Wide-Ranging Crystals

Crystals with a tunability range of as much as 460 nm -- about triple those of earlier crystals -- have the widest bandwidth and the most NIR-shifted wavelength range for laser operation ever demonstrated for the Cr3+ ion, said Robert R. Alfano, who earlier this month was awarded the Optical Society of America’s Charles Hard Townes Award for his discovery of and work on the supercontinuum.

Alfano is a science and engineering professor and director of the Institute for Ultrafast Spectroscopy and Lasers (IUSL) in the physics department at City College of New York (CCNY) , where the new crystal was developed.

The crystal is approximately 1 by 2 cm. (Photos: Daniel Moy, IUSL)

“For the first time, tunable laser operation was achieved at both the 1.33 µm and 1.55 µm telecommunication windows from a single optical center in trivalent chromium (Cr3+) doped LiInSiO4 (lithium iridium silicate) (Cr3+:LISO) and LiInGeO4 (lithium iridium germanate) (Cr3+:LIGO) single crystals," he said.

The Cr3+:LISO crystal was tunable in the 1160- to 1620-nm range; the Cr3+:LIGO crystal was tunable in the 1150- to 1600-nm range. Fosterite and Cunyite, crystals developed earlier at CCNY, have bandwidths of 165 nm (1173 to 1338 nm) and 144 nm (1348 to 1482 nm), respectively.

(Photo: Daniel Moy, IUSL)

Because of their strong optical absorption in the range of laser diode pump sources and quantum efficiency of 50 percent, the new materials have promise for use in miniature broadband laser devices for telecommunication industry, biomedical imaging, optical coherence tomography, laser spectroscopy, ultrafast pulse generation and remote sensing, Alfano said. The research team also included Alexei Bykov and Mikhail Sharonov, senior research associates at IUSL, and Vladimir Petricevic, associate professor of physics at CCNY. They reported their results in Optics Letters.

For more information, visit: www.ccny.cuny.edu