Proposal Number: ECS-9810845 Principal Investigator: Qing Hu (MIT) Title: Terahertz Lasers Basedon Intersubband Transitions Abstract The proposal is to develop tunable solid-state terahertz lasers based on intersubband transitions in quantum well cascade. The target frequency (1 - 10 THz) represents a technologically important region between traditional microwave and optical technologies. Closely related theoretical and experimental work will be conducted for the realization of the THz laser source that will have wide applications for spectroscopy in chemistry and biology, plasma diagnotics, astrophysics, imaging, and communications.