JPH05149793A - Wavelength detecting device - Google Patents

Abstract

PURPOSE:To easily detect the oscillating wavelength of a semiconductor laser device, etc., by detecting laser light with a light output detector and another light output detector incorporating a filter, the transmissivity of which has a wavelength dependency, and comparing the output signals of both detectors with each other. CONSTITUTION:Laser light from a semiconductor laser element 3 is equally emitted to the light output detectors 7a and 7b of this wavelength detector 5. Since a filter 8, the transmissivity (k) of which has a monotonous wavelength dependency over its wavelength detecting extent, is provided on the light receiving surface of the detector 7a, the signal intensity Ia of the detector 7a becomes Ia=kXIb, where Ib represents the signal intensity of the detector 7b. Therefore, since the signal intensity ratio Ia/Ib obtained by means of a signal comparator becomes a function proportional to the transmissivity (k), the wavelength of the laser light can be detected by detecting the ratio Ia/Ib. In addition, when the ratio Ia/Ib deviates from a preset wavelength, a Peltier element drive circuit is actuated and controls the temperature of a Peltier element 2 so as to tune the laser light from the element 3 to a preset wavelength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting an oscillation wavelength of a semiconductor laser device or the like.

[0002]

2. Description of the Related Art In recent years, semiconductor laser devices have been used for optical information processing,
It has been actively studied as a light source for optical communication and excitation of a solid-state laser device. For example, as an application of a solid-state laser device to a light source for excitation, laser research, Vol. 16, No. 3,
It is described on pages 41 to 50 of 1988.

When the semiconductor laser device is applied to a light source for exciting a solid-state laser device, in order to sufficiently excite the laser medium of the solid-state laser device, the oscillation wavelength of the laser light output from the semiconductor laser device is set to a desired value of the laser medium. It is necessary to tune to the peak wavelength of the absorption spectrum of. For example, YA
In the G (Nd-doped) laser device and the YLF (Nd-doped) laser device, the peak wavelengths of the absorption spectrum of the laser medium are 805 to 809 nm and 795 to 805 nm, respectively. The wavelength of light is ± 0.5n with respect to the peak wavelength
It must be controlled within the range of m.

By the way, the semiconductor laser device has an individual difference in its oscillation wavelength, but has a property that the wavelength is shifted to about 0.3 nm long wavelength side or short wavelength side by the temperature rise or fall of 1 ° C., respectively. Conventionally, for example, a semiconductor laser device is installed on a Peltier device, and the temperature of the semiconductor laser device is changed by this Peltier device to tune the peak wavelength of the solid-state laser device and the oscillation wavelength of the semiconductor laser device.

[0005]

[Problems to be Solved by the Invention] However, in the past,
The confirmation of the tuning of the peak wavelength of the solid-state laser device and the oscillation wavelength of the semiconductor laser device is generally performed by monitoring the intensity of the laser light output by the solid-state laser device, and the oscillation wavelength of the semiconductor laser device can be adjusted. There was a problem that it was very complicated. In addition, a large-scale device such as a spectroscope is required to detect the oscillation wavelength of the light source in other cases, and the wavelength value cannot be easily checked.

In view of such a problem, the present invention has an object of simply detecting the wavelength of light output from a light source such as a laser device.

[0007]

A wavelength detector of the present invention compares an optical output detector, an optical output detector having a filter having wavelength dependence of transmittance, and output signals of these optical output detectors. It is characterized by comprising a signal comparator for

[0008]

The intensity ratio of the output signal obtained by detecting the light output from the light source such as a laser with the optical output detector and the optical output detector having a wavelength-dependent filter has a predetermined value with respect to the wavelength. Since it has a value, the oscillation wavelength of the light source can be easily detected.

Further, the optical output detector, the optical output detector having a filter having wavelength dependency of the transmittance, and the signal comparator can reduce the size.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described with reference to the drawings. 1 to 3 show a semiconductor laser device to which the wavelength detection device shown in FIG. 4 is applied, and are a schematic perspective view of a main part, a schematic front view of the main part, and a schematic block diagram, respectively.

In the figure, 1 is a TO-3 type package,
A Peltier element 2 is installed in the package 1. On this Peltier element 2, a semiconductor laser element 3 for outputting laser light from the front and rear end surfaces is fixed to a copper block 4, and below the semiconductor laser element 3, the semiconductor laser element 3 is output from the rear end surface of the laser element 3. A wavelength detector 5 for receiving the generated light is installed.

In the wavelength detecting device 5, as shown in FIG. 4, optical output detectors 7a and 7b, which are PIN photodiodes, for example, are provided on a ceramic insulating substrate 6 to detect the light output from the semiconductor laser device 3. For example, they are fixedly installed by a silver paste or the like in an adjacent state so as to receive equal amounts of light. On the light-receiving surface of one of the optical output detectors 7a and 7b, the transmittance (reflectance) has a monotonous wavelength dependence in the wavelength range in which the semiconductor laser element 3 can oscillate. A filter 8 made of a material is formed. For example, when the semiconductor laser device 3 oscillates light near 810 nm, the filter 8 has a SiO ₂ film (refractive index: 1.46) and a TiO ₂ film (refractive index: 2.36) having the transmittance characteristics shown in FIG. Can be used. The multilayer film is made from the total number 23 film TiO ₂ film and the SiO ₂ film are laminated alternately as SiO ₂ film is constituted between the TiO ₂ film, the film thickness of the SiO ₂ film 4, 20 film th Two
77.4 nm, and the film thickness of the 12th film is 554.8 nm
Except that the thicknesses of all TiO ₂ films and SiO ₂ films are 85.8 nm and 138.7 nm, respectively.

The Peltier device 2 and the semiconductor laser device 3
, And the wavelength detection device 5 are connected to the electrical connection pins of the package 1 by the gold wire lines 9, 9 ,.
0, 10 ... Each signal output from the optical output detectors 7a and 7b is an electrical connection pin 10,
The signal is input to the signal comparator 11 including a differential amplifier via 10, ... The signal subjected to the signal processing drives the Peltier device 2 for controlling the temperature via the Peltier device driving circuit 12. Also, the optical output detector 7
The signal output from b is controlled by an automatic power control (APC) circuit (not shown) and the semiconductor laser driving circuit 13 so that the optical output of the semiconductor laser element 3 becomes constant. The semiconductor laser device 3 is automatically controlled by the current (A
The optical output of the semiconductor laser device 3 may be controlled to be constant through the semiconductor laser drive circuit 13 by the CC) circuit.

Next, the operation of the wavelength detecting device 5 will be described.

The laser light output from the semiconductor laser element 3 is applied to the light output detectors 7a and 7b of the wavelength detecting device 5 in equal amounts, for example. Since the light output detector 7a has a filter 8 with a monotonic wavelength dependence transmittance k (reflectance) in the wavelength detection range on the light receiving surface, when the signal intensity of the optical output detector 7b is a I _b, The signal intensity I _a of the optical output detector 7a is

[0016]

[Equation 1]

[0017] Therefore, the signal having the signal intensity ratio I _a / I _b obtained by comparison in the signal comparator 11 is a function proportional to the transmittance k of the filter 8, and thus the signal having the signal intensity ratio I _a / I _b. The value of the wavelength of the laser beam output from the semiconductor laser element 3 can be detected by detecting

Therefore, when the signal having the signal intensity ratio I _a / I _b is different from the signal having a deviation from the preset wavelength, the signal having the signal intensity ratio I _a / I _b is selected. The Peltier device drive circuit 12 operates based on
The semiconductor laser device 3 is controlled by controlling the temperature of the Peltier device 2.
The wavelength of the light output from is tuned to the set wavelength.

In the above embodiment, the semiconductor device and the wavelength detecting device are built in the TO-3 package, but they may be built in the TO-5, TO-18, etc. package, and the Peltier device is also included. It can also be applied to those that do not use, and various applications are possible. Further, the wavelength detecting device of the present invention is not limited to the wavelength detection of the semiconductor laser device, but can be used for other light sources. When the divergence angle of the light output from the light source is so narrow that it does not enter both of the light output devices 7a and 7b, an appropriate light splitter such as a beam splitter may be used.

The signal intensity from the optical output detectors 7a and 7b detects the wavelength from the signal intensity ratio as described above, but when the output from the light source is set to a predetermined intensity, the The wavelength can be detected from the difference in signal strength.

Further, in the above embodiment, the multilayer film composed of the SiO ₂ film and the TiO ₂ film was used as a filter. However, in addition to the multilayer film, a-Si (amorphous silicon) and SiO _{2 are used.}
A dielectric multilayer film such as the above multilayer film can also be used. In the case of a filter composed of a multilayer film, the wavelength detection region can be changed by appropriately changing the film thickness or the number of laminated layers. In addition, any material can be used as long as it has a monotonic wavelength dependence in transmittance (reflectance) in the wavelength detection range. However, the monotonic wavelength dependence may be monotonic in terms of desired wavelength detection resolution.

Further, the optical output detector is not limited to the PIN photodiode as long as the wavelength dependence is substantially constant in the wavelength detection range, and various types can be used, but the detectors 7a and 7b are also usable.
Are desirable to have the same characteristics without a filter.

Further, although the filter is directly formed on the light receiving surface of the light output detector in the above embodiment, a light output detector having a filter interposed between the light source and the light receiving surface may be used.

The wavelength detector of the present invention can easily detect the wavelength output by a semiconductor laser device or the like. Further, since the wavelength detecting device of the present invention has a very small and simple structure, it can be built in the package of the semiconductor laser device as in the above-mentioned embodiments.

[0025]

According to the wavelength detector of the present invention, an output signal obtained by detecting light output from a light source such as a semiconductor laser device by an optical output detector and an optical output detector having a wavelength-dependent filter is used. By comparing with a signal comparator, the wavelength of the light to be output can be detected, so detection can be performed easily,
Further, the device can be downsized.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a wavelength detection device according to an embodiment of the present invention.

FIG. 2 is a schematic front view of a main part of the wavelength detection device.

FIG. 3 is a schematic block diagram of the wavelength detection device.

FIG. 4 is an enlarged perspective view of the wavelength detection device.

FIG. 5 is a diagram showing a transmittance characteristic of an example of a filter used in the wavelength detector.

[Explanation of symbols]

 5 wavelength detector 7a optical output detector 7b optical output detector 8 filter 11 signal comparator

Claims (1)

[Claims] 1. A wavelength detecting device comprising an optical output detector, an optical output detector having a filter having wavelength dependency of transmittance, and a signal comparator for comparing output signals of these optical output detectors.