SBIR Phase I funding not only allowed Aerius Photonics to create the technology for a new generation of compact, high-performance, low-cost LADAR transmitters applicable to aviation, automotive, law enforcement, recreational equipment, and other civilian markets, but also enabled the company to address the key risk factors (e.g., operational temperature range, power output, and beam quality) related to VCSEL usage in such varied applications. The company’s VCSEL approach therefore offers a promising cost/performance solution to the challenges of fabricating semiconductorbased LADAR systems.

Photodigm, Inc., devised the second SBIR-funded approach, which exploited a mature waveguide semiconductor laser technology—known as the Grating-Coupled Surface-Emitting Laser (GCSEL)—to develop a viable method for combining multiple output beams and directing output from the chip’s surface rather than its edge. Photodigm investigated the application of a high-power, eye-safe, 1550 nm GCSEL array with integrated lenses in military detection and ranging systems. GCSELs have the desirable traits of both conventional edge-emitting lasers and vertical-cavity semiconductor lasers.³ Their arrays exhibit a large active gain volume and wafer-level scalability favorable for high-power operation.⁴ Additionally, the GCSEL’s surfaceemitting nature simplifies the process of combining output beams from multiple lasers to achieve either a higher-power beam or a multiple-wavelength beam (see Figure 5). Foundries can easily form 1-D and 2-D high-power GCSEL arrays to accommodate a broad range of applications in LADAR, proximity sensing, machining, materials processing, and medical diagnostics and therapeutics. Ongoing improvements in output beam quality also make this device ideal for use in diode-pumped solid-state laser applications.

During Photodigm’s SBIR Phase I project, researchers led by Dr. S. David Roh successfully designed, fabricated, and characterized eye-safe, high-power GCSEL arrays with >2.5 W output power and lasing at 1535 nm (see Figure 6). The specific GCSEL under investigation also exhibits superior output beam quality compared to traditional, edge-emitting lasers. Photodigm researchers are now focused on improving the GCSEL’s power efficiency and output beam quality and exploring ways to achieve even higher power levels by combining multiple GCSEL arrays. This technology will enable the rapid development of low-cost, high-power, longwavelength, surface-emitting lasers, while circumventing major technical issues associated with conventional edge-emitting lasers and longwavelength VCSELs. Furthermore, the GCSEL architecture is extendable to both shorter and longer wavelengths (630-1900 nm and beyond), the large optical aperture area is less susceptible to catastrophic optical mirror damage, and the large gain volume allows higher-power operation compared to VCSELs. Most importantly, the GCSEL architecture provides a single-device technology platform versatile enough to be adapted for different applications.