Dan Botez
University of Wisconsin, USA
Title: High-index-contrast photonic-crystal quantum cascade lasers: Watt-range coherent mid-infrared power sources
Biography
Biography: Dan Botez
Abstract
Resonant leaky-wave coupling of antiguides has been used for phase-locking near-infrared (IR) lasers to high pulsed (10 W) and CW (1.6 W) near diffraction-limited (D.L.) powers. The structures are analogous to 2nd-order lateral distributed-feedback (DFB) structures; thus, they represent high-index-contrast (HC) (Δn ≈ 0.10) photonic-crystal (PC) structures that allow global coupling between array elements in an in-phase mode of uniform intensity profile. For mid-IR QCLs coherence over large apertures has been reported from PCDFB lasers and master-oscillator power-amplifier (MOPA) structures. PCDFBs involve diffraction gratings; thus, inherentlyhave low index contrast (Δn ~ 0.008) and have shown near-D.L. operation to only 0.5 W/facet pulsed power. Flared MOPAs, have shown near-D.L operation to 3.9 W, but have no index steps; thus, are vulnerable to thermal lensing in quasi-CW or CW operation. We have implemented resonant leaky-wave coupling in 8.4 μm-emitting arrays of QCLs. Preliminary results are 5.5 W near-D.L. peak powers. Such HC-PC structures hold potential for > 5 W quasi-CW coherent power in the 8-10 μm wavelength range, and > 5 W CW coherent power in the 4.5-5.5 μm wavelength range. Furthermore, in combination with single-lobe-emitting, 2nd-order metal/semiconductor gratings, such arrays hold potential for >15 W CW surface-emitted, coherent power from 2-D HC-PC mid-IR QCLs.
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