Dr Yabai He
BSc (Anhui University, China, 1982); PhD (Bonn, Germany, 1990);
Senior Research Fellow, MQ Photonics Research Centre; Department of Physics, Macquarie University, Sydney, NSW 2109, Australia;
Phone / fax: +61-2-9850-8311 / -8115; E-mail: yabai@ics.mq.edu.au
Yabai He was educated in China, completing his BSc at Anhui University in 1982, and Germany, taking a PhD in laser physics and quantum optics at the Institute of Applied Physics, University of Bonn (1986 - 90) with a PhD thesis was entitled "Design of a high-precision dye-laser spectrometer." He then worked in the Institute of Physical Chemistry at the renowned Swiss Federal Institute of Technology (ETH) in Zürich, Switzerland (1990 - 97), where he played a major role in developing an early continuous-wave (cw) variant of the cavity ringdown (CRD) spectroscopy technique [Y. He, M. Hippler and M. Quack, Chem. Phys. Lett. 289, 527 - 534 (1998)]. He has been continuously employed at Macquarie University (MQ) since 1997, apart from 6 months' work in the photonics industry in 2001 as a Senior R&D Engineer at Nortel Networks in Sydney.
Yabai has been active in experimental research for ~20 years in areas of laser physics, photonics, nonlinear optics and laser spectroscopy. Since arriving at MQ in 1997, he and Professor Brian Orr have formed a particularly productive research team within the MQ Photonics Research Centre(and its predecessor, the Centre for Lasers & Applications), as is evident from the recent publications from their Molecular and Optical Physics Laboratory (MOPL).
The Australian Optical Society (AOS) has recently recognised Yabai He's "significant achievement in technical optics" by awarding him the 2004 AOS Technical Optics Award. He received this award and presented an invited lecture at the 16th National Congress of the Australian Institute of Physics (Canberra, January 2005).
Yabai's research on novel the cw-CRD spectroscopy techniques is notable in realising superior detection sensitivity with less complicated instrumentation [first published as: Y. He and B. J. Orr, Chem. Phys. Lett. 319, 131 - 137 (2000); 335, 215 - 220 (2001)]. Major innovations are a rapidly-swept ringdown cavity (eliminating the use of a fast optical switch) and optical-heterodyne detection (facilitating a single optical transmitter-receiver module and multi-wavelength strategies for real-time multi-species spectroscopic sensing). This work has led to a patent application (now in the national phase in Europe, the USA and Australia) on spectroscopic gas-sensing in medicine, agriculture, industry and the environment. A comprehensive account of this work has been published [Y.He and B.J.Orr, Appl. Phys. B 75, 267 - 280 (2002)]. More recent CRD innovations in spectroscopy have incorporated a miniature continuous-wave swept-frequency laser that is widely tunable and requires less than 1 s to record wide-ranging absorption spectra with high sensitivity in a single rapid sweep of the laser frequency. A patent application for this work is in progress and two papers have been published [Y. He and B. J. Orr, Appl. Phys. B 79, 941 - 945 (2004); Appl. Opt. 44, 6752 - 6761 (2005)].
Another key research objective has been to develop wavelength-control strategies for nonlinear-optical laser-like devices - namely, pulsed tunable injection-seeded optical parametric oscillator (OPO) systems - to generate widely tunable, narrowband coherent light for high-resolution spectroscopic applications. Yabai's early innovations in this area entailed development of a new "intensity-dip" injection-seeding control scheme to maintain single-longitudinal-mode (SLM) OPO operation [G. W. Baxter, Y. He and B. J. Orr, Appl. Phys. B 67, 753 - 756 (1998); Y. He, G. W. Baxter and B. J. Orr, Rev. Sci. Instrum. 70, 3203 - 3213 (1999)] and to extend its scope to SLM operation of the seeded output wave from a multimode-pumped OPO [Y. He and B. J. Orr, Appl. Opt. 40, 4836 - 4848 (2001)]. MQ's ns-pulsed tunable OPO systems out-perform most other comparable coherent ns-pulsed light-source systems that have been designed for spectroscopic applications. A review article [Y. He, P. Wang, R. T. White and B. J. Orr, Optics and Photonics News 13(5), 56 - 60, 76 (2002)] has been published and further developments are addressed in a major ARC-funded research project on which He and Orr are working.
This advantage in high-performance OPO design has facilitated an ongoing cooperative research project with Dr Ken Baldwin's group at the Australian National University [R. T. White, Y. He, B. J. Orr, M. Kono and K. G. H. Baldwin, Optics Lett. 28, 1248 - 1250 (2003); J. Opt. Soc. Am. B 21, 1577 - 1585 (2004); J. Opt. Soc. Am. B 21, 1586 - 1594 (2004); Optics Express 12, 5655 - 5660 (2004); J. Opt. Soc. Am. B 24, 2601 – 2609 (2007)], yielding a 25-ns pulsed tunable coherent spectroscopic system with narrow optical bandwidth and low frequency chirp. This ability to measure the instantaneous frequency characteristics of OPO output on a pulse-by-pulse basis has also enabled a new heterodyne-assisted form of sub-Doppler pulsed laser spectroscopy, known as "CHAPS" [M. Kono, K. G. H. Baldwin, Y. He, R. T. White, and B. J. Orr, Optics Lett. 30, 3413 - 3415 (2005); J. Opt. Soc. Am. B 23, 1181 - 1189 (2006)]. Further developments in this area are the subject of a second major ARC-funded project.
Two other innovations in OPO design by Yabai include use of wavelength-selective optical feedback (covered by a PCT-phase patent application and reported at the CLEO 2003 conference) and use of a passive self-adaptive phase-conjugate OPO-cavity mirror based on a photorefractive crystal (also covered by a PCT-phase patent application) [Y. He and B. J. Orr, Opt. Lett. 29, 2169 - 2171 (2004)]. Photorefractivity also plays a vital role in a novel form of extended-cavity diode laser which attains robust tunable single-frequency operation with narrow linewidth novel form of extended-cavity diode laser attains robust tunable single-frequency operation with narrow linewidth by means of a self-pumped phase-conjugate reflector and a high-finesse filter [submitted for publication, June 2008].