Analysis of lateral-mode behavior in broad-area InGaN quantum-well lasers

Chow, Weng W.; Amano, Hiroshi

doi:10.1109/3.903077

Cited by 25 publications

(14 citation statements)

References 19 publications

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“…5 The important dynamical effect of filamentation of laser modes has been treated in theoretical simulations of Chow et al. 6,7 They also predict values of the antiguiding factor derived from a microscopic theory. 7 In contrast to the situation for group-III nitrides, there is a large body of interesting experimental results on the dynamics of LDs of the GaAs material system, e.g.…”

Section: Introductionmentioning

confidence: 98%

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

et al. 2006

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We combine a scanning near-field microscope (SNOM) with a time-resolved detection scheme to measure the mode dynamics of InGaN laser diodes emitting at 405 nm. Observed phenomena are filaments, mode competition, near-field phase dynamics, near-field to far-field propagation, and substrate modes. In this article we describe in detail the self-built SNOM, specialized for these studies. We also provide our recipe for SNOM tip preparation using tube etching. Then we compare the mode dynamics for a 3 µm narrow and a 10 µm wide ridge waveguide laser diode.

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Section: Introductionmentioning

confidence: 98%

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

et al. 2006

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“…Compared to typical near-infrared QW lasers, the antiguiding ͑self-focusing͒ factor R in 2 nm InGaN quantum wells is a factor of 3 higher, primarily because of the significantly heavier electron and hole effective masses in nitride semiconductors. 1 We also find a direct correspondence between beam steering and the effective pumped width as indicated in Fig. 3.…”

mentioning

confidence: 70%

“…However, this understanding may not apply to the wide-band-gap group-III nitride ͑III-N͒ material system because of its drastically different physical properties. 1 That this is indeed the case is demonstrated in our recent observation of lateral-mode instabilities on a microsecond time scale in a narrow ͑2.25 m wide͒ ridge-waveguide InGaN laser.…”

mentioning

confidence: 71%

“…These equations treat the wave-optical ͑diffractive͒ aspect of the intracavity laser field, and provide a microscopic description of InGaN quantum-well susceptibility. 1 We numerically solve these equations simultaneously with a partial differential equation (x, z, and t) that accounts for carrier diffusion effects on the total carrier density spatial distribution. Figure 2 shows ͑from left to right͒ the changes in the laser field with increasing injection current.…”

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confidence: 99%

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Microsecond time scale lateral-mode dynamics in a narrow stripe InGaN laser

Eichler¹,

Hofstetter²,

Chow³

et al. 2004

Applied Physics Letters

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Time-resolved measurements of the spectrum and the far field of InGaN-based laser diodes show lateral-mode changes and gradual tilting of the far field on a microsecond time scale. Numerical simulations based on a microscopic theory are in good agreement with the measurements. The observed effects are attributed to lateral carrier diffusion in combination with thermal lensing.For violet-blue diode lasers, there exist several important applications, such as optical storage and laser printing, requiring lateral mode stability. While the design of singlemode lasers is an ongoing problem, the underlying physical mechanisms leading to stable fundamental-lateral mode operation in conventional semiconductor lasers is, in principle, well understood. However, this understanding may not apply to the wide-band-gap group-III nitride ͑III-N͒ material system because of its drastically different physical properties. The investigated laser diodes were fabricated by OSRAM Opto Semiconductors. They were grown on a SiC substrate without ELO techniques by metalorganic chemical vapor deposition and consist of a 560 nm thick AlGaN:Si cladding, followed by a 120 nm GaN:Si lower waveguide layer, three 2 nm In 0.1 Ga 0.9 N/GaN quantum wells with GaN:Si barriers, an Al 0.2 Ga 0.8 N electron blocking layer, a 100 nm thick GaN:Mg upper waveguide layer, and a 400 nm thick AlGaN:Mg upper cladding layer. Contacts are deposited on a p-GaN cap layer on top of the ridge and on the n-SiC backside. The cleaved facets are coated with high reflectivity coating (Rϳ98%/70%).2 The devices are operated in junction side up configuration, which is possible due to the SiC substrate. Since we use short pulses in the microsecond range, the back contact of the device does not see a temperature increase during the pulse, as shown in Ref. 3. After each pulse, the laser has enough time to cool down again due to the very low duty cycle. Thus, the kind of mounting the device onto the heatsink has only negligible influence on the effects described in this letter.For measurements of the time-resolved optical spectrum, the light of the temperature stabilized laser diode is collimated and then focused on the entrance slit of a grating monochromator. At the output slit, the light of the actually selected wavelength is collected by a fast photomultiplier tube. Thus, for this particular wavelength the intensity distribution versus time can be observed on an oscilloscope connected to the photomultiplier tube. Scanning the selected wavelength of the monochromator over the range of the emission spectrum of the laser diode yields therefore a threedimensional graphics with time and wavelength as the x and y axis, respectively, and optical intensity as the z axis ͑color encoded͒. This plot, which is shown in Fig. 1 ͑top͒, allows to observe the evolution of the laser spectrum during a current pulse. The corresponding time-resolved far field is measured in the same manner. The only difference to the previous measurement is that the monochromator is now replaced by a step motor c...

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“…For broader ridges filaments build up, predicted by a large antiguiding-factor compared to other compounds [3]. Only few systematic theoretical [4,5] and experimental [6,7] investigations of filaments in (Al,In)GaN LDs are published.…”

mentioning

confidence: 97%

Spectral and time resolved scanning near‐field microscopy of broad area 405 nm InGaN laser diode dynamics

Braun

Meyer

Scholz

et al. 2008

Phys. Status Solidi (c)

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Ridge widths of GaN laser diodes (LDs) are typically in the order of few mm. In contrast to GaAs material systems, beam quality of GaN broad area lasers is still a critical point. By time resolved scanning near‐field optical microscopy (SNOM) on pulsed electrically pumped LDs with different ridge widths we observe dynamic features caused by thermal and carrier induced changes of the refractive index like filamentation and lateral mode competition, which strongly influence the far‐field of the LDs. Using a high spectral resolution spectrometer we can additionally resolve the individual longitudinal modes of the laser spectrum both time resolved and correlated to the lateral position in the waveguide. Especially on samples with broad ridges we observe complex spectral and spatial dynamics of the laser mode like different filaments lasing on different longitudinal mode combs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Analysis of lateral-mode behavior in broad-area InGaN quantum-well lasers

Cited by 25 publications

References 19 publications

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

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

Microsecond time scale lateral-mode dynamics in a narrow stripe InGaN laser

Spectral and time resolved scanning near‐field microscopy of broad area 405 nm InGaN laser diode dynamics

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