JP3511221B2 - Semiconductor laser module - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser module for optical communication. In recent years, a semiconductor laser module with an isolator has been widely used as an optical signal source for analog transmission, but these optical signal sources are required to have low internal reflection.

[0002]

2. Description of the Related Art In a conventional semiconductor laser module, in order to reduce internal reflection, a polarizer of an isolator of a semiconductor laser is tilted in an S polarization direction with respect to a polarization plane of the semiconductor laser.

FIG. 2 is a diagram for explaining the structure of a conventional semiconductor module. In this figure, 11 is a semiconductor laser, 1
Reference numeral 2 is a first lens, 13 is a Peltier cooler, 14 is a window, 15 is a case, 16 is a polarizer, 17 is a Faraday rotator, 18 is an analyzer, 19 is an isolator, and 20 is a carrier.

In an example of a conventional semiconductor module, a semiconductor laser 11 is mounted on a Peltier cooler (thermoelectric cooler) 13 via a carrier 20, as shown in the side view of FIG. The first lens 12 is arranged in the emission direction of the radiated light, and the first lens 1 is provided in the case 15 that houses them.
A window 14 for emitting the light passing through 2 to the outside is formed, and the light emitted from the window 14 to the outside is incident on an isolator 19 including a polarizer 16, a Faraday rotator 17, and an analyzer 18. Has become.

Then, the window 14 of the semiconductor laser 11
Is arranged so as to be inclined with respect to the polarization plane of the semiconductor laser 11 in the P polarization direction (the oscillation direction of the electric field vector of the light emitted from the semiconductor laser 11 and perpendicular to the paper surface), and the polarizer 16 of the isolator 19 or The incident surface of the Faraday rotator 17 of the isolator 19 is the semiconductor laser 11
It was arranged so as to be inclined in the S polarization direction (the direction perpendicular to the vibration direction of the electric field vector and parallel to the paper surface) with respect to the polarization plane of.

The reason is that the emitting surface of the semiconductor laser 11 is
Semiconductor laser window 14, polarizer 16 of isolator 19, Faraday rotator 17 of isolator 19
This was to prevent resonance from occurring between the incident surfaces of.

[0007]

However, when the polarizer 16 of the isolator 19 is tilted in the S polarization direction and the incident surface of the Faraday rotator 17 is in the S polarization direction as in the conventional semiconductor module, the temperature of the semiconductor laser 11 is reduced. It has been found that, when a change occurs in the semiconductor laser 11, the transmission characteristic changes when some resonance occurs in the optical path according to the change in the oscillation frequency of the semiconductor laser 11, and as a result, the composite secondary distortion of the semiconductor module increases. It is an object of the present invention to provide a means for reducing the composite secondary distortion caused by the internal reflection of a semiconductor laser module.

[0008]

A semiconductor laser according to the present invention.
In the module, (1) In a semiconductor laser module having a semiconductor laser and an isolator consisting of a polarizer, a Faraday rotator, and an analyzer, the window of the semiconductor laser is semi-conductive.
The P-polarization direction with respect to the plane of polarization of the body laser,
The polarizer in the isolator is the polarization of the semiconductor laser.
The isolator tilted in the P-polarization direction with respect to the wavefront and
The incident surface of the Faraday rotator at
Inclining in the P-polarization direction with respect to the plane of polarization of the body laser
Characterized in that it is not parallel to the window of the semiconductor laser
Or

(2) Semiconductor laser, and polarizer and Faraday rotator
A semiconductor laser module having an isolator consisting of an analyzer.
In the Joule, the window of the semiconductor laser is semiconducting
The P-polarization direction with respect to the plane of polarization of the body laser,
If the polarizer in the isolator is the laser diode of the semiconductor laser.
It is tilted in the P-polarization direction which is opposite to the tilt direction in India.
Or

(3) Semiconductor laser, and polarizer and Faraday rotator
A semiconductor laser module having an isolator consisting of an analyzer.
In the Joule, the window of the semiconductor laser is semiconducting
The P-polarization direction with respect to the plane of polarization of the body laser,
The polarizer in the isolator is the polarization of the semiconductor laser.
The P-polarization direction with respect to the wavefront, and the semiconductor laser
Tilts in the P-polarization direction opposite to the tilting direction of the laser window
The Faraday rotation in the isolator
The incident surface of the laser is P-polarized with respect to the polarization plane of the semiconductor laser.
Tilts in the same direction, and
Characterized by not being a line.

[0011]

[0012]

FIG. 3 is an explanatory view of the compound second-order strain temperature dependence of the semiconductor laser module with an isolator. The horizontal axis of this figure shows the temperature (° C.) of the semiconductor laser, and the vertical axis shows the composite second-order distortion (CSO: dBc). Here, complex second-order distortion is due to multi-channel transmission of analog signals,
It means the sum of all distortions generated by two adjacent carriers, and shows the decibel ratio (dBc) of the amplitude of the composite second-order distortion to the amplitude of the carrier.

In this figure, when S-polarized light is incident on the polarizer 16 and the Faraday rotator 17, when the temperature of the semiconductor laser changes as shown by the curve a,
The composite second-order distortion has changed significantly to about 28 dBc,
This indicates that some kind of resonance has occurred in the optical path of the semiconductor module.

On the other hand, the polarizer 16 according to the present invention
When the P-polarized light is incident on the Faraday rotator 17 and the curve b, as shown in the curve b, when the temperature of the semiconductor laser changes, the composite second-order distortion changes only about 2 dBc,
It shows that some resonance hardly occurs in the optical path of the semiconductor module. It should be noted that the polarizer of the isolator is tilted by 6 ° regardless of whether S-polarized light or P-polarized light is incident on the polarizer 16 or the Faraday rotator 17.

When a structure in which the polarizer of the isolator is inclined in the P polarization direction with respect to the plane of polarization of the semiconductor laser, as in the case of another semiconductor laser module according to the present invention, the light emitting surface of the semiconductor laser and the isolator are used. As a result, the composite second-order distortion can be reduced without causing resonance between the polarizers.

Further, if a structure in which the window of the semiconductor laser is tilted in the P polarization direction with respect to the plane of polarization of the semiconductor laser is adopted, resonance is caused between the light emitting surface of the semiconductor laser and the window of the semiconductor laser. Without happening
As a result, the composite secondary distortion can be reduced.

Further, when the incident surface of the Faraday rotator of the isolator is tilted in the P polarization direction with respect to the polarization plane of the semiconductor laser and is not parallel to the window of the semiconductor laser, the light of the semiconductor laser is Resonance does not occur between the emitting surface and the entrance surface of the Faraday rotator of the isolator, and as a result, the composite second-order distortion can be reduced.

At the same time, the window of the semiconductor laser is tilted in the P polarization direction with respect to the polarization plane of the semiconductor laser, and the polarizer of the isolator is tilted in the P polarization direction opposite to the tilt direction of the window of the semiconductor laser. By adopting the configuration described above, resonance does not occur between the window of the semiconductor laser and the polarizer of the isolator, and as a result, the composite second-order distortion can be reduced.

[0019]

EXAMPLES Examples of the present invention will be described below. Figure 1
It is a structure explanatory view of a semiconductor laser module of one example of the present invention. In this figure, 1 is a semiconductor laser, 2 is a first lens, 3 is a Peltier cooler, 4 is a window, 5 is a case, 6 is a polarizer, 7 is a Faraday rotator, 8 is an analyzer, 9 is an isolator, and 10 is a carrier. Is.

In an example of a semiconductor module of one embodiment of the present invention, as shown in the plan view of FIG. 1, a semiconductor laser 1 is mounted on a Peltier cooler 3 via a carrier 10, and the semiconductor laser 1 is mounted on the semiconductor laser 1. The case 5 in which the first lens 2 is arranged in the emitting direction of the radiated light and accommodates these
A window 4 for emitting the light that has passed through the first lens 2 to the outside is formed in the outside, and the light emitted to the outside from the window 4 is an isolator 9 including a polarizer 6, a Faraday rotator 7, and an analyzer 8. It is designed to be incident on.

The window 4 of the semiconductor laser is arranged in a state of being tilted in the P polarization direction with respect to the polarization plane of the semiconductor laser 1, and the polarizer 6 of the isolator 9 is in the P polarization direction with respect to the polarization plane of the semiconductor laser 1. Or the incidence plane of the Faraday rotator 7 of the isolator 9 is inclined in the P polarization direction with respect to the polarization plane of the semiconductor laser 1, and the analyzer 8 of the isolator 9 is polarized in the direction of the polarization direction of the semiconductor laser 1. It is arranged so as to be inclined in the P-polarized direction with respect to the wavefront. However, the window 4 of the semiconductor laser 1
Thus, the incident surface of the Faraday rotator 7 of the isolator 9 is not parallel.

The semiconductor laser module of this embodiment is
It has the characteristics as shown by the curve b in FIG. 3, and even if the temperature of the semiconductor laser 1 changes by ± 5 ° C., the composite secondary distortion is 2 dB.
It can be suppressed to c or less.

In the above embodiments, the present invention has been described as a semiconductor laser module for analog transmission, but the present invention is not limited to the semiconductor laser module for analog transmission, and a high bit rate of about 10 Gb / s or more. It can also be applied to digital signal processing at rate.

In the semiconductor laser module of this embodiment, the window 4 of the semiconductor laser is arranged in a state of being inclined in the P polarization direction with respect to the polarization plane of the semiconductor laser 1, and the polarizer 6 of the isolator 9 is arranged in the semiconductor laser 1. Of the Faraday rotator 7 of the isolator 9 is inclined in the P polarization direction with respect to the polarization plane of the semiconductor laser 1, and the analyzer 8 of the isolator 9 is The semiconductor laser 1 is described as being arranged in a state of being inclined in the P-polarized direction with respect to the plane of polarization of the semiconductor laser 1. However, with some of these configurations, the resonance that occurs in the optical waveguide can be reduced and the composite secondary distortion can be reduced. It goes without saying that the effect of reduction is obtained.

[0025]

As described above, according to the present invention,
It is possible to realize a semiconductor laser module that does not generate a significant composite secondary distortion even if the temperature fluctuates, which greatly contributes to the field of optical communication using the semiconductor laser module as a light source.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a semiconductor laser module according to an embodiment of the present invention.

FIG. 2 is a configuration explanatory view of a conventional semiconductor module.

FIG. 3 is an explanatory diagram of a compound second-order strain temperature dependency of a semiconductor laser module with an isolator.

[Explanation of symbols]

1 Semiconductor laser 2 First lens 3 Peltier cooler 4 wind 5 cases 6 Polarizer 7 Faraday rotator 8 Analyzer 9 Isolator 10 careers 11 Semiconductor laser 12 First lens 13 Peltier Coola 14 wind 15 cases 16 Polarizer 17 Faraday Rotator 18 Analyzer 19 Isolator 20 career

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01S 3/00-5/50

Claims (3)

(57) [Claims] 1. A semiconductor laser, and a semiconductor laser module having the isolator comprising a polarizer and a Faraday rotator and an analyzer, the window of the semiconductor laser to the polarization plane of the semiconductor laser
In contrast, the polarizer in the isolator is tilted in the P polarization direction, and
Is inclined in the P polarization direction with respect to the polarization plane of the
The entrance surface of the Faraday rotator in the
Inclination in the P-polarization direction with respect to the plane of polarization of the semiconductor laser
A semiconductor laser module, which is not parallel to the window of the semiconductor laser. 2. A semiconductor laser , a polarizer and Faraday.
Half with an isolator consisting of a rotator and an analyzer
In the conductor laser module, the window of the semiconductor laser is aligned with the polarization plane of the semiconductor laser.
In contrast, the polarizer in the isolator is tilted in the P polarization direction, and
Semiconductors laser module that characterized by being inclined in opposite of P polarization direction to the inclination direction of The Wind. 3. A semiconductor laser , and a polarizer and Faraday.
Half with an isolator consisting of a rotator and an analyzer
In the conductor laser module, the window of the semiconductor laser is aligned with the polarization plane of the semiconductor laser.
In contrast, the polarizer in the isolator is tilted in the P polarization direction, and
P polarization direction with respect to the polarization plane of the
In the P-polarization direction opposite to the tilt direction of the window of the conductor laser
Tilting of the Faraday rotator in the isolator
The plane of incidence is P-polarized with respect to the plane of polarization of the semiconductor laser.
Semiconductors laser module that wherein the non-parallel and the window of the semiconductor laser with slopes.