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Silicon-based micro-lasers developed for industrial applications

From the left: Doris Ng, Lee Chee Wei, and Wang Qian. Absent: Tan Ai Ling. Photo courtesy: A*STAR Data Storage Institute
From the left: Doris Ng, Lee Chee Wei, and Wang Qian. Absent: Tan Ai Ling. Photo courtesy: A*STAR Data Storage Institute

By BizLED Bureau

Dec 8, 2016: By combining silicon materials and light emitting semiconductor materials is likely to develop a new micro scale laser pointer, which is being studied by Keh-Ting Ng Doris and colleagues at the Data Storage A*STAR Institute.

Silicon material has completely revolutionized the electrical equipment manufacturing. This semiconductor can be easily processed into small components like transistors, by using methods that can be scalable to industrial levels. This would help to develop hundreds of thousands of elements on a single chip. The functionality of these integrated circuits can be expanded by helping them to create, manipulate and detect light.

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These optoelectronic devices, can further speed up the processing of digital information, and lead to micrometer-scale lasers, which can be used, for example, in barcode scanners. However, the problem is that silicon is not an efficient light generator.

Ng and her team designed and produced a laser that is compatible with silicon fabrication techniques. This has been done by combining silicon and another semiconductor material—indium gallium arsenide phosphide (InGaAsP)—that can emitt light.

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“Our results demonstrate a promising approach for efficient and compact active optoelectronic devices on silicon using a very thin III-V semiconductor layer,” says Ng.

In any laser structure, the optical feedback is very important. It should have the ability to hold light within the structure and drive further light generation. In conventional lasers, this is achieved by putting a mirror on both sides of the light-generating region. But in this study, Ng used a cylindrical device geometry to trap the generated light at the walls of the device. The team then forced it to propagate round the inside of the cylinder, which is called a whispering gallery mode as the same impact traps sound waves in a circular room like a cathedral dome.

First, the team began with a silicon substrate, on which they deposited a thin layer of silicon oxide. The InGaAsP film, which is optically active, is 210 nanometers thick, and fabricated separately and then bonded on top of the silicon oxide.

The team etched through the material to create cylinders of two or three micrometers in diameter. The devices with three-micrometer diameter emitted laser light with a wavelength of 1,519 nanometers, which is close to what is used in commercial optical communications systems.

The whispering gallery mode of this device extends over both the silicon and the InGaAsP regions. Whoile InGaAsP provides light amplification, silicon guides the light.

“Next we hope to apply these ideas to devices operating at room temperature,” says Ng. “Operation at higher temperature will require fine-tuning of the laser design and fabrication,” she added.

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