975 nm high power diode lasers with high efficiency and narrow vertical far field enabled by low index quantum barriers

Crump, P.; Pietrzak, A.; Bugge, F.; Wenzel, H.; Erbert, G.; Tränkle, G.

doi:10.1063/1.3378809

Cited by 34 publications

(19 citation statements)

References 10 publications

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“…The most natural approach for achieving narrow vertical far field is to simply increase waveguide thickness, although sophisticated designs are needed to suppress lasing in higher order vertical modes [26]. The resulting broadening of the optical mode reduces the modal gain, hence increasing threshold, so typically at least two quantum wells are required for reasonable performance [22]. When no special measures are taken, a waveguide thickness of > 7-8 µm is found to be necessary for operation with Θ V 95% < 30°, and this compromises performance strongly, leading to low internal efficiency, η i and high electrical resistance [25,27].…”

Section: Design Approach For Simultaneous High Efficiency and Narrow mentioning

confidence: 99%

“…In the ELOD design presented here, an alternative approach is followed, making use of the barriers between the quantum wells, as discussed in detail in Refs. [22,25]. If the barriers are selected to have lower n than the waveguide layer, they can suppress the active region waveguiding.…”

Section: Design Approach For Simultaneous High Efficiency and Narrow mentioning

confidence: 99%

“…We present here a summary of recent studies performed at the Ferdinand-Braun-Institut on BA lasers that have been specifically optimized for wavelength stabilization with external VHGs. These devices are termed throughout ELOD lasers, as they operate with extremely low vertical divergence, whilst sustaining high efficiency and high reliable powers [12,[21][22][23]. These ELOD designs were developed within the project SpektraLas, a part of the German national development program "INLAS", and their assessment for use in spectral beam combining systems is planned as part of the recently started EU program BRIDLE 1 .…”

Section: Introductionmentioning

confidence: 99%

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Low-loss smile-insensitive external frequency-stabilization of high power diode lasers enabled by vertical designs with extremely low divergence angle and high efficiency

et al. 2013

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Broad area lasers with narrow spectra are required for many pumping applications and for wavelength beam combination. Although monolithically stabilized lasers show high performance, some applications can only be addressed with external frequency stabilization, for example when very narrow spectra are required. When conventional diode lasers with vertical far field angle, Θ V 95% ~ 45° (95% power) are stabilized using volume holographic gratings (VHGs), optical losses are introduced, limiting both efficiency and reliable output power, with the presence of any bar smile compounding the challenge. Diode lasers with designs optimized for extremely low vertical divergence (ELOD lasers) directly address these challenges. The vertical far field angle in conventional laser designs is limited by the waveguiding of the active region itself. In ELOD designs, quantum barriers are used that have low refractive index, enabling the influence of the active region to be suppressed, leading to narrow far field operation from thin vertical structures, for minimal electrical resistance and maximum power conversion efficiency. We review the design process, and show that 975 nm diode lasers with 90 µm stripes that use ELOD designs operate with Θ V 95% = 26° and reach 58% power conversion efficiency at a CW output power of 10 W. We demonstrate directly that VHG stabilized ELOD lasers have significantly lower loss and larger operation windows than conventional lasers in the collimated feedback regimes, even in the presence of significant (≥ 1 µm) bar smile. We also discuss the potential influence of ELOD designs on reliable output power and options for further performance improvement.

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Section: Design Approach For Simultaneous High Efficiency and Narrow mentioning

confidence: 99%

Section: Design Approach For Simultaneous High Efficiency and Narrow mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Low-loss smile-insensitive external frequency-stabilization of high power diode lasers enabled by vertical designs with extremely low divergence angle and high efficiency

et al. 2013

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“…To promote high-performance lasing in the lasers with thick vertical waveguides the active region needs typically to be placed close to the center of the optical cavity to allow significant optical overlap with the fundamental mode. A moderately asymmetric [7,8] positioning of the active region off-center in the cavity may improve the vertical mode discrimination also in the waveguides with a high refractive index step by suppressing lasing of the high order optical modes. Optical losses < 0.4 cm −1 were reported for thick undoped waveguide laser diodes with vertical beam divergence 30 o FWHM [9].…”

Section: Introductionmentioning

confidence: 98%

High differential efficiency tilted wave laser

et al. 2014

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We report results on 1060 nm GaAs/GaAlAs-based Tilted Wave Lasers employing multiple InGaAs quantum wells without strain compensation as active medium. The devices are edge-emitting lasers composed of a thin active waveguide optically coupled to a thick passive waveguide responsible to form a tilted optical wave that results in two narrow lobes in the vertical far field profile of the emitted laser light. Devices with different thicknesses of the passive waveguide have been fabricated. The laser with the 26 µm-thick waveguide has low internal losses of 1.4 cm -1 , reaches for the as cleaved facets device with 1.5 mm-long cavity the differential efficiency of 81%. The 50 µm broad area device demonstrates the maximum wall-plug efficiency in the continuous wave (cw) mode ~50% and the linear output power up to and above 4 W. The laser light is concentrated in two narrow vertical beams, each 2 o full width at half maximum in a good agreement with theory.

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“…There is a need in cost-and energy-efficient high brightness laser diodes for multiple applications [1][2][3][4][5][6][7][8][9][10][11], and material processing is the most evident example. Conventional laser diodes provide high brightness in a single mode regime.…”

Section: Introductionmentioning

confidence: 99%

Passive cavity laser and tilted wave laser for Bessel-like beam coherently coupled bars and stacks

Ledentsov

Shchukin

Maximov³

et al. 2015

SPIE Proceedings

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Ultralarge output apertures of semiconductor gain chips facilitate novel applications that require efficient feedback of the reflected laser light. Thick (10-30 µm) and ultrabroad (>1000 µm) waveguides are suitable for coherent coupling through both near-field of the neighboring stripes in a laser bar and by applying external cavities. As a result direct laser diodes may become suitable as high-power high-brightness coherent light sources. Passive cavity laser is based on the idea of placing the active media outside of the main waveguide, for example in the cladding layers attached to the waveguide, or, as in the case of the Tilted Wave Laser (TWL) in a thin waveguide coupled to the neighboring thick waveguide wherein most of the field intensity is localized in the broad waveguide. Multimode or a single vertical mode lasing is possible depending on the coupling efficiency. We demonstrate that 1060 nm GaAs/GaAlAs-based Tilted Wave Lasers (TWL) show wall-plug efficiency up to ~55% with the power concentrated in the two symmetric vertical beams having a full width at half maximum (FWHM) of 2 degrees each. Bars with pitch sizes in the range of 25-400 µm are studied and coherent operation of the bars is manifested with the lateral far field lobes as narrow as 0.1 o FWHM. As the near field of such lasers in the vertical direction represents a strongly modulated highly periodic pattern of intensity maxima such lasers or laser arrays generate Bessel-type beams. These beams are focusable similar to the case of Gaussian beams. However, opposite to the Gaussian beams, such beams are self-healing and quasi non-divergent. Previously Bessel beams were generated using Gaussian beams in combination with an axicon lens or a Fresnel biprism. A new approach does not involve such complexity and a novel generation of laser diodes evolves.

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975 nm high power diode lasers with high efficiency and narrow vertical far field enabled by low index quantum barriers

Abstract: High-peak-power pulsed operation of 2.0 m (AlGaIn)(AsSb) quantum-well ridge waveguide diode lasers Continuous-wave operation of =3.25 m broadened-waveguide W quantum-well diode lasers up to T=195 K

Cited by 34 publications

References 10 publications

Low-loss smile-insensitive external frequency-stabilization of high power diode lasers enabled by vertical designs with extremely low divergence angle and high efficiency

Low-loss smile-insensitive external frequency-stabilization of high power diode lasers enabled by vertical designs with extremely low divergence angle and high efficiency

High differential efficiency tilted wave laser

Passive cavity laser and tilted wave laser for Bessel-like beam coherently coupled bars and stacks

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