JPH03142986A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To stably oscillate a semiconductor laser even if a temperature varies by forming films each having reflectivity wavelength dependency on both light emitting end faces, and providing wavelength selectivity by using the dependency. CONSTITUTION:Films 1, 2 each having reflectivity wavelength dependency are formed on both light emitting end faces of a semiconductor laser device 3, and wavelength selectivity is provided by using the dependency. That is, Al2O3 films 1, 2 are formed on the two emitting faces by using a GaSlAs (Fabry-Perot type) semiconductor laser 3, and so designed that the reflectivity becomes maximum. Thus, even if a temperature varies, its oscillation wavelength is stable, and oscillation wavelength stability can be enhanced in a practical temperature range without narrowing a stable temperature range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a semiconductor laser used in optical communications, optical information processing equipment, and the like.

[Conventional technology] Semiconductor lasers used in optical communications, optical information processing, etc.
It is desired that the oscillation wavelength be stable against temperature changes and optical output changes.

In a typical Fabry-Perot semiconductor laser, the oscillation wavelength has no threshold gain difference (no wavelength selectivity) in the longitudinal mode in which it can oscillate, so the oscillation wavelength is determined by the gain peak wavelength of the active layer. Since the active layer gain peak wavelength varies greatly with temperature, the oscillation wavelength also varies greatly with temperature. However, if the oscillation wavelength changes significantly with changes in temperature, there are many practical problems due to lack of stability.

Therefore, in order to improve this problem, the present inventors formed a dielectric reflective film, which is sufficiently thicker than the wavelength within the film, on the light emitting end facet of the semiconductor laser, and We have already proposed a method to add a threshold gain difference using the rate wavelength dependence.

According to this proposal, if an optical length of 9λ is used as the thickness of the dielectric, a stable oscillation wavelength can be obtained in a temperature range of approximately 160° C.

[Problems to be Solved by the Invention] In the conventional method described above, in order to further strengthen the oscillation wavelength stability (for example, to reduce the oscillation wavelength change with respect to temperature change per 1°C), it is necessary to increase the dielectric film thickness. Needs to be thicker.

However, there is a problem in that increasing the film thickness narrows the temperature range in which the oscillation wavelength is stable.

This can be explained as follows. There are several wavelengths at which the oscillation wavelength is stable as the gain peak wavelength changes due to temperature changes. Among them, the adjacent stabilizing wavelengths are λ.

, λm+□, the difference 1λm+1−λfn1 is
It can be shown that it is inversely proportional to the thickness of the dielectric.

Therefore, if the dielectric thickness is increased, 1λ −λ
1 becomes smaller, the oscillation wavelength jams from λ to λ with a smaller Ge m + 1 m change in the in-peak wavelength, that is, a smaller temperature change.
There is a problem that m+1 shives.

The present invention solves the problems of the prior art described above, and aims to improve the stability of the oscillation wavelength in a practical temperature range without narrowing the oscillation wavelength and narrowing the stable temperature range. purpose.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration. That is, the present invention provides a semiconductor laser device that has both light emitting end faces and emits laser light from both light emitting end faces,
The semiconductor laser device is characterized in that a film having wavelength dependence of reflectance is formed on both of the light emitting end faces, and wavelength selectivity is imparted by utilizing the wavelength dependence of reflectance.

Further, in the present invention, it is preferable that a dielectric multiple reflection film is used and the film thickness is sufficiently thicker than the wavelength within the dielectric in order to determine the dependence of reflectance on wavelength.

Further, in the present invention, it is preferable that the film thicknesses of the dielectrics formed on both light emitting end faces be substantially equal.

[Function] According to the above configuration of the present invention, a film having wavelength dependence of reflectance is formed on both light emitting end faces of the semiconductor laser device, and the film having wavelength dependence of reflectance is used to provide wavelength selectivity. Therefore, the oscillation wavelength is stable even when there is a temperature change, and the oscillation wavelength stability can be improved in a practical temperature range without narrowing the stable temperature range.

In other words, if a dielectric reflective film is formed on one of the light emitting end faces of a semiconductor laser, and the film thickness is sufficiently thicker than the internal wavelength of the film, the reflectance will change from R to (R + △ R), and the threshold gain increases as shown in equation (1) below.

6g + 1. = (1/2L) l 'n ((
On the other hand, if a similar dielectric material is formed on both light emitting end faces of a semiconductor laser, the reflectance of each end face will change from Rf and Rr to (Rf+△ Rf
).

(Rr+ΔRr), and the threshold gain increases by an amount shown by the following equation 0.

6g + h 1=(1/2L) I n [((Rf
+△Rf)/Rfll(Rr+△Rr)/Rr
)] Increases by ””・■.

Furthermore, if the thickness of the dielectric is made equal, Rf=Rr=R, △Rf=△Rr=△R, so
The above equation 0 becomes the following equation (3).

6g −=1/L In ((R+△R)
/R) · (3)+h Compared to the above equation (1), in this equation (3), the threshold gain change is twice as large, indicating that the wavelength stability is further enhanced.

In addition, both equations (1) and (3) above are ((R + △R)/
R), so 1λ −λ 1 is a variable m+1
m, and the wavelength stable temperature range remains the same.

[Example] The present invention will be explained in more detail below using Examples.

Note that the present invention is not limited to the following examples.

FIG. 1 is an external view of a semiconductor laser according to an embodiment of the present invention. In the drawing, a film 1.2 having a wavelength/length dependence of reflectance is formed on both light emitting end faces of a semiconductor laser device 3, and wavelength selectivity is imparted by utilizing the wavelength dependence of the reflectance. Ta.

More specifically, Ga with a gain peak wavelength of 780 nm
An A/As (Fabry-Perot type) semiconductor laser 3 was used. In addition, Al2O3 (optical length 9λ, thickness 9 times the wavelength inside the dielectric) 1.2 is formed on the two light exit surfaces, and at a wavelength of 780 nm, the threshold gain is the lowest (that is, the reflectance is Designed to be the most expensive. The resonator length is 250 μm.

FIG. 2 shows the wavelength dependence of the threshold gain of the device (for simplicity, the minimum threshold gain is set to zero).

The solid line in Figure 2 indicates Al2O on both light emitting surfaces of the semiconductor laser.
The dashed line shows the case where AA'203 is formed to have an optical length of 9λ and a thickness of 9λ on one side of the semiconductor laser, and the other side is formed between the folds. This is the case.

It can be seen that although the threshold gain change is larger in the solid line than in the broken line, the interval between the minimum threshold gain wavelengths remains unchanged.

FIG. 3 shows the temperature dependence of the oscillation wavelength.

As in the case of single-sided AA'2039λ, the wavelength stable temperature range is -60 to 100°C.

It can also be seen that the wavelength change with respect to temperature is reduced from 1.1 A/deg to 0.6 A/deg.

[Effects of the Invention] As described above, according to the present invention, a film having reflectance wavelength dependence is formed on both light emitting end faces of a semiconductor laser device, and wavelength selection is performed by utilizing the reflectance wavelength dependence. This allows the semiconductor laser to oscillate stably even when the temperature changes, without narrowing the stable temperature range.
We were able to distantly trace the remarkable effect of increasing the oscillation wavelength stability.

[Brief explanation of the drawing]

FIG. 1 is an external view of a semiconductor laser device according to an embodiment of the present invention, FIG. 2 is a diagram showing wavelength dependence of threshold gain in an embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 3 is a diagram showing the temperature dependence of the oscillation wavelength in an example. 1: Film with wavelength dependence of reflectance: Film with wavelength dependence of reflectance: Semiconductor laser device Figure 1: Broken line 2 A12's is formed on the single-light emission surface of the semiconductor laser to a thickness of optical length 9λ. , the other light exit surface is at temperature ('C)

Claims (3)

[Claims] (1) In a semiconductor laser device that has both light emitting end faces and emits laser light from both light emitting end faces, a film having a reflectance wavelength dependent is formed on both the light emitting end faces, and the reflectance is wavelength dependent. A semiconductor laser device characterized in that it has wavelength selectivity by taking advantage of its properties. (2) The semiconductor laser device according to claim 1, wherein a dielectric multi-reflection film is used as the reflectance wavelength dependence, and the film thickness is sufficiently thicker than the wavelength within the dielectric. (3) The semiconductor laser device according to claim 2, wherein the dielectrics formed on both light emitting end faces have substantially the same thickness.