A comprehensive design optimization of 1.55-μm high power InGaAsP/InP board area lasers is performed aiming at
increasing the internal quantum efficiency (IQE) while maintaing a low internal loss of the device as well. The P-doping
profile and separate confinement heterostructure (SCH) layer band gap are optimized respectively with commercial
software Crosslight. Analysis of lasers with different p-doping profiles shows that, although heavy doping in P-cladding
layer increases the internal loss of the device, it ensures a high IQE because higher energy barrier at the SCH/P-cladding
interface as a result of heavy doping helps reduce the carrier leakage from the waveguide to the InP-cladding layer. The
band gap of the SCH layer are also optimized for high slope efficiency. Smaller band gap helps reduce the vertical
carrier leakage from the waveguide to the P-cladding layer, but the corresponding higher carrier concentration in SCH
layer will cause some radiative recombination, thus influencing the IQE. And as the injection current increases, the
carrier concentration increases faster with smaller band gap, therefore, the output power saturates sooner. An optimized
band gap in SCH layer of approximately 1.127eV and heavy doping up to 1e18/cm3 at the SCH/P-cladding interface are
identified for our high power laser design, and we achieved a high IQE of 94% and internal loss of 2.99/cm for our design.
High power single-mode ridge waveguide 1060-nm semiconductor lasers are reported. The lasers consist of
compressively strained double InGaAs/GaAs quantum wells and a GaAs/AlGaAs separate confinement vertical structure.
A super large vertical optical cavity is employed to have a low internal loss, large optical spot size and low vertical
optical divergence angle. The material composition and thickness of waveguide layers and claddings layer are optimized
systematically. The active layer is detuned from center of the waveguide and thickness of cladding layers is optimized to
guaranty single mode lasing of the large optical cavity. The large vertical cavity laser structure with thickness of 4 μm
allows the lasers have a low internal loss of less than 0.6 /cm, a large optical spot size about 1μm and a vertical
divergence angle about 20 degree. For lateral optical confinement, a double trench ridge waveguide is employed to
maintain single-lateral-mode operation. Based on the optimization, 1.5 W continue wave optical power is achieved for
broad area lasers with 1mm longitude cavity length. Narrow stripe ridge waveguide lasers of 1mm cavity length with
single mode current and optical power of 700 mA and 340 mW is obtained. Suggestions for further improvements in
terms of single mode power and applications of the high power semiconductors are discussed.
A high power single-lateral-mode double-trench ridge waveguide semiconductor laser is reported. The laser has a compressively strained double quantum-well (DQW) and an GaAs/AlGaAs separate confinement structure. The ridge waveguide is defined by two trenches of finite width on either side of the ridge, which will result mode radiation towards outside of the trenches. The relationship between the leakage loss and the waveguide geometry of the each lateral mode is studied with effective index method. The relationship under different bias condition is evaluated. Based on the simulation, lasers with various trench width, trench depth and ridge width are fabricated and tested. With optimized geometry parameters, a laser of 1.5-mm cavity length with a maximum single-lateral-mode operation current of 550 mA is obtained. The threshold current and the slope efficiency of the laser is 30 mA and 0.72 W/A, respectively. The maximum single-lateral-mode power is up to 340 mW.
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