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March 17, 2010

IUSL Holds CUNY Laser Intellectual Property Event April 21

IUSL Holds CUNY Laser Intellectual Property Event April 21

The supercontinuum, a light having both high spatial coherence and broad spectral bandwidth, was discovered 40 years ago by CUNY Distinguished Professor of Science and Engineering Robert R. Alfano and a colleague at GTE Laboratories.

Event Commemorates 50th Anniversary of Laser, 40th Anniversary of Supercontinuum

The year 2010 marks the 50th birthday of the laser and 40th year since the discovery of the supercontinuum, a light having both high spatial coherence and broad spectral bandwidth.  These anniversaries will be observed at CUNY Laser Intellectual Property Day, an open house event for laser companies and scientists, to be held Wednesday, April 21, by the Institute for Ultrafast Spectroscopy and Lasers (IUSL) at The City College of New York (CCNY).

“In the 40 years since the discovery of the supercontinuum, IUSL has conducted extensive research and development of supercontinuum laser sources as well as tunable lasers for a wide range of applications,” said Dr. Robert R. Alfano, Director of IUSL and CUNY Distinguished Professor of Science and Engineering.  “We are holding this special day to highlight laser technology available for licensing by laser companies.”

The event, which is supported by the Office of CCNY Provost Zeev Dagan, will include: presentations from CUNY Vice Chancellor for Research Gillian Small, the CUNY technology transfer office, faculty members, companies and inventors; a tour of City College’s laser and crystal-growing facilities, and discussions with inventors and the technology transfer officer.

Professor Alfano reported discovery of the supercontinuum in 1970 with Stanley Shapiro, his colleague at the time on the technical staff at GTE Laboratories.  A supercontinuum is formed when a collection of nonlinear processes act together upon a picosecond (10-12) or femtosecond (10-15) duration pump beam causing severe spectral broadening of that beam while producing a smooth spectral continuum from distortion of the electronic clouds of the atoms in any materials.  

“When I discovered it, at first we thought it was noise,” he recalls.  “We asked ‘how could it be a real signal?’”

That unusual signal has been “described as one of the most important developments in physics of recent times,” a 2009 article in “Optics and Photonics News” noted.  While the supercontinuum was initially used as a white light source for resolved spectroscopy, further investigation into its properties led to the discovery that its absorption changes as a function of time, Professor Alfano continued.

Unlike conventional white light, supercontinuum light has coherence, i.e. its particles oscillate in phase, and it is directional.  “Supercontinuum light combines the useful features of laser light with the broad bandwidth of white light,” he added.

The supercontinuum has been the enabling technology behind two Nobel prizes: the 1999 prize in chemistry to Ahmed H. Zewail, for his studies of the transition states of chemical reactions using femtosecond supercontinuum spectroscopy, and the 2005 in physics to John L. Hall and Theodor W. Hänsch for their contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique using the octave in the supercontinuum.

The supercontinuum is also being used in Japan for telecommunications system that enable bandwidth measured in terabits (1015) per second.  Another supercontinuum application has been in super resolution optical microscopy.  Stefan Hell of the Max Planck Institute has developed time-resolved laser spectroscopy with a resolution measured in hundreds of nanometers.  “We’re getting nanometer scale resolution with optical waves,” noted Professor Alfano, who predicted that future advances will come in the medical field.

In addition to research on the supercontinuum, IUSL is engaged in developing tunable lasers crystals as well as photonics applications for telecommunications, defense, healthcare and other industries.  Recent developments include the LISO (LiInSiO4) and LIGO (LiInGeO4) Cr3+ laser crystals, which are capable of operating in the near-infrared spectrum between 1,150 and 1,620 nanometers.

These crystals extend the family of ruby and alexandrite lasers that can operate in this range for possible 6 femtosecond pulse generation and telecommunications applications.  The broad spectrum of these materials is suited for optical coherence tomography, condensed matter physics and biological and chemical time-resolved applications. 

When combined with Ti: sapphire crystals, the LISO and LIGO crystals could produce pulses as short as two femtoseconds.  A combination of supercontinuum generation and pulse compression could result in bursts in the attosecond (10-18) range.