Wide-ridge metal-metal terahertz quantum cascade lasers with high-order lateral mode suppression

Terahertz quantum cascade lasers with wide-ridge metal-metal waveguides are prone to lasing in high-order lateral modes, which reduce the maximum light output power from these devices. We have demonstrated, theoretically and experimentally, that the output power can be improved severalfold by introducing ``side absorbers'' into the waveguide structure, which enforce lasing in the TM(00) mode with minor temperature performance deterioration. Lasers without side absorbers operate up to 168 K, a current record for devices processed using indium/gold wafer bonding.