Multiple vertical mode high power 975 nm diode lasers restricted to single vertical mode operation through use of optical facet coatings

Crump, P.; Wenzel, H.; Ressel, P.; Erbert, G.; Tränkle, G.

doi:10.1049/el:20092704

Cited by 3 publications

(1 citation statement)

References 4 publications

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“…The poor beam quality is not convenient for practical applications. To improve the far-field pattern, in the near-infrared region, Crump et al [2] successfully shifted the lasing from the second-order mode to the fundamental mode by antireflection coating of Al 2 O 3 on the front facet of the device emitting at 975 nm. However, this approach is infeasible for the midinfrared QCLs owing to the difficulty of forming very thick Al 2 O 3 film.…”

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Far-field improvement of quantum cascade lasers through high-reflection coatings

et al. 2011

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A new approach has been developed for quantum cascade lasers to improve beam quality. Using two carefully designed high-reflection coatings, the fundamental mode was selected to have the lowest threshold current and the horizontal far-field pattern has been greatly improved, in good agreement with simulations.Introduction: The quantum cascade laser (QCL) is a compact and powerful semiconductor light source in mid-and far-infrared wavelength ranges for applications such as chemical sensing and pollution monitoring. For an edge-emitting QCL, the far-field pattern is often multiple lobes because the higher-order transverse mode has the lowest threshold current owing to the smaller mirror loss [1]. The poor beam quality is not convenient for practical applications. To improve the far-field pattern, in the near-infrared region, Crump et al.[2] successfully shifted the lasing from the second-order mode to the fundamental mode by antireflection coating of Al 2 O 3 on the front facet of the device emitting at 975 nm. However, this approach is infeasible for the midinfrared QCLs owing to the difficulty of forming very thick Al 2 O 3 film.In this Letter, we report the design of two multilayer high-reflection coatings for the front and rear facets, respectively. By modifying the mirror loss of each mode, the fundamental mode can have the lowest threshold and the far-field pattern has been improved greatly.The active region of our device consists of 30 periods of strain-compensated In 0.68 Ga 0.32 As/In 0.37 Al 0.63 As well and barrier layers. The layer sequence and thickness are similar to those reported in [3]. Our device is 13 mm wide and 2 mm long. The emitting wavelength is 4.72 mm.

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Far-field improvement of quantum cascade lasers through high-reflection coatings

et al. 2011

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Efficiency-optimized monolithic frequency stabilization of high-power diode lasers

Crump¹,

Schultz²,

Wenzel³

et al. 2012

J. Phys. D: Appl. Phys.

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High-power GaAs-based diode lasers produce optical energy with extremely high efficiencies, but their spectrum is too broad for many applications (4–5 nm with 95% power content). Narrow spectra (<1 nm) can be achieved using monolithically integrated gratings and recent advances in semiconductor technology have largely eliminated the losses associated with this step. However, it remains challenging to develop designs that simultaneously achieve high power, high efficiencies and narrow spectra over a wide operation range. We review here the design choices necessary for optimized performance, using 975 nm broad-area lasers with uniform overgrown distributed feedback (DFB) gratings as a worked example, focusing on the role of the grating coupling strength. The steps necessary to minimize losses in the grating region are also reviewed. In addition, we show that special measures are needed to sustain narrow spectra in broad-area DFB lasers as they can support multiple longitudinal, lateral and vertical modes.

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940nm QCW diode laser bars with 70% efficiency at 1 kW output power at 203K: analysis of remaining limits and path to higher efficiency and power at 200K and 300K

et al. 2016

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Multiple vertical mode high power 975 nm diode lasers restricted to single vertical mode operation through use of optical facet coatings

Cited by 3 publications

References 4 publications

Far-field improvement of quantum cascade lasers through high-reflection coatings

Far-field improvement of quantum cascade lasers through high-reflection coatings

Efficiency-optimized monolithic frequency stabilization of high-power diode lasers

940nm QCW diode laser bars with 70% efficiency at 1 kW output power at 203K: analysis of remaining limits and path to higher efficiency and power at 200K and 300K

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