Substrate Modes of (Al,In)GaN Semiconductor Laser Diodes on SiC and GaN Substrates

Laino, V.; Roemer, Friedhard; Witzigmann, Bernd; Lauterbach, C.; Schwarz, Uli; Rumbolz, C.; Schillgalies, Marc; Furitsch, M.; Lell, A.; Härle, V.

doi:10.1109/jqe.2006.884769

Cited by 44 publications

(18 citation statements)

References 35 publications

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“…This we explain as a consequence of low confinement of the mode by AlGaN claddings. Indeed, we observed leakage of the mode into the GaN subcontact layer and also GaN substrate (the effect observed previously by many groups) [8][9][10][11][12]. The leakage to the substrate could possibly be a crucial factor responsible for surprisingly strong coupling between the emitters.…”

Section: Performance and Characterizationsupporting

confidence: 72%

Violet blue laser mini‐bars

Holc¹,

Wiśniewski²,

Leszczyński³

et al. 2009

Phys. Status Solidi (c)

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We demonstrate the construction of violet blue multi‐quantum‐well (MQW) InGaN/GaN laser mini‐bars, a novel system in nitride‐based devices. It consists of three laser stripes, closely spaced with 40 μm pitch. The width of the stripe was 3 microns. Structures were fabricated on high pressure grown, low dislocation density substrates. Under cw operation the measured spectra demonstrate sharp, almost single line emission (FWHM ∼ 1.43 Å). Measurements of the optical far field pattern revealed that when operated under threshold the device was emitting light from all three stripes, whereas during lasing we observed the optical mode only in the area of the middle laser stripe. The behaviour of optical mode suggests the formation of the supermode (coherent emission from all three devices). The maximum optical output power was 270 mW at 402 nm and the slope efficiency was 0.7 W/A. This device offers the possibility to overcome the optical output power limit, characteristic for narrow stripe devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Section: Performance and Characterizationsupporting

confidence: 72%

Violet blue laser mini‐bars

Holc¹,

Wiśniewski²,

Leszczyński³

et al. 2009

Phys. Status Solidi (c)

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“…Details and results of these simulations can be found in [1]. The two-dimensional simulation model shows a periodic interference pattern in the substrate [1], very similar to what can be found in measurements (see Fig. 1).…”

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confidence: 73%

“…This so-called substrate mode causes a periodic modulation of the total loss of the laser mode. We observe this as periodic modulation in the gain spectra measured by the Hakki-Paoli method and by a dependency of the threshold current on the n-cladding layer thickness [1]. The far-field shows side-lobes rising from the substrate mode travelling at an angle to the waveguide which is determined by the effective refractive index of the mode and the refractive index of the substrate.…”

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confidence: 76%

“…An oscillation period of about 1 µm can be extracted from this pattern. These simulations can be used to optimize the vertical structure (within the constraints given by growth conditions) in order to minimize the impact of the substrate modes [1].…”

mentioning

confidence: 99%

“…The AlGaN n-cladding layer is 800 nm thick with an Al concentration of about 5 %, the thickness of the bulk GaN substrate is approximately 100 µm. The detailed epitaxial structure of the LDs is given in Table 1 in [1].…”

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confidence: 99%

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Experimental and theoretical study of substrate modes in (Al,In)GaN laser diodes

Braun

Lauterbach

Schwarz

et al. 2007

Phys. Status Solidi (c)

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In semiconductor laser diodes, high refractive index epitaxial layers can act as parasitic waveguides and cause severe losses to the mode propagating in the laser waveguide. For (Al,In)GaN laser diodes the parasitic modes are typically caused by the SiC or GaN substrate or buffer layers. Substrate modes have an impact on near-field and far-field of the waveguide mode, on laser threshold, and on gain spectra. We present scanning near-field measurements of the substrate mode and demonstrate that the period of the standing wave in the GaN substrate varies over a wide range and critically depends on the effective refractive index of the waveguide mode.1 Introduction For (Al,In)GaN laser diodes (LD) on bulk GaN substrates the refractive index of the substrate is higher than that of the effective refractive index of the waveguide. Thus any part of the waveguide mode tunneling as evanescent wave through the n-side AlGaN cladding can propagate in the substrate. Reflected under a small angle of incidence from the bottom surface of the substrate it will form a standing wave. This so-called substrate mode causes a periodic modulation of the total loss of the laser mode. We observe this as periodic modulation in the gain spectra measured by the Hakki-Paoli method and by a dependency of the threshold current on the n-cladding layer thickness [1]. The far-field shows side-lobes rising from the substrate mode travelling at an angle to the waveguide which is determined by the effective refractive index of the mode and the refractive index of the substrate. We also observe the standing wave in the substrate by a measurement of the near-field intensity on the cleaved surface of the substrate just below the laser ridge waveguide. This is the most direct observation of the substrate mode.For a quantitative analysis we establish a two-dimensional finite element electromagnetic solver, to simulate periodic variations in the cavity loss that reproduce measurements of the modal gain in terms of absolute value and oscillations amplitude. Details and results of these simulations can be found in [1]. The two-dimensional simulation model shows a periodic interference pattern in the substrate [1], very similar to what can be found in measurements (see Fig. 1). An oscillation period of about 1 µm can be extracted from this pattern. These simulations can be used to optimize the vertical structure (within the constraints given by growth conditions) in order to minimize the impact of the substrate modes [1].Here we concentrate on near-field measurements of the substrate mode intensity distribution. We demonstrate that the spatial period of the substrate mode varies over a wide range and critically depends on the effective refractive index of the waveguide.

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Physics and Technology of AlGaInN‐Based Laser Diode

Schwarz

2021

Digital Encyclopedia of Applied Physics

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Laser diodes in the green, blue, violet, and ultraviolet spectral range are made from the binary compound semiconductors AlN, GaN, and InN and their ternary and quaternary mixed crystals. The fundamental properties of these AlGaInN laser diodes are introduced. These are double‐heterostructure laser diodes with separate confinement of electrons and holes in quantum wells and photons in an optical waveguide. A rate equation description of the static and temporal behaviors of optical output power and carrier density is introduced, as are substrates, crystal growth, and microtechnology processing methods. The routes toward longer wavelength in the green spectral region, shorter wavelength ultraviolet lasing, and higher power operation in broad‐area laser diodes are discussed. Several different realized laser designs, including vertical‐cavity surface‐emitting lasers (VCSELs), multi‐section short‐pulse lasers, and distributed Bragg reflector (DBR) lasers are introduced. The family of AlGaInN laser diodes constitutes a large variety of applications, as outlined at the end of the article.

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Substrate Modes of (Al,In)GaN Semiconductor Laser Diodes on SiC and GaN Substrates

Cited by 44 publications

References 35 publications

Violet blue laser mini‐bars

Violet blue laser mini‐bars

Experimental and theoretical study of substrate modes in (Al,In)GaN laser diodes

Physics and Technology of AlGaInN‐Based Laser Diode

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