Single-mode interband cascade lasers for petrochemical process monitoring
Nowadays, only GaSb-based interband-cascade lasers (ICL) allow covering the 3 – 5 μm spectral range with CW emission above RT and power consumption compatible with the development of battery powered photonic sensors. This wavelength range is particularly important since it includes the fundamental absorption lines of various gases of high interest from an industrial and environment point of view (methane, ethane) but also for daily life (nitric oxide, carbon oxide, formaldehyde). Practical sensing systems require CW emission in single spectral mode. Several types of ICLs based on loss coupling have recently demonstrated single mode emission with SMSR > 30 dB. Still, these approaches are expensive because they require extensive e-beam lithography. In addition, the metallic grating deposited on top or on both sides of the mesa induces optical losses which reduce the laser output power. The ESR will work on an innovative approach never implemented with ICLs yet: the slotted laser. He/she will be involved in the heterostructure and device design, perform the device processing and characterise the lasers for spectroscopy application, including using QEPAS systems at UM. This type of laser has been successfully fabricated for operation at telecommunication wavelengths at 1.3 μm and 1.55 μm achieving single mode emission with SMSR exceeding 40dB. Appropriately positioned single or multiple slots create scattering centres along the length of the FP cavity leading to strong spectral perturbations which allows for conversion of multi-longitudinal mode emission into single longitudinal mode emission. The slotted laser design is regrowth free, with the slots and ridge/mesa both etched in the same process step, leading to significant time and cost savings in addition to an increased device yield. This concept can be directly transferred to QCL/ICL technology. The resulting lasers will be tested in intracavity QEPAS/PTS with ESRs 1.1, 2.3, 2.4 for the analysis of methane, ethane and propane at wavelengths around 3.35 μm.
- Design and growth of the laser heterostructure for operation at MIR (3.35 μm)
- Device processing including fabrication of slots using optical lithography techniques
- Advanced electro-optical characterisation of the single mode MIR lasers
* N.B. Secondments and timings shown are indicative only, and may be subject to change.