JP2003258362A - Laser module and optical transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide highly reliable laser module and optical transmission system which obtain sure wavelength locker function by a simple structure and are easily miniaturized. <P>SOLUTION: A laser module has a laser element (101), an optical element (310) having minimum optical transmittance in a specified wavalength band, a first photodetector (330) which is mounted on one surface of the optical element and can detect light emitted from the laser element without transmitting it through the optical element, and a second photodetector (350) which is mounted on the other surface of the optical element and can detect light emitted from the laser element and transmitted through the optical element. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser module and an optical transmission system, and more particularly to wavelength multiplexing (Waveleng).
The present invention relates to a laser module and an optical transmission system suitable for use as a wavelength-stabilized light source in an optical communication system such as a th Division Multiplexing (WDM) system.

2. Description of the Related Art In recent years, in various optical application fields, a technique for locking the wavelength of light emitted from a light source such as a semiconductor laser within a specific range is required.

For example, in the field of optical communication systems, a WDM system capable of passing a number of wavelength channels through a single optical fiber, and a DW which is a further evolution of the WDM system.
The DM (Dense Wavelength Division Multiplexing) method has been developed and has contributed to the increase in the amount of communication information. However, also in these communication methods, stabilization and locking of the wavelength of the light source are essential.

In order to control the wavelength of the light source with high accuracy, a wavelength discriminating function is necessary. That is, it is necessary to equip the laser module with a wavelength discriminating function that has a function of monitoring a change in the wavelength of the light source and feeding it back to the light source. Documents disclosing such a laser module include, for example, Japanese Patent Laid-Open No. 10-79723 and Japanese Patent Laid-Open No. 2000-2.
No. 23747 can be cited.

FIG. 15 is a perspective view showing the inside of a laser module prototyped by the inventor in the course of reaching the present invention.

FIG. 16 is a block diagram schematically showing the structure of an optical transmission system including the laser module shown in FIG.

That is, in the laser module shown in the figure, a Peltier module (electronic cooler) 200 is housed inside a package 115, and various optical elements such as a laser 101 are mounted on the Peltier module 200. It has a mounted structure. Here, the Peltier module 200 has a role of controlling the temperature of an optical element such as the laser (LD) 101.

A first condenser lens 113 is provided on the Peltier module 200 in front of the laser 101, and further, a package 11 is provided via a second condenser lens 114.
The optical fiber 111 is coupled to the outside of the optical fiber 5. The optical signal transmitted via the fiber 111 can be appropriately monitored by, for example, the wavelength meter 25 or the optical power meter 26.

When used in an optical communication system,
A receiving module (not shown) is connected to the end of the fiber 111.

On the other hand, a wavelength locker system is provided behind the laser 101. That is, the laser 10
The light emitted from the rear end face of the first lens 1 is first condensed by the lens 112, and thereafter, is incident on the beam splitter 108 arranged at an inclination. Beam splitter 10
The light reflected by the incident surface of the light receiving element 8 is the light receiving element (PD) 1
02, the laser (LD) drive circuit 23 is monitored.
By feeding the monitor signal to the laser 1,
The output of 01 can be stabilized.

On the other hand, the light that has passed through the beam splitter 108 passes through the etalon 107 and the light receiving element (PD) 10
Monitored by 3. The etalon 107 has a Fabry-Perot type optical interference action, and its transmittance changes according to the wavelength of incident light. That is, when the wavelength of the laser 101 changes, the monitor output of the light receiving element 103 changes.
In order to cancel the component due to the fluctuation of the optical output of the laser 101, the “deviation” of the wavelength of the laser 101 can be detected by comparing the monitor outputs of the light receiving element 102 and the light receiving element 103. When the “deviation” of the oscillation wavelength of the laser 101 is detected in this way, it is fed back to the temperature control circuit 22. The wavelength of the laser 101 can be locked in a desired range by controlling the temperature of the Peltier module 200.

That is, this wavelength locker type laser diode module monitors the power of the laser light transmitted through the etalon which transmits only a specific wavelength, and controls the driving temperature of the laser diode by the Peltier module to control the wavelength of the laser light. It is fixed.

[0012]

However, the beam splitter 108 and the etalon 107 used in the laser module equipped with the wavelength discriminating function as shown in FIGS. 15 and 16 are usually about 2 × 2 mm thick and thick. It is also large, about 1 mm.

Also, regarding the light receiving elements 102 and 103, since it is not easy to dispose the semiconductor chips as they are, the light receiving elements 102 and 103 as semiconductor chips are usually mounted on the chip carrier 130. Therefore, its size is still 2 x 2 mm.
The thickness is as large as about 1 mm.

When a module is formed by using these optical parts and light-receiving element carriers, it is necessary to optically adjust the positional relationship of all the parts, and the assembly is complicated. Furthermore, when the arrangement is performed as illustrated in FIGS. 15 and 16, most of the mounting area on the Peltier module 200 is occupied, and it is difficult to reduce the size of the module. Further, while maintaining the same package size, the module It was also difficult to extend the function of.

The present invention has been made on the basis of the recognition of such a problem, and an object thereof is to obtain a reliable wavelength locker function with a simple structure, and at the same time, to downsize the laser module with high reliability. And to provide an optical transmission system.

[0016]

In order to achieve the above object, a first laser module of the present invention comprises a laser element, an optical element having a light transmittance having wavelength dependence, and one surface of the optical element. Mounted on the first light receiving element capable of detecting light emitted from the laser element, and mounted on the other surface of the optical element, emitted from the laser element and transmitted through the optical element. And a second light receiving element capable of detecting light.

According to the above structure, by integrating the etalon and the first and second light receiving elements, the number of parts is reduced as compared with the conventional one, and a compact, easy to assemble and highly reliable laser module is provided. it can.

A second laser module of the present invention is a laser element, an optical element having a light transmittance having wavelength dependence, and mounted on one surface of the optical element.
A first light detection unit that detects light emitted from the laser element without transmitting the light to the optical element; and a light transmission unit that transmits light emitted from the laser element toward the optical element. And a second light receiving element mounted on the other surface of the optical element and capable of detecting light emitted from the laser element and transmitted through the light transmitting section and the optical element. It is characterized by

According to the above construction, the etalon is integrated with the first and second light receiving elements, and the light transmitted through the light transmitting portion is detected by the second light receiving element, so that the number of parts is reduced as compared with the conventional case. A compact, easy to assemble, and highly reliable laser module can be provided.

Here, in the first light receiving element, if the light transmitting portion is provided substantially in the center of the light detecting portion, the light at the peak portion of the laser light is transmitted to the second light receiving element. It will be easy to give.

Further, if the second light receiving element has a light transmitting portion for transmitting the light emitted from the laser element and transmitted through the optical element, the axis alignment at the time of assembly becomes easy.

On the other hand, a third laser module of the present invention is a laser element, an optical element having a light transmittance having wavelength dependence, and mounted on one surface of the optical element.
A first light-receiving element capable of detecting light emitted from the laser element without passing through the optical element, and the first light-receiving element mounted on the other surface of the optical element and emitted from the laser element. A second light receiving element capable of detecting light transmitted through the optical element without being blocked by the light receiving element.

According to the above structure, the etalon and the first and second light receiving elements are integrated, and the light not blocked by the first light receiving element is detected by the second light receiving element, so that the number of components is larger than in the conventional case. , Compact and easy to assemble,
Moreover, a highly reliable laser module can be provided.

Here, the first and second light receiving elements are
If they are arranged so as to be displaced from each other with respect to the laser, they can be realized reliably and easily by using ordinary light receiving elements of the same size.

In addition, the second photodetector may be more than the first photodetector.
If the size of the light receiving element is larger, it becomes easier to adjust the output balance of these light receiving elements.

On the other hand, a fourth laser module of the present invention is a laser element, an optical element having a light transmittance having wavelength dependence, and mounted on one surface of the optical element,
A first light-receiving element capable of detecting light emitted from the laser element without passing through the optical element, and the first light-receiving element mounted on the other surface of the optical element and emitted from the laser element. A light receiving element and a second light receiving element capable of detecting light transmitted through the optical element are provided.

According to the above construction, the etalon is integrated with the first and second light receiving elements, and the light transmitted through the first light receiving element is detected by the second light receiving element. It is possible to provide a laser module that is compact, easy to assemble, and highly reliable.

Here, the first light receiving element has a light absorbing layer of a first thickness, and the second light receiving element is the first light receiving layer.
If a light absorption layer having a second thickness larger than the above thickness is provided, it becomes easy to reduce the amount of light absorption in the first light receiving element.

Alternatively, the first light receiving element has a light absorbing layer made of a material having a first absorptance in a wavelength band of light emitted from the laser element, and the second light receiving element is Even if it has a light absorption layer made of a material having a second absorptance higher than the first absorptance in the wavelength band of the light emitted from the laser element, the light absorption amount in the first light receiving element It becomes easy to reduce.

Further, in any of the above laser modules, if the optical element is an etalon in which light reflecting films are provided on both surfaces of a plate made of a light transmissive member, a predetermined wavelength selectivity can be obtained. Can be surely obtained.

If the first and second light receiving elements are flip-mounted on the optical element, no wire bonding step is required, and the durability against mechanical vibration and shock is further increased. Can be improved.

On the other hand, in the optical transmission system of the present invention, one of the laser modules described above and a first control loop for adjusting the drive current applied to the laser element based on the output signal from the first light receiving element. And a second control loop for adjusting the temperature of the laser element based on the output signal from the second light receiving element.

With the above arrangement, it is possible to provide an optical transmission system that is compact, has low cost, and has high reliability.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view illustrating the internal structure of a laser module according to an embodiment of the present invention.

FIG. 2 is a block diagram schematically showing the configuration of an optical transmission system equipped with this laser module.

In these figures, FIGS.
The same elements as those described above with reference to the same reference numerals.

In the case of this specific example shown in these drawings, the wavelength locker system provided at the rear of the laser 101 has the etalon 310 and the light receiving elements 330 and 350 provided on both sides thereof integrated with each other. It has an etalon unit 300A.

First, the overall structure of this module will be described. Like the example shown in FIGS. 15 and 16, the Peltier module (electronic cooler) 200 is housed inside the package 115, and the Peltier module 200 is mounted on the Peltier module 200. Has a structure in which various optical elements such as the laser 101 are mounted. And laser 1
In front of 01, a first condenser lens 113 is provided on the Peltier module 200, and is further coupled to the optical fiber 111 outside the package 115 via the second condenser lens 114. In an optical communication system or the like, for example, a receiving module (not shown) is connected to the end of the fiber 111.

On the other hand, a wavelength locker system is provided behind the laser 101. That is, the laser 10
The light emitted from the rear end face of No. 1 is first condensed by the lens 112, and then the etalon unit 300A
Incident on.

In the etalon unit 300A illustrated in FIGS. 1 and 2, the light receiving elements 330 and 350 are arranged substantially coaxially with respect to the incident light from the laser 101.

FIG. 3 is an assembly diagram for explaining the structure of the etalon unit 300A.

That is, a reflective film 312 is formed on both surfaces of the etalon 310 so as to obtain a predetermined transmittance characteristic, and an electrode pattern 314 is provided on the surface thereof. The light receiving element 330 is formed on the electrode pattern 314.
And 350 are flip-mounted.

The etalon 310 acts as a wavelength selective transmission filter having a specific transmission band. Reflective film 3 on both sides
By providing 12, a so-called “Fabry-Perot structure” is formed, which can be used as a filter having a desired wavelength selectivity. For example, by using a quartz plate having a refractive index of about 1.5 and a thickness of about 1 mm, the FSR of 100 GHz in the wavelength band of 1.55 μm can be obtained.
(Free spectrum range) is obtained.

On the other hand, in the light receiving element 330, a p-side electrode 332 and an n-side electrode 333 are formed on the surface of the semiconductor chip. Inside the p-side electrode 332 formed in a ring shape, a light detection section 334 and a light transmission section 335 are formed in a substantially concentric shape. The light detection unit 334 absorbs light from the laser 101 and converts it into an electric signal. The light transmitting portion 335 is
The light from the laser 101 is not substantially absorbed but is transmitted.

On the other hand, also in the light receiving element 350, the p-side electrode 352 and the n-side electrode 353 are formed on the surface of the semiconductor chip. Then, inside the ring-shaped p-side electrode 352, a photodetector 354 is formed. Laser 1
A part of the light emitted from 01 passes through the light transmitting portion 335 of the light receiving element 330 and the light detecting portion 354 of the light receiving element 350.
Is absorbed by and converted into an electrical signal.

The etalon unit 30 as described above
The operation of 0A will be described below.

First, the light emitted from the rear of the laser 101 is converged by the condenser lens 112 and enters the first light receiving element 330. Then, a part of the light is detected by the light detection unit 3
The output of the laser 101 can be stabilized by being absorbed in 34 and converted into an electric signal and feeding the monitor signal to the laser (LD) drive circuit 23.

On the other hand, the light transmitting portion 3 of the first light receiving element 330.
The laser light transmitted through 35 or other portions is transmitted through the etalon 310, detected by the photodetector 354 of the second light receiving element 350, and monitored by the photocurrent monitor 24.

The etalon 310 has a Fabry-Perot type optical interference function, and its transmittance changes according to the wavelength of the incident light. Therefore, when the wavelength of the laser 101 changes, the monitor output of the light receiving element 350 changes. . In order to cancel the component due to the fluctuation of the optical output of the laser 101, the “deviation” of the wavelength of the laser 101 can be detected by examining the change in the balance of the monitor outputs of the light receiving element 330 and the light receiving element 350. In this way, when the “deviation” of the oscillation wavelength of the laser 101 is detected, the temperature control circuit 2
Give feedback to 2. The wavelength of the laser 101 can be locked in a desired range by controlling the temperature of the Peltier module 200.

As described above, the light receiving elements 330 and 350 in this example correspond to the light receiving elements 102 and 103 in FIGS. 15 and 16, respectively. As can be seen by comparing FIGS. 1 and 2 with FIGS. 15 and 16, in the present invention, the wavelength locker system is significantly downsized.

Specifically, in the case of the present invention, the beam splitter 108 is unnecessary, and further, the chip carrier 130 for mounting and handling the light receiving element is also unnecessary. Furthermore, in the present invention, etalon 3
Since the chip-shaped light receiving elements 330 and 350 are mounted and integrated on both surfaces of 10, the area occupied by the wavelength locker system can be greatly reduced, and the size of the entire laser module can be reduced.

Furthermore, according to the present invention, by integrating the etalon and the light receiving element, the optical arrangement relationship between them can be surely strengthened, and the optical components of these optics due to mechanical vibration, impact, etc. It is also possible to significantly suppress the “deviation” of the arrangement relationship. As a result, the reliability of the laser module can be improved.

In FIG. 3, the light receiving element 330,
Although the light receiving portions of 350, that is, the light detecting portions 334 and 354 are shown in a substantially circular shape, the present invention is not limited to this. That is, the planar shape of these light receiving portions can be various polygonal shapes such as quadrangle, elliptical shape, or other various shapes.

In addition, the light transmitting portion 335 of the light receiving element 330.
Need not be provided near the center of the light receiving portion as shown in FIG. 3, and may be provided near the end of the light receiving element, or may be provided near the center and at the end.

FIGS. 4 to 6 show the light receiving element 3 shown in FIG.
It is a schematic diagram showing some of the specific examples of the cross-sectional structure of 30. That is, these figures show the ring-shaped p-side electrode 332 of the light receiving element formed as a pin type photodiode.
Represents the cross-sectional structure in the vicinity of.

In the case of the structure illustrated in FIG. 4, the n-type light absorption layer 331B is laminated on the n-type semiconductor layer 331A,
A part thereof is removed and the n-type light transmission layer 331E is embedded. Then, an n-type window layer 331D is formed on these.
Are stacked, and a p-type region 331P is formed in a planar shape from the surface side. The p-side electrode 332 is provided so as to make electrical contact with the p-type region 331P.

The semiconductor layer 331A, the light transmission layer 331E and the window layer 331D are made of a semiconductor having a low absorptance with respect to the light of the laser 101, and the light absorption layer 331B is made of a material having a high absorptivity.

For example, when used in an optical communication system of 1.3 μm to 1.55 μm band, the semiconductor layer 331A, the light transmission layer 331E and the window layer 331D are made of InP.
(Indium phosphide) can be used, and the light absorption layer 331 can be used.
As the material of B, InGaAs (indium gallium arsenide) can be used.

In such a light receiving element, when a reverse bias voltage is applied to the pn junction, the light absorption layer 331B at the pn junction is depleted, and the excited carriers can be detected as a photocurrent. That is, the light absorption layer 33
The portion provided with 1B functions as a light detection unit 334 that detects the light from the laser 101. On the other hand, the light transmission layer 33
The portion embedded by 1E acts as a light transmitting portion 335 that transmits the light from the laser 101.

Next, in the case of the structure illustrated in FIG. 5, the light absorption layer 331B and the window layer 331D thereabove are removed to form the trench 331H in the central portion of the light receiving element. The light transmitting portion 335 can also be formed by removing the light absorbing layer 331B in this manner. In this case, a protective layer (not shown) may be provided on the inner wall surface of the trench 331H. Next, in the case of the structure illustrated in FIG. 6, the light absorption layer 33 is formed in the central portion of the light receiving element.
1B and the window layer 331D on it are removed, and are embedded by the light transmissive member 331Z. Even in this way, the light transmitting portion 335 can be formed. Light-transmissive member 3
It is desirable that the material of 31Z be a material that transmits light from the laser 101 and that is electrically insulating.
Specifically, an organic material such as polyimide, an inorganic material such as silicon oxide, or an insulating semiconductor can be used as the light transmissive member 331Z.

Also in the light receiving element shown in FIGS. 5 to 7, the light transmitting portion 335 of the light receiving element 330 does not necessarily have to be provided near the center of the light receiving portion, but may be provided near the end portion of the light receiving element. Alternatively, they may be provided in the vicinity of the center and at the ends.

Next, a modified example of the etalon unit that can be used in the laser module of the present invention will be described.

FIG. 7 is an assembly diagram schematically showing a first modified example of the etalon unit. In this figure, elements similar to those described above with reference to FIGS. 1 to 6 are marked with like reference numerals and not described in detail.

In the etalon unit 300B of this modified example, the second light receiving element 350 for detecting the light transmitted through the etalon 310 is also provided with the light transmitting portion 355.
The light transmitting portion 355 can have the same structure as that illustrated in FIGS. 4 to 5. Second light receiving element 350
By providing the light transmitting portion 355 on the axis, the axis of the etalon unit 300B can be easily aligned. That is, in the assembly process of the laser module, when fixing the etalon unit 300B on the Peltier module 200, by monitoring the light transmitted through the light transmitting portion 355 of the second light receiving element 350, the backward emission light of the laser 101 can be obtained. The etalon unit 300B can be arranged at the peak position of.

FIG. 8 is a sectional view schematically showing a second modification of the etalon unit that can be used in the present invention.

That is, this etalon unit 300C
In the case of, the first light receiving element 330 and the second light receiving element 350
Are n-side electrodes 333 and 35 provided on the back surface side, respectively.
Electrode pattern of etalon 310 according to 3 (not shown)
Mounted on. The p-side electrodes 332 and 352 of these light receiving elements are connected to the etalon electrode pattern 314 by the wire 360.

In this case, the first light receiving element 330 is the same as that shown in FIG.
As described above with reference to FIG. 6, the light transmitting portion 335 is included. Further, the n-side electrodes 333 and 353 on the back surface side are formed so as not to block the light transmitted through the light transmitting portion 335. The backward emission light L from the laser 101 is transmitted through the light transmission portion 335, transmitted through the etalon, and detected by the second light receiving element 350.

As described above, even if the light receiving elements are connected by wire instead of being flip-mounted, a compact, easy-to-assemble and highly reliable laser module can be obtained.

FIG. 9 is a sectional view schematically showing a third modified example of the etalon unit that can be used in the present invention. In the figure, details of the etalon 310 and the first and second light receiving elements 330 and 350 are omitted,
Only the arrangement relationship between them is shown.

In this modified example, the first and second light receiving elements 330 and 350 are arranged so as to be “shifted” from each other with respect to the backward emission light L of the laser. That is, the light L
Part of the light is detected by the first light receiving element 330, while the light transmitted through the etalon 310 is detected by the second light receiving element 3
Detected by 50.

Here, the first and second light receiving elements are
It may be flip-mounted to the etalon 310 as illustrated in FIG. 3, or may be connected using a wire as illustrated in FIG.

In the case of the laser module illustrated in FIGS. 1 and 2, the backward emission light L from the laser 101 is condensed by the lens 112 and is incident on the etalon unit as a Gaussian light beam or a light beam having a distribution similar thereto. To do. The full width at half maximum WL of the light beam L is, for example, 50
It is easy to set the thickness to about 0 μm to 1000 μm. Therefore, the width WP of the first and second light receiving elements 330 and 350
Is about half that, it is easy to displace them as shown in FIG. 9 and give the light L to both.

This modification is convenient in that it is not necessary to provide the light transmitting portion 335 as illustrated in FIGS. 3 to 6 in the first light receiving element 330. That is, by arranging the light receiving elements having a general structure, which are generally widely used, offset from each other as shown in the figure, it is possible to detect the deviation between the output of the laser 101 and the wavelength. As a result, it is possible to obtain a laser module that is lower in cost, compact, easy to assemble, and highly reliable.

FIG. 10 is a sectional view schematically showing a fourth modified example of the etalon unit that can be used in the present invention. Also in this figure, details of the etalon 310 and the first and second light receiving elements 330 and 350 are omitted, and only the positional relationship between them is shown.

In this modification, the first light receiving element 33 is used.
The width (size) WP1 of 0 is the width W of the second light receiving element 350.
It is formed smaller than P2. First light receiving element 33
0 directly detects a part of the backward emission light L from the laser, and the second light receiving element 350 detects the light L transmitted through the etalon 310.

Also here, the first and second light receiving elements may be flip-mounted on the etalon 310 as illustrated in FIG. 3, or the connection using wires as illustrated in FIG. It may have been done.

As described above, the beam size WL of the backward emission light L from the laser can be easily set to about 500 μm to 1000 μm, and within this range, the first
Of the second light receiving element 35
It is also easy to form a large 0. Since the first light receiving element 330 receives the light L directly, it is easy to obtain a signal of a sufficient level even if the size thereof, that is, the light receiving area is reduced. On the other hand, the second light receiving element 350 receives the light that has passed through the etalon 310 while being partially shielded by the first light receiving element 330, so that the light receiving area should be increased.

The present modified example is also convenient in that it is not necessary to provide the light transmitting portion 335 as illustrated in FIGS. 3 to 6 in the first light receiving element 330. That is, it is also possible to adjust the balance of the output signals from the first and second light receiving elements to a favorable range by appropriately arranging light receiving elements having a general structure that is generally widely used by changing their sizes. It will be easy.

FIG. 11 is a schematic view illustrating the planar arrangement relationship of the light receiving elements. That is, the first and second light receiving elements 330 and 350 can be arranged so as to be displaced in a substantially diagonal direction with respect to the main surface of the substantially quadrangular etalon unit. With such a shift, it is not necessary to provide the light transmitting portion 335 as described above with reference to FIGS.

However, the present invention is not limited to FIG.
Alternatively, the second light receiving elements 330 and 350 may be arranged so as to be displaced in the vertical direction or the horizontal direction of the etalon 310. Further, in FIG. 11, these light receiving elements are arranged so as not to overlap each other in a plan view, but they may be arranged so that part of the light receiving elements overlap each other.

FIG. 12 is another schematic view illustrating the planar arrangement relationship of the light receiving elements. In the case of this example,
The first light receiving element 330 having a small size and the second light receiving element 350 having a large size are arranged so as to be displaced from each other in a plan view.

Since the first light receiving element 330 directly receives the backward emitted light from the laser, it is easy to obtain a sufficient output even if it is not arranged near the center of the beam where the light intensity reaches its peak. On the other hand, the second light receiving element 350 is
Since the light transmitted through the etalon 310 is received, it is easier to secure the output level by increasing the light receiving area and detecting near the center of the light beam.

As described above, by appropriately adjusting the sizes of the first and second light receiving elements and shifting the arrangement relationship as appropriate,
The balance of the output signals from these light receiving elements can be optimized.

FIG. 13 is a conceptual diagram showing another modification of the etalon unit that can be used in the present invention. Also in this figure, the details of the etalon 310 and the first and second light receiving elements 330 and 350 are omitted, and only the essential parts are shown.

In this modification, the thickness of the light absorption layer 331B of the first light receiving element is thinner than the thickness of the light absorption layer 351B of the second light receiving element light. When the thickness of the light absorption layer of the light receiving element is reduced, the incident light is not completely absorbed, but part of the light is absorbed and part of the light is transmitted. Therefore, by forming the light absorption layer 331B of the first light receiving element to be thin, its absorptance is reduced, a part of the laser light L is transmitted through the etalon 310, and the second light receiving element 350 is formed.
Can be given to.

In this case, the thickness of the light absorption layer 351B of the second light receiving element 350 is the same as the light absorption layer 331 of the first light receiving element.
Although it may be about the same as B, if it is formed relatively thick as shown in the drawing, it can be more surely absorbed.

For example, wavelength 1.3 μm to 1.55 μm
In the case of a band optical communication system, InGaAs having a composition that lattice-matches with InP can be used as the material of the light absorption layer of the light receiving element, and the light absorption layer 331B made of this material.
By making the thickness of the light receiving layer thinner than the thickness of the light absorption layer 351B, it is possible to reduce the amount of light absorption as shown in FIG.

Further, when the thickness of the light absorption layer 331B of the first light receiving element is reduced as described above, the first and second light receiving elements can be arranged coaxially as shown in the drawing. However, also in this modified example, as shown in FIGS. 9 to 12, the arrangement of the light receiving elements may be shifted from each other,
Moreover, you may change the size.

FIG. 14 is a conceptual diagram showing a further modified example of the etalon unit that can be used in the present invention. Also in the figure, the etalon 310, the first and the second
The details of the light receiving elements 330 and 350 are omitted and only the main parts are shown.

In this modified example, the light absorption layer 331B of the first light receiving element and the light absorption layer 351 of the second light receiving element light.
The material of B is different. That is, the light absorption layer 331
As the material of B, a material having a slightly low absorption coefficient for the backward emission light L from the laser is adopted. On the contrary,
As the material of the light absorption layer 351B, it is desirable to use a material having a high absorption coefficient for the light L.

For example, wavelength 1.3 μm to 1.55 μm
In the case of a band optical communication system, the material of the light absorption layer 331B is InGaAsP having a composition having a slightly lower absorption coefficient in this wavelength band, while the light absorption layer 351B is used.
InGaA having a composition that is lattice-matched to InP
s can be used. With this configuration, the amount of light absorbed by the first light receiving element 330 can be reduced, and the unabsorbed light can be provided to the second light receiving element.

In the case of this modification, the light absorption layer 331B is used.
And the thickness of the light absorption layer 351B may be the same or different. For example, in order to increase the amount of light transmitted to the etalon 310, a material having a low absorption coefficient may be used as the material of the light absorption layer 331B and the thickness thereof may be thin.

Also in this modification, the first and second light receiving elements can be arranged coaxially as shown in the drawing. However, also in this modified example, as illustrated in FIGS. 9 to 12, the arrangement of the light receiving elements may be shifted from each other or the size thereof may be changed.

The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples.

For example, the specific structure of the laser module is not limited to that shown in the drawings, and any structure having a laser and a wavelength discriminating element such as an etalon for discriminating the wavelength from the laser can be used. The scope of the present invention is included in a range in which a person skilled in the art can appropriately change the design.

More specifically, for example, a part of the light emitted from the front end face of the laser rather than the rear end face may be supplied to the etalon unit as described above with reference to FIGS.

Further, the structure and material of the light receiving element or the material and structure of the etalon can be appropriately selected and used according to the wavelength of the light emitted from the laser, and the present invention includes these.

As described in detail above, according to the present invention,
By integrating the light receiving element for laser power monitoring, the light receiving element for wavelength monitoring, and the etalon, parts such as the beam splitter and chip carrier for the light receiving element are not required, and at the same time, these light receiving element and etalon Optical adjustment with and becomes unnecessary.

As a result, the size of the laser module can be reduced, the assembly can be greatly simplified, and a laser module having high durability against mechanical vibration and shock can be provided.

That is, according to the present invention, it is possible to provide a laser module which is smaller in size and higher in reliability than conventional ones and which is lower in cost in an advanced optical communication system such as a WDM system or a DWDM system. The industrial advantages are enormous.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating an internal structure of a laser module according to an embodiment of the present invention.

FIG. 2 is a block diagram schematically showing the structure of the laser module shown in FIG.

FIG. 3 is an assembly diagram illustrating a structure of an etalon unit 300A.

FIG. 4 is a schematic diagram showing a specific example of a sectional structure of the light receiving element 330 shown in FIG.

5 is a schematic diagram showing a specific example of a cross-sectional structure of the light receiving element 330 shown in FIG.

6 is a schematic diagram showing a specific example of a cross-sectional structure of the light receiving element 330 shown in FIG.

FIG. 7 is an assembly diagram schematically showing a first modified example of the etalon unit.

FIG. 8 is a sectional view schematically showing a second modified example of the etalon unit that can be used in the present invention.

FIG. 9 is a sectional view schematically showing a third modified example of the etalon unit that can be used in the present invention.

FIG. 10 is a sectional view schematically showing a fourth modified example of the etalon unit that can be used in the present invention.

FIG. 11 is a schematic view illustrating a planar arrangement relationship of light receiving elements.

FIG. 12 is another schematic view illustrating the planar arrangement relationship of the light receiving elements.

FIG. 13 is a conceptual diagram showing another modified example of the etalon unit that can be used in the present invention.

FIG. 14 is a conceptual diagram showing a further modified example of the etalon unit that can be used in the present invention.

FIG. 15 is a perspective view showing the inside of a laser module prototyped by the inventor in the course of reaching the present invention.

16 is a block diagram schematically showing the structure of the laser module shown in FIG.

[Explanation of symbols]

22 Temperature control circuit 23 Drive circuit 25 wavelength meter 26 Optical Power Meter 101 laser 102, 103 light receiving element 104 thermistor 107 Etalon 108 Beam splitter 111 optical fiber 112, 113, 114 condenser lens 115 packages 130 chip carrier 200 Peltier module 300A-Etalon unit 310 Etalon 312 Reflective film 314 electrode pattern 330 Light receiving element 331 semiconductor chip 331A Semiconductor layer 331B Light absorption layer 331D window layer 331E Light transmission layer 331H trench 331P p-type region 331Z Light transmissive member 332 p-side electrode 333 n-side electrode 334 Photodetector 335 Light transmission part 350 light receiving element 351 semiconductor chip 351B Light absorption layer 352 p-side electrode 353 n-side electrode 354 Photodetector 355 Light transmission part 360 wire L laser light

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Reiji Ono             8 East Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa             Shiba Electronics Engineering Co., Ltd. F-term (reference) 5F073 AB25 BA01 EA03 FA02 FA25                       FA30 GA12 GA13 GA22

Claims (13)

[Claims] 1. A laser element, an optical element having a light transmittance having wavelength dependence, and a first element mounted on one surface of the optical element and capable of detecting light emitted from the laser element. A laser comprising: a light receiving element; and a second light receiving element mounted on the other surface of the optical element and capable of detecting light emitted from the laser element and transmitted through the optical element. module. 2. A laser element, an optical element having a light transmittance having wavelength dependence, and a light mounted on one surface of the optical element and transmitting light emitted from the laser element to the optical element. A light detection unit that detects without light, a light transmission unit that transmits the light emitted from the laser element toward the optical element,
And a second light receiving element mounted on the other surface of the optical element and capable of detecting light emitted from the laser element and transmitted through the light transmitting section and the optical element. A laser module comprising: 3. The laser module according to claim 2, wherein in the first light receiving element, the light transmitting portion is provided substantially in the center of the light detecting portion. 4. The second light receiving element has a light transmitting portion for transmitting the light emitted from the laser element and transmitted through the optical element, according to any one of claims 1 to 3. The laser module described. 5. A laser element, an optical element whose light transmittance has wavelength dependency, and a light which is mounted on one surface of the optical element and transmits light emitted from the laser element to the optical element. A first light-receiving element that can be detected without light, and a light that is mounted on the other surface of the optical element and that is emitted from the laser element and transmitted through the optical element without being blocked by the first light-receiving element. A laser module comprising: a second light-detecting element that can be detected. 6. The laser module according to claim 5, wherein the first and second light receiving elements are arranged in a mutually shifted position when viewed from the laser. 7. The size of the second light receiving element is larger than that of the first light receiving element.
Alternatively, the laser module according to item 6. 8. A laser element, an optical element having a light transmittance having wavelength dependence, and a device mounted on one surface of the optical element and transmitting light emitted from the laser element to the optical element. A first light receiving element that can be detected without detection, and a first light receiving element that is mounted on the other surface of the optical element and that is capable of detecting the light emitted from the laser element and transmitted through the first light receiving element and the optical element. A laser module comprising: two light receiving elements; 9. The first light receiving element has a light absorbing layer of a first thickness, and the second light receiving element has a light absorbing layer of a second thickness larger than the first thickness. 9. The method according to claim 8, further comprising:
The laser module described. 10. The first light receiving element has a light absorbing layer made of a material having a first absorptance in a wavelength band of light emitted from the laser element, and the second light receiving element is In the wavelength band of the light emitted from the laser device, the second absorption ratio is higher than the first absorption ratio.
9. The laser module according to claim 8, further comprising a light absorption layer made of a material having the above absorption rate. 11. The laser according to claim 1, wherein the optical element is an etalon in which light reflecting films are provided on both surfaces of a plate-shaped body made of a light transmissive member. module. 12. The laser module according to claim 1, wherein the first and second light receiving elements are flip-mounted on the optical element. 13. A laser module according to claim 1, and a first control loop for adjusting a drive current applied to the laser element based on an output signal from the first light receiving element. And a second control loop for adjusting the temperature of the laser element based on an output signal from the second light receiving element.