A Laser for Your Eyes

An experimental set-up of the laser operating on a new crystal type. (Source: N. Leonyuk)

An experimental set-up of the laser operating on a new crystal type. (Source: N. Leonyuk)

A team of the Lomonosov Moscow State University scientists and the Bela­rusian National Technical University has created a unique laser, which is a compact light source with wavelengths harmless to the human eye. The develop­ment can be used in medicine, communi­cations systems and also in research.

“In collaboration with our colleagues of the Center for Optical Materials and Techno­logies, Bela­rusian National Technical University, we have developed a highly efficient diode-pumped eye-safe laser, which can be used in ophthal­mology, communi­cation systems and ranging”, says Nikolay Leonyuk from Lomo­nosov Moscow State University. The development of such laser became possible to the fact that the team of scientists had created a laboratory growth technol­ogy of single crystals with desired properties.

The emission with wavelengths of 1500 – 1600 nm is agreeably safe for the eyes and seems prospective for practical applications in medicine, ranging determining the distance from the observer to the object, communi­cation systems and optical location. This feature is explained with, first, the fact that the light-refracting system of the eye have a suffi­ciently high absorption coef­ficient in this part of the spectrum, so only a small fraction of the energy reaches the sensitive retina. Second, the radiation in the 1500 – 1600 nm spectral range suffers low losses passing through the atmo­sphere, and it makes advan­tages for their appli­cations in telecoms.

To date, among the sources of radiation in this spectral range, the most widely used are the solid-state lasers based on phosphate glasses co-doped with erbium and ytterbium ions. Such lasers are also relatively simple, compact and capable of operating in adjusted Q-mode required for producing short impulses. In the meantime, the main dis­advantage restric­ting the usage of erbium phosphate glasses in continuous diode systems is a low thermal conductivity of the matrix. To avoid such limitation, Er and Yb containing crystal­line matrix can be used.

In the issued research, GdAl3 (BO3)4 single crystals co-doped with Er and Yb were used to improve the efficiency of generation pulse energy and repetition rate, and henceto increase the maximal measure­ment range, reducing errors and time spending. These single crystalsare charac­terized by a record value of thermal conductivity and high thermo­chemical stability as well as mechanical strength.

“The created solid-state laser based on yttrium gadolinium borate crystals (Er,Yb:GdAl3 (BO3)4 is a unique compact source of emission with varying eye-safe wave­lengths”, says Nikolay Leonyuk. “Reliable laser design, along with high perfor­mance makes it possible to be widely used in laser ranging systems, metrology andlaser-induced breakdown spectros­copy.“

Using of laser diode as a pump source increase the lifetime of laser up to 100,000 hours. The laser system is easy to use and plug and play, it does not require water cooling, as well as does not generate any vibration during laser operations. Compared with the widely used cw erbium fiber lasers, the (Er,Yb):GdAl3 (BO3)4-based laser is charac­terized by linear laser radiation and lower price. (Source: Lomon. Univ.)

Reference: K. N. Gorbachenya et al.: Eye-safe 1.55  μm passively Q-switched Er,Yb:GdAl3(BO3)4 diode-pumped laser, Opt. Lett. 41, 918, DOI: 10.1364/ol.41.000918

Link: Dept. Crystallography and Crystal Chemistry (N. Leonyuk), Moscow State University, Russia

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