JP2000012968A - Wavelength variable laser light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser light source device of a simple and small-sized construction, which stably emits light in a range of light emittable wavelengths of the laser light source. SOLUTION: A wavelength rocker 4 is provided at one light beam emitting end of a semiconductor laser 1. An interference light filter 3 and a photodiodes PD1 and PD2, for receiving transmitting light and reflected light from the interference light filter 3, are disposed in a wavelength rocker 4. The output ratio between the photodiodes PD1 and PD2 is calculated and the wavelengths are controlled in such a way that the output ratio is a specified value. The semiconductor laser 1 and the wavelength rocker 4 are sealed in an optical module 11 and is mounted on a substrate with other blocks. In this way, a small-sized device can stably emit light with the desired wavelengths.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable wavelength semiconductor laser light source device used for optical communication, optical information processing, optical measurement, and the like.

[0002]

2. Description of the Related Art At present, in optical communication, wavelength multiplexing communication in which a large amount of light is transmitted by multiplexing light of a plurality of wavelengths on an optical fiber as compared with the case of using light of a single wavelength. A method is being considered. In order to realize wavelength division multiplexing communication, laser light of a large number of wavelengths is transmitted at intervals of, for example, 0.4 nm or less within a relatively narrow wavelength band in which an optical signal can be amplified as it is, so that the wavelength of the laser light source is sufficient It is necessary to stabilize and oscillate at an arbitrary wavelength. Further, in optical information processing and optical measurement, stabilization of the wavelength of a laser light source is an important issue in order to increase the density of information and increase the accuracy of measurement.

In order to stabilize the emission wavelength of a laser light source, for example, an element having a reference wavelength characteristic is used by some method, and an error from the emission wavelength is detected and fed back to the laser light source. For this reason, conventionally, a device that stabilizes the wavelength based on the absorption of atoms or molecules using the absorption of atoms or molecules, or the wavelength of the reference light or light source using holography, grating or Mach-Zehnder interferometer or Fabry-Perot interferometer, is determined by dithering. A method of modulating and adjusting the wavelength is known. Dithering is to slightly oscillate the wavelength of light by some method. The dither is used to determine the difference and the direction from the reference wavelength and feed back to the laser light source to stabilize the emission wavelength.

In Japanese Patent Application Laid-Open No. 60-74687, light from a semiconductor laser is separated without dithering, and two filters having slightly different wavelengths are used. A method has been proposed in which the light is detected by a conversion element and fed back to a semiconductor laser so that the light intensity ratio is constant.

[0005]

However, in such a conventional method, the light source is slightly changed by dither to change the emission wavelength, the direction is electrically determined, and the change with respect to the reference is detected. Since the feedback is made to the semiconductor laser as the light source, the light of the light source is modulated. For this reason, there is a possibility that the signal may overlap with the modulated signal as information, and there is a drawback that an electric filter such as a low-pass filter or the like is required to eliminate the influence of dither. In addition, since dither is used, the control system becomes complicated. When the dither has a movable part, there is a problem that reliability is low and life is shortened. In the method of JP-A-60-74687,
In order to split light, an optical coupler such as a beam splitter is required. The beam splitter has a drawback that it is affected by the polarization of the light, and the spectral ratio is easily changed depending on the temperature, and it is difficult to produce an element that stably splits the light at a predetermined ratio ideally. Also, the filter has a disadvantage that it is difficult to manufacture two optical filters having slightly different transmission wavelengths. Further, a method of fixing the wavelength by feedback using a wavelength meter has been proposed, but has a disadvantage that periodic calibration is required.

The present invention has been made in view of such conventional problems, and can be miniaturized with an extremely simple structure without using a dither or an optical coupler, and can accurately emit laser light of any wavelength. It is an object to provide a semiconductor laser light source device that can emit light.

[0007]

According to a first aspect of the present invention, there is provided a wavelength-variable semiconductor laser capable of continuously changing the wavelength of light, and light from the semiconductor laser is incident through a space. An optical filter that transmits light of a predetermined wavelength and reflects the other, and first and second optical filters that respectively receive light transmitted through the optical filter and light reflected by the optical filter.
A light receiving element, an output ratio calculating means for calculating an output ratio of the first and second light receiving elements, and a wavelength for controlling an emission wavelength of the light source such that the output ratio by the output ratio calculating means becomes a predetermined value. An electronic circuit unit comprising: a control unit; and an optical module that seals the semiconductor laser, the optical filter, and the first and second light receiving elements; The optical module is characterized by being housed in the same case.

According to a second aspect of the present invention, in the wavelength tunable laser light source device of the first aspect, a temperature detecting element is provided near the optical filter and detects a temperature near the optical filter; Temperature compensating means for compensating for a change in characteristics of the optical filter due to a change in temperature based on the output of the optical filter.

The invention of claim 3 of the present application is directed to claim 1 or 2
In the wavelength tunable laser light source device described above, the optical filter is formed by alternately stacking a low refractive index film and a high refractive index film having an optical thickness of λ / 4 with respect to a transmission wavelength λ. It is an optical filter.

According to a fourth aspect of the present invention, in the wavelength tunable laser light source device of the second aspect, the interference light filter has an optical filter such that the transmission wavelength λ continuously changes in a predetermined direction of the substrate. An incident position adjusting means for continuously changing an incident position of incident light from the laser light source to the interference light filter in a predetermined direction, wherein the thickness of the laser light source device is changed continuously. Is further provided.

According to a fifth aspect of the present invention, in the wavelength tunable laser light source device according to any one of the first to fourth aspects, the wavelength control means is configured to control the output ratio calculated by the output ratio calculation means to a predetermined value. Error detecting means for detecting a difference from the reference value, a reference value setting means for setting a reference value to the error detecting means, and an error value detected by the error detecting means being zero.
Semiconductor laser drive means for controlling the emission wavelength of the semiconductor laser so that

According to the present invention having the above features,
The laser light source emits light, and the laser light is incident on the optical filter. The light incident on the optical filter includes the light being condensed by a lens and incident, but it is assumed that the light is incident through a space without using an optical fiber or the like. Since this filter transmits light of a predetermined wavelength and reflects the other light, the transmitted light and the reflected light are received by the first and second light receiving elements, respectively, and the output ratio is calculated by the output ratio calculating means. Then, by controlling the emission wavelength of the laser light source so that the output ratio becomes a predetermined value, laser light of a predetermined wavelength can be emitted. According to a second aspect of the present invention, the temperature of the optical filter is detected to compensate for a change in characteristics due to the temperature change. According to a third aspect of the present invention, such an optical filter is realized by an interference optical filter having a multilayer film. Further, a multi-layer interference light filter is provided which uses a wavelength variable interference light filter configured such that a transmission wavelength continuously changes in a predetermined direction, and changes a light receiving position thereof. By doing so, the emission wavelength of the laser light source can be changed. In the invention, the reference value is set by the reference value setting means, and the difference between the output ratio calculated by the output ratio calculation means and the reference value is detected by the error detection means as an error. By controlling the laser light source so that the error becomes zero by the light source driving means,
The emission wavelength of the laser light source can be adjusted.

[0013]

FIG. 1 is a view showing an entire optical system of a wavelength tunable laser device according to a first embodiment of the present invention. As shown in this figure, in this embodiment, a multi-electrode type semiconductor laser is used. The multi-electrode wavelength tunable semiconductor laser 1 is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-5603.
As shown in No. 0, by controlling the temperature and the current supplied to the plurality of electrodes, the emission wavelength can be set to, for example, 6
It can be changed within a range of 0 nm or less. The semiconductor laser 1 emits laser light to both sides of the chip. Therefore, the laser light emitted downward in the figure is used for monitoring.
Here, the laser light is transmitted through a lens 2 to an interference light filter 3.
Incident on The interference light filter 3 is a band-pass type optical filter having a transmission wavelength substantially at the center of a wavelength at which a laser light source can emit light, and a photodiode PD1, which is a first light receiving element, is arranged at a position for receiving transmitted light. Further, a photodiode PD2 as a second light receiving element is disposed at a position where the light reflected by the interference light filter 3 can be received. Interference light filter 3 and photodiodes PD1, PD
Numeral 2 is used as a wavelength locker 4 for monitoring the wavelength and fixing the wavelength.

On the other hand, an isolator 6 is arranged on the other emission surface of the semiconductor laser 1 via a lens 5. The isolator 6 regulates the light transmission direction, and the emitted light is connected to the optical fiber 9 via the lens 7 and the collimator 8. The optical fiber 9 guides the emitted laser light to a desired position. Here, the semiconductor laser and the lenses 2 and 5 are arranged in a temperature adjustment module 10 capable of controlling the temperature using a temperature control element such as a Peltier element. The wavelength locker 4, the temperature adjustment module 10, the isolator 6, and the lens 7 are entirely enclosed in an airtight optical module 11. Outside the optical module 11, an electronic circuit for controlling the temperature based on the outputs from the photodiodes PD1 and PD2 is provided.

Next, the interference light filter 3 will be described.
The interference light filter 3 is an optical filter whose output transmittance and reflectivity change in accordance with the wavelength of light incident within the wavelength range in which the semiconductor laser 1 can emit light. Assuming that the transmission wavelength is λ, such an interference light filter can be configured by alternately stacking low-refractive-index films and high-refractive-index films having an optical thickness of λ / 4.

Next, the wavelength controller of the semiconductor laser light source device will be described. The wavelength control unit includes an output ratio calculating unit 12.
And wavelength control means 13A. The output ratio calculating means 12 includes a photodiode P serving as first and second light receiving elements.
The output ratio of D1 and PD2 is calculated, and the output is given to the wavelength control means 13A. Wavelength control means 13
A controls the emission wavelength of the laser light source so that the output ratio of the output ratio calculation means 12 becomes a predetermined value. The emission wavelength of the semiconductor laser 1 is adjusted by changing the drive current supplied to the plurality of electrodes or changing the ambient temperature.

Next, the output ratio calculating means 12 and the wavelength control means 13A will be described in detail with reference to FIG. Outputs from the first and second photodiodes PD1 and PD2 are provided to I / V converters 21 and 22 in the output ratio calculating means 12, and are converted into voltage signals. The outputs of the I / V converters 21 and 22 are provided to an adder 23 and a subtractor 24. The respective outputs are added and subtracted and provided to a divider 25. The divider 25 normalizes the light incident on the wavelength locker 4, and detects the wavelength of the input light based on the output ratio. Here, the I / V converters 21 and 22, the adder 23, the subtractor 24, and the divider 25 are output ratio calculating means 12 for detecting the wavelength of the laser beam based on the output ratio of the first and second light receiving elements.
, And the output is provided to the error detector 26. A reference voltage is applied to the other input terminal of the error detector 26. This reference voltage is configured to be adjustable between + V _CC and −V _DD by reference value setting means 27, for example, a variable resistor VR1. The error amplifier 26 detects a difference between the reference voltage and the input voltage as an error signal, and supplies the error signal to the PID control unit 28. The PID control unit 28 performs PID control so that the error signal becomes 0, and the output is fed back to the semiconductor laser 1 via the semiconductor laser driving unit 29. Semiconductor laser driver 1
9 controls the drive currents of the plurality of electrodes of the semiconductor laser 1 and the temperature of the semiconductor laser 1 in the temperature control module 10 so that the emission wavelength of the semiconductor laser 1 is reduced to, for example, 6
Control is performed so as to change within a range of 0 nm or less. Here, the error detector 26 and the variable resistor VR1, the PID control unit 28, and the semiconductor laser driving unit 29 that supply a reference voltage to the error detector 26 are controlled by the laser light source so that the output ratio by the output ratio calculation unit 12 becomes a predetermined value. Wavelength control means 13A for controlling the emission wavelength of the light.

FIG. 3A is a diagram showing the overall configuration of the laser light source device. In this embodiment, the optical module 11, the output ratio calculating means 12, the wavelength control means 13
Each electronic component 14 of A is mounted on one printed circuit board 15. By mounting all the components on the printed board in this way, the laser light source device can be made extremely small and lightweight.

FIG. 3B is a perspective view showing a state where the laser light source device according to this embodiment is housed in a case 16. In this embodiment, a reference voltage setting knob 17 provided by the variable resistor VR1 is provided so that the emission wavelength can be adjusted from outside the case 16.

Next, the operation of the laser light source device according to this embodiment will be described. FIGS. 4A and 4B are graphs showing the transmittance and reflectance characteristics of the interference light filter 3. The wavelength range in which the semiconductor laser 1 can emit light is λ1 to λ2.
Then, the center wavelength λ3 of the interference light filter 3 is selected such that the reflectance and the transmittance continuously change during this period.
For example, it is selected so as to be equal to the wavelength at one end of the wavelength that can emit light, for example, λ1. The interference light filter 3 has the wavelength λ
3 has the property of transmitting the light of No. 3 and reflecting the other light as shown in FIG. At this time, with respect to the emission wavelength λ of the semiconductor laser 1 (λ1 ≦ λ ≦ λ2), the optical outputs obtained by the photodiodes PD1 and PD2 are respectively shown in FIG.
(C) and (d) are obtained. That is, the outputs obtained from the photodiodes PD1 and PD2 correspond to the transmittance characteristics shown in FIG. 4A and the reflectance characteristics shown in FIG. 4B, respectively.

Accordingly, assuming that the I / V conversion outputs of the photodiodes PD1 and PD2 are A and B, they are added and subtracted, and the result is divided by the divider 25 to obtain (AB) / (A +
B) is calculated. The level normalized by the division is as shown in FIG. As described above, the wavelength monitor signal changes continuously according to the emission wavelength of the laser light source. The difference between the level of the wavelength monitor signal and the reference voltage of the error detector 26 is used as an error signal, and control is performed so that the error signal becomes zero, so that the error signal matches the reference voltage set in the error detector 26. The wavelength of the semiconductor laser 1 can be controlled. For example, if the reference voltage is 0 V, PD1, P
When the output level of D2 is equal to the wavelength λ4, the error signal becomes 0, and the emission wavelength of the semiconductor laser 1 can be controlled to λ4. The reference voltage is set to level V1 in FIG.
, The wavelength is locked to λ5 on the short wavelength side. By changing the reference voltage of the error detector 26 in this manner, the emission wavelength can be adjusted within the wavelength range of λ1 to λ2 shown in FIGS.

According to this embodiment, the semiconductor laser 1 is sealed in the temperature control module 10 and the optical module 11 including the wavelength locker 4, and the whole is mounted on a printed circuit board 15. Therefore, the light of the semiconductor laser can be guided directly to the interference filter 3. Therefore, it is not necessary to consider a change in the polarization direction as compared with the case where the light is guided to the interference filter using an optical fiber, an optical coupler, or the like, and the wavelength accuracy can be improved. Further, a highly reliable laser light source device which is small and lightweight, has no moving parts, and can be realized.

Although not explicitly shown in this embodiment,
The output level from the semiconductor laser 1 can be detected by the output from the adder 23 regardless of the emission wavelength. Therefore, by adjusting the output level of the semiconductor laser so that the output of the adder 23 becomes constant, the semiconductor laser 1
Can be kept constant. Such output level monitoring and output level control are widely performed by semiconductor lasers, and in this embodiment, the photodiodes PD1 and PD2 can be used as output monitoring elements.

Next, a second embodiment of the present invention will be described. In this embodiment, as shown in FIG. 6, a change in characteristics of the interference filter 3 due to a temperature change is compensated. Therefore, a temperature detecting element, for example, a thermistor 31, is provided near the interference filter 3 as shown in FIG. FIG. 7 shows an output ratio calculating means 1 according to the second embodiment.
2, the configuration of the wavelength control means 13B is shown, and the output of the thermistor 31 is given to the temperature detection means 32 as shown in FIG. The temperature detecting means 32 detects a temperature based on a signal from the thermistor, and its output is given to an adder 33 in the wavelength controlling means 13B. Adder 33
Is to add the output of the error detector 26 and the temperature detection signal to compensate for a change in the characteristic based on the temperature change of the interference light filter 3. The temperature compensating means for compensating the characteristic change accompanying the change is constituted. Other configurations are the same as those of the first embodiment.

In this embodiment, even if the temperature of the wavelength locker 4 in the optical module 11 changes, the characteristics of the interference light filter 3 based on the temperature change can be compensated, so that the desired value can be accurately obtained regardless of the temperature change. Can be emitted.

Next, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, as shown in FIG. 8, as an interference light filter in a wavelength locker, an interference light filter 41 whose transmitted wavelength continuously changes according to the incident position of light is used. In order to mechanically change the incident position on the interference light filter 41, an incident position adjusting means is provided. The incident position adjusting means, for example, rotates the interference light filter 41 by rotating a screw as shown in FIG.
Slide adjustment mechanism 42 for sliding in the X-axis direction shown in FIG.
It may be constituted as. In this case, the interference light filter 41
The incident position on the light source can be changed within a predetermined range. In this embodiment, the transmission wavelength of the interference light filter is continuously changed by changing the incident position within the wavelength variable range of the semiconductor laser 1. FIG. 9 shows the characteristics of the interference light filter 41 itself.
As shown in (2), an optical filter having a sharp characteristic that is sufficiently narrower than the range of the wavelengths capable of emitting light (λ1 to λ2) is set.
Other configurations are the same as those of the first embodiment described above. The outputs of the photodiodes PD1 and PD2 are given to the output ratio calculating means 12, and the emission wavelength is controlled by the wavelength control means 13A. Further, similarly to the above-described second embodiment,
A thermistor 31 may be provided near the interference light filter to detect the temperature, and the wavelength control means 13B may compensate for the characteristic based on the temperature change.

FIG. 10 is a perspective view showing the overall configuration of a wavelength tunable laser light source device according to this embodiment. In this embodiment, similarly to the first embodiment, the optical module 11 and the electronic circuit unit 14 are mounted on the printed circuit board 15 and stored in the case 16. A knob 43 is provided from the outside of the case so that the incident position of the interference light filter 41 can be changed. Further, a reference voltage setting knob 17 using the variable resistor VR1 is provided at the same time. Other configurations are the same as those of the first embodiment.

The interference light filter 41 is provided in Japanese Patent Publication No. 7-92530.
As shown in the figure, high refractive index films and low refractive index films are alternately laminated, and the optical thickness of the laminated wavelength is continuously changed. Next, the interference light filter will be described with reference to FIG. The tunable interference light filter 41 according to the present embodiment is configured by depositing a multi-layered substance on a substrate 51 such as glass or silicon. The substrate 51 is made of a material having a high light transmittance in a wavelength range to be used, and a dielectric or a semiconductor is used. In this embodiment, quartz glass is used. And this substrate 51
On top of this, a multi-layer film 52 made of a deposition material, a dielectric, a semiconductor, or the like having a high light transmittance at a wavelength to be used is deposited. Here, it is assumed that the multilayer film 52 is formed from a lower multilayer film 53, a cavity layer 54, and an upper multilayer film 55 as shown.
An antireflection film 56 is formed on the lower surface of the substrate 51 by vapor deposition.

[0029] Here, the multilayer film 52, the material used as the deposition material of the antireflection film 56, for example, Si O ₂ (refractive index _{n = 1.46), Ta 2 O} 5 (n = 2.15), Si (n = 3.46)
And Al ₂ O ₃ , Si ₂ N ₄ , MgF and the like are used. In the present embodiment, the multilayer films 53 and 55 are formed by alternately stacking low-refractive-index films and high-refractive-index films. Here, the thickness d, the transmission wavelength λ, and the refractive index n are set to have the following relationship. λ = 4nd (1) That is, each layer has an optical thickness nd of λ / 4. By alternately stacking low-refractive-index films and high-refractive-index films, the full width at half maximum (FWHM) of the transmittance peak is reduced. The thickness d _c of the cavity layer 54 is the transmission wavelength λ,
The following relationship is established with the refractive index n. λ = 2nd _c (2) That is, the optical thickness nd _c of the cavity layer 54 is λ / 2.

The interference light filter 4 according to the present embodiment will now be described.
1 is that the substrate 51 is an elongated plate-like substrate, the refractive index of the multilayer film 52 is constant, and the film thickness is continuous since the transmission wavelength and the film thickness have the relationship of the formulas (1) and (2). The transmission wavelength λ is changed by changing the transmission wavelength λ. Then, the transmission wavelength of the wavelength variable interference light filter 5 is set to λ _a
~λ and _{c (λ a <λ c)} , the transmission wavelength at the center point (x = x _b) and lambda _b. The upper and lower multilayer films 53 and 55
A first deposited material film having a first refractive index n _{1 and} a second deposited material film having a second refractive index n ₂ having a lower refractive index, respectively;
It is configured by alternately stacking. That is, as shown in an enlarged view of the circular portion in FIG. 11A, the respective film thicknesses are continuously changed as shown in FIG. 11C. In FIG. 11C, the low refractive index film of the lower multilayer film 53 is 53L, the high refractive index film is 53H, the high refractive index film of the upper multilayer film 55 is 55H, and the low refractive index film is 55L. And with respect to the transmission wavelength lambda _a end x _a on the X-axis of the filter of FIG. 11 (a), respectively a low refractive index film and a high refractive index film in the above equation (1), it holds true (2) Set as follows. The x _b, the transmission wavelength lambda _b at x _c, lambda _c
Is set so that the expressions (1) and (2) are satisfied at the wavelengths λ _b and λ _c . The film thickness between them is also set such that the change in wavelength changes linearly. Accordingly, the thickness of each layer is determined by the positions x _{a to} x _c on the X-axis as shown in the figure.
And the film thickness increases in the positive direction of the X-axis.

The interference light filter 41 for continuously changing the film thickness is provided on the substrate 51 with the multilayer film 52.
When the substrate is formed by vapor deposition, it can be realized by arranging the substrate in an inclined manner so as to continuously change the distance from the vapor deposition source.

Although the film thickness of the interference light filter 41 is continuously changed, each film thickness is fixed, and the refractive indexes n ₁ and n ₂ of the multilayer film 52 are continuously changed in the X-axis direction. The optical thickness may be varied continuously by changing the optical thickness.

The interference light filter 41 thus configured has a narrow band characteristic. Therefore, by mechanically moving the position where light enters the interference light filter 41 in the X-axis direction using the slide adjustment mechanism 42, the transmission wavelength itself can be continuously changed.

Next, the operation of this embodiment will be described. In this embodiment, in order to greatly change the emission wavelength of the laser light source, the adjustment knob 43 of the slide adjustment mechanism 42 is rotated to change the incident position of the incident light on the interference light filter 41, and the interference shown in FIG. Optical filter 41
Can be changed. In this way, the wavelength at which light can be emitted can be greatly changed. Therefore, the emission wavelength is roughly adjusted according to the incident position on the interference light filter 41, and fine adjustment of the wavelength is performed by the reference value setting means 17.
By changing the reference voltage, the user can set the wavelength to an arbitrary value. As described above, in the present invention, by using one interference light filter, the wavelength can be accurately controlled without using a beam splitter or a filter having two adjacent transmission wavelengths.

In this embodiment, the interference light filter 41 is used.
Although the transmission wavelength is continuously changed in the longitudinal direction, the interference light filter may have a circular shape and the transmission wavelength continuously changes along the radial direction. In this case, as the incident position adjusting means,
Instead of the slide adjustment mechanism, a rotation mechanism that rotates along the axis of the incident position can be provided to change the transmission wavelength.

In the third embodiment, the slide adjustment mechanism 42 and the knobs 43 and 17 of the variable resistor VR1 are used.
Can be adjusted from outside the case, but the wavelength may be changed only by the knob 43 of the slide adjustment mechanism 42 without providing the reference value setting means by the variable resistor VR1.

In the first to third embodiments described above,
Although an adder, a subtractor and a divider for calculating the output ratio are provided as the signal processing circuit, it goes without saying that the ratio of the two I / V converters may be directly calculated. Further, the ratio between the added value and one output from the photodiode can be calculated and used as a wavelength monitor signal. Further, it goes without saying that the output ratio calculation means and the wavelength control means can be realized using a microcomputer.

In each of the above embodiments, a multi-electrode type semiconductor laser is used as a semiconductor laser. However, a semiconductor laser of a distributed feedback type or the like is used, and the wavelength is adjusted by changing the ambient temperature. Is also good. In a distributed feedback semiconductor laser, the wavelength can be changed within a range of several nm by temperature control.

[0039]

As described above in detail, according to the first to fifth aspects of the present invention, the emission wavelength of the light source is controlled from the ratio between the incident light and the reflected light by using the interference light filter. ing. Therefore, unlike the conventional wavelength control method, it is not necessary to use a beam splitter in which it is difficult to keep the spectral ratio accurately and constant, and it is not necessary to control the temperature. Further, it becomes unnecessary to use two filters having wavelength selection characteristics close to each other. Also, a part of the two emitted lights of the semiconductor laser is used for wavelength control, and there is no need to split the light into the wavelength control unit via an optical fiber or an optical coupler, etc. There is no need to consider the change in direction. Furthermore, since these optical system parts are modularized, they can be mounted on a printed circuit board together with the wavelength control means, and the entire light source can be extremely miniaturized. Therefore, accurate wavelength control can be performed with an extremely simple structure.

In addition, according to the first to third aspects of the present invention, there is obtained an effect that there is no movable portion and the reliability can be improved. According to the second aspect of the present invention, a constant wavelength output can be obtained irrespective of a temperature change of the interference light filter. According to the fourth aspect of the present invention, since the transmission wavelength is changed by controlling the incident position on the interference light filter, a filter having a steep characteristic can be used as the interference light filter, and the accuracy of wavelength setting is improved. be able to. According to the fifth aspect of the present invention, the emission frequency of the laser light source can be adjusted by changing the reference value set by the reference value setting means.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an entire configuration of a wavelength tunable laser light source device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an output ratio calculation unit and a wavelength control unit of the laser light source device according to the present embodiment.

FIG. 3 is a perspective view showing components on a printed circuit board and an external appearance of the laser light source device according to the present embodiment.

FIG. 4 is a graph showing a filter characteristic of the laser light source device and a light receiving characteristic of the photodiode according to the present embodiment.

FIG. 5 is a graph showing a change in an error signal with respect to a wavelength.

FIG. 6 is a schematic diagram showing an entire configuration of a wavelength tunable laser light source device according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of an output ratio calculation unit and a wavelength control unit of the laser light source device according to the second embodiment.

FIG. 8 is a schematic diagram showing the entire configuration of a wavelength tunable laser light source device according to a third embodiment of the present invention.

FIG. 9 is a graph showing characteristics of the interference light filter according to the third embodiment.

FIG. 10 is a perspective view illustrating an overall configuration of a laser light source device according to a third embodiment.

FIG. 11A is a cross-sectional view illustrating a configuration of an interference light filter having a single cavity structure according to a third embodiment of the present invention, and FIG. 11B is a graph illustrating a change in transmittance on the X-axis; (C) is an enlarged sectional view of the circular portion of (a).

[Explanation of symbols]

 Reference Signs List 1 semiconductor laser 2, 5 lens 3, 41 interference light filter 4 wavelength locker 6 isolator 7 lens 8 collimator 9 optical fiber 10 temperature adjustment module 11 optical module 12 output ratio calculation means 13A, 13B wavelength control means 32 temperature detection means 42 slide adjustment mechanism

[Procedure amendment]

[Submission date] May 14, 1999 (1999.5.1
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

[0007]

According to a first aspect of the present invention, there is provided a wavelength tunable semiconductor laser for continuously changing the wavelength of light, and light of the semiconductor laser is incident through a space.
Is, the interference light Fi <br/> filter which reflects other by transmitting part of the incident light, the light and the interference transmitted through the interference optical filter
First and second light receiving elements for respectively receiving the light reflected by the optical filter , output ratio calculating means for calculating an output ratio of the first and second light receiving elements, and an output ratio by the output ratio calculating means There a wavelength control means for controlling the emission wavelength of the semiconductor laser to a predetermined value, the semiconductor laser, the interference
Optical filters and the first, the optical module for sealing the second light receiving element, the interference light from said semiconductor laser Fi
The incident position of the incident light on the
Changing the incident position adjusting means;
Provided near to detect the temperature near the interference light filter
A temperature detecting element, and a temperature detector based on an output of the temperature detecting element.
A change in characteristics of the optical filter due to a temperature change is determined by the output ratio.
Correcting the target value of the output ratio output from the calculating means
Temperature compensation means for compensating by the interference
The optical filter has an optical thickness of λ / 4 with respect to the wavelength λ.
Low- and high-refractive-index films alternately stacked on the substrate
And at least the wavelength tunable of the semiconductor laser
Within the range, the wavelength λ is continuous with the predetermined direction of the substrate.
The optical thickness is changed continuously so that it changes continuously.
The electronic module and the incident position adjusting means constituting the output ratio calculating means, the wavelength controlling means, and the optical module are housed in the same case.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

According to a second aspect of the present invention, in the wavelength tunable laser light source device according to the first aspect, the wavelength control means includes:
The output ratio calculated by the output ratio calculating means and a predetermined
Error detecting means for detecting a difference from a reference value;
Reference value setting means for setting a reference value to the means;
Error value detected by the temperature compensating means.
Of the semiconductor laser so that the compensated value becomes zero.
Semiconductor laser driving means for controlling a light wavelength.
It is characterized by the following.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009] Claim 1 of the present application having such features.
According to the invention, the laser light source is caused to emit light, and the laser light
Is incident on the optical filter. The incidence on the optical filter is a lens
Includes incident light, but optical fiber etc.
Instead, it enters through a space. This filter is
Transmits light of a specified wavelength and reflects others
And reflected light are received by the first and second light receiving elements, respectively.
Then, the output ratio is calculated by the output ratio calculating means. So
The emission wavelength of the laser light source so that the output ratio becomes a predetermined value.
Controlling the laser beam to emit laser light of a predetermined wavelength.
Can be made. Then, this optical filter is formed by a multilayer film.
Realization by the interference light filter
Variable wavelength type configured so that the transmission wavelength changes continuously
To change the light receiving position
The emission wavelength of the laser light source can be changed.
Wear. Further, the temperature of the interference light filter is detected by the temperature detecting means.
To compensate for changes in characteristics due to temperature changes.
Constant regardless of the temperature change of the interference light filter
The wavelength output is obtained.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

In the invention of claim 2, in addition to the above, the reference value
The reference value is set by the setting means, and the error detection means
Output ratio and reference value calculated by the output ratio calculation means
Is detected as an error. And by the light source driving means
Control the laser light source so that the error becomes zero.
Thus, the emission wavelength of the laser light source can be finely adjusted.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Deleted

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Deleted

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction contents]

[0039]

As described in detail above, according to the first and second aspects of the present invention, the emission wavelength of the light source can be controlled from the ratio between the incident light and the reflected light by using the interference light filter. ing. Therefore, unlike the conventional wavelength control method, it is not necessary to use a beam splitter in which it is difficult to keep the spectral ratio accurately and constant, and it is not necessary to control the temperature. Further, it becomes unnecessary to use two filters having wavelength selection characteristics close to each other. Also, a part of the two emitted lights of the semiconductor laser is used for wavelength control, and there is no need to split the light into the wavelength control unit via an optical fiber or an optical coupler, etc. There is no need to consider the change in direction. Furthermore, since these optical system parts are modularized, they can be mounted on a printed circuit board together with the wavelength control means, and the entire light source can be extremely miniaturized. Therefore, accurate wavelength control can be performed with a very simple configuration. Also controls the position of incidence on the interference light filter.
Since the changing of the transmission wavelength by Rukoto interference light
A filter with steep characteristics can be used as a filter.
In this case, the accuracy of wavelength setting can be improved. to this
In addition, a constant wave regardless of the temperature change of the interference light filter
An excellent effect of obtaining a long output can be obtained.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction contents]

In addition, according to the second aspect of the present invention, the emission wavelength of the laser light source can be finely adjusted by changing the reference value set by the reference value setting means.
The above effect can be obtained.

Claims (5)

[Claims] 1. A wavelength-variable semiconductor laser capable of continuously changing the wavelength of light, and light from the semiconductor laser is incident through a space, transmits light of a predetermined wavelength, and reflects the other light. An optical filter; first and second light receiving elements for respectively receiving light transmitted through the optical filter and light reflected by the optical filter; and an output for calculating an output ratio of the first and second light receiving elements. Ratio calculating means; wavelength controlling means for controlling the emission wavelength of the light source such that the output ratio of the output ratio calculating means has a predetermined value; the semiconductor laser, the optical filter, and the first and second
An optical module for enclosing the light receiving element, wherein the output ratio calculating means, the electronic circuit part constituting the wavelength control means, and the optical module are housed in the same case. Tunable laser light source device. A temperature detecting element provided near the optical filter for detecting a temperature near the optical filter; and a temperature for compensating for a change in characteristics due to a temperature change of the optical filter based on an output of the temperature detecting element. 2. The wavelength tunable laser light source device according to claim 1, further comprising a compensator. 3. The interference optical filter according to claim 1, wherein the optical filter has a low refractive index film and a high refractive index film having an optical thickness of λ / 4 with respect to a transmission wavelength λ. 3. The wavelength tunable laser light source device according to claim 1, wherein: 4. The interference light filter, wherein an optical thickness thereof is continuously changed so that a transmission wavelength λ continuously changes in a predetermined direction of a substrate. 3. The wavelength tunable type according to claim 2, further comprising an incident position adjusting means for continuously changing an incident position of the incident light from the laser light source to the interference light filter in a predetermined direction. Laser light source device. 5. An error detecting means for detecting a difference between an output ratio calculated by the output ratio calculating means and a predetermined reference value, a reference value for setting a reference value in the error detecting means. A semiconductor laser driving means for controlling an emission wavelength of the semiconductor laser so that an error value detected by the error detecting means becomes zero.
5. The wavelength tunable laser light source device according to claim 4.