WO2003069419A2 - An artificial environment module - Google Patents

An artificial environment module Download PDF

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Publication number
WO2003069419A2
WO2003069419A2 PCT/GB2003/000700 GB0300700W WO03069419A2 WO 2003069419 A2 WO2003069419 A2 WO 2003069419A2 GB 0300700 W GB0300700 W GB 0300700W WO 03069419 A2 WO03069419 A2 WO 03069419A2
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WO
WIPO (PCT)
Prior art keywords
temperature
chip
sensor
optic
package
Prior art date
Application number
PCT/GB2003/000700
Other languages
French (fr)
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WO2003069419A3 (en
Inventor
Andrew Leech
Phil Thurman
Xue Yongkuan
Original Assignee
Bookham Technology Plc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bookham Technology Plc filed Critical Bookham Technology Plc
Priority to AU2003205896A priority Critical patent/AU2003205896A1/en
Publication of WO2003069419A2 publication Critical patent/WO2003069419A2/en
Publication of WO2003069419A3 publication Critical patent/WO2003069419A3/en

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Classifications

    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D23/00—Control of temperature
    • G05D23/19—Control of temperature characterised by the use of electric means
    • G05D23/1927—Control of temperature characterised by the use of electric means using a plurality of sensors
    • G05D23/193—Control of temperature characterised by the use of electric means using a plurality of sensors sensing the temperaure in different places in thermal relationship with one or more spaces
    • G05D23/1931—Control of temperature characterised by the use of electric means using a plurality of sensors sensing the temperaure in different places in thermal relationship with one or more spaces to control the temperature of one space
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/024—Arrangements for cooling, heating, ventilating or temperature compensation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/64—Heat extraction or cooling elements
    • H01L33/645—Heat extraction or cooling elements the elements being electrically controlled, e.g. Peltier elements

Definitions

  • the present invention relates to an artificial environment module, in particular for optical devices.
  • the temperature and stress levels present on the chip In order to achieve optimal performance from optical circuit chips or other such devices sensitive to temperature or stress changes, it is desirable to control the temperature and stress levels present on the chip within very tight tolerances, for example to within ⁇ 0.1 °C variation.
  • the refractive index of material such as silicon, silica and other similar materials changes with temperature and stress changes, and these changes in refractive index results in a reduction in performance of the device.
  • FIG. 1A An existing device which has been developed is shown in Figure 1A.
  • an integrated optics chip 14 on the substrate 12 is supported within a casing 4 on studs 3.
  • the casing 4 has a base portion and a lid portion formed of Kovar.
  • the substrate 12 incorporates a substrate heater 13 and a thermoelectric cooler 5 is provided within the casing 4 below the substrate 12.
  • on-chip sensors are associated with the thermoelectric cooler and/or heater. These on- chip sensors monitor the temperature of the chip and control the activity of the thermoelectric controllers and heaters accordingly.
  • the chip still experiences thermal and stress effects which are directly attributable to a change in ambient temperature. It is an aim of the present invention to significantly improve the environment to which a chip is subjected within a package.
  • an artificial environment module comprising: an " outer casing defining an inner environment; an inner casing located in the inner environment and containing an optic device; a package sensor for monitoring the temperature of the inner casing; a device sensor for locally monitoring the temperature of the optic device; a package temperature controller for heating and/or cooling the inner casing in dependence on the temperature sensed by the package sensor to minimise variations in the temperature with respect to changes in ambient temperature; and a separate local temperature controller provided within the inner casing for locally heating and/or cooling the optic device in dependence on the temperature measured by device sensor.
  • the outer casing is made of a material of relatively low thermal conductivity
  • the inner casing is made of a material of relatively high thermal conductivity.
  • the inner casing is made of a material having a thermal conductivity of at least 150Wm/K, further preferably at least 200Wm/K.
  • Materials whose thermal conductivity exhibits an anisotropic character, such as graphite in an aluminium matrix may also be used; preferred such materials are ones having a thermal conductivity in at least one axis of at least 150Wm/K, and further preferably at least 200Wm/K; more preferred such materials are ones having an average thermal conductivity of at least 150Wm/K, and further preferably at least 200Wm/K.
  • preferred materials for the inner casing include aluminium, aluminium graphite (graphite in an aluminium matrix) and aluminium nitride.
  • an artificial environment module comprising: an outer casing defining an inner environment; an inner casing located in the inner environment and containing an integrated optics chip; a temperature adjustment means operable to selectively heat or cool the inner environment and located in the inner environment externally of the inner casing; a package sensor located within the inner casing whereby the temperature adjustment means is controlled in dependence on the temperature sensed by the package sensor to minimise variations in the temperature within the inner casing with respect to changes in ambient temperature; and a further temperature adjustment means located within the inner casing and associated with a sensor on the integrated optics chip.
  • an artificial environment module comprising: an outer casing defining an inner environment; an inner casing located in the inner environment and containing an optic chip including at least a first portion defining a thermally-sensitive optic element; a package sensor for monitoring the temperature of the inner casing; a package temperature controller for heating and/or cooling the inner casing in dependence on the temperature sensed by the package sensor to minimise variations in the temperature with respect to changes in ambient temperature, and whose operation in response to changes in ambient temperature does not induce stress in the optic chip; an on-chip sensor for locally monitoring the temperature of the first portion of the optic chip; and at least one local temperature controller provided in thermal contact with the first portion of the optic chip for locally heating and/or cooling the first portion of the optic chip in dependence on the temperature measured by the on-chip sensor.
  • Figure 1A is a schematic sectional view of an existing optics package
  • Figure 1B is a schematic sectional view of an embodiment of an artificial environment module in accordance with an embodiment of the invention.
  • Figure 2 is a plan view of the chip within the module
  • Figure 3 is a plan view of a chip in an earlier package
  • Figure 4 is a chart illustrating the power consumption variation with temperature of the module of Figure 1 ;
  • Figure 5 is a chart illustrating the variation of power consumption with temperature for an earlier package
  • Figure 6 is a diagram illustrating the change in internal temperature with respect to ambient temperature of the module of Figure 1 ;
  • Figure 7 is a chart illustrating the change in temperature of an inner environment of the module with respect to ambient temperature.
  • FIG. 8 to 10 are alternative arrangements for heating the inner casing.
  • Figure 1B illustrates a schematic sectional view through a module according to one embodiment of the present invention.
  • the module denoted generally by the reference numeral 2 comprises an outer case 4 made from a material which preferably provides a hermetic seal between its interior 6 and the exterior environment 8.
  • the interior 6 provides an artificial environment for an optical package as discussed further herein.
  • the optical package comprises an inner case 10 inside which is located a chip carrier 12 which supports an optical chip 14.
  • the chip carrier 12 incorporates an integrated heater.
  • a first thermoelectric controller 16 is provided in the interior 6 of the outer casing 4, outside the optical package.
  • a second thermoelectric controller 18 is provided inside the inner casing 10 which defines the optical package.
  • a package sensor 20c is provided on a wall of the inner casing, in this case within the inner casing 10 in a plane below that of the chip carrier 12 and displaced to one side of it (see Figure 2).
  • the package sensor 20c is a temperature sensor which is attached to the base portion 10a and is thus active to control the temperature of the base using the first thermoelectric controller 16 as a heat pump and a heater.
  • two monitors 20a, 20b are provided in the interior 6. These monitoring sensors are used for evaluation of the package and are not present in the device as sold.
  • the aim of the structure of Figure 1B is to provide a module which creates an artificial unchanging environment around the chip 14 so that the chip 14 is as nearly as possible unaffected by any changes in ambient temperature.
  • the artificial environment is created by controlling the temperature of the walls of the module (the inner casing 4) so as to keep the temperature of the internal environment 6 stable.
  • the inner casing 10 comprises a base portion 10a and a lid 10b.
  • the optical package is constructed as follows. In the existing device of Figure 1A, the chip 14 is wholly supported by a substrate 12. To construct the optical package of Figure 1 B, a portion of the substrate 12 is removed from below the chip 14 to allow the thermoelectric controller 18 to be placed adjacent the chip 14 on its underside.
  • the second thermoelectric controller 18 is placed on the base portion 10a and the chip 14 is then placed above it and in contact with the second thermoelectric controller 18.
  • the lid portion 10b is then located with respect to the base portion 10a.
  • a layer of thermal grease is provided between the second thermoelectric controller 18 and the chip 14.
  • Thermal grease is also used in the joint between the lid portion 10b and the base portion 10a to give as high thermal conductivity through the package walls as possible.
  • the package is manufactured from Kovar and the chip carrier 12 is Al 3 0 2 with a thick film hybrid heater.
  • the first monitor 20a is attached to the lid portion 10b and the second monitor 20b is attached under the base portion 10a in the vicinity of the second thermoelectric controller. These monitor local package temperatures.
  • FIG 2 is a schematic plan view of the chip 14 on which the arc portion 22 represents an array waveguide grating (AWG) comprising a plurality of curved silicon ridge waveguides arranged in a manner known in the art. Input and output waveguides are not shown in Figure 2.
  • Figure 2 shows the package sensor 20c located off the chip 14 in a diagrammatic sense.
  • On the chip 14 are two further sensors 20d, 20e.
  • the sensor 20d is located in the region of the array waveguide grating 22 and the sensor 20e is located on the chip 14 in such a place that when the package is constructed it is in the vicinity of the second thermoelectric controller 18.
  • the sensor 20d is used to control the heater integrated within the chip carrier 12 while the sensor 20e is used to control the second thermoelectric controller 18.
  • each sensor is connected to the heater or controller which it is controlling via suitable electrical interconnects and control circuitry. That is, the package sensor 20c is connected to the first thermoelectric controller 16, the sensor 20d is connected to the integrated heater in the chip carrier 12 and the sensor 20e is connected to the second thermoelectric controller 18.
  • the aim of the package is to reduce the effect of ambient temperature changes on the chip 14 and the chip carrier 12. This is done by controlling the thermoelectric controllers 16, 18 and the integrated heater on the chip carrier 12 in line with the monitored temperature changes using the sensors 20c, 20d and 20e.
  • the design is very effective, as indicated by the following experimental data.
  • Figure 4A is a chart showing the power consumption for the thermoelectric controllers and the heater for the module 2 of Figure 1.
  • the curve labelled Base Tec relates to the first thermoelectric controller 16 while the curve labelled Voa TEC relates to the second thermoelectric controller 18.
  • Figure 4B is a chart similar to that of Figure 4A but for an alternative embodiment in which the inner casing is made of Aluminium in place of Kovar.
  • Other preferred materials for the inner casing include aluminium graphite and aluminium nitride.
  • Figure 5 is a similar chart to that of Figures 4A and 4B, but utilising an existing package having three thermoelectric controllers associated with sensors as illustrated in Figure 3.
  • Figure 3 is a plan view of a chip 14 showing first and second thermistors 24a, 24b in the region of the array waveguide grating 22, and a third thermistor 24c which is in the location of the output waveguide. These are associated respectively with thermoelectric controllers which are labelled AWG TEC, Voa TEC and WG TEC in Figure 5.
  • a comparison of the charts of Figures 4 and 5 show that the change in power consumption for the heating device in the AWG region of the chip is around 60% less for the design of Figure 1 B than for the other design used for comparison purposes.
  • Figure 6 shows the change in temperature of the areas of the chip 14 associated with thermistors 24a, 24b, 24c (AWG1 , AWG2 and AWG in Figure 6).
  • the two sensors 24a, 24b near the array waveguide grating show that the temperature change across the array is small.
  • Table 1 compares the changes with the previous design, and also with the Aluminium embodiment.
  • Figure 7 shows the relationship between ambient temperature and the temperature as measured by the monitoring sensors 20a and 20b located respectively on the centre of the lid portion 10b and below the hot side of the second thermoelectric controller.
  • the sensor 20a is labelled Lid in Figure 7
  • the sensor 20b is labelled Under VOA Tec in Figure 7.
  • the package walls of the outer casing 4 made from very high thermally conductive material, such as aluminium, preferably with a lower limit of 200W/mK.
  • material having a lower thermal conductivity still represents a considerable improvement as indicated by the above discussion which related to a prototype where the casing wall was made of Kovar and steel parts with a conductivity of less than 20W/mK.
  • the module of Figure 1B solves temperature and stress control difficulties associated with optical circuit chips or other devices sensitive to temperature or stress change.
  • the described design for an environmental chamber isolates the chip or other sensitive device from any external changes in temperature, stress and, if the outside wall 4 is hermetic, then any changes in external atmospheric conditions. This isolation allows the device control to be more accurate than previous designs which simply use heaters or TECs in close proximity to the chip.
  • the second thermoelectric controller 18 is needed only when the optic chip defines one or more optic devices (now shown) that in operation generate relatively large amounts of heat (such as pin diode absorption attenuators, including variable optical attenuators), because in those situations heat must be removed. The heat which is removed can be reused to heat the package walls. When the optic chip does not include such devices, the second thermoelectric controller 18 is not necessary.
  • thermoelectric controller can be replaced by a heater in cases where the temperature of the module will never be below ambient temperature.
  • Figures 8 to 10 illustrate different possibilities for heating and cooling the inner casing. It is possible for the wall of the inner casing 10 to incorporate an integrated heater as denoted by reference numeral 30 in Figure 8. Thus, in the embodiment of Figure 8 there is a thermoelectric controller 18, a heater integrated into the substrate 12 and heaters integrated into the walls of the inner casing 10.
  • an additional heater 32 for example a ceramic heater, is mounted on an inner surface of the wall of the inner casing 10.
  • a heater is provided within the inner casing 10 in the form of a copper heater 34.
  • heaters and TECs are used, other technologies such as heat pipes could be used.

Abstract

An artificial environment module (2) comprising: an outer casing (4) defining an inner environment (6); an inner casing (10) located in the inner environment and containing an optic chip (14) including at least a first portion defining a thermally-sensitive optic element; a package sensor (20c) for monitoring the temperature of the inner casing; a package temperature controller (16) for heating and/or cooling the inner casing in dependence on the temperature sensed by the package sensor to minimise variations in the temperature with respect to changes in ambient temperature, and whose operation in response to changes in ambient temperature does not induce stress in the optic chip; an on-chip sensor for locally monitoring the temperature of the first portion of the optic chip; and at least one local temperature controller (18) provided in thermal contact with the first portion of the optic chip for locally heating and/or cooling the first portion of the optic chip in dependence on the temperature measured by the on-chip sensor.

Description

AN ARTIFICIAL ENVIRONMENT MODULE
The present invention relates to an artificial environment module, in particular for optical devices.
In order to achieve optimal performance from optical circuit chips or other such devices sensitive to temperature or stress changes, it is desirable to control the temperature and stress levels present on the chip within very tight tolerances, for example to within ± 0.1 °C variation. The refractive index of material such as silicon, silica and other similar materials changes with temperature and stress changes, and these changes in refractive index results in a reduction in performance of the device.
However, it is very difficult to achieve the necessary environmental control. In an existing device which has been developed is shown in Figure 1A. In that device, an integrated optics chip 14 on the substrate 12 is supported within a casing 4 on studs 3. The casing 4 has a base portion and a lid portion formed of Kovar. The substrate 12 incorporates a substrate heater 13 and a thermoelectric cooler 5 is provided within the casing 4 below the substrate 12. In this device on-chip sensors are associated with the thermoelectric cooler and/or heater. These on- chip sensors monitor the temperature of the chip and control the activity of the thermoelectric controllers and heaters accordingly.
However, in such a device the chip still experiences thermal and stress effects which are directly attributable to a change in ambient temperature. It is an aim of the present invention to significantly improve the environment to which a chip is subjected within a package.
One aspect of the present invention provides an artificial environment module comprising: an" outer casing defining an inner environment; an inner casing located in the inner environment and containing an optic device; a package sensor for monitoring the temperature of the inner casing; a device sensor for locally monitoring the temperature of the optic device; a package temperature controller for heating and/or cooling the inner casing in dependence on the temperature sensed by the package sensor to minimise variations in the temperature with respect to changes in ambient temperature; and a separate local temperature controller provided within the inner casing for locally heating and/or cooling the optic device in dependence on the temperature measured by device sensor.
In a preferred embodiment, the outer casing is made of a material of relatively low thermal conductivity, and the inner casing is made of a material of relatively high thermal conductivity. In one embodiment, the inner casing is made of a material having a thermal conductivity of at least 150Wm/K, further preferably at least 200Wm/K. Materials whose thermal conductivity exhibits an anisotropic character, such as graphite in an aluminium matrix, may also be used; preferred such materials are ones having a thermal conductivity in at least one axis of at least 150Wm/K, and further preferably at least 200Wm/K; more preferred such materials are ones having an average thermal conductivity of at least 150Wm/K, and further preferably at least 200Wm/K. Examples of preferred materials for the inner casing include aluminium, aluminium graphite (graphite in an aluminium matrix) and aluminium nitride.
According to another aspect of the present invention, there is provided an artificial environment module comprising: an outer casing defining an inner environment; an inner casing located in the inner environment and containing an integrated optics chip; a temperature adjustment means operable to selectively heat or cool the inner environment and located in the inner environment externally of the inner casing; a package sensor located within the inner casing whereby the temperature adjustment means is controlled in dependence on the temperature sensed by the package sensor to minimise variations in the temperature within the inner casing with respect to changes in ambient temperature; and a further temperature adjustment means located within the inner casing and associated with a sensor on the integrated optics chip. According to another aspect of the present invention, there is provided an artificial environment module comprising: an outer casing defining an inner environment; an inner casing located in the inner environment and containing an optic chip including at least a first portion defining a thermally-sensitive optic element; a package sensor for monitoring the temperature of the inner casing; a package temperature controller for heating and/or cooling the inner casing in dependence on the temperature sensed by the package sensor to minimise variations in the temperature with respect to changes in ambient temperature, and whose operation in response to changes in ambient temperature does not induce stress in the optic chip; an on-chip sensor for locally monitoring the temperature of the first portion of the optic chip; and at least one local temperature controller provided in thermal contact with the first portion of the optic chip for locally heating and/or cooling the first portion of the optic chip in dependence on the temperature measured by the on-chip sensor.
For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made by way of example to the accompanying drawings in which:
Figure 1A is a schematic sectional view of an existing optics package;
Figure 1B is a schematic sectional view of an embodiment of an artificial environment module in accordance with an embodiment of the invention;
Figure 2 is a plan view of the chip within the module;
Figure 3 is a plan view of a chip in an earlier package;
Figure 4 is a chart illustrating the power consumption variation with temperature of the module of Figure 1 ;
Figure 5 is a chart illustrating the variation of power consumption with temperature for an earlier package;
Figure 6 is a diagram illustrating the change in internal temperature with respect to ambient temperature of the module of Figure 1 ;
Figure 7 is a chart illustrating the change in temperature of an inner environment of the module with respect to ambient temperature; and
Figures 8 to 10 are alternative arrangements for heating the inner casing. Figure 1B illustrates a schematic sectional view through a module according to one embodiment of the present invention. The module denoted generally by the reference numeral 2 comprises an outer case 4 made from a material which preferably provides a hermetic seal between its interior 6 and the exterior environment 8. The interior 6 provides an artificial environment for an optical package as discussed further herein. The optical package comprises an inner case 10 inside which is located a chip carrier 12 which supports an optical chip 14. In this embodiment, the chip carrier 12 incorporates an integrated heater. A first thermoelectric controller 16 is provided in the interior 6 of the outer casing 4, outside the optical package. A second thermoelectric controller 18 is provided inside the inner casing 10 which defines the optical package.
A package sensor 20c is provided on a wall of the inner casing, in this case within the inner casing 10 in a plane below that of the chip carrier 12 and displaced to one side of it (see Figure 2). The package sensor 20c is a temperature sensor which is attached to the base portion 10a and is thus active to control the temperature of the base using the first thermoelectric controller 16 as a heat pump and a heater. In addition, two monitors 20a, 20b are provided in the interior 6. These monitoring sensors are used for evaluation of the package and are not present in the device as sold.
The aim of the structure of Figure 1B is to provide a module which creates an artificial unchanging environment around the chip 14 so that the chip 14 is as nearly as possible unaffected by any changes in ambient temperature. The artificial environment is created by controlling the temperature of the walls of the module (the inner casing 4) so as to keep the temperature of the internal environment 6 stable. The inner casing 10 comprises a base portion 10a and a lid 10b. The optical package is constructed as follows. In the existing device of Figure 1A, the chip 14 is wholly supported by a substrate 12. To construct the optical package of Figure 1 B, a portion of the substrate 12 is removed from below the chip 14 to allow the thermoelectric controller 18 to be placed adjacent the chip 14 on its underside. The second thermoelectric controller 18 is placed on the base portion 10a and the chip 14 is then placed above it and in contact with the second thermoelectric controller 18. The lid portion 10b is then located with respect to the base portion 10a. A layer of thermal grease is provided between the second thermoelectric controller 18 and the chip 14. Thermal grease is also used in the joint between the lid portion 10b and the base portion 10a to give as high thermal conductivity through the package walls as possible. In the embodiment, the package is manufactured from Kovar and the chip carrier 12 is Al302with a thick film hybrid heater.
The first monitor 20a is attached to the lid portion 10b and the second monitor 20b is attached under the base portion 10a in the vicinity of the second thermoelectric controller. These monitor local package temperatures.
In addition to the package sensor and monitors, additional sensors are provided on the chip 14. Figure 2 is a schematic plan view of the chip 14 on which the arc portion 22 represents an array waveguide grating (AWG) comprising a plurality of curved silicon ridge waveguides arranged in a manner known in the art. Input and output waveguides are not shown in Figure 2. Figure 2 shows the package sensor 20c located off the chip 14 in a diagrammatic sense. On the chip 14 are two further sensors 20d, 20e. The sensor 20d is located in the region of the array waveguide grating 22 and the sensor 20e is located on the chip 14 in such a place that when the package is constructed it is in the vicinity of the second thermoelectric controller 18. The sensor 20d is used to control the heater integrated within the chip carrier 12 while the sensor 20e is used to control the second thermoelectric controller 18.
Although the connections are not shown in the figures, it will be appreciated that each sensor is connected to the heater or controller which it is controlling via suitable electrical interconnects and control circuitry. That is, the package sensor 20c is connected to the first thermoelectric controller 16, the sensor 20d is connected to the integrated heater in the chip carrier 12 and the sensor 20e is connected to the second thermoelectric controller 18. The aim of the package is to reduce the effect of ambient temperature changes on the chip 14 and the chip carrier 12. This is done by controlling the thermoelectric controllers 16, 18 and the integrated heater on the chip carrier 12 in line with the monitored temperature changes using the sensors 20c, 20d and 20e. The design is very effective, as indicated by the following experimental data.
Figure 4A is a chart showing the power consumption for the thermoelectric controllers and the heater for the module 2 of Figure 1. In Figure 4A, the curve labelled Base Tec relates to the first thermoelectric controller 16 while the curve labelled Voa TEC relates to the second thermoelectric controller 18.
Figure 4B is a chart similar to that of Figure 4A but for an alternative embodiment in which the inner casing is made of Aluminium in place of Kovar. Other preferred materials for the inner casing include aluminium graphite and aluminium nitride.
Figure 5 is a similar chart to that of Figures 4A and 4B, but utilising an existing package having three thermoelectric controllers associated with sensors as illustrated in Figure 3. Figure 3 is a plan view of a chip 14 showing first and second thermistors 24a, 24b in the region of the array waveguide grating 22, and a third thermistor 24c which is in the location of the output waveguide. These are associated respectively with thermoelectric controllers which are labelled AWG TEC, Voa TEC and WG TEC in Figure 5. A comparison of the charts of Figures 4 and 5 show that the change in power consumption for the heating device in the AWG region of the chip is around 60% less for the design of Figure 1 B than for the other design used for comparison purposes.
This reduction in the variation of the power consumption of the local temperature controllers in thermal contact with the optic chip with changes in ambient temperature results in reduced stress on the optic chip and thus less optical drift (frequency offset) for the arrayed waveguide grating (AWG) device.
In addition, reference is made to Figure 6 which shows the change in temperature of the areas of the chip 14 associated with thermistors 24a, 24b, 24c (AWG1 , AWG2 and AWG in Figure 6). The two sensors 24a, 24b near the array waveguide grating show that the temperature change across the array is small. Table 1 compares the changes with the previous design, and also with the Aluminium embodiment.
Figure imgf000008_0001
TABLE 1
Figure 7 shows the relationship between ambient temperature and the temperature as measured by the monitoring sensors 20a and 20b located respectively on the centre of the lid portion 10b and below the hot side of the second thermoelectric controller. The sensor 20a is labelled Lid in Figure 7, and the sensor 20b is labelled Under VOA Tec in Figure 7.
As can be seem from the above, it is very beneficial to have the package walls of the outer casing 4 made from very high thermally conductive material, such as aluminium, preferably with a lower limit of 200W/mK. However, material having a lower thermal conductivity still represents a considerable improvement as indicated by the above discussion which related to a prototype where the casing wall was made of Kovar and steel parts with a conductivity of less than 20W/mK.
The module of Figure 1B solves temperature and stress control difficulties associated with optical circuit chips or other devices sensitive to temperature or stress change. The described design for an environmental chamber isolates the chip or other sensitive device from any external changes in temperature, stress and, if the outside wall 4 is hermetic, then any changes in external atmospheric conditions. This isolation allows the device control to be more accurate than previous designs which simply use heaters or TECs in close proximity to the chip. It will be appreciated that the second thermoelectric controller 18 is needed only when the optic chip defines one or more optic devices (now shown) that in operation generate relatively large amounts of heat (such as pin diode absorption attenuators, including variable optical attenuators), because in those situations heat must be removed. The heat which is removed can be reused to heat the package walls. When the optic chip does not include such devices, the second thermoelectric controller 18 is not necessary.
It will also be appreciated that the first thermoelectric controller can be replaced by a heater in cases where the temperature of the module will never be below ambient temperature.
Figures 8 to 10 illustrate different possibilities for heating and cooling the inner casing. It is possible for the wall of the inner casing 10 to incorporate an integrated heater as denoted by reference numeral 30 in Figure 8. Thus, in the embodiment of Figure 8 there is a thermoelectric controller 18, a heater integrated into the substrate 12 and heaters integrated into the walls of the inner casing 10.
In the embodiment of Figure 9, an additional heater 32, for example a ceramic heater, is mounted on an inner surface of the wall of the inner casing 10.
In the embodiment of Figure 10, a heater is provided within the inner casing 10 in the form of a copper heater 34.
It will be appreciated that, although in the described embodiment, heaters and TECs are used, other technologies such as heat pipes could be used.

Claims

CLAIMS:
1. An artificial environment module comprising: an outer casing defining an inner environment; an inner casing located in the inner environment and containing an optic device; a package sensor for monitoring the temperature of the inner casing; a device sensor for locally monitoring the temperature of the optic device; a package temperature controller for heating and/or cooling the inner casing in dependence on the temperature sensed by the package sensor to minimise variations in the temperature with respect to changes in ambient temperature; and a separate local temperature controller provided within the inner casing for locally heating and/or cooling the optic device in dependence on the temperature measured by device sensor.
2. A module according to claim 1 , wherein the outer casing is made of a material of relatively low thermal conductivity, and the inner casing is made of a material of relatively high thermal conductivity.
3. A module according to claim 2, wherein the inner casing is made of a material having a thermal conductivity of at least 150W/mK, preferably at least 200Wm/K.
4. A module according to claim 2, wherein the inner casing is made of a material selected from the group consisting of aluminium, aluminium graphite and aluminium nitride.
5. An artificial environment module according to any of claims 1 to 4, wherein the inner casing includes a base portion and a lid portion joined together, and wherein the joint between the lid portion and the base portion comprises thermal grease.
6. A module according to any preceding claim, wherein the optic device is an optic chip including a first portion defining a thermally-sensitive optical element, the device sensor includes an on-chip sensor mounted on the first portion of the chip and the local temperature controller is a resistive heater for locally heating the first portion in dependence on the temperature measured by the device sensor.
7. A module according to claim 6, wherein the resistive heater is integrated with a substrate for the optic chip.
8. A module according to claim 6, wherein the optic chip further includes a second portion defining a second optical element that in operation generates a relatively large amount of heat compared to said thermally-sensitive optical element, and wherein the module further includes a second on-chip sensor mounted on the second portion of the chip and a second local temperature controller for locally cooling said second optical element in dependence on the temperature measured by the second on-chip sensor.
9. A module according to any preceding claim, wherein the package temperature controller is located between the inner and outer casings.
10. A module according to claim 9, wherein the package temperature controller is a thermoelectric cooler mounted in thermal contact with both the inner and outer casings.
11. A module according to any preceding claim wherein the package temperature controller is a resistive heater.
12. A module according to claim 1, wherein the optic device includes an optic chip defining a thermally-sensitive interferometric optic element.
13. A module according to claim 12, wherein the interferometric optic element is selected from the group consisting of a demultiplexer, a multiplexer and an optical channel monitor.
14. A module according to any preceding claim, wherein the package sensor is located in proximity to the package temperature controller.
15. An artificial environment module comprising: an outer casing defining an inner environment; an inner casing located in the inner environment and containing an integrated optics chip; a temperature adjustment means operable to selectively heat or cool the inner environment and located in the inner environment externally of the inner casing; a package sensor located within the inner casing whereby the temperature adjustment means is controlled in dependence on the temperature sensed by the package sensor to minimise variations in the temperature within the inner casing with respect to changes in ambient temperature; and a further temperature adjustment means located within the inner casing and associated with a sensor on the integrated optics chip.
16. An artificial environment module comprising: an outer casing defining an inner environment; an inner casing located in the inner environment and containing an optic chip including at least a first portion defining a thermally-sensitive optic element; a package sensor for monitoring the temperature of the inner casing; a package temperature controller for heating and/or cooling the inner casing in dependence on the temperature sensed by the package sensor to minimise variations in the temperature with respect to changes in ambient temperature, and whose operation in response to changes in ambient temperature does not induce stress in the optic chip; an on-chip sensor for locally monitoring the temperature of the first portion of the optic chip; and at least one local temperature controller provided in thermal contact with the first portion of the optic chip for locally heating and/or cooling the first portion of the optic chip in dependence on the temperature measured by the on-chip sensor.
PCT/GB2003/000700 2002-02-15 2003-02-14 An artificial environment module WO2003069419A2 (en)

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AU2003205896A1 (en) 2003-09-04
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