In this paper we present an extensive theoretical and numerical analysis of monolithic high-index contrast grating, facilitating simple manufacture of compact mirrors for very broad spectrum of vertical-cavity surface-emitting lasers (VCSELs) emitting from ultraviolet to mid-infrared. We provide the theoretical background explaining the phenomenon of high reflectance in monolithic subwavelength gratings. In addition, by using a three-dimensional, fully vectorial optical model, verified by comparison with the experiment, we investigate the optimal parameters of high-index contrast grating enabling more than 99.99% reflectance in the diversity of photonic materials and in the broad range of wavelengths.

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In the present work, we use spatially resolved thermoreflectance (SR TR) to measure temperature distribution over the facet of pulsed operated quantum cascade lasers. The laser beam probes the change in the refractive index caused by current-induced heating of working device. The technique has a spatial resolution of about ~1 µm and temperature resolution better than 1 K. It gives an insight into distribution and relative importance of heat sources within the laser.

In this paper we investigate chip bonding technology of GaAs/AlGaAs quantum cascade lasers (QCLs). Its results have strong influence on final performance of devices and are essential for achieving room temperature operation. Various solders were investigated and compared in terms of their thermal resistance and induced stress. The spatially resolved photoluminescence technique has been applied for a device thermal analysis. The soldering quality was also investigated by means of a scanning acoustic microscopy. The particular attention has been paid to Au-Au die bonding, which seems to be a promising alternative to the choice between hard and soft solder bonding of GaAs/AlGaAs QCLs operating from cryogenic temperatures up to room temperatures. A good quality direct Au-Au bonding was achieved for bonding parameters comparable with the ones typical for AuSn eutectic bonding process. High performance room temperature operation of GaAs/AlGaAs QCLs has been achieved with the state-of-the-art parameters.