An InGaAlAs/InP membrane external-cavity surface-emitting laser (MECSEL) operating at 1770 nm is reported for the first time. A record high power of 7.7 W is registered at -20°C. This is the record high emission power registered for any surface emitting InGaAlAs-based semiconductor laser at a wavelength longer than 1480 nm. A power value of 3.5 W is measured at 20 °C. The lasing is observed up to 60 °C. The high-power emission is achieved due to lateral and longitudinal power scaling realized by enlarging the pump spot diameter to $400~\mu \text{m}$ and the double-side pumping (DSP) of a single chip of extended thickness. We analyze the thermal properties and evaluate the temperature inside the laser membrane. We present the characteristic temperature (T0) as a function of temperature. The T0 is measured to be 70 K at -20°C and 26 K at 55 °C. Our data support the explanation that the increase in the maximum power of the DSP MECSEL originates from an improvement in the thermal properties rather than from more uniform carrier injection into the quantum wells.

Mathematical modeling of thermal behavior of edge-emitting lasers requires the usage of sophisticated time-consuming numerical methods like FEM (Finite Element Method) or very complicated 3D analytical approaches. In this work, we present an approach, which is based on a relatively simple 2D analytical solution of heat conduction equation. Our method enables extremely fast calculation of two crucial physical quantities; namely, junction and mirror temperature. As an example subject of research, we chose self-made p-side-down mounted InGaAs/GaAs/AlGaAs laser. Purpose-designed axial heat source function was introduced to take into account various mirror heating mechanisms, namely, surface recombination, reabsorption of radiation, Joule, and bulk heating. Our theoretical investigations were accompanied by experiments. We used micro-Raman spectroscopy for measuring the temperature of the laser front facet. We show excellent convergence of calculated and experimental results. In addition, we present links to freely available self-written Matlab functions, and we give some hints on how to use them for thermal analysis of laser bars or quantum cascade lasers.

We consider the possibility of improvement of metal–metal waveguides designed for terahertz quantum cascade lasers (THz QCL) with respect to waveguide losses. We calculate solving Helmholtz equation by transfer matrix method. The essence of our work is the error analysis. We notice that the refractive indices of metals in THz range are known with very poor accuracy. We present divergences among numerous measurements and calculations reported in the literature. In addition, we point out that optical properties of metals and semiconductors depend on temperature which varies throughout the working device. At last, we present our scanning electron microscope photos showing that semiconductor–metal and metal–metal interfaces are not perfect. In adjacent areas mixing of materials occurs and hence the spatial refractive index distribution is perturbed. Our error analysis shows that today's accuracy of refractive index data (±37% is the best reported in the literature) makes the problem of optimization of considered waveguides ambiguous. According to our calculations the precision level of about ±10% is required. Once improving the precision turns out to be impossible, we suggest focusing the design works on criteria such as choosing metals minimizing the risk of damaging the active region by atom migration, providing the best ohmic contact or allowing the most effective heat removal.

A proprietary open-source simulation and optimization framework, named LMR, has been used to model LMR sensors with cylindrical geometry. Particular attention is given to the analysis of two fitness functions used in parameter optimization: the commonly applied Mean Squared Error (MSE) and a...