JP2002329920A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module in which an optical fiber and an optical element can be connected surely and with a simple constitution, which can be miniaturized without mounting a thermoelectric cooling element and an optical-output monitoring device, whose heat dissipating property is superior, and which is of long-term stability and superior in a high-speed property. SOLUTION: The optical module M is formed in such a way that an element mounting substrate 3 on which an optical semiconductor element 1 used to perform a transmitting operation or a receiving operation is arranged and installed is housed inside a package 9. The substrate 3 is arranged and installed on a baseplate 13 for heat dissipation constituting the bottom face of the package 9. The substrate 3 and the baseplate 13 are constituted of materials having thermal conductivity of 150 W(m.K) or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module used for transmitting and receiving optical transmission such as optical fiber communication and optical interconnection.

[0002]

2. Description of the Related Art Conventionally, in the case of an optical module in which an optical signal emitted from a semiconductor laser is optically connected to an optical fiber via a lens, the semiconductor laser is disposed on a cooling element in order to prevent heat generation of the semiconductor laser. Structure was taken.

For example, an optical module disclosed in Japanese Patent Publication No. 6-105819 discloses a semiconductor laser 101 and an optical fiber 102 in a hermetically sealed package 107 as shown in FIG. System 10
The optical fiber 102 covered with the sleeve 106 is fixed on the side surface of the casing 110 that houses the airtight package so as to maintain the optical coupling state. ing.

A part of the airtight package 107 includes:
A temperature detecting means 108 for detecting an ambient temperature of an optical coupling portion between the semiconductor laser 101 and the optical fiber 102 is provided. Further, below the airtight package 107, when the temperature detecting means 108 detects a temperature rise around the optical coupling portion, the temperature of the semiconductor laser module including the package 107 is controlled to be constant. An electronic cooling element 109 is provided.

A casing 110 has a hole 111 for taking out an optical fiber 102, a semiconductor laser 101,
A hermetic sealing terminal 112 connected to each terminal such as the temperature detecting means 108 and the electronic cooling element 109 is provided.

[0006] The hermetic package 107 constituting the semiconductor laser module is provided with the casing 1 described above.
10 and a thermoelectric cooling element 109 is interposed between the hermetic package 107 and the casing 110 and is hermetically sealed.
The optical fiber 102 is led out of the casing 110 through a take-out hole 113 of the casing 110 so as to be in contact with the outer surface of the casing 110 and the inner wall surface of the casing 110. Then, the hermetic sealing terminals 11 each having the semiconductor laser module and the casing 110 are provided.
2 only.

[0007]

However, the above-mentioned optical module has the following problems.

First, even when the temperature around the optical coupling changes, it is necessary to arrange the semiconductor laser on the electronic cooling element in order to obtain a stable optical output.

Further, in order to stabilize the temperature of the electronic cooling element, it is necessary to arrange the temperature detector on the same electronic cooling element.

In addition, a monitoring photodiode for detecting light emitted from behind the semiconductor laser has to be arranged behind the semiconductor laser. In addition, since the monitor photodiode is generally a surface light receiving type,
It was necessary to arrange a sub-carrier made of ceramics or the like, which had been mounted in advance, in alignment with the optical axis. Therefore, it was difficult to reduce the size of the optical module in terms of space.

Further, the electric circuit for controlling the electronic cooling element, the temperature detector, and the monitoring photodiode becomes complicated, and the device for driving the optical module itself becomes complicated, and, consequently, the optical communication system itself And increase communication costs.

Therefore, recently, a new semiconductor laser capable of driving the semiconductor laser without cooling has been developed. However, even in this non-cooled type semiconductor laser, a rise in the temperature of the semiconductor laser becomes a problem, and a mounting method excellent in heat dissipation is desired.

Particularly, in a semiconductor laser for excitation used in an optical fiber amplifier or the like, the light output from the semiconductor laser is very large at 300 mW or more, and the applied current is 400 to 500 mW or more. There is a problem that heat is generated at a high temperature and stable operation cannot be obtained. Generally, even in the case of an uncooled type semiconductor laser, it is necessary to suppress the temperature rise when the semiconductor laser is driven to 10 ° C. or less, and a mounting structure for efficiently dissipating such a high-power semiconductor laser. Was difficult.

[0014]

In order to solve the above problems, an optical module according to the present invention is an optical module in which an element mounting base on which an optical semiconductor element is provided is housed in an airtight package. An element mounting base is disposed on a heat-dissipating bottom plate constituting a bottom surface of the hermetic package, and the element mounting base and the heat-dissipating bottom plate are each 150 W /
It is characterized by being made of a material having a thermal conductivity of (m · K) or more.

In particular, the heat-dissipating bottom plate has an extension for attaching to an external substrate, and the optical semiconductor element is a semiconductor laser, and the light is transmitted from the semiconductor laser to the outside of the hermetic package. Signal is emitted, and the optical signal from the semiconductor laser is
The light is emitted to the outside of the hermetic package via a lens, and the lens is fixed to the element mounting base via a member having a thermal conductivity of 50 W / (mK) or less. I do.

Specifically, for example, an optical module including an optical fiber and an optical semiconductor element optically connected to the optical fiber, wherein at least the optical fiber and the optical semiconductor element are connected by a lens coupling optical system. While being optically connected, the optical semiconductor element is hermetically sealed in a housing, and a single crystal glass of quartz or sapphire for optically coupling to a side wall of the housing.
Alternatively, a transparent window portion made of polycrystalline glass is formed.

In particular, the bottom of the housing has a thermal conductivity of 15%.
It is preferable to provide an electric terminal made of a metal substrate having 0 W / (m · K) or more, and a side wall portion made of metallized ceramic.

The optical semiconductor element optically connected to the optical fiber or the base holding the optical semiconductor element is mounted and fixed on a base made of metal or ceramic having a thermal conductivity of 150 W / (m · K) or more. In addition, at least one lens optically connected to the optical semiconductor element is held in a metal casing having a thermal conductivity of 50 W / (m · K) or less, and has a thickness equal to the distance between the optical semiconductor element and the lens. It is preferable to join to a metal or ceramic substrate via a metal substrate having a conductivity of 50 W / (m · K) or less.

Furthermore, it is preferable to provide a convex portion for fixing to the external heat dissipation base or a hole for fixing to the bottom of the housing.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings schematically shown.

FIG. 1 is a perspective view showing a state in which an optical module M according to the present invention is disposed on a heat dissipation base 20 via an electric circuit board 19, and FIG. 2 is an exploded perspective view of the optical module M.
FIG. 3 is a sectional view of the optical module M.

In an optical module M according to the present invention, a chip carrier 2 and a metal substrate 3 which constitute an element mounting substrate on which a semiconductor laser 1 as an optical semiconductor element is disposed are housed in an airtight package composed of a casing 9 and the like. Consisting of The element mounting base is disposed on the heat-dissipating bottom plate 13 constituting the bottom surface of the hermetic package, and the element mounting base and the heat-dissipating bottom plate 13 have a thermal conductivity of 150 W / (m · K) or more. And a material having

The heat-dissipating bottom plate 13 has an extension for attaching to a heat-dissipating base 20 which is an external substrate.

Further, an optical signal from the semiconductor laser 1 is emitted through the lens 16 to the outside of the hermetic package, and the lens 16 is driven at 50 W / (mK).
It is fixed to the element mounting base via a member having the following thermal conductivity (a metal plate 5 having a frame shape so that light can pass).

More specifically, for example, the semiconductor laser 1 as an optical semiconductor element for light emission is hermetically sealed by a case 9 provided with wiring, and is provided on a side wall of the case 9 constituting an airtight package. Lead 10 for supplying power to semiconductor laser 1
Is installed. In addition, in order to take out an optical signal from the semiconductor laser 1, the optical signal is optically coupled to an optical fiber 8 provided outside the housing 9. The heat generated by the semiconductor laser 1 is radiated from the heat radiation bottom plate 13 of the housing 9 to the heat radiation base 20 provided below the optical module.
An electric circuit board 19 for supplying power to the optical module M is arranged above the optical module M, and the electric terminals 12 of the housing 9 are connected.

Further, the structure of the optical module M will be described in detail. The semiconductor laser 1 has a thermal conductivity of 160 W
/ (M · K) is mounted and fixed on a ceramic chip carrier 2 mainly made of aluminum nitride with AuSn solder.

Here, the semiconductor laser 1 is made of InxGa1-
A yAs1-yPy-based or AlxGa1-xAs-based semiconductor laser is used. The semiconductor laser 1 needs to be evaluated for characteristics generally called burn-in, and it is desirable to mount the semiconductor laser 1 on the chip carrier 2 for evaluation. The chip carrier 2 on which the semiconductor laser 1 is disposed is made of copper-containing copper having a thermal conductivity of 200 W / (m · K) and containing 20% by weight of copper.
Using a tungsten alloy as a main material, AuSn
Joined with solder.

The optical fiber 8 optically connected to the semiconductor laser 1 is constituted by a fiber pigtail 7 fixed to a ferrule 17 made of zirconia ceramics press-fitted in a metal fitting 7 made of stainless steel and an epoxy-based adhesive 18. ing.

In the optical module M, the semiconductor laser 1 and the optical fiber 8 are optically coupled with a high efficiency through an aspheric lens 16. The lens 16 is made of stainless steel or W, Ti,
Materials containing Co, C, etc. as main components (for example, SF20T)
The lens is fixed to the lens holder 4 of a cylindrical metal fitting made of a material such as a low-melting glass or is integrally formed.

In order to couple the optical signal emitted from the semiconductor laser 1 to the optical fiber 8 with high efficiency, the interval between the semiconductor laser 1 and the lens 16 and the interval 8 between the lens 16 and the optical fiber are important. N. A (numerical aperture) and the N.F. A Further, it is desirable that the interval is optimally calculated from the magnification of the aspherical lens. Also, in order to perform the optical coupling with high efficiency, generally, while driving a semiconductor laser and monitoring an optical signal, an active lens that accurately aligns a lens, an optical fiber, and the like and fixes the optical fiber at a position where the maximum coupling efficiency is obtained. The alignment method is best.
The optical module M of the present invention also has an optimal structure using the present alignment method.

The N.D. of the semiconductor laser 1 described above is used. A. Is 0.
3 to 0.6; A. Is 0.2 to 0.1
If the optical system has a magnification of about 3 to 6 times, highly efficient coupling can be obtained.

Here, the chip carrier 2 is mounted so that the light emitting end is disposed on one end surface of the metal base 3 on which the chip carrier 2 on which the semiconductor laser 1 is mounted is mounted.
A frame-shaped metal plate 5 having a thickness equal to the distance between the semiconductor laser 1 and the lens 16 that can provide a specified magnification is joined by solder or the like. The lens holder 4 is adjusted and fixed via the metal plate 5 so that the center of the optical axis of the lens coincides with the emission position of the semiconductor laser 1. The metal plate 5 is provided with a through hole in the thickness direction in order to secure an optical path.
By using an iron / nickel / kovar alloy or stainless steel of 0 W / (m · K) or less, the metal plate 5 and the lens holder 4 can be joined by YAG welding, and highly reliable lens fixing can be achieved.

The use of the metal plate 5 makes it possible to suppress variations in the distance between the semiconductor laser 1 and the aspherical lens 16 between products in the optical axis direction. It is possible to obtain high optical coupling efficiency characteristics as well.

The housing 9 for hermetically sealing the semiconductor laser 1 is
A metal base 13 mainly made of a copper-tungsten alloy containing 10% by weight of copper having a thermal conductivity of 160 W / (m · K) on a bottom plate, and a frame material made of an iron-nickel-cobalt alloy as a silver It is a brazed metallized package. On the side wall of the housing 9, ceramics such as alumina are metallized with Au, and similarly, an electric terminal 12 to which a lead 10 of an iron-nickel-cobalt alloy is brazed as a main raw material is brazed. Thus, an optical module capable of high-speed transmission can be provided.

On the other hand, a sapphire single crystal glass 14 whose outer periphery is metallized is brazed and fixed to the optical coupling portion. The substrate 3 on which the chip carrier 2 and the lens holder 4 are mounted is fixed and mounted inside the housing 9 by soldering, and the electrodes 11b provided on the electric terminals 12 are wired with the Au wires 11a for electrical connection. After doing
The inside is interpolated and filled with dry nitrogen, and a metal cover 1 such as stainless steel or an iron-nickel-cobalt alloy is
At 5, the hermetic sealing is performed by resistance heating welding.

The optical connection of the optical fiber 8 is based on the semiconductor laser 1.
Is driven via the lead 10 or the like, and the fiber pigtail 7 is held and aligned via the fiber holder 6 so as to be at a position where the maximum coupling can be obtained. When the maximum coupling is obtained, the fiber pigtail 7 is connected to the fiber holder 6.
And fixed by YAG welding.

Further, the periphery of the joint interface between the metallized package 9 and the fiber holder 6 is fixed by YAG welding while the fiber holder 6 is finely adjusted and the maximum coupling is maintained, whereby the optical module M is completed.

A through hole 21 for fixing to the heat radiating base 20 is provided at an extending portion of the heat radiating bottom plate 13 constituting the housing 9 of the optical module M, and this through hole 21 is screwed or the like. By fixing, it is possible to easily fix to the heat dissipation base 20.

Further, as shown in FIG. 4, a fixing hole may be provided in the rear portion of the package to fix the package to the heat dissipation base. According to such a configuration, when the optical module is fixed to the heat dissipation base, a stress generated at the time of mounting or a residual stress applied to the housing after the mounting is not applied to the periphery of the optical coupling portion, and the reliability is further improved. High fixing can be realized.

In the optical module M of the present invention, after the semiconductor laser 1 is mounted on the ceramic substrate 4 having a thermal conductivity of, for example, 170 W / (m · K), the thermal conductivity is 200 W / (m).
(K) is mounted on the metal substrate 5, and the heat radiation bottom plate 13 is mounted on the heat radiation substrate 20 having a thermal conductivity of 160 W / (m · K).

The thermal conductivity of each of these substrates is important. FIG. 5 is a graph showing an analysis of a temperature rise of the semiconductor laser (InxGa1-yAs1-yPy) when the thermal conductivity of the heat radiation bottom plate is changed. The heat value of the semiconductor laser at this time was 0.8 W.

According to FIG. 5, the thermal conductivity is 150 W / (m
Since the temperature rise of the semiconductor laser is suppressed to 10 ° C. or less if K) or more, the use of a material having such thermal conductivity as the radiating bottom plate particularly increases the light output from the optical module to over 50 mW. This is suitable in terms of heat radiation during output. Further, in consideration of the thermal resistance in the heat radiation path, the thermal conductivity of the substrate on which the semiconductor laser is mounted and the substrate on which the substrate is mounted are preferably 150 W / (m · K) or more.

However, for a substrate having a large thermal conductivity,
It is difficult to join and fix the lens holder by highly reliable YAG welding. Generally, YAG welding needs to be locally heated and melted, and it is difficult to join materials having high thermal conductivity. Therefore, a high thermal conductivity substrate has 50
A metal substrate of W / mk or less may be attached, and the metal substrate and the lens holder may be YAG-welded.

FIG. 5 shows the results of measurement using an InxGa1-yAs1-yPy semiconductor laser as a semiconductor laser. However, for example, an AlxGa1-xAs-based semiconductor laser can be similarly discussed. Further, in the present invention, a light emitting element has been described as an example of an optical semiconductor element. However, a similar effect can be expected for a light receiving element such as a photodiode, and may be appropriately changed without departing from the gist of the present invention. Can be implemented.

[0045]

As described above, the optical module of the present invention comprises an element mounting base on which an optical semiconductor element is provided, housed in an airtight package, and the element mounting base forms a bottom surface of the airtight package. The device mounting substrate and the heat dissipation bottom plate are made of a material having a thermal conductivity of 150 W / (m · K) or more. With such a configuration, the temperature rise of the optical semiconductor element can be reduced as much as possible without using a cooling element, a temperature detection element, or the like that has been conventionally used to prevent the temperature increase of the optical semiconductor element. Since the semiconductor element can be hermetically sealed, a small-sized optical module having excellent long-term stability and reliability can be easily provided.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a state in which an optical module M according to the present invention is disposed on a heat dissipation base and an electric circuit board.

FIG. 2 is an exploded perspective view schematically illustrating an embodiment of the optical module according to the present invention.

FIG. 3 is an end view schematically illustrating an embodiment of the optical module according to the present invention.

FIG. 4 is a perspective view schematically illustrating another embodiment of the optical module according to the present invention.

FIG. 5 is a graph showing the relationship between the temperature rise of a semiconductor laser and the thermal conductivity.

FIG. 6 is a cross-sectional view illustrating a conventional optical module.

[Explanation of symbols]

 1: semiconductor laser (optical semiconductor element) 2: chip carrier (component of element mounting substrate) 3: substrate (component of element mounting substrate) 4: lens holder 6: fiber holder 7: fiber pigtail 8: optical fiber 9: Housing (component of airtight package) 12: Electric terminal 13: Bottom plate for heat radiation M: Optical module

Claims (4)

[Claims] 1. An optical module comprising an element mounting base on which an optical semiconductor element is disposed and housed in an airtight package, wherein the element mounting base is disposed on a heat-dissipating bottom plate constituting a bottom surface of the airtight package. An optical module, wherein the element mounting base and the heat dissipation bottom plate are made of a material having a thermal conductivity of 150 W / (m · K) or more. 2. The optical module according to claim 1, wherein said heat-dissipating bottom plate has an extension for attaching to an external substrate. 3. The optical semiconductor device according to claim 1, wherein the optical semiconductor element is a semiconductor laser, and an optical signal is emitted from the semiconductor laser to the outside of the hermetic package. Optical module. 4. An optical signal from the semiconductor laser is emitted to the outside of the hermetic package through a lens, and the lens has a thermal conductivity of 50 W / (mK) or less through a member. The optical module according to claim 3, wherein the optical module is fixed to the element mounting base.