In this talk we will review our recent demonstrations of mid-IR lasers grown on (001) Si or Ge substrates (diode lasers, interband cascade lasers, quantum cascade lasers) and compare their performance to those grown on their native substrates. We will demonstrate light coupling from lasers grown on patterned Si photonics wafers to passive SiN waveguides, with a coupling efficiency in line with simulations. Finally, we will discuss and evaluate strategies to enhance the coupling efficiency.
The successful development of mid-infrared (2-5µm) lasers monolithically integrated with Si-based photonics opens a door to realization of low-cost smart optical gas sensors for environmental monitoring and control of industrial processes. We will discuss our recent results on interband cascade lasers emitting between 3 and 4 µm grown on silicon substrates demonstrating high tolerance of these devices to threading dislocations. The high performance of the developed lasers makes them a good candidate for use as light sources in silicon photonics.
Type-II Quantum Well (QW) Interband Cascade Lasers (ICLs) have become the most efficient laser source in the mid-infrared spectral range spanning 3 μm to 6 μm. In order to use ICLs for gas sensing applications, they must be fabricated for single-mode emission. Distributed feedback (DFB) ICLs are commercially available single-mode lasers and offer low threshold currents for these types of applications but this technology is expensive and time consuming to fabricate since they require e-beam lithography. Slotted waveguides are explored in this work as an inexpensive alternative to electron beam (e-beam) lithography since standard UV photolithography can be used to fabricate the larger, reflective defects (slots) in the waveguide. The geometry of the slot pattern must be simulated beforehand in order to design a photolithography mask for the ICL growth so limitations and behavior of key design parameters will be presented. For 8 μm narrow ridge slotted ICLs emitting near 3.5 μm around 20 °C, single-mode emission was achieved with threshold currents in the range of 60 mA to 80 mA and output power of 2+ mW/facet. Single-mode emission was only reached for certain temperatures and injected current values, but for all operating conditions the number of longitudinal cavity modes supported was suppressed with respect to a Fabry-Pérot ICL; thus, validating the success of the first Sb based slotted laser.
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 report a type-II interband cascade laser grown on an on-axis silicon substrate. We demonstrate continuous-wave lasing operation at temperatures up to 50°C at 3.5µm with a threshold current of 45 mA at room temperature and 20 mW/facet output power. We extrapolate a mean time to failure of at least 300,000 h, which we attribute to the design of the active region eliminating the non-radiative recombination process.
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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