Development of THz Quantum Cascade Laser as a Local Oscillator for Heterodyne Receivers

We are developing THz-QCL (quantum cascade laser) as a local oscillator for heterodyne receivers. THz-QCLs are made of GaAs/Al0.15Ga0.85As using resonant LO phonon scattering depopulation scheme, and processed in a metal-metal waveguide using gold-gold thermo compression wafer bonding technique. CW mode operation of the THz-QCL has been achieved up to a heat-sink temperature of 74 K at the lasing frequency of 3.1 THz using a device with the size of 40 μm wide and 1.5 mm long fabricated by dryetching method. The peak output power was measured to be about 34 μW at a heat-sink temperature of 15 K. We have also detected the QCL output with an HEB (Hot Electron Bolometer) mixer as a change in the I-V characteristic of the HEB mixer. The HEB mixers using an NbTiN ultra thin film as the superconducting material are coupled with the THz radiation by a quasioptics twin slot antenna. The receiver noise temperature was measured to be 5600K in DSB.