High-Power, Monolithic THz Sources via Difference Frequency Generation in Phase-Locked Arrays of Quantum Cascade Lasers

The technical objectives of this proposal are: 1) the design of high-index-contrast (HC) photonic-crystal (PC) THz, difference-frequency-generation (DFG) quantum cascade lasers (QCLs) with midinfrared pumps at 8 micron and 9 micron wavelengths; 2) design and demonstrate operation of a 4 THz DFG-QCL with the midinfrared pumps operating at 8 and 9 microns; and 3) Theoretically demonstrate the feasibility of HC-PC QCL structures with high, room-temperature THz performance. 8- and 9-micron-emitting HC-PC QCLs of a built-in index step an order of magnitude higher than in conventional PC QCL devices will be designed, as to achieve stable-beam operation in quasi-CW operation to high coherent average powers. An 8- and 9-micron-emitting, single-element QCL will be fabricated and used for experimentally demonstrating 4 THz generation at room temperature in pulsed operation. HC-PC QCL structures will be designed to emit at wavelengths of 8 and 9 microns, and be suitable for room-temperature, nonlinear-optical generation of THz radiation, via intracavity DFG, at both 1 THz and 4 THz. The overall design will be for generating 10 mW average power at 3-4 THz, and mW average power at 1-2 THz, delivered in diffraction-limited beams.