A new type of semiconductor laser, grown on cheap silicon wafers instead of expensive specialty substrates, could slash the cost and power consumption of mid-infrared light sources. These interband cascade lasers (ICLs) emit light in the 3-to-15-micron wavelength range, a spectral region rich with the fingerprints of molecules such as methane, carbon dioxide, and ammonia. Today’s ICLs are grown on gallium antimonide or indium arsenide substrates, which are costly and conduct heat poorly. The team will instead grow the lasers on silicon, using a novel quantum well design with strained InAsP layers that has already shown improved performance at long wavelengths (10–14 microns). A hybrid cladding layer—combining a highly doped semiconductor plasmon layer with a superlattice—will further confine light and draw heat away from the device. If successful, the lasers could power compact, battery-operated sensors for detecting pipeline leaks, monitoring greenhouse gases, checking food contamination, and diagnosing disease. Because the lasers sit on silicon, they could eventually be integrated directly with silicon electronics, creating monolithic mid-infrared photonic chips. The project also advances fundamental understanding of quantum-engineered semiconductor heterostructures.
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We propose to develop efficient, low cost and reliable mid-infrared (3 to 15 µm) interband cascade lasers (ICLs) on Si substrates for many applications such as chemical sensing, greenhouse gas detection, environmental monitoring, detection of contaminations in food commodities, and industrial process control. These ICLs are desirable and enabling components for mid-infrared (IR) sensor systems for Mid-IR Si photonics. The research will build on our newly proposed innovative quantum well (QW) region containing strained InAsP layers for ICLs and on extensive experience and achievements in ICL structures and devices, as well as on the molecular beam epitaxy (MBE) growth and device fabrication of Si-based quantum dot lasers. ICLs using the new QW active region with InAsP layers have been demonstrated by our University of Oklahoma team with significantly improved device performance in the long wavelength region (10-14 µm) compared to the commonly used regular W-QW active region, suggesting enhanced optical gain. Hence, we will apply this innovative QW active region to ICLs in a wide mid-IR spectrum (3-10 µm) to significantly improve their device performance. Additionally, we will use advanced waveguide configuration with hybrid cladding layers (with both highly doped semiconductor plasmon layer and superlattice or quaternary AlGaAsSb layer) and grow ICLs on Si substrates, which have much reduced cost and notably higher thermal conductivity compared to GaSb or InAs substrates. As such, ICLs will have improved optical confinement and enhanced thermal dissipation, resulting in further reduced power consumption and higher output power, as well as lowered cost. Here it should be mentioned that University College London (UCL) MBE group is one of a few MBE facilities with As, P and Sb capacity within one MBE chamber worldwide, and only one in the UK. The approach and tasks involve design and modelling of ICLs, molecular beam epitaxial growth of device structures, material characterization, and device fabrication and testing. These ICLs will significantly benefit many useful applications, especially where high power is required or mid-IR systems must be operated with batteries and energy cost/availability is a concern, including space applications with strict constraints on size and electric power. The availability of high-performance ICLs will greatly enhance the capabilities of mid-IR laser instruments and their applications in many areas. As these lasers will be fabricated on Si substrates, it will offer a route of monolithically integrate Mid-IR laser sources for Si electronics for a wide arrange of applications from sensor, detection of pipe leaks and explosives, food safety, medical diagnostics, and industrial process control, to space applications. This project explores the quantum engineering of novel semiconductor heterostructures to demonstrate and develop such much-needed semiconductor lasers. It is well lined up with UK National Semiconductor Strategy and two EPSRC challenge themes, Manufacturing the Future and Digital Economy. The objectives of the project also include to advance the understanding and knowledge of the new heterostructures and their behaviours in semiconductor lasers. The project offers graduate and undergraduate students unique opportunities to pursue education, training and research in multidisciplinary topics. This project not only advances the understanding and knowledge of semiconductor sciences, but also generates new knowledge in the design of quantum-engineered structures and broadens their applications.
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