Influence of ridge geometry on lateral mode stability of (Al,In)GaN laser diodes

Abstract

PACS 42.55.Px, 42.60.Lh, 78.45.+h Height and width of the ridge forming the laser diode waveguide determine threshold current density and lateral mode stability. We measure the optical near-field of the laser mode and simulate the twodimensional mode distribution including waveguide losses and optical gain. The simulations show that weak guiding and not current spreading is the major cause for increased threshold current densities in weakly guided laser diodes. The near-field measurements show fundamental and higher order modes for nominally identical ridge laser diodes. We demonstrate that asymmetric losses in the waveguide bias the lateral mode competition towards higher order modes for an intermediate range of index guiding. This asymmetric damping is specific for (Al,In)GaN laser diodes due to absorption introduced in the p-waveguide by magnesium doping. This competition of lateral modes can also be seen spectrally as two longitudinal mode combs of different optical gain.

Time-resolved scanning near-field microscopy of InGaN laser diode dynamics

“…Topics studied so far with this setup are filaments, mode competition, near-field phase dynamics, near-field to far-field propagation, and substrate modes. [20][21][22][23] We start in section two with the description of the time-resolved SNOM setup. In the third section the parameters for tube-etching of the SNOM fiber tips are given.…”

Continuous-wave operation of a $(20\bar{2}\bar{1})$ InGaN laser diode with a photoelectrochemically etched current aperture

“…Indeed, the ridge etch depth plays a fundamental role in achieving both low threshold current density and mode stability. 5) In particular, shallow-etched narrow ridge LDs (ridge whose remaining p-side waveguide thickness is ∼100 nm or more) suffer from high lateral current leakage [6][7][8] and strong antiguiding. Antiguiding (or linewidth enhancement factor), 9) an effect derived from the Kramers-Kronig relation and defined as the ratio of the imaginary part to the real part of the refractive index, 10) adversely affects nitride LD performance, since it reduces the difference in effective index step between the active region and the cladding, and causes optical mode instability in a high-contrast ridge waveguide.…”

Optical Properties of Edge‐Emitting Lasers: Measurement and Simulation

“…This near degeneracy of the gain of modes of different orders was confirmed by Hakki-Paoli gain measurements [2]. This near degeneracy of the gain of modes of different orders was confirmed by Hakki-Paoli gain measurements [2].…”