Measurement and simulation of filamentation in (Al,In)GaN laser diodes

Abstract

(Al,In)GaN-based laser diodes with ridge widths broader than a few micrometer tend to show filamentation effects in the lateral direction. By time-resolved scanning near-field optical microscopy, we find different kinds of filaments depending on ridge width and lateral position. We investigate these effects systematically and compare them to the results of corresponding simulations, which are based on a simple rate equation model including the lateral dimension. By this comparison we find a consistent and reasonable set of material parameters that can describe the laser diode. Furthermore, we discuss several reasons for filamentation dynamics like ridge asymmetry or spatial hole-burning, as well as critical temperatures that induce filamentation.

(Al,In)GaN laser diodes in spectral, spatial, and time domain: near-field measurements and basic simulations

“…These simulations result in a number and width of the filaments which are in agreement with measurements. For the parameters and details of the simulations see Scholz et al (2008).…”

“…Examples of applications with a potential large marked volume are laser TV or laser displays for embedded projection (Steegmüller et al 2008). While narrow ridge waveguide LDs, which are common for optical data storage, produce a stable emission from the fundamental lateral mode, the near-field pattern of InGaN LDs with ridge broader than 2.5 µm is composed of several filaments Scholz et al 2008). The buildup of filaments is a crucial issue, as it influences the beam pattern as well as degradation and maximum output power limited by catastrophic optical damage (COD).…”

Stimulated emission in GaN-based laser diodes far below the threshold region

“…For decades, the researchers were striving their efforts on reducing the threshold current [1][2][3][4][5], improving the output power [6][7][8][9], and expanding the wavelength range [10][11][12][13][14] among other things. They focus their attentions mainly on the behavior of LDs above the threshold region.…”

(Al,In)GaN laser diodes in spectral, spatial, and time domain: Near-field measurements and basic simulations

“…The buildup of filaments is a crucial issue, as it influences the beam pattern as well as degradation and maximum output power limited by catastrophic optical damage (COD). While the filaments can be described in terms of carrier dynamics, the temperature profile within the waveguide determines the configuration of the filaments [3]. (AI,In)GaN LDs can exhibit a rather large spectral line shift under large signal modulation.…”