2007/05/16 by J. Kröll, Josef Kröll, Juraj Darmo +10
Chemistry · Physics and Astronomy · #Advanced Fiber Laser Technologies #Laser-Matter Interactions and Applications #Spectroscopy and Laser Applications #cond-mat.mtrl-sci
paper · pdf · doi:10.1038/nature06208
PDF file format, 16 pages, 5 figures
arxiv created 2007/05/16 · openalex publication_date 2007/10/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The development of the semiconductor quantum cascade laser (QCL) [1] has enabled bright coherent sources operating at frequencies between the optical (>100 THz) and electronic (<0.5 THz) ranges opening this frequency region for fundamental science investigations [2-5] as well as for applications [6]. However, detailed information about the internal processes in QCLs and their ultrafast dynamics are needed for their further development towards high output power, longer wavelengths and stable pulsed operation. We introduce a novel approach to study the gain and dynamics of a terahertz (THz) QCL [7] using phase resolved measurements of the stimulated emission. This is enabled by direct recording of the emitted electric field with <100 fs time resolution. For the case of the THz QCL we demonstrate the validity of the quantum mechanical description of the laser. We show for the first time the real bandwidth of the terahertz gain medium, the current dependence of this gain, and the losses associated with the wave propagation in the laser waveguide.