Continuous Wave Semiconductor Laser at Terahertz Frequencies

基于热空穴价带内跃迁的p-Ge激活介质，将研制出可在太赫兹频率范围内调谐、功率和光谱密度足以满足应用要求的连续波锁模半导体激光器。采用一种新的行波激励方案和开腔设计，并结合单轴应力增益优化，在锁模模式下实现了传统热孔PGE激光器无法实现的连续波运转。行波激发将使活性介质的本征加热降低1-2个数量级。施加单轴应力将通过分裂轻孔和重孔的子带来增加增益。该激光器将产生重复频率~1 GHz的连续~10ps太赫兹脉冲。这种连续波锁模操作将使该激光器在远红外分子和固态光谱学、TRZ射电天文学和卫星/近地太赫兹通信等应用中具有吸引力。所获得的知识将为未来基于p-Ge布居反转机制的THz激光器的薄膜/外延层方案提供建议。研究生和本科生研究助理将获得半导体物理和工艺、太赫兹技术、激光原理、光谱技术和射频/微波电子学方面的经验。

A continuous-wave mode-locked semiconductor laser, widely tunable in the terahertz frequency range, and with power and spectral density sufficient for applications, will be developed, based on the p-Ge active medium working on intra-valence-band transitions of hot holes. Continuous wave operation, which is inaccessible for traditional hot-hole pGe lasers, will be achieved in the mode-locked regime using a new traveling wave excitation scheme and an open cavity design in combination with gain optimization by uniaxial stress. Traveling wave excitation will decrease the intrinsic heating of the active medium by 1 to 2 orders of magnitude. Application of uniaxial stress will increase the gain by splitting the light-and heavy-hole subbands. The laser will generate a continuous train of ~ 10 ps pulses of THz radiation with ~1 GHz repetition rate. This continuous wave mode-locked operation will make this laser attractive for applications that include far-infrared molecular and solid-state spectroscopy, TRz radioastronomy, and satellite/near-earth THz communications. The knowledge gained will suggest future thin-flim/epi-layer schemes for THz lasers based on p-Ge population inversion mechanisms. Graduate and undergraduate research assistants will gain experience in semiconductor physics and processing, THz technology, laser principles, spectroscopic techniques, and rf/microwave electronics.