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

Light versus current (
L
versus
I
) 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 the
L
versus
I
plot becomes linear. In addition to determining threshold current and differential quantum efficiency, we compute the TE
00
mode patterns, active region charge density distribution, and the power level
P*_{1}
at which spatial hole burning causes the TE
01
mode to begin lasing. The maximum power density at the facet for that power level
P*_{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 (TE
00
) spatial mode to powers well in excess of 50 mW.