Semiconductor laser design with an asymmetric large optical cavity waveguide and a bulk active layer near p-cladding for efficient high-power red light emission

Abstract

A semiconductor laser design for efficient, high power, high brightness red light emission is proposed, using a large optical cavity asymmetric waveguide and a bulk active layer positioned very close to the p-cladding. The low threshold carrier density associated with the broad active layer, as well as the proximity of the active layer to the p-cladding, ensure that the electron leakage current, the major detrimental factor in red lasers, stays modest in a broad range of excitation levels. This in turn promises high-power, efficient operation.

Threshold and power of pulsed red-emitting diode lasers with a bulk active layer near p-cladding under high-temperature operation

“…The bulk (GaInP) AL is positioned at a very short distance (50 nm) from the pcladding (note that the location of the active layer, bulk or Quantum Well, near the p-cladding is currently widely accepted for high-power semiconductor lasers [4,5,8,9,10,11]). As noted previously [1][2][3], in a waveguide of this type, unlike in most structures with Quantum Well based active layers, the AL itself contributes noticeably to the waveguiding properties of the structure, strongly affecting the shape of the mode. Thus, the thickness da of the active layer becomes an important and useful parameter in varying and potentially optimising the laser design and properties.…”

“…In the previous papers (see [1,2,3] and references therein), we proposed and analysed a high-power semiconductor laser design using an asymmetric large optical cavity waveguide (with different refractive index steps at the interfaces between the Optical Confinement Layer (OCL) and the nand p-claddings, and a relatively thick (typically bulk) active layer (AL) positioned very near the p-cladding. The design was shown to offer a number of advantages for lasers operating in a pulsed regime at wavelengths from visible (red) [3] through near infrared (800-900 nm [2]) to the eye safe wavelengths (~1.5 m [1], as confirmed by the recent experimental results [4,5]). Specifically for red lasers, an important advantage of this design, in addition to single transverse mode operation with a relatively narrow far field, included a suppressed current leakage and hence improved injection efficiency at high pulse power.…”

“…Specifically for red lasers, an important advantage of this design, in addition to single transverse mode operation with a relatively narrow far field, included a suppressed current leakage and hence improved injection efficiency at high pulse power. However no actual threshold current densities and, correspondingly, output powers were calculated in [3]; besides, temperature dependence of laser performance was not investigated in detail. Here, we present the analysis of the threshold current and light-current characteristics of lasers of this design under different pulsed operated conditions, including those leading to laser heating, study the effect of this heating on the optimal laser design, and show that this design promises competitive performance at elevated power operation.…”

“…The refractive index profile of the structure considered is essentially the same as used in [3] and is reproduced schematically in Fig. 1a for convenience, alongside the near field (transverse mode intensity profile) of the laser emission, with the inset magnifying the field in the pcladding.…”

“…[6] ), with a fully disordered (random) structure so designed to emit at 650-660 nm at room temperature depending on the threshold carrier density value [7]. As in [3], the waveguide used is a large optical cavity (LOC) strongly asymmetric one, with the refractive index step at the interface between the OCL and the n-cladding substantially smaller than that at the OCL/p-cladding interface. The bulk (GaInP) AL is positioned at a very short distance (50 nm) from the pcladding (note that the location of the active layer, bulk or Quantum Well, near the p-cladding is currently widely accepted for high-power semiconductor lasers [4,5,8,9,10,11]).…”