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CLEO/QELS delivers postdeadline feast

01 Jun 2006

The postdeadline session at last week's event featured breakthroughs in femtosecond sources, superlensing, supercontinuum generation and lots more.

MOPA laser

Researchers at Northrop Grumman Space Technology in the US presented details of a high-power phase-conjugated master oscillator power amplifier (MOPA) laser. Operating at a repetition rate of 5 kHz and producing 4 kW with an optical-to-optical efficiency of 21%, the team believes this is the brightest pulsed solid-state laser demonstrated to date.

High brightness pulsed lasers are being developed for long-range tracking and imaging of targets. Hagop Injeyan and colleagues concluded by saying that their MOPA source "addresses the needs of next generation illumination lasers."

Paper reference: CPDA1

Femtosecond OPO

Majid Ebrahim-Zadeh and Masood Ghotbi from the ICFO in Barcelona, Spain, reported a femtosecond optical parametric oscillator (OPO) with continuous tuning across the red-orange-yellow-green as well as emission in the UV. Based on the nonlinear material bismuth triborate, which is also known as BIBO, the OPO produced 120 fs pulses and average powers of 270 mW between 480-710 nm and 100 mW between 240 - 355 nm. The researchers hope to enhance the OPO's performance by improving the crystal and mirror coatings and by using a ring resonator.

Paper reference: CPDA2


A team from Columbia University, US, and the Institute of Microelectronics in Singapore Science Park II, Singapore, claimed to have made the first near-field observations of negative refraction superlensing at near infrared wavelengths in photonic crystal metamaterials. Experimental results indicated superlensing phenomena with subwavelength resolution of 0.7 microns (0.47λ), a loss of less than 3 dB and a superlensing bandwidth of 9 nm.

Paper reference: CPDA4

Slow light

Delaying and advancement of optical pulses using stimulated Brillouin scattering (SBS) in As2Se3 chalcogenide fiber was the focus of a paper authored by Luc Thevenaz from EPFL in Switzerland and colleagues from Japan and Spain. "A maximum delay of 37 ns was achieved in 5-m long fiber for a pump power as low as 60 mW, the best power efficiency ever reported in SBS slow light generation," concluded the authors.

Paper reference: CPDA9

Supercontinuum generation

Researchers in the UK from Imperial College and the University of Bath revealed how dispersion-decreasing tapered photonic crystal fibers (PCFs) can be used to generate a supercontinuum at blue and UV wavelengths. According to the team, the tapered geometry enables cascaded four-wave-mixing processes, leading to enhanced supercontinua at short wavelengths. The result was a spectral flatness of better than 3 dB from 395 to 850 nm with a spectral power density ranging from 2.5 to 5 mW/nm.

Paper reference: CPDA11


A team from France and Austria described what it believes is the first direct time-domain measurements of quantum cascade laser (QCL) structures. The authors explained that there is currently little or no information on the losses and gains in QCLs and the intersubband dynamics of the devices.

"We present unique THz time-domain spectroscopy measurements of QCLs that target these questions," said the authors. "By coupling broadband THz pulses into the laser waveguide, the internal processes within the active region and their dynamics are probed."

Paper reference: CPDB8

Coherent LIDAR

Details of a multi-functional all-fiber coherent LIDAR capable of high-resolution target ranging and velocimetry and measuring atmospheric winds were unveiled by Farzin Amzajerdian from NASA's Langley Research Center and Diego Pierrottet from Coherent Applications, both US. The researchers said the primary aim of the system is to aid NASA's space exploration initiative for manned and robotic missions to the Moon and Mars. Operating at 1.57 microns, the LIDAR uses differential absorption to measure CO2 concentration along the laser beam. The use of fiber-optic components is said to produce a highly efficient, compact and reliable design suitable for integration into a landing vehicle.

Paper reference: CPDB9

CLEO/QELS was held in Long Beach, California, US between 21-26 May 2006.

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