InAs-based quantum cascade lasers (QCL) demonstrated high performance in the long-wavelength mid-infrared range. Hard baked photoresist usually employed for electrical insulation in these devices exhibits some drawbacks related to the polymer nature of this material. Wire bonding is difficult because of the mechanical softness of the photoresist. Besides, optical properties of such insulator can be altered when the laser is operated at elevated temperature. Conventional dielectrics with potentially suitable characteristics introduce optical loss and/or current leakage when fabricated using standard deposition techniques. We report manufacturing of InAs-based QCLs using spin-on-glass that ensured high performance of the devices.
We present an investigation on the electrical and optical properties of tapered quantum cascade lasers emitting at 14-15 μm, based on the InAs/AlSb system. In tapered lasers the active zone volume is increased to obtain higher optical power outputs without degrading the beam quality. Devices with three different taper angles of 1°, 2° and 3° were examined in terms of electrical, optical, and spectral properties and were compared with conventional ridge waveguide lasers.
The integration of mid-IR lasers with Si-based platforms is needed for the development of smart sensor grids. Here we review our recent results on laser diodes (LDs), interband-cascade lasers (ICLs) and quantum-cascade lasers (QCLs), all grown on on-axis (001) Si substrates and covering emission wavelengths from 2 to 10 µm. In addition, we will demonstrate that etching facets is a viable route toward cavity definition either on plain wafers or recessed Si wafers.
The integration of mid-IR lasers with Si-based platforms is needed for the development of smart sensor grids. Here we review our recent results on GaSb-based laser diodes (LDs) and InAs/AlSb quantum-cascade lasers (QCLs), grown on on-axis (001) Si substrates by molecular-beam epitaxy, and covering emission wavelengths from 2 to 10 µm. Threshold current densities well below 1 kA.cm-2 are achieved in both cases. Ridge LDs operate cw up to 80 °C and emit around 10 mW at room temperature whereas QCLs exhibit performances comparable to their counterpart grown on native InAs substrates. In addition, we will demonstrate that etching facets is a viable route toward cavity definition.
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