LASER COOLING: Optical refrigerator cools semiconductor payload to 165 K

In optical refrigeration, laser light creates anti-Stokes fluorescence upconversion in a material, which carries heat away from the material. Earlier this year, a group at the University of New Mexico and the Universita di Pisà (Pisa, Italy) demonstrated laser cooling of a ytterbium-doped yttrium lithium fluoride (Yb:YLF) crystal to 155 K; however, only the crystal was cooled, and not a useful "payload" in addition.1

Now, the same researchers have used a Yb:YLF crystal to cool a useful semiconductor payload to 165 K.2 This is important because at present, relatively easy-to-use thermoelectric coolers can only cool down to 170 K and thus reaching lower temperatures requires the use of much more complex cryogenic cooling.

At 165 K, the cooling power and cooling load meet at 20 mW.

A realistic payload

The payload was a 2 μm thick gallium arsenide semiconductor passivated by a gallium indium phosphide coating, with a double-heterostructure geometry having a high external quantum efficiency (in other words, it was similar to real-life semiconductor devices, some of which need cooling). It weighed 5 μg, was adhesive-contacted to the Yb:YLF crystal, and was optically transparent at the 1023 nm laser wavelength used for the experiment.

The payload and cooling crystal were placed in a vacuum chamber; a 9 W continuous-wave Yb:YAG thin-disk laser supplied light to the cooling crystal in a nonresonant cavity geometry. A small amount of light from an outside laser diode was coupled into the semiconductor structure to measure its temperature via the shift in bandgap. The temperature of the Yb:YLF crystal itself was measured by monitoring its fluorescence spectrum.

As would be expected, the cooling power of the setup is greatest when the crystal is at room temperature, and declines as its temperature drops. Conversely, at room temperature the cooling load (the amount of heat that must be removed from the crystal to keep it at its current temperature) is zero and rises as the temperature cools. At the temperature where the load and the power are the same, the crystal and its payload can be cooled no further (see figure). At room temperature (300 K), the cooling power of the setup was 140 mW, which dropped to 20 mW at 165 K.

The researchers believe that by reducing radiative load and improving crystal material quality, temperatures down near that of liquid nitrogen (77 K) could be reached.–John Wallace

1. D.V. Seletskiy et al., Nature Photon., 4, 3, 161 (2010).
2. D.V. Seletskiy et al., Opt. Exp., 18, 17, 18061 (Aug. 16, 2010).


More Laser Focus World Current Issue Articles
More Laser Focus World Archives Issue Articles

Most Popular Articles


Femtosecond Lasers – Getting the Photons to the Work Area

Ultrashort-pulse lasers, both picosecond and femtosecond, are now available from a large number of manufacturers, with new players entering the field at a ra...

Ray Optics Simulations with COMSOL Multiphysics

The Ray Optics Module can be used to simulate electromagnetic wave propagation when the wavelength is much smaller than the smallest geometric entity in the ...

Multichannel Spectroscopy: Technology and Applications

This webcast, sponsored by Hamamatsu, highlights some of the photonic technology used in spectroscopy, and the resulting applications.

Handheld Spectrometers

Spectroscopy is a powerful and versatile tool that traditionally often required a large and bulky instrument. The combination of compact optics and modern pa...

Opportunities in the Mid-IR

The technology for exploiting the mid-IR is developing rapidly:  it includes quantum-cascade lasers and other sources, spectroscopic instruments of many...
White Papers

Accurate LED Source Modeling Using TracePro

Modern optical modeling programs allow product design engineers to create, analyze, and optimize ...

Miniature Spectrometers for Narrowband Laser Characterization

In less than 60 years, lasers have transformed from the imagined “ray gun” of science fiction int...

Improve Laser Diode Performance by Reducing Output Cable Inductance using Twisted Pair Cable

The intent of this article is to provide information regarding the performance of twisted pair ca...
Technical Digests

Fiber for Fiber Lasers

The development of higher-power and higher-energy fiber lasers has benefited from many advances i...

SCANNERS FOR MATERIALS PROCESSING: Serving demanding applications

Galvanometer-based scanners are an essential component in laser-based materials-processing system...

Click here to have your products listed in the Laser Focus World Buyers Guide.


SCHOTT and Applied Microarrays Establish Distribution Partnership for NEXTERION® Products

01/22/2013 SCHOTT and Applied Microarrays, Inc. have established a partnership for the distribution of SCHOT...

SCHOTT North America and Space Photonics, Inc. Sign Exclusive Licensing Agreement for Covert Communications Technology

01/22/2013 WASHINGTON, D.C.—October 18, 2012—Space Photonics Inc. and SCHOTT North America, Inc. today annou...
Social Activity
Copyright © 2007-2015. PennWell Corporation, Tulsa, OK. All Rights Reserved.PRIVACY POLICY | TERMS AND CONDITIONS