GB2404281A

GB2404281A - Optoelectronic assembly with thermoelectric cooler

Info

Publication number: GB2404281A
Application number: GB0317531A
Authority: GB
Inventors: David John Kenneth Meadowcroft
Original assignee: Agilent Technologies Inc
Current assignee: Agilent Technologies Inc
Priority date: 2003-07-25
Filing date: 2003-07-25
Publication date: 2005-01-26
Also published as: GB0317531D0

Abstract

An optoelectronic assembly, used in optical communications networks, has an optoelectronic device (OED) and a thermoelectric cooler (TEC) disposed in a housing. The thermoelectric cooler has a first surface thermally coupled to the optoelectronic device and a second surface coupled to the housing. The OED may comprise a laser and optical detector. The optoelectronic assembly is characterised in that a region of the housing comprises the second surface of the TEC.

Description

240428 1

OPTOELECTRONIC ASSEMBLY

Optical communications networks are increasingly being operated at faster data rates and over longer transmission links. One consequence of these factors is that the optical transmitters are being driven at greater frequency, using increased drive currents. An effect of this is that the heat generated by the optical transmitter increases which could cause catastrophic failure of the transmitter unless some form of cooling is used to regulate the temperature of the transmitter.

Thermoelectric coolers (TECs) are conventionally used to control the temperature of the transmitter as they can provide precise temperature control and are suited to applications where there is limited space. TECs comprise two ceramic plates that are separated by e-type and p-type semiconductor material. By applying an appropriate voltage to the semiconductor material it is possible to transfer heat from one of the ceramic plates to the other plate, thus creating a hot plate and a cold plate. Thus a TEC can be used to cool or heat a device through controlling the voltage applied to the TEC.

Conventionally, the transmitter and associated driver circuitry are enclosed to provide protection from environmental contamination (water, grease, etc.) and a TEC, or other cooling device, is coupled to the exterior of the transmitter housing. By controlling the temperature of the housing, the TEC can control the temperature of the devices within the housing. - 2

According to a first aspect of the present invention there is provided an opto-electronic assembly comprising an opto-electronic device, a housing and a thermoelectric cooler, the opto-electronic device being received within the housing and a first surface of the thermoelectric cooler being thermally coupled to the opto-electronic device, the assembly being characterized in that a region of the housing comprises a second surface of the thermoelectric cooler.

One advantage provided by the present invention is that the optoelectronic device is directly cooled by the thermoelectric cooler (TEC), which provides for greater control of the temperature of the optoelectronic device.

Furthermore, by placing the TEC within the hermetic package that the optoelectronic device is received within, the reliability of the TEC is improved.

The housing may comprise a substantially cylindrical form.

Furthermore, a first end-face of the substantially cylindrical housing may comprise the second surface of the thermoelectric cooler. The integration of the CD header and the hot plate of the TEC decreases the volume occupied by the TEC and the opto-electronic device and also provides more effective heat path by which energy can be dissipated from the opto-electronic device.

The second end-face of the substantially cylindrical housing may comprise an optically transparent material. - 3

The thermoelectric cooler and the opto-electronic device may be received upon the first end-face of the housing and the cylindrical region and the second end-face of the housing may be coupled to the first end-face of the housing. The first end-face and the cylindrical region of the housing may be secured with a collar. The cylindrical region of the housing may act as a heat sink.

A preferred embodiment of the invention control will now be described by way of illustration only and with respect to the accompanying drawings, in which Figure 1 shows a schematic depiction of an opto electronic assembly according to the present invention; Figure 2 shows a schematic depiction of the opto electronic assembly of Figure 1, to which an opto electronic device has been attached; and Figure 3 shows a schematic depiction of the opto electronic assembly of Figure 2, to which a cap has been applied.

Figures 1 to 3 show schematic depictions of an opto electronic assembly 100 according to the present invention. Referring to Figure 1, housing 10 comprises a base 20, which is also the hot plate of a thermoelectric cooler (TEC). Connected to the base are one or more thermoelectric couples 22, which are connected to the base via metallised regions 21. Further metallised regions 23 are also provided to enable the connection of transmitter - 4 - components (such as the laser, TEC, AND, etc.) to external circuits.

In an alternative embodiment of the present invention, the base 20 may be formed with a layer of material 26 having a low thermal conductivity coefficient, to reduce the heat flow back from the hot plate of the TEC to the cold plate.

A example of a suitable material for use as the base 20 is aluminium nitride and aluminium oxide (Al203) may be used as the insulating layer.

Referring to Figure 2, the cool plate 30 of the TEC is attached to the thermoelectric couples 22 to form the TEC.

The cool plate comprises metallised regions that enable the thermoelectric couples to be soldered to the cool plate and also enable one or more components 40 to be mounted onto the cool plate. These components 40 comprise a laser 42 and may further comprise one or more of a back facet optical detector 44, TEC control circuit 46, laser drive circuit 48, etc. The cool plate 30 of the TEC is preferably made from aluminium nitride as it has a high coefficient of thermal conductivity.

Figure 2 also shows a collar 12 that is attached to the circumference of the base 10 to enable the hermetic connection of a cap 14 (see Figure 3) to the base 10.

Referring to Figure 3, the cap conventionally has a cylindrical form with a transparent window 16 arranged such that the light emitted by the laser may exit the housing. For the sake of clarity Figure 3 shows the - 5 housing to be translucent but it will be understood that the materials conventionally used to form the cap are opaque. It is preferred that the materials used to form the collar 12 and the cap 14 have good heat conductivity properties in order that the cap can act as a further heatsink for the TEC. Preferred materials are molybdenum for the collar and stainless steel for the cap, although it will be appreciated that different materials with similar properties may be used.

Figures 1 to 3 show that the TEC comprises six thermocouples but it will be understood that a greater number of couples having a smaller area may be provided.

Alternatively, if the cooling that is required from the TEC is not as great then a smaller number of couples may be provided. The couples are formed from conventional thermocouple materials such as appropriately doped bismuth telluride.

It will be appreciated that it is possible, in theory, to arrange the TEC such that the cylindrical cap 14 forms the hot plate of the TEC, rather than using the header base 20 on which the opto-electronic devices are received.

However, the implementation described above with reference to Figures 1 to 3 is preferred as it is significantly easier to implement. - 6

Claims

1. An opto-electronic assembly (100) comprising an opto electronic device (42), a housing (10) and a thermoelectric cooler (20, 22, 30), the optoelectronic (42) device being received within the housing and a first surface of the thermoelectric cooler (30) being thermally coupled to the opto-electronic device, the assembly being characterized in that a region (20) of the housing (10) comprises a second surface of the thermoelectric cooler.

2. An opto-electronic assembly according to claim 1, wherein the housing (10) comprises a substantially cylindrical form.

3. An opto-electronic assembly according to claim 2, wherein a first endface (20) of the substantially cylindrical housing comprises the second surface of the thermoelectric cooler.

4. An opto-electronic assembly according to claim 3, wherein the second end-face (16) of the substantially cylindrical housing comprises an optically transparent material.

5. An opto-electronic assembly according to claim 4, wherein the thermoelectric cooler and the opto-electronic device (42) are received upon the first end-face (20) of the housing and the cylindrical region (14) and the second - 7 end-face (16) of the housing are coupled to the first end- face (20) of the housing.

6. An opto-electronic assembly according to claim 5, - wherein the first end-face and the cylindrical region of the housing are secured with a collar (12).

7. An opto-electronic assembly according to any of claims 2 to 6 wherein the cylindrical region (16) of the housing acts as a heat sink.