JPS60195985A - Constant output semiconductor laser element - Google Patents

Abstract

PURPOSE:To obtain a microminiature and inexpensive constant output semiconductor laser element by forming a semiconductor layer, a drive circuit, a light spectral analyzer and a light power detector on a ferrodielectric substrate for foring a photoconductive waveguide. CONSTITUTION:Partial step is formed on an insulating substrate 1, and a laser diode 2 is arranged. The laser output is led by a photoconductive waveguide 3 formed of a thin film into a light spectral analyzer 4. The waveguide 3 is formed by diffusing an impurity such as Ti in the substrate 1 of LiNbO3. Part of the laser output is fed through the waveguide to a photoreceptor 5 formed of a photodiode. The photoreceptor 5 transmits an electric signal is response to the received light amount to a controller 6 to control the laser output light to be always at constant level. The elements are formed by using a semiconductor IC manufacturing technique to determine the positions of the elements in high accuracy.

Description

[Detailed description of the invention] [Field to which the invention pertains]

The present invention relates to a semiconductor laser device, and more specifically, to a constant output semiconductor laser device in which a semiconductor laser and a circuit element for making its output light constant are integrated on the same substrate. .

[Technology behind the invention]

In general, many optical output elements that generate laser light tend to have a temperature increase due to internal heat generation. The reason is that the optical output part of a semiconductor laser, the active layer, is generally narrow, less than 1 μm in width, and the original output cross section is small, yet it is only 80mW.
This is because it produces a high output and has a high energy density, so it generates a large amount of heat. The amount of heat dissipated by the laser excavation changes depending on the surrounding temperature, and the temperature of the active layer itself also changes. Then, the thermal equilibrium state changes, and the number of electrons and holes injected into the conduction band and valence band becomes limited.
The frequency with which recombination occurs changes. This changes the level of the laser output light. Furthermore, the optical output changes greatly due to fluctuations in the semiconductor laser driving pressure. These factors cause instability in the optical output.

[Prior art and its problems]

Conventionally, to solve this problem, a material with good thermal conductivity, such as diamond, was used as a heat sink. However, it has the disadvantage that it is expensive and that the wafer process and bonding process are increased due to the use of In as an adhesive. The method used was to stabilize the output light of the laser by detecting the reflected light with a photoelectric conversion element, etc., and feeding the detection signal to the current/voltage control drive circuit.However, 1- By using a mirror, skill is required to adjust the angle tm of transmitted light and reflected light, and in addition, due to the unevenness of the reflectance distribution of the mirror itself, the transmitted light and reflected light are adjusted at a constant rate. The drawback was that it was difficult to branch out. Furthermore, such conventional devices, ie, a semiconductor laser as an optical output section and a half mirror as a demultiplexer,
1. When constructing a constant output semiconductor laser output device using a photodiode as a photodetector and a FET as a dynamic circuit, they are connected to each other through an optical and electrical circuit via an interface. The disadvantages are that the process of aligning the optical axis is complicated and difficult, and the device becomes large. The instability of the optical output in conventional semiconductor laser output devices has determined the limit of accuracy as a laser measuring device. For example, when measuring the propagation loss of the original fiber, if the optical output of the laser input to the fiber is unstable, the output light from the fiber will also change as the intensity of the incident light changes. Therefore, even if the sensitivity of the photodetector is stable, the propagation loss of the original fiber cannot be accurately detected.

[Purpose of the invention]

The present invention was devised to eliminate these drawbacks, and its purpose is to mount a semiconductor laser as an optical output section, an optical waveguide branch as a demultiplexer, and a photodetector on the same substrate. The object of the present invention is to provide a constant output semiconductor laser using a diode or the like. In other words, a semiconductor laser, a driving surface path, an optical waveguide, an optical demultiplexer for monitoring the laser output light, and an original power detector are mounted on a strong current substrate that forms an optical waveguide using semiconductor processing and photoetching technology. The present invention provides an ultra-small and inexpensive constant output semiconductor laser device constructed using microfabrication technology. This integrated constant output semiconductor laser device does not require an optical demultiplexer half mirror, and the semiconductor laser, optical waveguide, optical branching path, and optical power detector are each formed using photoetching technology. The positions of the elements are determined with high precision. Therefore, it is an object of the present invention to provide a constant output semiconductor laser device that does not require complicated and difficult operations such as optical axis alignment. To summarize the configuration of the present invention as described above,

[Summary of the invention]

The gist of this invention is listed as follows. (a) Using an optical waveguide branch as a splitter, a part of the semiconductor laser light output is branched for detection. The extracted light output is guided to the photodetector element using the all-optical waveguide,
It is detected using a photoelectric conversion element. (b) Optical waveguides are constructed on the same substrate using semiconductor circuit manufacturing technology, photoetching, etc. (c) In order to keep the laser light output constant, a control drive circuit that compares and judges the electric signal and the standard signal received from the detection element and generates voltage and current to control the laser light output ( 6). In addition, the second embodiment (Fig. 4 (a) and (b)) describes a technique for detecting a part of laser light as an electrical signal using a photoelectric converter that has both the functions of an optical demultiplexer and a light receiving element. disclosed. (e) A constant output semiconductor laser device made of a single substrate with a feed bank function was realized.

[Structure of the invention (examples)]

Next, the configuration of the present invention will be explained with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of the present invention, FIG. 2(a) is a diagram showing an A-AWR plane view thereof, and FIG.
b) is a functional schematic representation of the plan view. In Fig. 1, first, a part of the step is provided on an insulating substrate (11), and a laser diode (2) is arranged.The laser output light is sent to an optical demultiplexer (4) through an optical waveguide made of a thin film. Ferroelectric substrates such as L i N b 03 are conductors, but they can also diffuse impurities such as Ti.Also, ferroelectric substrates such as L i N b 03 are conductors, but they can also be used to diffuse impurities such as Ti. A cull of good optical conductor is formed on a part of the dielectric substrate.The first part of the optical demultiplexer
As an example, as shown in FIG. 3, a lip is formed by arranging Ti diffusion waveguides close to each other on an electrically shielding material such as LiNbO3. A part of the laser output branched here is also sent to a light receiver (5) composed of a photodiode or the like through an optical waveguide. The light receiver (5) sends an electrical signal corresponding to the amount of light received to the control circuit (6). The photodiode is made using conventional semiconductor integrated circuit technology. Here, it is compared with a reference Ig input from the outside to determine its magnitude, and is controlled so that the laser output light is always at a certain level. Control is performed by controlling laser drive voltage and current. In the semiconductor laser device of the present invention, each of the above-mentioned elements is provided on the same substrate, so that the dimensions and the like can be made with high precision using semiconductor IC manufacturing technology, so that products of the same quality can be manufactured. FIG. 4 is a second embodiment of the present application, and is a diagram showing a charging converter for an original IC having the function of combining the optical splitter and the light receiving element. That is, Fig. 4 shows a photoelectric converter that utilizes the thermoelectric effect associated with absorption and heat generation of source energy, in which the lyco/thin film pair, 15 and 16 are electrode pairs, 17 is laser input light, and 8 is laser output light. shows. The p-type amorphous silicon thin film in the figure absorbs light and generates heat, and forms a thermoelectric body with the paired n-type amorphous silicon thin film. In this example, a buried optical waveguide (for example, LiN
bO3 substrate (formed by Ti diffusion), a part of the optical waveguide is removed by etching, and the removed recess is filled with a p-type amorphous silicon thin film deposited on the ferroelectric substrate. . The p-type amorphous silicon thin film has a light absorption characteristic that is line length dependent, and has an absorption coefficient of 10' to 103a++-'. Therefore, if the length of the concave portion of the optical waveguide is set to 1 to 10 μm,
The amount of laser light absorbed by the p-type amorphous silicon thin M region is 0.1 to 100 inches. 1 In this case, once the wavelength of the laser light and the amount of light to be absorbed are determined, it can be configured by a combination of the composition of the p-type amorphous silicon thin film and the length of the recess in the optical waveguide. The p-type amorphous silicon thin film in the recessed portion generates heat due to absorption of laser light and becomes high in temperature. The n-type amorphous silicon thin film provided in contact with a part of the p-type amorphous silicon thin film near the recess constitutes a thermoelectric body with the p-type amorphous silicon thin film, and the vicinity of the recess forms a hot junction with each amorphous silicon thin film. Separate pairs of electrodes form cold junctions. Since amorphous silicon thin films generally have good thermal conductivity, each amorphous silicon thin film has a strip-like shape as shown in FIG. 4 in order to increase detection sensitivity. Regarding the method of forming an amorphous silicon thin film having high conductivity and Seebeck coefficient, the method described in "Thermocouple Element" (Japanese Patent Application No. 108728-1988) is used. As described above, in the second embodiment of the present invention, the thermoelectric effect, photovoltaic effect, and photoconductive effect in a broad sense that a junction formed of a semiconductor has, and the optical multiplication that a P-i-n structure has. The effect is that by combining the light absorption properties of a light-transmitting semiconductor, a portion of the light energy incident on the semiconductor is absorbed by the semiconductor and photoelectrically converted, converting the light energy into 4g of electricity. This method uses a new type of photodetector that detects the magnitude of incident light by passing most of the incident light energy that is not absorbed.

【Effect of the invention】

As mentioned above, according to the first and second embodiments of the present application, the optical signal section and the electric circuit section can be made on the same substrate by a mutually compatible manufacturing process. There is an advantage that the connection position with the optical waveguide can be matched with extremely high precision. There are other effects as well: (,) In order to prevent the output of the semiconductor laser from changing due to factors such as temperature and applied current, the laser diode and photodetector are placed on the same substrate. By providing a feedback device m that adjusts the driving current and voltage so as to keep the optical output constant at all times, it is possible to construct a composite constant output semiconductor laser device that is ultra-compact and provides stable laser output. (b) Since photoetching technology can be used to form the semiconductor, it is possible to construct a constant output semiconductor laser device that is ultra-small and has good dimensional accuracy. (,) Since the conventional incident light separation method is not used to detect the original energy, the incident light separation mirror, optical switch, and switching drive circuit are unnecessary, so the optical 11 converter is inexpensive. A semiconductor laser device can be constructed. Therefore, the constant output semiconductor laser device of the present invention has industrial advantages.
The use of semiconductor lasers can be made more stable and reliable.

[Brief explanation of drawings]

Figure 1 is a diagram showing the first embodiment of the present invention, Figure 2 (,)
2(b) is a functional schematic representation of the plan view of FIG. 1, FIG. 3 is an optical demultiplexer for the original IC, and FIG. 4 is a cross-sectional view taken along line A-A in FIG. (a) is a diagram showing a converter for optical IC light, which is the second embodiment of the present application, and FIG.
It is a figure which shows the a part enlarged view of figure (a). In the figure, 1 is an insulating substrate, 2 is a laser diode, 3 is an optical waveguide, 4 is an optical demultiplexer, 5 is a light receiving element, 6L is a control drive circuit, 7 is a signal input terminal, 8Fi is an optical output, and 9 is a demultiplexer. waved optical output, -, 13 is p-type amorphous silicon thin film, 14 ttin type amorphous silicon thin film, 15 is electrode, 16 is electrode, 17 is optical input, 19
indicates a photoelectric converter. Patent Applicant Anritsu Electric Co., Ltd. Agent Patent Attorney Ryutabe@1 Figure 2 (b)

Claims (1)

[Claims] a substrate having insulating properties; a laser light emitting device produced on the substrate; a control drive circuit produced on the substrate and driving the light emitting device; an optical waveguide formed integrally with the substrate; an optical demultiplexer provided in the middle of the optical waveguide and bypassing a part of the optical output passing through the optical waveguide; □Receives the cold output through the circuit, photoelectrically converts it to the optical output of the light emitting element f, 61i! 'Qi No. □7 in the control-dynamic circuit
4- A light-receiving element produced on the substrate □ for back-up; a reference signal input terminal for applying a reference electric signal to the control drive circuit to match the photoelectric output of the light-receiving element; A constant output semiconductor laser device characterized by stabilizing the output.