Advanced terahertz quantum cascade lasers for frequency comb and mode locking operation

点击翻译按钮获取中文摘要

Electromagnetic waves in the terahertz (THz) frequency range (1-10 THz, 1THz = 1E12 Hz) have received intensive attention over the last decade owing primarily to their potential to revolutionize important applications, including, among many others, bio-chemical species detection, astronomical spectroscopy, terahertz imaging and optical wireless communication. Since their inception in 2002, THz quantum cascade lasers (QCLs) have quickly emerged as a promising coherent light source because of their compactness, high efficiency and wavelength tenability; however, there is significant difficulty in properly adapting these devices for practical applications, the most promising of which is high-performance spectroscopy. In response to this challenge, the proposed research program aims to develop a THz QCL-based frequency comb device to generate stable and uniform multiple-wavelength emissions in the THz range, which would allow high-resolution, easy-to-operate THz spectral measurements. This would lay the groundwork for innovations that have strong potential for much faster and low-cost detection of life-threatening diseases (such as skin cancer), more accurate and expeditious screening of dangerous explosives at security checkpoints, and much wider and reliable deployment of advanced environmental monitoring and protection. ***This proposed program is targeted to tackle the fundamental and technical challenges inherent to bring THz technology to fruition. The objectives combine experimental and theoretical approaches and will include 1) development of a comprehensive knowledge base on the underlying physics of phase locking in the metal-metal ridge waveguide of THz QCLs; 2) development of a simulation package that can numerically calculate the material and waveguide dispersion as well as the gain spectrum of the device; 3) design of a quantum active region that can produce a broad and flat gain spectrum and develop a waveguide with zero overall dispersion over a wide frequency range; 4) fabrication and characterization of QCLs for frequency comb and/or mode-locking operation.***The direct outcome of this research will be the demonstration of a novel terahertz frequency comb laser, which could, in the longer term, lead to the first passive mode-locked THz lasers for high power and high repetition rate operation. The research will develop an in-depth understanding of intersubband transition in semiconductor quantum structures and phase-locking mechanisms in laser waveguide with chirped grating designs. Fabricated devices will carry over impacts in the areas of high-resolution terahertz spectroscopy, biological and medical sciences, terahertz communication, terahertz imaging. The research program will also bring to bear excellent training opportunities for HQP who will lead innovation in tomorrow's knowledge-based economy.**