Castellano Fabrizio, Li Lianhe, Linfield Edmund H, Davies A Giles, Vitiello Miriam S
NEST, CNR - Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, 56127, Pisa, Italy.
School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK.
Sci Rep. 2016 Mar 15;6:23053. doi: 10.1038/srep23053.
Mode-locked comb sources operating at optical frequencies underpin applications ranging from spectroscopy and ultrafast physics, through to absolute frequency measurements and atomic clocks. Extending their operation into the terahertz frequency range would greatly benefit from the availability of compact semiconductor-based sources. However, the development of any compact mode-locked THz laser, which itself is inherently a frequency comb, has yet to be achieved without the use of an external stimulus. High-power, electrically pumped quantum cascade lasers (QCLs) have recently emerged as a promising solution, owing to their octave spanning bandwidths, the ability to achieve group-velocity dispersion compensation and the possibility of obtaining active mode-locking. Here, we propose an unprecedented compact architecture to induce both frequency and amplitude self-modulation in a THz QCL. By engineering a microwave avalanche oscillator into the laser cavity, which provides a 10 GHz self-modulation of the bias current and output power, we demonstrate multimode laser emission centered around 3 THz, with distinct multiple sidebands. The resulting microwave amplitude and frequency self-modulation of THz QCLs opens up intriguing perspectives, for engineering integrated self-mode-locked THz lasers, with impact in fields such as nano- and ultrafast photonics and optical metrology.
工作在光频的锁模梳状光源支撑着从光谱学和超快物理学到绝对频率测量和原子钟等一系列应用。将其操作扩展到太赫兹频率范围将极大地受益于紧凑的基于半导体的光源。然而，任何紧凑的锁模太赫兹激光器（其本身本质上就是一个频率梳）的开发，如果不使用外部刺激，尚未实现。高功率、电泵浦量子级联激光器（QCL）最近已成为一种有前途的解决方案，这得益于其倍频程跨度带宽、实现群速度色散补偿的能力以及获得主动锁模的可能性。在这里，我们提出了一种前所未有的紧凑架构，以在太赫兹QCL中诱导频率和幅度自调制。通过在激光腔中设计一个微波雪崩振荡器，它能对偏置电流和输出功率进行10 GHz的自调制，我们展示了以3太赫兹为中心的多模激光发射，具有明显的多个边带。太赫兹QCL产生的微波幅度和频率自调制为工程集成自锁模太赫兹激光器开辟了有趣的前景，对纳米和超快光子学以及光学计量学等领域产生影响。
