Cascadable high-performance optic switches and optical logic based on vertical-cavity surface-emitting lasers

Abstract

ABsTRAc:TVertical-cavity surface-emitting lasers (VCSELS) are high-speed optical sources that are readily integrable with phototransistors and photothyristors to form a versatile family of intelligent optical switches or smart pixels that can perform switching, logic, regeneration, and memory functions. Their surface-normal format facilitates the monolithic integration of two-dimensional arrays for applications in photonic switching networks and optical computing architectures. is INTRODUCTION:Vertical-cavity surface-emitting lasers (VCSELS) are high-speed optical sources with good optical power, low beam divergence, and excellent modal and spectral characteristics. Recently, significant progress has been made in improving the room-temperature, cw operating characteristics of VCSELs,3 which have demonstrated high modulation speed (8 GHz small-signal bandwidth)4, low threshold current density (770 A/cm2),1 high differential quantum efficiency ( > 80%),1,2 and high output power (18 mW).3 Because of their surface-normal format and low beam divergence (80 far-field full-width5), VCSELS can be readily integrated into two-dimensional source arrays that may be applicable in parallel optical computing, communication, interconnection, and switching networks. The VCSELS have been, for the most part, short wavelength, (In)GaAs-based devices, and the room temperature, cw operation of efficient InGaAsP/InP-based VCSELS for optical fiber applications has not yet been demonstrated. The operating characteristics of VCSELS are severely limited by thermal constraints arising from a high series resistance, a high operating voltage and the resultant high power dissipation level. Significant progress has been made towards meliorating these problems, and VCSELs with a power dissipation level significantly below 10 mW has been achieved, 488