Microstrip antenna coupled distributed feedback terahertz quantum-cascade lasers

By introducing coupled microstrip antennas on distributed feedback terahertz quantum-cascade lasers, the radiation efficiency of each aperture is greatly enhanced. Single mode emission from a 31-period antenna-coupled perfectly phase matched (PM) third-order DFB laser yields ~ 4 times improvement in output power comparing with a traditional corrugated third-order DFB laser fabricated on the same gain medium. The 31-period device has ~ 15 × 25° beam divergence and 4 mW pulsed power (4% duty-cycle) at 10K with maximum lasing temperature 134K(pulsed). When phase matching condition is met, emissions from 81 apertures (4-mm long) are coherently combined to form a narrow beam with ~ 12.5° divergence.