Coherent PCSEL Arrays for Chip-Scale Directed Energy

This project is to investigate chip-scale high power high brightness laser sources based on coherent photonic crystal surface-emitting laser (PCSEL) arrays. While high power VCSEL arrays are commercially available, they are incoherently coupled and multimode, with low beam quality and low brightness. To achieve coherently coupled VCSEL arrays, very large number of VCSEL elements are needed due to the limitations in maximum achievable powers of few mW from aperture size limited single mode VCSELs. On the other hand, very large area single mode high brightness PCSELs have been demonstrated with powers of a few W to 10’s and even 100’s W. The power can be scaled up to kW levels with much less PCSEL elements, which simplifies the control/feedback schemes for coherently coupled PCSELs. Additionally, by taking advantage of the intrinsic lateral coupling features in the PCSEL cavities, near-field based feedback and monitoring structures can be designed and incorporated for active coherency control. These unique features and innovative designs can lead to few element high power high brightness laser sources for on-chip DE applications with both high performance and improved SWaP. The proposed research is based on advances realized over the last 18 years by the team on defect-free photonic crystal cavities for free-space beam manipulation and light-matter interactions. A PCSEL modeling and simulation package was developed by Semergytech in 2021, as the first commercial package for PCSEL design and performance estimate. Over 1W output power was achieved recently at UTA. These results prepare us well to further advance the PCSEL array technology. The proposed structure has the following innovative features: (1) Much reduced array element sizes (2-3 orders less) due to intrinsically large aperture high power SM PCSELs; (2) On-chip near-field based feedback monitoring and control architecture, which offers fast and accurate phase control for the coherent PCSEL array operations; (3) All on-chip architecture for simplified optical design and thermal management with high reliability and low SWaP; (4) Potential beam shaping and beam steering capabilities with the control of the array element phases; and (5) Scalable architecture based on integrated photonics/electronics, which enables high power high brightness laser sources at different power levels.