JPS60154208A - Photodetecting device - Google Patents

Abstract

PURPOSE:To obtain a small-sized photodetecting device which suits to integration by extracting a light output with specific wavelength through a waveguide type directional coupler, and obtaining the output current of a semiconductor photodetecting element. CONSTITUTION:For example, optical waveguides 21 and 22 are arranged in parallel, the wavelength lambda of light made incident on the optical waveguide 21 is lambda0, and this light travels to the optical waveguide 22 completely. In this case, lambda0 is the center wavelength of the waveguide type directional coupler. The ratio of output currents I1 and I2 of semiconductor photodetecting elements D1 and D2 provided at end parts of the optical waveguides 21 and 22 has wavelength characteristics as shown in a graph when the semiconductor photodetecting elements are equal in quantum. Consequently, it is evident that I1/I2 is a function of the wavelength lambda within a wavelength range, so a wavelength signal is detected in the form of the ratio of the output currents of the semiconductor photodetecting elements.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a device for receiving optical output of a specific wavelength and converting it into an electrical signal.

Conventional technology A dynamic single-wavelength semiconductor laser that stably operates in a single-axis configuration even during direct modulation in the long wavelength band.

References 1 below. 2. 3, etc., and electrically changing the oscillation wavelength of the semiconductor laser has also become successful as shown in Document 4, which will be described later.

By realizing such dynamic single-wavelength semiconductor lasers that can change wavelengths, it is possible to realize semiconductor lasers that operate stably at a specific single wavelength, which is essential for high-density wavelength multiplexing communications and optical heterodyne communications. It is requested.

As shown in FIG. 1, the above-mentioned semiconductor laser device consists of a wavelength variable single-wavelength semiconductor laser l, a control section C, and an oscillation wavelength and optical output monitor SM.
This function constantly monitors the oscillation wavelength and optical output and immediately corrects any fluctuations that occur.

Conventionally, there have been various reports regarding the semiconductor laser l.
The control section C can be easily realized with an electrical integrated circuit, but there is no conveniently small part for monitoring the wavelength and optical output, and experiments require only a large spectrometer and photoreceiver. The disadvantage is that they must be used together.

Reference 1 Distributed feedback semiconductor laser (K, Utakae
tal, Electron Lett, PP9
61-962.

1981) Reference 2 Distributed reflection wall semiconductor laser (Y, Abe eta
l, Electron Le mouth, PP410~41
1.

1982) Reference 3 C1eaved-Coupled-Cav
ity semiconductor laser (W, T, Tsang et a
l, 100C' 8329B5-4PD, 1983
) Reference 4 l00C'83 (29B-IPI), 29B-
3FD, 29B-4PD) OBJECTS OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and provide a small and practical light receiving device for monitoring the oscillation wavelength and optical output of a semiconductor laser.

Structure of the Invention In order to achieve the above-mentioned object, the present invention has two wires located in parallel within a certain length range and whose propagation constants match at a specific wavelength in the parallel ranges of a certain length. At least one waveguide-type directional coupler composed of optical waveguides is provided in combination on the same substrate, and one semiconductor light-receiving element is provided at one end of each optical waveguide,
It is something to do.

action of invention The present invention is used to monitor the optical output of a specific wavelength.

A combination of a waveguide type directional coupler with wavelength selectivity and a semiconductor photodetector is used.

The operation of the waveguide-based directional coupler will be explained with reference to FIG. 2 showing the basic structural unit of the present invention.

When the optical waveguides 21 and 22 are arranged in parallel, when the wavelength λ of the light incident on the optical waveguide 21 is λ = λO, if this element completely transfers to the optical waveguide 22, this λO is the waveguide type. The center wavelength of the directional coupler is good. The ratio of the output currents II and I2 of (the nine semiconductor light receiving elements 1 provided at the ends of each optical waveguide 21 and 22) I and Dx is:

When the quantum efficiency of each semiconductor photodetector is equal, the line length characteristic shown in Fig. 3 is shown, and as is clear from this, I 1 / I s is a function of the wavelength λ in the wavelength range, so the wavelength signal can be detected by the ratio of the output current of the semiconductor photodetector. ,,,.

At the same time, since the nine-element output is detected by the sum of I and I3, the optical output of this specific wavelength can be detected. - The wavelength characteristic of the output current I2 in this basic configuration is expressed by the following equation based on the theory of waveguide truncated directivity ei.

Here, Δneq: Constant determined by the waveguide structure e: Length of the coupling part λ; Wavelength Therefore, for rounding to increase wavelength sensitivity, Δneq is
Creating a waveguide structure that increases the size.

It is effective to lengthen the joint length l. However, in this case, since the wavelength period 5- of the sin function becomes small, the wavelength range of 1 to 1 is narrowed, resulting in a problem that the measurable wavelength band becomes small.

However, this problem can be solved by combining multiple basic structural units using waveguide type directional couplers with different center wavelengths, or by combining waveguide type directional couplers with slightly different center wavelengths. The wavelength sensitivity can be further increased by detecting a range of wavelengths based on the ratio of output currents of three or more semiconductor light receiving elements. .

In short, the present invention uses a combination of a waveguide type directional coupler and a semiconductor light receiving element, identifies a wavelength based on the ratio of output currents of each semiconductor light receiving element, and detects optical output based on the total value of the output currents. This is the basic principle.

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 4, which shows a first embodiment of a light receiving device according to the present invention, this embodiment includes a wavelength variable dynamic single-wavelength semiconductor laser 1 on the same semiconductor substrate 6.

Five different center wavelengths λ4. λ5. λ6. C. Waveguide type directional coupler with λδ, respectively 4. 5. 6゜7.
8, and six semiconductor light receiving elements Da, D4. D5゜D
o, D7. It also has a configuration that integrates D@.

By configuring in this way, the wavelength-cho-hen-kani dynamic mono-
The output light of the wavelength semiconductor laser l passes through waveguide type directional couplers 4 to 8 having different center wavelengths to semiconductor light receiving elements D4 to D.
8 and the semiconductor light receiving element D3 at the end of the optical waveguide 3.
The output current is identified, and the optical output and wavelength can be detected based on the identified output current, and the semiconductor laser l can be controlled to the desired optical output and wavelength.

Note that in this embodiment, the waveguide type directional coupler is not a scale that is directly installed only in the optical waveguide 3 into which the light to be measured is incident, but a scale that is once further guided through the waveguide type directional coupler 5. A wave-type directional coupler 6 is provided, indicating that such a configuration can also be used.

Referring to FIG. 5 showing a second embodiment of the present invention, this embodiment includes a substrate 11 on which a waveguide type directional coupler 9 and an IO are integrated, and semiconductor photodetectors D9°DIO, Dlst-
It has a configuration in which the integrated substrate 12 is combined, and the light to be measured 1
3 shows a light receiving device that receives light. In addition, between these two substrates 11 and 12, a lens, optical fiber, etc.
It goes without saying that it is also possible to provide a transmission medium and to divide the substrate 12 having the semiconductor light-receiving elements into a plurality of parts and provide one element to each of them.

The present invention has exactly the same effect as the above-mentioned first embodiment by combining it with a wavelength-machi dynamic single-layer conductor laser, and can also be used in combination with necessary substrates, media, etc. when necessary. It is something that can be done.

Effects of the Invention As explained above, according to the present invention, 4'ili+
By extracting the optical output of a fixed 10 wavelengths using a waveguide type directional coupler and obtaining the output current of the semiconductor light receiving element, there is an effect that a practical light receiving device suitable for integration on a vehicle can be obtained.

Furthermore, by using the present invention, a semiconductor laser device that operates stably at a specific single wavelength can be made smaller.

This has the great effect of making it possible to put it into practical use.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a semiconductor laser device that operates stably at a specific single wavelength, Fig. 2 is a basic structural unit diagram of a light receiving device according to the present invention, Fig. 3 is the wavelength characteristic of the output current shown in Fig. 2, and Figures 5 and 5 show first and second embodiments of the present invention, and Figure 4 shows a configuration in which the inventive device is integrated on the same substrate as a wavelength tunable truncated single-wavelength operating laser; FIG. 5 shows a configuration in which a substrate on which a waveguide type directional coupler section is integrated and a substrate on which a semiconductor light receiving element is integrated are combined. l... Wave-tunable dynamic single-wavelength semiconductor laser,
2... Optical output, 3... Optical waveguide into which the light to be measured is incident, 4 to 10... Waveguide type directional coupler, 11...・Nine substrates with integrated waveguide type directional couplers, 12... Substrate with integrated semiconductor light receiving elements, 13... Light to be measured, 21.22...
...Optical waveguide, D1 to D10゜9-1) 111-...Semiconductor photodetector, Il, Iz-
...Output current, λ...Wavelength, λO, ha~
λ10... Center wavelength of the waveguide directional coupler, C... Control section, M... Wavelength and optical output monitoring section. l O- lJx+ Sensei 4-1i21 Minelgao

Claims (1)

[Claims] A waveguide-type directional coupling consisting of two optical waveguides that are wrinkled in parallel within a certain length range, and whose propagation constants match at a specific wavelength in this parallel area of a certain length. At least one or more devices are provided in combination on the same substrate,
- A light receiving device comprising one semiconductor light receiving element at one end of each of the optical waveguides.