Mid-infrared High Performance Quantum Cascade Lasers and PbS/InP Heterojunction Photovoltaic Detectors

Zhijun Liu
Brown University

Friday, July 16, 2010 at 11:00am
Engr IV Maxwell Room 57-124

Abstract

Mid-infrared spectral region (wavelengths ~ 3-30 µm) is of particular interest due to the presence of strong fingerprint absorption of numerous species, which enables various applications in chemical sensing, spectroscopy, medical diagnosis, and countermeasure, among others. Compared to optical technologies in visible or near-infrared regions, mid-infrared photonics is considered as "underdeveloped" due to the lack of suitable optical components and/or their limited performance. With development in synthesis of atomic layer thick heterostructure superlattice and in understanding of light interaction with these nanostructures, breakthroughs have been made in the past decade, especially on the high performance quantum cascade (QC) lasers, which are revolutionizing both fundamental research and practical applications in the mid-infrared. In order to turn the potential applications into real-world uses, optical components with new level of performance and functionalities are in urgent need for different application purposes.

In this talk, I will first describe high performance mid-infrared QC lasers at different wavelengths within the first and second atmospheric windows, which include the performance optimization for high power, room temperature, continuous-wave operation, temperature-dependent optical gain and loss measurements, and new design concepts of deep-well QC lasers and quantum-box emitters. Following the discussion on intersubband QC lasers, I will talk about my recent efforts on realizing subwavelength interband microdisk lasers at telecom wavelength, and a near-infrared and short-wave infrared dual-band photovoltaic detector using PbS nanocrystals on InP substrate. Finally I will conclude with a brief discussion on future research directions.

Biography
Zhijun Liu received the B.S. and M.S. degrees in physics from Sichuan University, Chengdu, China, in 2000 and 2003, respectively, and the Ph.D. degree in electrical engineering from Princeton University, Princeton, NJ, in 2008. His doctoral research was on high-performance mid-infrared quantum cascade lasers for sensing applications. Since October 2008, he has been with the Division of Engineering, Brown University, Providence, RI, as a Postdoctoral Research Associate. His current research interests include subwavelength lasers and infrared photovoltaic devices using lead salt nanocrystals and carbon nanotubes.