PFI-TT: Reliable High-Power Circular-Beam Semiconductor Lasers

University Of Notre Dame, Notre Dame IN

Investigators

Abstract

The broader impact/commercial potential of this Partnerships for Innovation - Technology Translation (PFI-TT) project is the demonstration of a new class of reliable, high-beam-quality semiconductor lasers capable of producing a circular, nearly ideal output laser beam operating in a power range which is currently inaccessible by existing technologies without the use of external systems. Providing a higher quality, near perfect laser beam at much lower cost promises to enable new applications beneficial to society: faster data networks, innovative healthcare solutions, enhanced autonomous vehicle safety, and improved consumer products. This will be achieved by eliminating external optical components which incorporate additional beam degradation. These advances result from the more-easily manipulatable and focusable beam producing a more intense, laser focused spot. The new processing methods employed will also have significant additional promise for increasing the density of future photonic integrated circuits, critical for supporting society’s rapidly growing needs for internet and data center applications. The proposed project specifically addresses a long-standing limitation of most edge-emitting diode lasers – their inherently asymmetric, highly elliptical, and thus astigmatic (hard to focus) output beams in 10-500 mW range. Devices like vertical cavity surface emitting laser (VCSEL) can emit a circular output beam, but are limited to maximum output powers of ~5-10 mW. The proposed innovation uses a novel method to fabricate edge-emitting lasers, employing a deep etch through the active electron-hole recombination region followed by a special wet thermal oxidation process to ameliorate etch damage while smoothing and passivating the etched sidewall. With this high-index-contrast design, single-mode circular output lasers with powers 80 times greater than that of commercial single-mode VCSELs have been achieved. The focus of this project is to lifetest packaged lasers with facet passivation coatings and demonstrate their capability for long-life, continuous operation (e.g., 5000-10000 hours) as required for successful commercialization. The oxide-semiconductor interface properties will be assessed and optimized using time-resolved photoluminescence; beam quality including astigmatism will be characterized, and the expected high-speed RF modulation performance evaluated. Alternative approaches including quantum-dot active region material and atomic layer deposition dielectrics will also be explored. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.