ASSP 2005 delves into high powers, new wavelengths

VIENNA, AUSTRIA-The 2005 Advanced Solid-State Photonics topical meeting (ASSP; February 6-9, 2005) marked the 20th anniversary of the Optical Society of America’s (OSA) topical meeting that started out simply as “Tunable Solid State Lasers” and has evolved to encompass the wider field of solid-state lasers, nonlinear optics, and associated technologies.

First held in 1983, ASSP was originally run on an ad-hoc basis; with the adoption of OSA management in 1985, this meeting has thrived and represents one of the most successful and well-attended of the many OSA topical meetings. From a modest start with 134 attendees in 1985, the meeting in Vienna set a new record in attendance and exhibitors with 373 registrants and 39 tabletop exhibitors. The meeting had three days of solid technical sessions, including a marathon schedule on Monday that included evening postdeadline and poster sessions. The range of topics was broad, including the latest advances in the rapidly developing area of high-power fiber lasers and femtosecond sources. The overall quality of the papers was very high, and many of the papers at the poster sessions, which usually are limited-interest presentations, would have been well-suited for oral presentation at other meetings.

Some areas that stood out included high-power diode-pumped solid state lasers-for example, a 1-kW-average-power, 5-ns-pulsewidth, 10-kHz pulse-rate system from Fraunhofer ILT (Aachen, Germany) designed for laser materials processing, and the Mercury system at Lawrence Livermore National Laboratory (Livermore, CA), now producing 35 J/pulse. High-power fiber lasers were presented, including a 66-W thulium-doped fiber laser with 61% slope efficiency, developed at the University of Southampton (Southampton, England) in cooperation with the University of Sydney (Sydney, Australia), and an all-fiber, polarized, ytterbium-doped 400-W system developed by a team from the University of Michigan (Ann Arbor, MI), Nufern (East Granby, CT) and Fraunhofer USA (Plymouth, MI) and emitting at 1086 nm (see figure). Mid-IR tunable lasers based on the material Cr:ZnSe were presented, with work reported from the Technical University of Vienna (Vienna, Austria) and Coherent Technologies (Santa Clara, CA).

Work was presented on directly diode-pumped ytterbium-doped materials that produce high average powers in mode-locked, femtosecond-duration pulses, with the majority of work on new crystals emerging from a variety of French and German groups. High-power femtosecond sources were described that were based on fiber lasers and in some cases used photonic fibers for pulse compression, with application to precision laser machining. Here, work from German, French and US groups was reported, with the leading efforts centered in Europe.

Nonstandard wavelengths

The theme for this year’s postdeadline session was, in general, higher powers at nonstandard wavelengths. Fiber lasers as pump sources for solid-state crystals were discussed in two papers, with a 60-W continuous-wave (CW) 1645-nm Er:YAG laser reported by the University of Southampton and a 40-W CW 2050-nm Ho:YLF laser reported by Q-Peak (Bedford, MA). A group from the Massachusetts Institute of Technology (Cambridge, MA) announced the demonstration of an octave-spanning mode-locked Ti:sapphire laser with carrier stabilization, with application to optical clocks, and a French group demonstrated a high-peak power photonic-crystal fiber. The session concluded with a description by Craig Denman, from the Air Force Research Laboratory/Directed Energy Directorate (Kirtland AFB, NM), of a 50-W single-frequency 589-nm source for sodium-guide-star applications.

-Peter Moulton and Merrill Apter

Peter Moulton is president of Qpeak (Bedford, MA) and Merrill Apter is vice president of sales and marketing at nLight Corporation (Vancouver, WA).