[22p-P02-1~7] 3.8 Terahertz technologies (formerly 3.9)

▲ [22p-P02-2] 3~10THz optical gain mappings of ZnO/ZnMgO THz quantum cascade laser

〇WANG LI¹, Tsung-Tse LIN¹, Thomas Grange², Stefan Birner², Hideki Hirayama¹ (1.RIKEN, 2.nextnano, Germany)

Keywords:quantum cascasde lasers

Terahertz quantum cascade lasers suffer from low-temperature operation and limited THz frequency below 7HZ. The small longitudinal optical (LO) phonon energy in GaAs (36meV) is responsible for both limits. In order to overcome them, the high LO-phonon energy materials zinc oxide (ZnO) has been paid attention thanks to its large LO-phonon energy of 72meV which is nearly 2 times of that in GaAs. However, as studied in this work, ZnO material owns strong electron-phonon coupling strength which can significantly broaden the quantum states. As phonon resonance is generally introduced for the THz-QCLs design, it needs to answer the question in ZnO/ZnMgO THz-QCLs, (1) Is this broadening can totally suppress the optical gain below the cavity threshold even since low temperature? (2) If so, are there strategies to relax this effect? In this work, we study the broadening of ZnO Thz-QCLs and the design with suppressing this broadening.