Quantum Dot Photonic Crystal Surface Emitting Lasers (PCSELs) by Epitaxial Regrowth

Semiconductor diode lasers using self-assembled InAs quantum dot (QD) active regions have been studied extensively due to their excellent device performance, such as low sensitivity to operating temperature, and record-low threshold current densities. To date QD lasers have been realized as edge emitters, vertical cavity surface emitting lasers (VCSELs) or vertical external cavity surface emitting lasers (VECSELs). In this study we make use of a different laser architecture to realize vertically emitting QD lasers - the photonic crystal surface emitting laser (PCSEL). The photonic crystal surface emitting laser (PCSEL) is able to simultaneously achieve high beam quality, high room temperature continuous wave output power, compact form factor, electrical injection, and with lesser fabrication complexity. The operation of the PCSEL is based on a two-dimensional photonic crystal (PC) cavity that creates feedback at a single wavelength for laterally scalable devices.
PCSEL devices were fabricated by wafer fusion, deposition of conducting layer over 'PC-slab-on- substrate' and epitaxial regrowth. The fabrication of PCSEL by epitaxial regrowth has emerged as a promising method due to the elimination of light absorbing defects, higher device yield and better device performance. The Epitaxial regrowth begins with an initial growth containing a bottom cladding layer, active region, and PC region. In a second step, the PC layer is patterned by Electron Beam Lithography (EBL) and Inductively Coupled Plasma (ICP) dry etch. Lastly, the patterned surface is regrown with top cladding and a top contact layer.

PCSELs with active regions using InAs quantum dots (QDs) are novel and low-cost solution for long- wavelength gap between 1100 nm and 1300 nm. In this present work, InAs/InGaAs/GaAs quantum-dot PCSEL was fabricated by epitaxial regrowth method using molecular beam epitaxy (MBE). Laser heterostructure with active region of three layers of InAs dots-in-well (DWELL) was optimized for 1200 nm design wavelength. The performance and characteristics of PCSELs were investigated and analyzed by optical pumping at room temperature.