JPH02155286A - Wavelength-tunable semiconductor laser device - Google Patents

Abstract

PURPOSE:To stabilize an oscillation wavelength and to simplify manufacturing steps by combining a semiconductor laser having a non-diffraction grating structure and a piezoelectric member so disposed as to directly or indirectly compress the laser. CONSTITUTION:Pressure is applied to a semiconductor laser by using a piezoelectric member such as crystal, Rochelle salt, BaTiO3, etc., to variably control the oscillation wavelength of a laser. As a semiconductor laser, non-grating structure which is heretofore known such as GaAs, etc., is employed. As a pressure transfer member, a rigid material such as hard resin, glass, iron, etc., is employed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wavelength tunable semiconductor laser device used for optical recording (wavelength multiplexing recording), optical communication, and the like.

[Prior art]

Conventionally, as a wavelength tunable semiconductor laser device, carriers are injected into the diffraction grating portion of a semiconductor laser whose resonator has a periodic structure like a diffraction grating, such as a DBR (distributed reflection type) or DFB (distributed feedback type) laser. There are methods that change the refractive index and effectively change the lattice constant to change the oscillation wavelength, and methods that physically change the lattice constant of the diffraction grating of a semiconductor laser that has a periodic structure similar to the above. A method is known in which the oscillation wavelength is changed by changing the oscillation wavelength.

Laser devices using the former carrier injection, such as D
As shown in Figure 1(a), a BR laser device has a DBR region consisting of a diffraction grating on both sides (or one side) of an active region, and has a wavelength (longitudinal mode) that satisfies the Bragg reflection condition.
The oscillation wavelength is selected by utilizing the fact that the oscillation wavelength is reflected. Therefore, the lattice constant of the diffraction grating does not change, but the oscillation wavelength also changes.

Therefore, as shown in the figure, an attempt has been made to change the oscillation wavelength by flowing a current It in the DBR region and injecting carriers to change the refractive index of the diffraction grating medium and effectively change the lattice constant. However, in this method, the degree of temperature rise of the semiconductor laser differs depending on the current density of It, so modulating It has the disadvantage that the oscillation wavelength becomes unstable due to temperature instability. There is.

On the other hand, the latter laser device that utilizes physical changes in the lattice constant is shown in Figures 1(b) and 2 (1 in the figure is a piezoelectric member,
10 is a DFB region), for example, in a DFB laser, the piezoelectric member 1 is arranged in parallel with the diffraction grating, and the piezoelectric member is driven to change the lattice constant. However, in this case, the piezoelectric member layer must be provided during the epitaxial growth process of the semiconductor laser, which complicates the manufacturing process.

Further, both of the amphibodiic conductor laser devices utilize a semiconductor laser having a diffraction grating structure, and such lasers require a complicated process to create the diffraction grating.

[Problem to be solved by the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks in the prior art, and to eliminate temperature instability which causes instability in the oscillation wavelength of semiconductor lasers.

Another object of the present invention is to provide a tunable oscillation semiconductor laser device with a non-diffraction grating structure that is easy to manufacture.

[Structure and operation of the invention]

The tunable oscillation semiconductor laser device of the present invention is a combination of a semiconductor laser having a non-diffraction grating structure and a piezoelectric member arranged to compress the laser directly or indirectly. Note that the piezoelectric member is driven by an electric signal to generate pressure.

The principle of tunable oscillation wavelength of the device of the present invention will be explained with reference to the drawings.

Generally, the energy gap or energy band width (Eg) of a solid changes with the interatomic distance, as schematically shown in FIG. In the case of this figure, if the interatomic distance becomes closer due to external pressure, Eg becomes smaller. Depending on the band structure, some become large, while others take a maximum value (or minimum value) at an appropriate interatomic distance. In the case of a semiconductor laser, since the emission spectrum changes as Eg changes, the oscillation wavelength can be controlled by pressure. For example, in the case of Ga As, Eg (usually 1.4
eV) is approximately I Xl0-seV/ba depending on the pressure.
It is said that it increases at a rate of r. In other words, a pressure of about 100,100 O/Cm causes a wavelength fluctuation of about 70 degrees.However, the above is a case where pressure is applied isotropically, and in reality, In order to apply a certain amount of pressure, for example, by placing a semiconductor laser into the liquid,
This requires applying pressure to the liquid, which is difficult to achieve. However, it has been confirmed that the above-mentioned effects can be exerted to some extent even by applying pressure in the axial direction alone.

The present invention utilizes the above principle to variably control the oscillation wavelength of a laser by applying pressure to a semiconductor laser using a piezoelectric member.

Although there are no particular limitations on the type of piezoelectric member used in the present invention, a piezoelectric member that generates a large force is more effective. Ordinary piezoelectric members can easily generate a large force of about 100 Kgf/am''. Specific examples of such piezoelectric members include quartz, Rochelle salt, BaTi○, PZT.
(P bT'xo, P bZro,) system, CdS,
ZnO, 5in2; Polyvinyldene fluoride; Polymer and PZ
Examples include composites with ferroelectric ceramics such as T-based ceramics.

Therefore, using these ordinary piezoelectric members, for example, 1O:1
It is possible to apply a compressive force of 100100 O/cm'' to the semiconductor laser by transmitting the compressive force to the semiconductor laser with an area ratio of .

Examples of the structure of a wavelength tunable semiconductor laser device using the piezoelectric member as described above are shown in FIGS. 4 to 6. 4 and 5 (in the figures, 2 is a pressure transmitting member, 3 is a semiconductor laser, and 4 is a stand), the pressure of the piezoelectric member 1 is transmitted to the semiconductor laser via the pressure transmitting member. There is.

In the case of FIG. 4, the pressure is applied in one axial direction, and in the case of FIG. 5, it is applied in two axial directions. In addition, in FIG. 4, the pressure transmitting member has a truncated pyramid shape in which the area ratio of the upper surface in contact with the piezoelectric member and the lower surface in contact with the semiconductor laser is approximately 10:1, thereby increasing the pressure of the piezoelectric member by 10 times. It is possible to transmit the signal to a semiconductor laser.

Further, depending on the characteristics of the piezoelectric member or the variable wavelength range, the piezoelectric member may directly compress the semiconductor laser as shown in FIG.

In any case, as a semiconductor laser, GaAs, Ga
All conventionally known non-lattice structures such as AQAs, InGaAQP, and InGaAsP can be used.

Further, as the pressure transmission member, rigid materials such as hard resin, glass, and general metals such as iron, nickel, aluminum, zinc, stainless steel, and brass can be used.

Note that the maximum size of the semiconductor laser is 0.1 mm x 0.
Since it is about 1 mm, even if the area is 10 times that, l
Since it is within mm x 1 mm, there is no need to worry about it becoming too large as a laser light source.

[Function and effect of the invention]

As described above, the wavelength tunable semiconductor laser device of the present invention combines a piezoelectric member with a semi-conductor laser having a non-diffraction grating structure, so there is no temperature instability and the oscillation wavelength is stable. Since there is no need to provide a piezoelectric material layer during the Evitacal growth process or create a diffraction grating, there is an advantage that the manufacturing process can be simplified.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are explanatory diagrams of conventional wavelength tunable DBR and DFB semiconductor laser devices, respectively, and FIG.
FIG. 3 is a cross-sectional view of an example of an FB semiconductor laser device, and FIG. 3 is a schematic diagram of an energy gap in a solid for explaining the principle of the wavelength tunable semiconductor laser device of the present invention.
The figures are cross-sectional views of each example of the device of the invention.

Claims (1)

[Claims] 1. A wavelength-tunable semiconductor laser device that combines a semiconductor laser with a non-diffraction grating structure and a piezoelectric member arranged to compress the laser directly or indirectly through a pressure transmission member.