Optimization of THz quantum cascade lasers with an active module based on two-quantum wells for high-temperature operation

Over the past two decades, the operation temperature of terahertz quantum cascade lasers (THz QCLs) has continuously increased from cryogenic level to the current record value of 250 K (about -23°C) [1]. Here we review the state-of-the-art and future prospects of high-temperature THz QCL designs with two-quantum wells in active module based on conventional heterojunction GaAs/AlGaAs and alternative material system HgCdTe. We have analyzed the temperature dependence of the peak gain and predicted the maximum operation temperatures of the given designs.

Net Water Drag Coefficient during High Temperature Operation of Polymer Electrolyte Fuel Cells

For polymer electrolyte fuel cell (PEFC) systems in vehicle applications, net water drag coefficient ( ) is an essential index and must be negative for system operation. The feasibility of PEFC operation at temperatures over 100C was examined here by measuring and comparing the current density (j) - characteristics using PEFCs with either an Aquivion or Nafion membrane. The effect of cell temperature ( ) on was evaluated at range from 80 to 120C. Results clearly demonstrated that, for both membrane types, significantly increased increasing . Results also confirmed that, at a constant flow rate of H2 at the anode, decreased with decreasing stoichiometric ratio of air ( ), although the effect of on was relatively small. Finally, the effect of relative humidity (RH) balance of supplied gases in both sides (anode/cathode) on water transport at temperature up to 120C was examined for the Aquivion cell. Results revealed that could be significantly decreased by decreasing the RH of hydrogen supplied to the anode (RHA) and that the control of RHA is an effective method for lowering at elevated temperature operation.

Friction surface modifiers of carbon-containing material for high-temperature operation

The results of high-temperature tribological tests of carbon-containing material in friction on heat-resistant stainless steel 40X13 in the temperature range from 20 to 700 °C under atmospheric conditions are presented. Friction surface modifiers “Argolon-2D” material improve antifriction properties and decrease friction coefficient value. Friction coefficient when using Ni-Se-PTFE modifier at load of 0.67 MPa and speed of 0.16 m/s is less by 5% than at speed of 0.05 m/s, and at speed of 0.25 m/s friction coefficient is less by 13% than at speed of 0.05 m/s. At 500 °C and a load of 0.67 MPa the friction coefficient when using Ni-Se-PTFE modifier is 30% higher than when using InSb-PTFE modifier, and the friction coefficient when using CuO-PTFE modifier is 1.2 times higher than when using InSb-PTFE modifier.

Reduced Dimensionality Multiphysics Model for Efficient VCSEL Optimization

The ICT scene is dominated by short-range intra-datacenter interconnects and networking, requiring high speed and stable operations at high temperatures. GaAs/AlGaAs vertical-cavity surface-emitting lasers (VCSELs) emitting at 850–980 nm have arisen as the main actors in this framework. Starting from our in-house 3D fully comprehensive VCSEL solver VENUS, in this work we present the possibility of downscaling the dimensionality of the simulation, ending up with a multiphysics 1D solver (D1ANA), which is shown to be capable of reproducing the experimental data very well. D1ANA is then extensively applied to optimize high-temperature operation, by modifying cavity detuning and distributed Bragg’s reflector lengths.