Dynamics of quantum cascade lasers: numerics

Research output: Chapter in Book/Report/Conference proceedingConference paper


Since the original demonstration of terahertz quantum-cascade lasers (QCLs), the performance of these devices has shown rapid improvement. QCLs can now deliver milliwatts or more of continuous-wave radiation throughout the terahertz frequency range (300 GHz to 10 THz). Therefore, QCLs have become widely used in various applications such as spectroscopy, metrology or free-space telecommunications. For many of these applications there is a need for compact tuneable quantum cascade lasers. Nowadays most tuneable QCLs are based on a bulky external cavity configuration. We explore the possibility of tuning the operating wavelength through a fully integrated on-chip wavelength selective feedback applied to a dual wavelength QCL. Our numerical and analytical analyses are based on rate equation models describing the dynamics of QCLs extended to include delayed filtered optical feedback. We demonstrate the possibility to tune the operating wavelength by altering the absorption and/or amplification of the signal in the delayed feedback path. The tuning range of a laser is limited by the spectral width of its gain. For interband semiconductor lasers this spectral width is typically several tens of nm. Hence, the laser cavity supports the existence of multiple modes and on chip wavelength selective feedback has been demonstrated to be a promising tuning mechanism. We have selected a specific QCL gain structure with four energy levels and with two lasing transitions in the same cascade. In this scheme, the two lasing modes use a common upper level. Hence, the two modes compete in part for the same carriers to account for their optical gain. We have added delayed wavelength specific filtered optical feedback to the rate equation model describing these transitions. We have calculated the steady states and their stability in the absence of delay for the feedback field and studied numerically the case with non-zero delay. We have proven that wavelength tuning of a dual wavelength QCL through filtered optical feedback is possible in this system under certain circumstances.
Original languageEnglish
Title of host publicationProceedings of SPIE
Subtitle of host publicationConference on Semiconductor Lasers and Laser Dynamics VII
Number of pages6
Publication statusPublished - 2016
EventSPIE Photonics Europe 2016: Optics, Photonics and Digital Technologies for Imaging Applications IV - Square, Brussels, Belgium
Duration: 3 Apr 20167 Apr 2016
Conference number: 9896


ConferenceSPIE Photonics Europe 2016
Internet address


Dive into the research topics of 'Dynamics of quantum cascade lasers: numerics'. Together they form a unique fingerprint.

Cite this