The Waterloo Institute for Nanotechnology (WIN) presents a seminar by Dr Dan Botez, Professor at the University of Wisconsin-Madison, United States.
High-Coherent Power, Photonic-Crystal Mid-Infrared Quantum Cascade Lasers
Abstract
In the near-infrared (IR) spectral range monolithic coherent-power scaling to watt-range levels has been successfully done only by using resonant leaky-wave coupling of antiguided semiconductor lasers. Since such devices are analogous to 2nd-order lateral distributed-feedback (DFB) structures, they represent high-index-contrast (HC) (Δn ≈ 0.10) photonic-crystal (PC) structures that allow global coupling between array elements into an array mode of uniform intensity profile. We have recently extended the concept to mid-IR (8.4 μm-emitting) phase-locked arrays of quantum cascade lasers (QCLs), which resulted in 5.5 W near diffraction-limited pulsed power; that is, an order of magnitude higher coherent power than previously reported from large-aperture (~ 100 μm) PC-type QCLs. The potential of mid-IR-emitting HC-PC lasers will be discussed.
Another class of photonic-crystal, mid-IR QCL structures of interest is grating-coupled surface-emitting (GCSE) lasers, involving first-order diffraction from 2nd-order DFB gratings. Although efforts on such devices date back to 2000, progress has been slow since lasing in a single-lobe beam-pattern, so-called symmetric-mode operation, is generally not favored, and grating-outcoupling efficiencies have been modest. Thus, although hundreds of mWs of surface-emitted power have been reported, the beams were multimode and/or two-lobed, so-called antisymmetric-mode operation. We have introduced the concept of obtaining high-power, single-lobe GCSE QCLs by suppressing antisymmetric-mode operation via resonant coupling to the antisymmetric surface-plasmon modes of metal/semiconductor 2nd-order DFB gratings. Preliminary experimental results include 0.40 W single-lobe, diffraction-limited surface-emitted power; that is, two orders of magnitude higher power than reported in the past from GCSE QCLs. Prospects of combining the two approaches into a two-dimensional PC surface-emitting QCL will be discussed as well.
Biography
Dan Botez received B.S. (“summa cum laudae”), M.S. and Ph.D. degrees in electrical engineering from the University of California, Berkeley, in 1971, 1972, and 1976, respectively. In 1977 he joined RCA Labs, Princeton, NJ, where his research focused on new types of highpower, single-mode lasers, which became commercial products and were instrumental in the first demonstration of high-data-rate optical recording with diode lasers. In 1986 he joined TRW Inc., Redondo Beach, CA where his research concentrated on novel types of high-power, phaselocked arrays. As a result, he co-invented the resonant-optical-waveguide array (1988) which represents the first photonic-crystal (PC) laser for single-spatial-mode selection in large-aperture devices. That led in 1990 to “breaking” the 1-W coherent-power barrier for diode lasers. In 1993 he became the Philip Dunham Reed Professor of Electrical Engineering at the University of Wisconsin-Madison. There, his work on Al-free lasers led to record-high CW powers and wallplug efficiencies. Recent work has focused in mid-infrared-emitting quantum cascade lasers: conduction-band engineering for maximizing their CW wallplug efficiencies, and high-indexcontrast PC devices for generating high coherent powers.
Prof. Botez is a Phi Beta Kappa member, Life Fellow of IEEE, and Fellow of the Optical Society of America (OSA). In 1995 he was awarded the “Doctor Honoris Causa” degree by the Polytechnical University of Bucharest, and in 2010 he was the recipient the OSA Nick Holonyak Jr. Award. He has authored or coauthored over 430 scientific publications, and holds 54 patents.