Impact of longitudinal refractive index change on the near-field width of high-power broad-area diode lasers

Abstract

Typical for broad-area laser (BAL) diodes operating in a continuous-wave mode is a narrowing of the near-field (NF) width at the output facet for high injection currents (output powers). This phenomenon increases the facet load of BALs, resulting in a reduction in the level of catastrophic optical mirror damage. In this letter, we demonstrate theoretically that thermally induced changes in the refractive index in both lateral and longitudinal directions not only cause the NF narrowing at the front facet but also a broadening of the NF at the back facet. In contrast, a sole lateral self-heating induced variation in the refractive index (commonly referred to as thermal lensing) does not result in a NF narrowing. Our theoretical findings are confirmed by measurements of the current-dependent profiles of the NF at the back and front facets of a BAL with a stripe width of 120 μm emitting at 960 nm. Furthermore, our quasi three-dimensional thermo-electro-optic simulations indicate that a longitudinally homogeneous device temperature can reduce the front-facet load while keeping the beam quality unchanged compared with the experimental results.

Effect of spatial hole burning on output characteristics of high power edge emitting semiconductor lasers: A universal analytical estimate and numerical analysis

“…Indeed, to begin with, the analysis here, in common with a number of studies in the literature (see, e.g., Refs. 7,8,16,17,and 19), is one-dimensional, leaving aside the laterally multimode nature of the broad-area laser emission. Such an approach is most rigorously justified for a narrow-stripe single lateral mode laser (the results for such a design can be obtained by scaling the stripe width, the current, and the power in our calculations down by the same factor of 30-50).…”

“…When applied to a broad-area laser with parameters as in Table I, the model effectively assumes that there are so many lateral modes in the laser emission that the light intensity, averaged over time, fills the entire stripe approximately evenly. We also ignore the interplay of longitudinal and lateral nonuniformity in self-heating, 19 effectively restricting the analysis to a pulsed operating regime.…”

Light Emitting Devices Based on Quantum Well-Dots

“…In the temperature range of 220-320 K, the characteristic temperature T 0 is 163 K. Typical characteristic temperatures of QD lasers with undoped active regions are 50-70 K, whereas the use of p-type modulation doping of active region allows one to increase it above 1000 K [60]. The characteristic temperature of the QW lasers typically slightly exceeds 100 K [70]. Note that QWD active region was undoped.…”

Beam-combining scheme of high-power broad-area semiconductor lasers with Lyot-filtered reinjection: modeling, simulations, and experiments

“…To mimic a heating-induced red-shift of the lasing wavelengths and a corresponding broadening of the far-fields, we assume additional linear bias current I-dependent contributions to the gain peak wavelength and the excess refractive index, δ h n = (c h n + L h n (x))I [4]. The heating-induced lateral profile L h n (x) within the emitter can be approximated by a negative parabola [7] or, even better, by a suitable Lorentzian or supergaussian, but, in general, should be estimated experimentally or precomputed using the heat transport model defined within the transversal cross-section of the BAL [8]. The amplitude of L t n in our case was about 10 −4 A −1 .…”

“…All these parameters depend onn j andñ j , j = 1, 2, the length of the BC L, the focal length of the SAC lenses f , the cumulative widths of the air gaps between the corresponding lens and the external mirror l 1 and l 2 , the HWP-and lens-induced fixed phase shift factors ϕ wp and ϕ ln (see Appendix). The exact definitions of these parameters are collected in (8) in Appendix. In our numerical examples, we have used the following parameters of the EC: R e = 0.04, f = 20 mm, L ∈ [4, 20] mm, l 1 = l 2 = 200 mm−f − L (distance between diode facets and outcoupling mirror fixed at 200 mm, neglected longitudinal extension of the PBS),n 1 = 1.644,n 2 = 1.480,ñ 1 = 1.666, n 2 = 1.487.…”