JPH02197185A - Semiconductor laser assembly with built-in electronic cooling element - Google Patents

Abstract

PURPOSE:To enable the high speed drive of a semiconductor laser keeping the reduction minimum in temperature difference between two faces of an element by a method wherein a high electric conductor where an LD chip is mounted is directly fixed to a metal case. CONSTITUTION:An LD chip 21 is mounted on end fixed to a stem 31 formed of a material which is high in electric conductivity and low in thermal conductivity. The stem 31 is extended to be directly connected and fixed to the inner face of a metal case 27. A high frequency board 32, on which an electric signal transmitting pattern is formed, is pasted on the stem 31. And, the stem 31 is mounted on a Peltier element 23, where the element 23 is composed of a semiconductor element possessed of the Peltier effect sandwiched between ceramic boards 24 and 25. then a current and a voltage applied to the electrodes of the element 23 are controlled, thermal energy is transferred in one direction through the element 23 to enable the element 21 to be cooled down to an appropriate temperature.

Description

[Detailed Description of the Invention] Summary Regarding a semiconductor laser assembly with a built-in electronic cooling element, the present invention aims to drive the semiconductor laser at high speed while minimizing the decrease in the temperature difference between two surfaces of the electronic cooling element. A built-in electronic cooling element is mounted and fixed on a high electrical conductor, the high electrical conductor is fixed to one side of the electronic cooling element, and the other side of the electronic cooling element is fixed to the inner surface of a metal casing. In the semiconductor laser assembly, the high electrical conductor is formed from a material with low thermal conductivity, and the high electrical conductor is directly connected to the inner surface of a metal housing.

FIELD OF THE INVENTION The present invention relates to a semiconductor laser assembly with a built-in electronic cooling element.

In optical communication systems, generally a semiconductor laser (hereinafter referred to as LD) is modulated with a time-series electrical signal, and this modulated light is guided through a lens system to an optical fiber serving as a transmission path. The LD is usually provided as an LD assembly by being integrated with a lens placed just before the LD (hereinafter referred to as the lens), and this LD assembly is integrated with a normal lens system and an optical fiber for connection. Used as a module. Since the characteristics of optical elements such as LDs used in such LD modules are easily affected by temperature, it is desirable to operate them under a constant temperature environment using an electronic cooling element such as a Beltier element.

In addition, with the recent demand for faster speeds in optical communication systems, LDs can be expanded to 10Gb/10Gb while maintaining their reliability.
It has become necessary to drive at approximately s. For this reason, L.D.
, an LD assembly in which an electronic cooling element such as a Beltier element and related parts are hermetically sealed inside a single metal housing has been provided, but in conventional LD assemblies, the temperature of the LD is stabilized by the electronic cooling element. Since priority was given to LD, the high-speed drive characteristics of the LD cannot be said to be good. Therefore, there is a need for a semiconductor laser assembly that can achieve both high-speed drive characteristics of the LD and temperature stabilization of the LD using an electronic cooling element.

Conventional technology FIG. 4 shows a cross-sectional view of a conventional LD assembly.

Reference numeral 1 denotes an LD chip, which is mounted and fixed on a stem 2 made of a highly electrically conductive material such as metal. The stem 2 is mounted on the Bertier element 3. The Bertier element 3 is constructed by fixing electrodes (not shown) on two ceramic substrates 4.5, and sandwiching a plurality of semiconductors 6 having the Bertier effect between these electrodes. One ceramic substrate 4 is in surface contact with the stem 2, while the other ceramic substrate 5 is fixed to the inner surface of the metal casing 7 by surface contact. By metallizing the ceramic substrates 4 and 5,
The metal housing 7 and the ceramic substrate 5 are joined together, the ceramic substrate 4.5 is joined to the electrodes, the electrodes are joined to the semiconductor 6, and the ceramic substrate 4 and the stem 2 are joined together by soldering. .

The metal housing 7 is provided with at least a signal human power lead 8 and an earth lead 10 connected to the housing 7, and the signal human power lead 8 is connected to an LD drive circuit (not shown). The signal input lead 8 is connected to the LD chip 1 via a wire 9, and the ground lead 10 is connected to the stem 2 via a wire 11. Reference numeral 12 denotes an insulating material such as glass or Teflon for insulating the signal input lead 8 from the metal casing 7. The LD chip 1 mounted on the stem 2 is driven via a signal input lead 8, a wire 9.11, and a ground lead 10.

However, when the Beltier element 3 is driven by controlling the voltage and current values applied to the electrodes of the Beltier element 3, the thermal energy is carried in one direction by the Beltier element 3, and a temperature difference occurs between the ceramic substrates 4.5. The LD chip 1 is cooled to an appropriate operating temperature.

Problem to be Solved by the Invention By the way, when the drive signal becomes high frequency, the lead 8 lO
The electrical impedance components of the wires 9 and 11 and the capacitance of the Beltier element 3 cause effects such as fluctuations and interference in the optical output waveform. To prevent this, it is sufficient to reduce the electrical resistance R of the leads and wires given by the following equation.

R-(1/σ)・(L/S)...■Here, σ
is the electrical conductivity, L is the length of the lead or wire, and S is the cross-sectional area of the lead or wire. ■From the formula, to reduce the electrical resistance R, (a) increase σ, (mouth)
It can be seen that there are solutions such as decreasing L and (c) increasing S.

On the other hand, if a lead wire with low electrical resistance is used, heat from outside the LD assembly will flow into the LD chip via the thermal resistance 'Rth of the following equation.

RLh-N/ni)・(L/S)...■Here,
The thermal conductivity, L, and S are the same as in equation (2) above. ■
Since Equation and Equation 0 have the same form, increasing the conductivity of the electrical signal also increases the thermal conductivity, and the Bertier element 3
It can be seen that the temperature difference between the ceramic substrates 4° and 5 becomes small. Therefore, there is a problem in that it is very difficult to ensure good high frequency characteristics while effectively bringing out the characteristics of the Beltier element.

The present invention has been made in view of these points, and its purpose is to drive a semiconductor laser at high speed while minimizing the decrease in temperature difference between two surfaces of an electronic cooling element. An object of the present invention is to provide a semiconductor laser assembly with a built-in electronic cooling element.

Means for Solving the Problems FIG. 1 shows a diagram of the principle of the present invention. In the figure, 21 is an LD chip, which is mounted and fixed on a high electrical conductor 22. High electrical conductor 22 is formed from a material with low thermal conductivity and is directly connected to the inner surface of metal housing 27 . The high electrical conductor 22 is mounted on one side of the electronic cooling element 23, and the other side of the electronic cooling element 23 is mounted on a metal casing 2.
It is fixed to the inner surface of 7 by surface contact. The electronic cooling element 23 has a conventionally known configuration, and is constructed by sandwiching a semiconductor element 26 having a Peltier effect between ceramic substrates 24 and 25, similar to the conventional example described above. 28 is a signal input lead, and a wire 29 connects the LD chip 21.
The LD chip 21 is driven at high speed by a drive circuit (not shown) connected to the signal lead 28 for human power. 30 is an insulating material for insulating the signal input lead 28 from the metal casing 27.

In order to prevent as much as possible the heat from outside the LD assembly from flowing into the LD chip 21 through RLh shown in the above-mentioned equation 0, the cross-sectional area perpendicular to the length and L of the high electrical conductor 22 is The ratio of S is made as large as possible, and the material of the high electrical conductor 22 is a metal with low thermal conductivity.
In other words, it is characterized by using a material with low thermal conductivity.

Function In the present invention, the high electrical conductor 2 on which the LD chip 21 is mounted
By directly connecting and fixing 2 to the metal casing 27, it is possible to ensure a much lower electrical resistance than conventional wire connections, and by selecting the dimensions and materials of the high electrical conductor 220, low thermal conductivity can be achieved. By doing so, it is possible to minimize the decrease in the temperature difference between the two sides of the electronic cooling element 23.

Example Embodiments of the present invention will be described in detail below based on the drawings.

In the description of this embodiment, the same components as those in the principle diagram shown in FIG. 1 will be denoted by the same reference numerals, and the description thereof will be partially omitted.

FIG. 2 is a sectional view of a first embodiment of the present invention, in which an LD chip 21 is mounted and fixed on a stem 31 made of a material with high electrical conductivity and low thermal conductivity. Examples of specific materials for the stem 31 include titanium, stainless steel, Kovar, and the like.

The stem 31 is extended and directly connected and fixed to the inner surface of the metal housing 27. The stem 31 is mounted on an electronic cooling element (hereinafter referred to as a Beltier element) 23 such as a Beltier element. The Vertier element 23 has a conventionally known configuration, and is constructed by sandwiching a semiconductor element 26 having a Peltier effect between ceramic substrates 24 and 25. When the Beltier element 23 is driven by controlling the voltage and current values applied to electrodes (not shown) of the Beltier element 23, thermal energy is carried in one direction by the Beltier element 23, and the LD chip 21 can be cooled to an appropriate temperature. can.

On the other hand, a high frequency substrate 32 such as an alumina ceramic substrate on which an electric signal transmission pattern is formed is attached on the stem 31, and an electronic component 33 for high-speed driving of the LD is mounted on this high frequency substrate 32. The pattern on 32, the electronic component 33 and the LD chip 21 are wires 34.3
Connected by 5. 36 is a center conductor of the coaxial connector, which is electrically connected to the pattern on the high frequency board 32. Reference numeral 30 denotes an insulating material made of glass, Teflon, or the like for electrically insulating the center conductor 36 from the metal casing 27. In FIG. 2, the stem 31 is an insulating material 30.
Although shown as if connected to the insulating material 30, the stem 31 is directly connected to the inner surface of the metal housing 27 rather than to the insulating material 30.

Further, the electronic component 33 for high-speed driving is provided in the LD assembly because it is advantageous to shorten the distance between the LD chip and the driving circuit as much as possible for high-speed driving.

As mentioned above, the high frequency board 32 uses an insulator such as alumina or ceramic, and its thermal conductivity is sufficiently low. effect can be maintained.

FIG. 3 is a sectional view of a second embodiment of the present invention. In the first embodiment shown in FIG. If the ground pattern can ensure sufficient electrical conductivity, the stem can be divided into 31a and 31b as shown in FIG. 3, one stem 31a is mounted on the Vertier element 23, and the other stem 31b is It may be connected and fixed to the inner surface of the metal housing 27.

Effects of the Invention Since the semiconductor laser assembly of the present invention is configured as detailed above, it has the effect that the operating temperature of the semiconductor laser can be appropriately controlled without deteriorating the high-speed characteristics of the semiconductor laser assembly.

[Brief explanation of the drawing]

1 is a diagram showing the principle of the present invention, FIG. 2 is a cross-sectional view of a first embodiment of the present invention, FIG. 3 is a cross-sectional view of a second embodiment of the present invention, and FIG. 4 is a cross-sectional view of a conventional example. 21... LD chip, 22... High electrical conductor, 2
3...Electronic cooling element, 24.25...Ceramic substrate, 6...Semiconductor, 27...Metal casing, 8.
...Signal input lead, 1...Stem, 32...High frequency board, 3.
...Electronic components for high-speed drive, 6...Center conductor of coaxial connector.

Claims (1)

[Claims] A semiconductor laser (21) is mounted and fixed on a high electric conductor (22), and the high electric conductor (22) is connected to an electronic cooling element (22).
3), and an electronic cooling element (23
) in a semiconductor laser assembly with a built-in electronic cooling element, the other surface of which is fixed to the inner surface of a metal housing (27), wherein the high electrical conductor (22) is made of a material with low thermal conductivity, and the high electrical conductor (22) is made of a material with low thermal conductivity; A semiconductor laser assembly with a built-in electronic cooling element, characterized in that (22) is directly connected to the inner surface of a metal casing (27).