March 14, 2012
Optics Express Focus Issue: Modular Ultrafast Lasers
Ultrafast lasers, lasers that emit light pulses that are as short as a few femtoseconds, have enabled a wide-range of fundamental science and applications over the past two decades. To highlight recent state-of-the-art developments in femtosecond lasers, the Optical Society (OSA) today published a series of papers as part of an upcoming special Focus Issue on Modular Ultrafast Lasers in its open-access journal Optics Express. The issue is organized and edited by Wilson Sibbett and Tom Brown of the University of St Andrews in the United Kingdom, and focuses on developments based on solid-state, semiconductor and fiber lasers.
The demonstration of Kerr-lens mode locking, a paradigm shifting approach to generating ultrashort pulses first reported in 1990, signified the beginning of the era of practical femtosecond lasers that opened up a greatly enlarged range of applications. Today, the many different types of femtosecond lasers exhibit a wide variety of operating properties and complement each other well. While many current user requirements are covered, there are significant applications for which they are either not sufficiently well developed or inadequately adapted. By taking a modular approach, it is now possible to target and combine the strengths of different laser types to facilitate a push toward a truly flexible ultrafast laser platform that is amendable to external electronic control.
Ultrafast lasers have uses in a wide range of fields, including biology and medicine, chemistry, telecommunications, manufacturing and energy research. For example, ultrafast lasers are used for drilling and cutting high-precision holes such as in medical stents; ophthalmologic procedures such as corneal surgery; and medical imaging.
"Research and applications of ultrafast lasers has been expanding in recent years, producing a range of exciting developments from fundamental science to advanced laser eye surgery," said Brown. "The next generation of femtosecond lasers is likely to continue to impact a broad range of science and technology that will rely on user-specified outputs. Our goal in organizing this focus issue is to highlight the overall field of practical ultrafast lasers and how it has continued to develop strongly with a diverse and versatile range of ultrafast source options."
Key Findings and Select Papers The following papers are some highlights of the Optics Express Focus Issue on Modular Ultrafast Lasers. All are included in Volume 20, Issue 7 and can be accessed online at http://www.opticsinfobase.org/oe.
The paper by Leindecker et al. from Stanford University, IMRA America Inc. and BAE Systems describes using a femtosecond fiber laser operating at 2 µm to pump an optical parametric oscillator (OPO) based on quasi phase-matched-semiconductor material (orientation patterned GaAs — OP-GaAs). The output from the OPO produces a very broad bandwidth through the infrared. This could be used to generate a broad bandwidth frequency comb for precision metrology or for spectroscopy throughout the fingerprint region.
Paper: "Octave-spanning ultrafast OPO with 2.6-6.1µm instantaneous bandwidth pumped by femtosecond Tm-fiber laser," Optics Express, Vol. 20, Issue 7, pp. 7046-7053 (2012). http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-20-7-7046
In their paper, Olle et al. from Cambridge University and from the Lebedev Physical Institute in Moscow, demonstrate how superradiance, a pulse formation method quite different from those normally encountered in ultrafast lasers, can be used to generate ultrashort pulses in the violet spectral region with high peak powers from a semiconductor laser. Such devices could be used in the future for advanced biological imaging and data storage applications.
Paper: "Ultrashort superradiant pulse generation from a two-section GaN/InGaN laser diode," Optics Express, Vol. 20, Issue 7, pp. 7035-7039 (2012). http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-20-7-7035
Savitski et al. from the University of Strathclyde and the University of St Andrews show how the controllable pulse duration output from a femtosecond laser can be used to achieve different modes of operation in a combined optical trapping and non-linear imaging application. By optically addressing the saturable absorber in the laser cavity, the laser can be made to switch rapidly and reversibly between continuous wave (CW) and femtosecond output, effectively switching on and off a multiphoton fluorescence process in a latex sphere that remains trapped due to the CW output from the laser.
Paper: "Optical trapping with 'on-demand' two-photon luminescence using Cr:LiSAF laser with optically addressed saturable Bragg reflector," Optics Express, Vol. 20, Issue 7, pp. 7066-7070 (2012). http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-20-7-7066
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