GeSn Lasers With Broad Wavelength Coverage

Optoelectronic device including optically pumped GeSn lasers on Si with broad wavelength coverage from 2 to 3 μm. (Source: UARK)

Imagine creating a material for the digital infor­mation highway that allows a fast lane of laser light that zips data past the tradi­tional silicon chips. A multi-insti­tutional team of researchers, led by Univer­sity of Arkansas engi­neering professor Shui-Qing Yu and a leading Arkansas semi­conductor equipment manu­facturer, have made signi­ficant improvements to a new kind of laser, a semicon­ducting device that is injected with light, similar to an injection of electrical current. This optically pumped laser, which is made of germanium tin grown on silicon substrates, could lead to faster micro-proces­sing speed at much lower cost.

The new findings demonstrated that the most recent version of this type of laser is capable of covering a broader wave­length range, from 2 to 3 micrometers, while using a lower lasing threshold and higher operation tempera­ture of about 180 Kelvin, which means less power con­sumption. The alloy germanium tin is a promising semi­conducting material that can be easily inte­grated into electronic circuits, such as those found in computer chips and sensors. The material could lead to the develop­ment of low-cost, lightweight, compact and low-power consuming elec­tronic compo­nents that use light for infor­mation trans­mission and sensing.

Germanium tin harnesses efficient emission of light, a feature that silicon, the standard semi­conductor for computer chips, cannot do. In recent years, materials scientists and engi­neers, including Yu and several of his colleagues on this project, have focused on growing germanium tin on silicon substrates to build an opto­electronics superchip that can transmit data much faster than current chips. In 2016, Yu and his colleagues reported the fabri­cation of their first-gene­ration, optically pumped laser.

The researchers first achieved a lasing operations tempera­ture up to 110 Kelvin. The most recent tempera­ture achieved by their laser is 180 Kelvin, the highest reported for a germanium tin laser thus far. Broader wavelength range means poten­tially more capa­city to transmit data, Yu said. A lower lasing threshold and higher operation tempera­ture faci­litate less power consump­tion, which keeps costs down and helps with design simpli­city. Yu said these improve­ments indicate the device is closer to practical application.

Yu attributed the superior laser perfor­mance to unique epitaxial growth approaches the researchers developed based on newly dis­covered methods of growing the material. “The results reported in this work show a major advance toward laser sources for inte­grated photonics,” Yu said. (Source: UARK)

Reference: J. Margetis et al.: Si-Based GeSn Lasers with Wavelength Coverage of 2–3 μm and Operating Temperatures up to 180 K, ACS Phot., online 15 December 2017; DOI: 10.1021/acsphotonics.7b00938

Link: Dept. of Electrical Engineering, Univ. of Arkansas, Fayetteville, USA 

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