JPS63227094A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To switch oscillation wavelengths at high speed by utilizing the difference of oscillation wavelengths due to the difference of the axial modes of a semiconductor laser and selecting oscillation axial modes in response to incident beams to the laser. CONSTITUTION:One axial mode is selected and a semiconductor laser 10 having two oscillation axial modes such as a distributed feedback type (DFB) laser is oscillated in the semiconductor laser 10, and an oscillation mode is changed over by mode jumping in the laser 10 when beams having a wavelength corresponding to the other axial mode are projected to the laser 10. That is, the oscillation wavelength of the semiconductor laser 10 can be switched by stable input beams 21 from the outside. Memory and arithmetic operation by the difference of wavelengths can be conducted by utilizing hysteresis characteristics between the intensity of input beams 21 and the oscillation wavelength of output beams 11. The switching of oscillation axial modes is used, thus allowing operation at high speed.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention relates to a semiconductor laser device used for optical communication, optical information processing, optical storage, etc. The present invention relates to a semiconductor laser device.

(Prior Art) Conventionally, when optical information requires calculation, storage, etc., it is necessary to convert light into electricity and then convert it back into light. Beyond this/
Electricity and electricity/light conversion are obstacles to processing the enormous amount of information contained in light. Therefore, in accordance with the requirements of optoelectronics, it is desired to develop an optical information processing device that can input and output using only light. However, an element used in this type of device, that is, an element that can perform storage, arithmetic processing, etc. using only light, has not yet been put into practical use.

In addition, as an element considered for application to optical information processing equipment, for example, the literature (Odagiri et al., Institute of Electronics and Communication Engineers General Conference 937
(1983), an optical memory device using an optical bistable semiconductor laser using a saturable absorber has been proposed. However, when using a saturable absorber,
Since its response time is determined by the lifetime of spontaneous emission, it has problems such as being unsuitable for high-speed operation.

(Problems to be solved by the invention) As described above, elements conventionally used as optical information processing devices have not yet been put into practical use, and optical memories using bistable semiconductor lasers using saturable absorbers cannot operate at high speeds. There were problems such as unsuitability.

Furthermore, if the oscillation wavelength of a single semiconductor laser could be changed, the application to various uses would be expanded, but it was not possible to switch the laser oscillation frequency easily and at high speed.

The present invention has been made in consideration of the above circumstances, and its purpose is to be able to switch the oscillation wavelength by optical input, to perform this switching at high speed, and to improve optical communications and optical information. An object of the present invention is to provide a semiconductor laser device that can be applied to processing, optical storage, and the like.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to utilize the difference in oscillation wavelength due to the difference in the axial mode of a semiconductor laser, and to change the oscillation axial mode depending on the light incident on the laser. It's about choosing.

That is, the present invention has at least two oscillation axis modes,
A first semiconductor laser selects and oscillates one mode among these axial modes, and operates in a single mode at a wavelength that substantially matches one of the plurality of axial modes that can be oscillated by this laser, and generates laser light. and a second semiconductor laser that enters the first semiconductor laser, the semiconductor laser device comprising: a second semiconductor laser that enters the first semiconductor laser; It is designed to switch the oscillation wavelength.

(Operation) A semiconductor laser having two oscillation axis modes, such as a distributed feedback (DFB) laser, typically oscillates with one axis mode selected. When light with a wavelength corresponding to the other axial mode is incident on this laser, the oscillation mode of the laser is switched due to mode jumping. That is, the oscillation wavelength of the semiconductor laser can be switched using stable input light from the outside. Furthermore, there is a hysteresis characteristic between the intensity of the human-powered light and the oscillation wavelength of the output light, and by utilizing this hysteresis characteristic, it becomes possible to perform storage and calculation operations based on differences in wavelength. Since switching of the oscillation axis mode is utilized, high-speed operation is theoretically possible.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic configuration diagram schematically showing a semiconductor laser device according to an embodiment of the present invention. This device is composed of a first semiconductor laser 10 and a second semiconductor laser 20, and the laser beam 21 of the second semiconductor laser 20 is
The light is guided to the first semiconductor laser 10, and the first semiconductor laser 1
0 laser light 11 is extracted as output light.

The first semiconductor laser 10 is responsible for optical storage operation and is a normal DFB laser. This DFB laser is a dynamic single mode laser that oscillates in a stable axial mode even during high-speed modulation, and if edge reflection is ignored, there are two oscillation axial modes (λ0, λ) that are symmetrical with respect to the Bragg wavelength. do. And in general there is always one mode (λ0)
is selected and oscillates. The second semiconductor laser 20 provides optical input to the first semiconductor laser 10, and is a DFB laser in which a part of the diffraction grating is shifted by λ/4 to match the oscillation wavelength and the Bragg wavelength. This laser 20 always oscillates with a single wavelength, and its oscillation wavelength λ1' approximately corresponds to a mode (λ□) different from the mode in which the first semiconductor laser 10 oscillates when there is no human light. It has become something to do.

The current I in the first semiconductor laser 10 is equal to or higher than the threshold value 1th.
When bias is applied, this laser 10 oscillates at wavelength λ0. However, light from the second semiconductor laser 20 (wavelength λ,') that is the same as or close to the other axial mode wavelength λ1
When input, the first semiconductor laser 10 causes a mode jump and its oscillation wavelength changes to λ1.

Here, when the intensity P of the light 21 input to the first semiconductor laser 10 changes from a sufficiently small state to an increasing direction, the wavelength is λ0 when P<Pl, as shown in FIG. 2(a).
However, when P>Pl, the oscillation wavelength changes to λ1. Moreover, once the wavelength becomes λ, even if the amount of incident light is reduced, <p>p, <However, Pl
<p2), the wavelength remains unchanged from λ1, and when P<Pl, the wavelength returns to λ0. This situation is shown in FIG. 3, and it can be seen that there is a hysteresis characteristic in the oscillation wavelength of the first semiconductor laser 10 with respect to the incident light intensity P. In FIG. 3, the horizontal axis represents the incident light intensity P, and the vertical axis represents the oscillation wavelength λ.

The above hysteresis characteristics enable optical storage. That is, assume an incident light pulse in which the L level is set between Pl and Pl and the H level is set to 22 or more as shown in FIG. 4(a). The output oscillation wavelength of the first semiconductor laser 10 is usually λ. However, when the above pulse is input, the first semiconductor laser 10 is activated as shown in FIG. 4(b).
The output oscillation wavelength of is switched to λ1. In other words, the output oscillation wavelength of the first semiconductor laser 10 is in a state of optical storage. This state of optical storage is maintained even after the incident light reaches the L level. Also, to eliminate optical memory,
I bias may be set below the threshold value 1th, or the incident light intensity may be set below P1.

Note that the bias current I flowing through the first semiconductor laser 10
The relationship between the optical input width of blas and the hysteresis is as shown in FIGS. 5(a) to 5(c) (the culm input width increases as Iblas increases (it is also possible to set Pi -0).

A feature of wavelength-based optical storage is that high-speed operation is possible in principle because the storage operation is performed by mode jumping using the injection locking phenomenon of a semiconductor laser.

Thus, according to this embodiment, the oscillation wavelength of the first semiconductor laser 10 can be switched by simply changing the oscillation output of the second semiconductor laser 20.

That is, the oscillation wavelength of the laser 10 can be selected between two modes depending on the intensity of the light incident on the first semiconductor laser 10, and this can be used for optical storage. In this case, unlike an optical memory using a bistable semiconductor laser using a saturable absorber, high-speed operation is possible in principle, and its usefulness is enormous. Further, one cell can be realized by combining two DFB lasers, and it can be formed monolithically, which is effective for integration and miniaturization.

Note that the present invention is not limited to the embodiments described above. For example, the first semiconductor laser may have three or more oscillation modes, in which case optical storage of three or more values becomes possible. However, the wavelength corresponding to the oscillation mode of the first semiconductor laser is set to λ0. λ1. When λ2 is assumed, two types of wavelengths of light are required to be input to this laser. For this purpose, the second semiconductor laser may have two oscillation modes, or two second semiconductor lasers may be used.

Further, the first and second semiconductor lasers are not limited to DFB lasers, and the first semiconductor laser has at least two oscillation axis modes, and the second semiconductor laser has an oscillation axis mode of the first semiconductor laser. It is sufficient if it operates in a single mode at a wavelength that substantially matches one of the wavelengths. Furthermore, by using a plurality of the structures of the present invention as one cell, various optical calculations can be performed.

It is possible to perform optical information processing, etc. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, the oscillation wavelength of the first semiconductor laser can be switched by the optical output of the second semiconductor laser, and this switching can be performed at high speed. can. Therefore, it is possible to realize a semiconductor laser device that can be expanded to various uses and can be applied to optical communication, optical information processing, optical storage, etc., and its usefulness is tremendous.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram schematically showing a semiconductor laser device according to an embodiment of the present invention, FIGS. 2 and 3 are schematic diagrams for explaining the operation mode of the device, and FIG. FIG. 5 is a schematic diagram for explaining the optical storage principle of the device, and FIG. 5 is a schematic diagram for explaining changes in hysteresis width due to differences in bias. 10... First semiconductor laser, 11... Laser light (
output light), 20... second semiconductor laser, 21...
Laser light (input light). Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 3

Claims (4)

[Claims] (1) A first semiconductor laser that has at least two oscillation axis modes and oscillates by selecting one of these axial modes; a second semiconductor laser that operates in a single mode at a matching wavelength and inputs laser light into the first semiconductor laser, and by controlling the optical output of the second semiconductor laser, A semiconductor laser device characterized by switching the oscillation wavelength of a semiconductor laser. (2) The semiconductor laser device according to claim 1, wherein the first and second semiconductor lasers are each a distributed feedback laser. (3) The first semiconductor laser is a laser having two oscillation axis modes, and the second semiconductor laser is a laser having two oscillation axis modes, and the second semiconductor laser is a laser having two oscillation axis modes.
Claim 1 or 2, wherein the semiconductor laser is a laser that operates in a single mode at a wavelength substantially corresponding to a mode different from the mode in which it oscillates when there is no incident light. Semiconductor laser equipment. (4) The second semiconductor laser has a part of the diffraction grating at λ/
3. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is a 4-shifted distributed feedback laser.