity semiconductor laser according to an embodiment of the present invention. FIG.
As shown in the figure, in the external cavity semiconductor laser according to this embodiment, the semiconductor laser 7 provided with an anti-reflection film (not shown) and the beam conversion unit 6 having a beam conversion function is relatively low in the silicon substrate 1. Formed on the surface.

A comb-shaped electrode 2 to which a micro mirror 5 is fixed and two anchors 4 to which a doubly supported beam 3 is fixed are formed on a relatively high surface of the silicon substrate 1. These components are integrally formed on the silicon substrate 1, and the connection between the micromirror 5 and the comb-shaped electrode 2 is supported by the doubly supported beam 3 in a state separated from the silicon substrate 1. .

When a voltage is applied between the comb electrode 2 and the anchor 4, the micromirror 5 moves in the optical axis direction of the semiconductor laser 7 by a distance corresponding to the applied voltage, and the cavity length (the front side of the semiconductor laser 5) End face and micro mirror 3
Is controlled, and when the applied voltage is lost, the micromirror 5 returns to the original position by the tension of the doubly supported beam 3.

A specific embodiment will be described below with reference to a schematic configuration diagram. FIG. 2 is a schematic configuration diagram of an upper surface of the external cavity semiconductor laser according to the first embodiment.

A beam conversion unit 6 is provided at an end of the semiconductor laser 7.
Further, the beam conversion unit 6 is provided with an antireflection film 8 made of a dielectric multilayer film or the like. A comb-shaped electrode 2 to which a micromirror 5 is fixed and two anchors 4 to which a doubly supported beam 3 is fixed are provided. A connection portion between the micromirror 3 and the comb-shaped electrode 2 is formed by a doubly supported beam 3 on a substrate (see FIG. (Not shown). These components are integrally formed on a substrate (not shown).

The semiconductor laser 7 and the beam converter 6 are described in the document "Integrated Coupler of Semiconductor Laser and Optical Fiber Using Microlens, Transactions of the Institute of Electronics, Information and Communication Engineers, CI, vol. J77-C." -I No.6 p
p390-397, June 1994 "may be used.
It is manufactured by providing a lens made of glass material or the like near the end surface of a stripe type semiconductor laser and integrally forming the semiconductor laser and the lens on the same substrate. Do.

The light emitted from the semiconductor laser 7 is condensed by the lens of the lens-integrated semiconductor laser, which is a beam conversion unit 6, and the condensed light enters the micromirror 5 via the antireflection film 8. Is done. Further, the incident light is reflected by the micromirror 5 while its phase is controlled (while the resonator length is controlled) by the voltage applied between the comb-shaped electrode 2 and the anchor 4,
The reflected return light is again incident on the semiconductor laser 7 via the antireflection film 8 and is taken out from the end face of the semiconductor laser.

According to this, the light emitted from the semiconductor laser 7 is condensed by the beam converter 6 so that the amount of light reflected back to the semiconductor laser is reduced by the micro mirror 5.
And the laser operation is stabilized.

FIG. 3 is a schematic structural view of the upper surface of the external cavity semiconductor laser according to the second embodiment. The same components as those in the first embodiment are denoted by the same reference numerals. In this embodiment, the beam conversion unit 6
It is characterized in that it is constituted by a tapered waveguide 9 connected to the active layer 7a of the semiconductor laser 7.

FIG. 4 is an external view of a beam converter 6 composed of a semiconductor laser 7 and a tapered waveguide 9. As shown in FIG. 4, the waveguide connected to the active layer 7a has a tapered shape. A waveguide 9 is formed, and the taper-shaped waveguide 9 performs beam conversion of changing the spot size of the laser beam stimulatedly emitted from the active layer 7a. Such a laser diode with spot size conversion is described in detail in a document such as "1995 IEICE Electronics Society Conference, SC-1-3," and the length of the active layer is 3
00 to 400 (μm), taper shape length 300 (μm)
m), and the active layer and the tapered waveguide 9 are made of InGa.
In the case of using AsP (MQW) or InGaAsP (bulk type), it has been confirmed that the spot size of the light incident on the tapered waveguide 9 gradually increases to about 2.5 to 3 (μm). .

The light emitted from the semiconductor laser 7 has its spot size converted by the tapered waveguide 9 which is the beam conversion unit 6. The light whose spot size has been converted is incident on the micromirror 5 via the antireflection film 8. Further, the incident light is reflected by the micromirror 5 while its phase is controlled by a voltage applied between the comb-shaped electrode 2 and the anchor 4, and the reflected return light is again reflected by the anti-reflection film 8. The laser beam is incident on the semiconductor laser 7 via the interface and is taken out from the end face of the semiconductor laser.

According to this, the spot size of the light emitted from the semiconductor laser 7 can be increased by the beam conversion unit 6 and, as a result, the NA can be reduced and the spread angle of the emitted light can be narrowed. The amount of reflected return light is less likely to depend on the displacement of the micromirror 5, and operation can be stabilized. Further, such a tapered waveguide 9 can be manufactured in a small size by optical integration technology.

FIG. 5 is a schematic configuration diagram of the upper surface of the external cavity semiconductor laser according to the third embodiment. The same components as those in the first embodiment are denoted by the same reference numerals. This embodiment is characterized in that, instead of providing the antireflection film 8, the end face of the beam converter 6 is processed to form the antireflection section.

As shown in FIG. 5, in this embodiment, the external cavity laser is provided so that the direction of the end face 10 of the beam converter 6 is oblique to the optical axis of the semiconductor laser. The end face is machined. In addition, since there is a refractive index difference between the air and the beam conversion unit 6 and light is refracted,
The semiconductor laser 7 and the beam converter are arranged so that the optical axis direction of the laser beam is oblique to the direction perpendicular to the plane of the micromirror 5 so that the beam-converted light is appropriately incident on the micromirror 5. 6 are arranged.

The light emitted from the semiconductor laser 7 is subjected to beam conversion by the beam converter 6. This beam-converted light is incident on the micro mirror 5 via the end face 10. Further, the incident light is reflected by the micromirror 5 while its phase is controlled by a voltage applied between the comb-shaped electrode 2 and the anchor 4, and the reflected return light passes through the end face 9 again. The laser beam is then incident on the semiconductor laser 7 and taken out from the end face of the semiconductor laser.

According to the end face 10, since the direction in which the end face 10 is present is not orthogonal to the optical axis direction, the amount of light reflected from the end face 10 can be reduced. It is possible to obtain the same operation as that of the film. The angle between the direction in which the end face 10 exists and the direction of the optical axis of the semiconductor laser may be set to, for example, about 8 °. In addition, as shown by the dotted line in FIG. In the laser device, the end face of the tapered waveguide 9 having the smaller taper thickness may be processed.

As described above, according to the embodiment of the present invention, the amount of light reflected back to the semiconductor laser 5 hardly depends on the displacement of the micromirror 5 due to beam conversion such as focusing and spot size expansion. Therefore, the operation can be stabilized. In addition, since the semiconductor laser 7 and the beam conversion unit 6 can be realized by a semiconductor laser integrally formed with a lens, a tapered waveguide 9, and the like, a simple and compact device configuration is obtained.

Further, an antireflection section can be realized by simple processing of the end face of the beam conversion section 6.

[0031]

As described above, according to the first and second aspects of the present invention, the beam conversion unit performs the beam conversion of the laser light oscillated from the semiconductor laser, so that the amount of light reflected back by the external reflecting mirror is obtained. Of the laser oscillation wavelength characteristic and the optical output characteristic can be stabilized.

In particular, according to the second aspect of the present invention, since the size of the beam conversion portion does not increase so much, the size of the external cavity semiconductor laser can be reduced, and the operation against disturbance can be further stabilized.

According to the third aspect of the present invention, the anti-reflection portion can be realized by simple processing.

[Brief description of the drawings]

FIG. 1 is an external configuration diagram of an external cavity semiconductor laser according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an upper surface of the external cavity semiconductor laser according to the first embodiment.

FIG. 3 is a schematic configuration diagram of an upper surface of an external cavity semiconductor laser according to a second embodiment.

FIG. 4 is an external view of a beam conversion unit 6 including a semiconductor laser 5 and a tapered waveguide 8.

FIG. 5 is a schematic configuration diagram of an upper surface of an external cavity semiconductor laser according to a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Comb electrode 3 Doubly supported beam 4 Anchor 5 Micromirror 6 Beam conversion part 7 Semiconductor laser 7a Active layer 8 Anti-reflection film 10 End face

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shinji Nagaoka 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (3)

[Claims] 1. A semiconductor laser having a cavity length controllable, comprising: a driving mechanism capable of controlling a cavity length by moving a reflecting mirror in a predetermined direction; and a semiconductor laser having an antireflection unit. A beam conversion unit that integrally forms a laser beam output from the antireflection unit on a substrate so as to be incident on the movable reflection mirror, and performs beam conversion of laser light emitted from the semiconductor laser to the semiconductor laser. An external cavity semiconductor laser comprising: 2. The external cavity semiconductor laser according to claim 1, wherein the beam conversion unit is configured by a tapered waveguide connected to an active layer of the semiconductor laser. 3. The end surface of the beam conversion unit according to claim 1, wherein the antireflection unit is formed by processing an end surface of the beam conversion unit such that the direction of the end surface is oblique to the optical axis direction of the semiconductor laser. An external cavity semiconductor laser characterized in that: