Quantum cascade laser integration on silicon-based waveguide circuits
Main Researcher: Gunther Roelkens
Quantum cascade lasers (QCLs) have enabled the generation of mid-ir light (3 – 12 µm) using epitaxially grown semiconductors. These lasers emit light because of transitions between energy levels inside the conduction band itself unlike traditional semiconductor lasers which emit light due to transitions between the conduction band and valence band. Integration of QCLs with silicon-based waveguide circuits allow the realization of compact hand held systems which can be used for sensing applications. However this integration varies significantly from the heterogeneous integration scheme using BCB bonding used in the telecom wavelength range as BCB absorbs heavily in mid-ir. Therefore, butt coupling of the QCL and the photonic chip has to be carried out using flip chip integration. Also since QCLs are power hungry devices, this integration scheme will provide efficient heat sinking and will thus ensure CW room temperature operation.
A schematic below shows a QCL integrated with a wavelength selective feedback circuit present on a photonic chip. This could be useful in realization of an integrated tunable QCL, which could replace the presently available EC-QCLs which use a moving grating for feedback.
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