Channeled substrate nonplanar laser analysis - Part II: Lasers with tapered active regions

Abstract

Light versus current (LversusI) characteristics are calculated for double-heterostructure diode lasers whose active regions decrease in thickness laterally from a maximum on axis. This variation produces lateral real refractive index waveguiding which in turn stabilizes the spatial mode such that the modal field becomes anastigmatic and theLversusIplot becomes linear. In addition to determining threshold current and differential quantum efficiency, we compute the TE00mode patterns, active region charge density distribution, and the power levelP*_{1}at which spatial hole burning causes the TE01mode to begin lasing. The maximum power density at the facet for that power levelP*_{1}is also obtained. All these characteristics are presented as functions of the various device parameters including carrier spontaneous recombination time, diffusion length, optical gain, unpumped band-to-band absorption, internal losses, antiguidance index, wavelength, cladding Al content, active region dimensions, current spreading resistance, facet reflectivity, laser length, and stripe width. Utilizing this information, a design is developed for a laser with low threshold current (40-50 mA) and high differential quantum efficiency (50-65 percent) that operates stable single lowest order (TE00) spatial mode to powers well in excess of 50 mW.