Jing Bai joined the Nano and Ultrafast Photonics research group in 2003 and is conducting PhD research on the design of quantum-cascade lasers (QCL) (a class of semiconductor laser) to enhance intracavity optical nonlinearities. QCL’s have shown superior performance in the mid-infrared portion of the spectrum and are beginning to make an impact in the far-infrared. It is found that the internal laser field in these devices can be a substantial fraction of the bias field, leading to strong nonlinear effects within the laser cavity itself. Thus, intracavity second- and third-harmonic generation in the mid-infrared have been observed recently, and other nonlinearities are under exploration. Possible applications include multicolor laser sources, fast optical switches, and optical detectors. Jing’s work proceeds in cooperation with another PhD student in the group, Shih-Hsuan (Steve) Hong, and Prof. Abdallah Ougazzaden at the University of Metz.
As a first step in describing intracavity nonlinearities in QCL’s, Jing is simulating intersubband carrier dynamics and the intersubband optical properties in the time domain. These simulations are based on few-level systems together with relevant intra- and intersubband scattering mechanisms (electron-phonon, electron-electron, electron impurity). An accurate computation of the carrier dynamics is essential to simulate the nonlinearities. These simulations will be generalized to resolve the dynamics in k-space to give the Boltzmann equations and also to include intersubband coherences (density matrix). In other words, Jing is moving towards the semiconductor Bloch equations for the several-subband system. These calculations will be compared with experimental measurements of intersuband dynamics carried out by Prof. Ougazzaden.
Once Jing’s simulations of the nonlinearities are verified, the calculations will be integrated with a dynamic model for the laser cavity being developed presently by Steven Hong.
Research Interests
- Quantum Cascade Laser (QCL) theory
- Nonlinear optics
- Density matrix calculations
- Terahertz and far-infrared sensing
Page Last Updated: 9 August 2005