IR imaging of laser structures for thermal control of Photonics Integrated circuits (PICs)

The Thermally Integrated Smart Photonics Systems (TIPS) H2020 project aims to develop a solution to meet the significant demands of data traffic growth, by designing a scalable, thermally-enabled, 3D integrated optoelectronic platform. Micro-thermoelectric coolers (TECs) and microfluidics will be integrated with optoelectronic devices to precisely control device temperature, and thus device wavelength. To understand the thermal-hydraulic behaviour of micro-scale heat exchangers, a range of exchanger geometries will be characterised hydraulically (via manometry and velocimetry) and thermally (via infra-red imaging). This paper will discuss the optical and thermal characterisation of existing active laser devices using infra-red imaging in order to obtain a baseline thermal resistance for the development of the heat exchangers. Thermographs of existing active devices were recorded to determine the thermal characteristics of the laser structure and the spatial temperature variation across the laser surface. The increase in temperature of an active laser as a function of dissipated power was found to be linear at 45°C/W. Repeatability and laser-to-laser variation tests showed good agreement. The spatial temperature variations in the x- and y- directions were ±8°C and ±3°C of the mean temperature, respectively. An understanding of the thermal characteristics of existing laser devices will allow for appropriate testing of the viability of microfluidic heat exchangers as coolers for micro-TECs.