High Power $1.5\mu$ m Pulsed Laser Diode With Asymmetric Waveguide and Active Layer Nearp-cladding

Abstract

We report first experimental results on a highpower pulsed semiconductor laser operating in the eye-safe spectral range (wavelength around 1.5 µm) with an asymmetric waveguide structure. The laser has a bulk active layer positioned very close to the p-cladding in order to eliminate current-induced nonuniform carrier accumulation in the p-side of the waveguide and the associated carrier losses. Moderate doping of the n-side of the waveguide is used to strongly suppress nonuniform carrier accumulation within this part of the waveguide. Highly p-doped InP p-cladding facilitates low series resistance. An as-cleaved sample with a stripe width of 90 µm exhibits an output power of about 18 W at a pumping current amplitude of 80 A. Theoretical calculations, validated by comparison to experiment, suggest that the performance of lasers of this type can be improved further by optimization of the waveguide thickness and doping as well as improvement of injection efficiency.

AlGaAs/GaAs asymmetric‐waveguide, short cavity laser diode design with a bulk active layer near the p ‐cladding for high pulsed power emission

“…We proceed next to analyse the power output of the laser. Similar to the previous work, [3, 17, 18] the light‐current characteristics P ( I ) was calculated self‐consistently alongside the power‐dependent internal loss and the effective threshold current , using the transcendental equation Here, similar to the previous work, is the current expended on creating the AL carrier density necessary for the gain to compensate the total losses , and the internal loss is calculated using the approach of Equation (2) with added contributions due to the direct and indirect two‐photon absorption as we...…”

“…As in [3,4], the p-OCL contribution to the current-induced carrier absorption α ðFCÞ j ðIÞ is negligible because of the strongly asymmetric AL position (very thin p-OCL). In its absence, other mechanisms of absorption become important.…”

“…The logic behind the structure design is the same as used earlier (Refs. [3, 4, 18] and references therein) in the work long‐wavelength lasers. The most important parameter to be maximised in high‐power lasers is the quantum efficiency, which is the product of injection and output efficiencies: η = η i η o ut .…”

“…With regard to the spectral range of laser emission, two strategies are possible. One involves working in the eye-safe spectral range of 1300-1600 nm, allowing high output power to be used, and requiring InGaAsP/InP [2][3][4] or AlGaInAs/InP [5][6][7][8][9] based sources and photodetectors. The other involves working at shorter wavelengths and can be further subdivided in two spectral regions: λ ∼ 0.9-1.1 µm [10][11][12][13] and λ < 0.9 µm, used [14,15] for the case of nanosecond pump pulses resulting in picosecond pulse emission under gain-switched operation.…”

О токовой зависимости эффективности инжекции и относительном вкладе скорости эмиссии и внутренних оптических потерь в насыщение ватт-амперной характеристики мощных импульсных лазеров (&lambda;=1.06 мкм)

“…[1] -поглощение на свободных носителях (free carrier absorption, FCA), σ e = 3 • 10 −18 см 2 и σ p = 7 • 10 −18 см 2 ; [2,3] -поглощение на свободных носителях с учетом продольной пространственной неоднородности распределения концентраций и коэффициента материального усиления G в резонаторе (longitudinal spatial hole burning, LSHB), σ e = 4 • 10 −18 см 2 и σ p = 12 • 10 −18 см 2 , σ e = 4 • 10 −30 см 2 и σ p = 12 • 10 −30 см 2 ; [4,5] -поглощение на свободных носителях с учетом двухфотонного поглощения (two-photon absorption, TPA) с последующим перераспределением концентрации свободных носителей (secondary FCA effect, TPA-generated carriers, FCA TPA), σ e = 3 • 10 −18 см 2 и σ p = 1 • 10 −17 см 2 , σ e = 5 • 10 −19 см 2 и σ p = 4 • 10 −17 см 2 . Тем не менее авторы работ [6,7], проведя анализ результатов одномерного и двумерного моделирования для значений σ e = 4 • 10 −18 см 2 , σ p = 12 • 10 −18 см 2 установили относительный вклад двух основных механизмов -поглощения на свободных носителях (FCA) и спонтанной рекомбинации в волноводных областях за счет утечки носителей из квантовой ямы (КЯ) (carrier leakage effect).…”