JPH06140717A - External resonator type semiconductor laser light source - Google Patents

Abstract

PURPOSE:To obtain an external resonator type semiconductor laser light source of stable module structure wherein optical axis alignment is easy and narrow spectral line width is obtained without making the external resonator long. CONSTITUTION:A nonreflection film 1A is formed on one end surface of a semiconductor laser 1, and a total reflection film 1B is formed on the other end surface. An external resonator is constituted by using the total reflection film 1B of the semiconductor laser 1 and a diffraction grating 2. A beam splitter 3 whose reflection factor is low is inserted in the inside of the external resonator, thereby reflecting a part of resonating light in two directions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser light source used in all fields of technology using an optical signal source, particularly in the field of optical coherent communication and optical coherent measurement technology.

[0002]

2. Description of the Related Art FIG. 2 shows the structure of a conventional external cavity type semiconductor laser light source. 2 is a semiconductor laser,
1A is a non-reflection film, 2 is a diffraction grating, 5 is an optical isolator,
Reference numeral 6 is a condenser lens, and 7 is an optical fiber. The semiconductor laser 1 is driven by an LD drive circuit 8 and is of Fabry-Perot type, and one end face thereof is provided with a non-reflection film 1A.
In FIG. 2, the semiconductor laser 1 emits light from the non-reflection film 1A side, is converted into parallel light by the lens 4A, and is incident on the diffraction grating 2. The diffraction grating 2 is an external reflector, reflects light of a specific wavelength, and returns it to the semiconductor laser 1.

An external resonator is formed by the end face of the semiconductor laser 1 not provided with the antireflection film 1A and the diffraction grating 2, and the semiconductor laser 1 oscillates in a single mode. The emitted light on the side where the anti-reflection film 1A is not applied is converted into parallel light by the lens 4B, enters the optical isolator 5, and enters the optical fiber 7 by the condenser lens 6.

When the diffraction grating is provided with the angle adjusting mechanism 9A and rotated, the selected wavelength is changed, and the wavelength can be tuned within the gain range (hundreds of tens of nm) of the semiconductor laser. Further, when the diffraction grating is provided with the parallel moving mechanism 10A and moved in parallel in the optical axis direction of the resonator, the phase condition of the resonator changes,
The wavelength is tuned in the frequency (several GHz) region of the longitudinal mode interval. Then, if the angle adjustment of the diffraction grating 2 and the parallel movement of the diffraction grating 2 are controlled at the same time, phase-continuous wavelength tunable becomes possible.

For example, 1992 IEICE Spring Conference
If the external cavity length is 120 mm, the C-266 has a spectral line width of approximately 10 kHz and a phase continuous wavelength tunable wavelength of approximately 65 GHz when the longitudinal mode spacing is 1.25 GHz (0.01 nm). ., VOL.E75-B, NO.6 JUNE 199
2 With P521-523, the spectral line width is 50 when the resonator length is 30 mm.
It is reported that phase continuous wavelength tunability of 0 kHz or less and 130 GHz was obtained.

[0006]

In the structure shown in FIG. 2, the output light of the semiconductor laser 1 on the non-reflection film 1A side is converted into parallel light by a lens and is incident on the diffraction grating 2 to form the non-reflection film 1A. The output light from the end face that is not formed is also converted into parallel light by the lens and is incident on the optical fiber 7. Therefore, parallel light must be generated on both sides of the semiconductor laser 1, and optical axis alignment becomes difficult. In addition, the structure of the module is long in the direction of the cavity and must be large, and it is sensitive to changes in the external environment, making it difficult to obtain a stable light source.

It is an object of the present invention to provide an external resonator type semiconductor laser light source having a stable module structure in which optical axis alignment is easy and a narrow spectral line width can be obtained without lengthening the external resonator.

[0008]

In order to achieve this object, the present invention provides a semiconductor laser 1 having a non-reflection film 1A on one end face and a total reflection film 1B on the other end face, and a semiconductor laser 1. The emitted light 12 on the side provided with the non-reflective film 1A is incident, and the total reflection film 1B of the semiconductor laser 1 and the diffraction grating 2 forming an external resonator, and the diffraction grating 2 are inserted into the external resonator and resonate. A beam splitter 3 having a low reflectance that reflects a part of light in two directions is provided.

[0009]

The structure of an embodiment according to the present invention is shown in FIG. In FIG. 1, 3 is a beam splitter, and 5A and 5B are optical isolators. In FIG. 1, a non-reflection film 1A and a total reflection film 1B are provided on the end surface of the semiconductor laser 1 so that the output light from the semiconductor laser is emitted in only one direction. Semiconductor laser 1
Is a Fabry-Perot type, and is driven by the LD drive circuit 8.

The light emitted from the antireflection film 1A side is converted into parallel light by the lens 4, passes through the beam splitter 3 and is incident on the diffraction grating 2. The diffraction grating 2 reflects the light transmitted through the beam splitter 3, and the reflected light again passes through the beam splitter 3 and enters the semiconductor laser 1. A resonator is formed by the total reflection film 1B of the semiconductor laser 1 and the diffraction grating 2. Therefore, the beam splitter 3 is arranged in the resonator.

At this time, of the light of the wavelength selected by the diffraction grating 2, the light of the wavelength satisfying the phase condition of the resonator resonates. Since the diffraction grating 2 and the total reflection surface 1B of the semiconductor laser 1 have a high reflectance, the resonator has a steep frequency characteristic, and light having a steep frequency characteristic is fed back to the semiconductor laser 1.
Light with a narrow spectral linewidth is obtained.

The light incident on the beam splitter 3 is subjected to an optical path change substantially at right angles to the resonator direction, and the beam splitter 3
The light is emitted in both directions. The emitted light has two outputs, and respectively enters the optical isolators 5A and 5B. In FIG. 1, the emitted light on the optical isolator 5A side is condensed by the condenser lens 6, enters the optical fiber 7, and becomes output light. The light emitted from the optical isolator 5B can be used as monitor light and can be used for frequency stabilization and the like.

By providing the angle adjusting mechanism 9A and rotating the diffraction grating 2, the selected wavelength is changed, and the wavelength can be tuned within the medium gain range (about hundred and several tens nm) of the semiconductor laser. Further, when the parallel movement mechanism 10A is provided and the diffraction grating 2 is moved in parallel to the optical axis direction of the resonator, the phase condition of the resonator changes, and the wavelength can be tuned in the frequency (several GHz) region of the longitudinal mode interval. Further, when the drive circuit 9 of the angle adjusting mechanism and the drive circuit 10 of the parallel moving mechanism are simultaneously controlled by the control circuit 11 for the diffraction grating 2, phase continuous wavelength tunable becomes possible.

[0014]

As described above, in the external cavity type semiconductor laser light source of the present invention, in order to emit the output light from the semiconductor laser in only one direction, it is necessary to produce two parallel lights on both sides of the semiconductor laser. Corner and optical axis alignment becomes easy. Further, the module structure does not become long in the resonator direction, and a small and stable structure can be realized. Furthermore, since both reflectances of the resonator are high, Q of the resonator is increased, a narrow spectral line width is obtained, and a two-output light source including monitor light is obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of an external resonator type semiconductor laser light source according to a conventional technique.

[Explanation of symbols]

 1 Semiconductor Laser 1A Non-Reflective Film 1B Total Reflection Film 2 Diffraction Grating 3 Beam Splitter 4 Lens 5A / 5B Optical Isolator 6 Condensing Lens 7 Optical Fiber 8 LD Drive Circuit 9 Drive Circuit of Angle Adjustment Mechanism 9A Angle Adjustment Mechanism 10 Parallel Movement Mechanism drive circuit 10A Parallel movement mechanism 11 Control circuit

Claims (1)

[Claims] 1. A semiconductor laser (1) having a non-reflection film (1A) on one end face and a total reflection film (1B) on the other end face, and a non-reflection film (1A) for the semiconductor laser (1). Emitting light (1
2) and a diffraction grating (2) which forms an external resonator with the total reflection film (1B) of the semiconductor laser (1) and a part of light which is resonated by being inserted into the external resonator. Two
An external resonator type semiconductor laser light source, comprising a beam splitter (3) having a low reflectance for reflecting in a direction.