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Physics professor Fernando Ponce of the Center for Nanophotonics (part of the Arizona Institute for Nano-Electronics at Arizona State University) has been awarded a three-year, $800,000 grant by the US Defense Advanced Research Projects Agency (DARPA) to conduct research on green lasers.

The grant is part of the 'Visible InGaN Injection Laser' (VIGIL) program, managed by Henryk Temkin (an electrical engineering professor at Texas Tech), which aims to develop lasers based on InGaN/GaN system operating at wavelengths equal to or longer than 500nm.

Injection lasers based on InGaN/GaN with emission in the 400nm spectral region have been developed for commercial applications, primarily information storage and retrieval. However, extension of the emission wavelength to the blue and green regions of the visible spectrum has been challenging. Lasers with emission wavelengths longer than 400nm suffer from rapidly increasing threshold current densities and lower output powers. A related problem is the rapid decrease in the internal quantum efficiency of InGaN in InN rich alloys, from about 50% in purple-emitting LEDs to about 20% in green-emitting devices. VIGIL’s aim is to achieve InGaN injection lasers of at least 500nm with performance levels similar or superior to those already demonstrated at 400nm.

VIGIL should culminate in a demonstration of a high-power (≥1W) injection laser operating continuous wave (CW) at room temperature with good stability (>1000hrs) and wall-plug efficiency (30%). Wafer yield of 20% on 2" diameter substrates is expected in order to assure low cost.

High-efficiency visible lasers would enable a variety of military photonic systems, ranging from monitoring water purity, providing effective pumps to mode-locked lasers with ultra-short pulse response, enabling compact and power efficient display engines, to detection systems based on differential absorption LIDAR. The effectiveness of such systems is a strong function of the capabilities of the laser source with regard to emission wavelength, power, efficiency, and cost. Achievement of VIGIL’s objectives should result in great improvement in the size, weight, performance, and cost of future military systems, DARPA says.

Using the new DARPA funding, Ponce’s research group will develop the fundamental understanding of the physics of growth, materials properties, and device performance of nitride heterostructures for injection lasers operating in the blue-green region.

An important task is to establish a correlation at the nanometer scale between atomic structure and the electrical and optical properties of the nanostructures, as well as to determine how this atomic structure is related to the crystal growth process and parameters, and how it affects light emission leading to lasing.

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Visit: www.darpa.mil/BAA/BAA07-28.html