8 results
Search Results
Now showing 1 - 8 of 8
- ItemSpatially modulated broad-area lasers for narrow lateral far-field divergence(Washington, DC : Soc., 2021) Zeghuzi, Anissa; Koester, Jan-Philipp; Radziunas, Mindaugas; Christopher, Heike; Wenzel, Hans; Knigge, AndreaA novel laser design is presented that combines a longitudinal-lateral gain-loss modulation with an additional phase tailoring achieved by etching rectangular trenches. At 100 A pulsed operation, simulations predict a far-field profile with 0.3° full width at half maximum (ΘFWHM=0.3∘) where a 0.4°-wide main lobe contains 40% of the emitted optical output power (Θ40%=0.4∘). While far-field measurements of these structured lasers emitting 10 ns long pulses with 35 W peak power confirm a substantial enhancement of radiation within the central 1∘ angular range, the measured far-field intensity outside of the obtained central peak remains high.
- ItemWavelength-stabilized ns-pulsed 2.2 kW diode laser bar with multiple active regions and tunnel junctions(Stevenage : IET, 2022) Ammouri, Nor; Christopher, Heike; Fricke, Jörg; Ginolas, Arnim; Liero, Armin; Maaßdorf, Andre; Wenzel, Hans; Knigge, AndreaThe improvement of the performance of a distributed Bragg reflector laser bar emitting near 905 nm through the use of multiple epitaxially stacked active regions and tunnel junctions is reported. The bar consisting of 48 emitters (each having an aperture of 50 µm) emits an optical power of 2.2 kW in 8 ns long pulses at an injection current of 1.1 kA. This corresponds to an almost threefold increase of the pulse power compared to a bar with lasers having only a single active region. Due to the integrated surface Bragg grating, the bar exhibits a narrow spectral bandwidth of about 0.3 nm and a thermal tuning of only 68 pm/K.
- ItemVersatile high power pulse-laser source for pico- and nanosecond optical pulses(London : Institute of Physics, 2020) Liero, Armin; Klehr, Andreas; Knigge, Andrea; Heinrich, WolfgangThis paper presents a pulse-laser source for the generation of ps and ns laser pulses with more than 50 W peak output power. The final stages of the drivers use GaN transistors and are capable of switching currents of 0.8 A with 200 ps minimum pulse width and 50 A with 3 ns minimum pulse width. The pulses can be externally triggered by ECL logic. Both single-pulse and pulse train modes are possible.
- ItemStability of ZnSe-Passivated Laser Facets Cleaved in Air and in Ultra-High Vacuum(New York, NY : IEEE, 2022) Boschker, Jos E.; Spengler, Uwe; Ressel, Peter; Schmidbauer, Martin; Mogilatenko, Anna; Knigge, AndreaCatastrophic optical mirror damage (COMD) is one of the main failure mechanisms limiting the reliability of GaAs based laser diodes. Here, we compare the facet stability of ZnSe-passivated ridge-waveguide lasers (RWLs) that are cleaved in air and subsequently cleaned using atomic hydrogen with RWLs that are cleaved in ultra-high vacuum. RWLs cleaved in ultra-high vacuum show a superior performance and reach power densities up to 58 MW/cm 2 under extended continuous wave operation at 1064 nm. This is attributed to the reduction of defects at the interface between ZnSe and the cleaved facet as evidenced by transmission electron microscopy and X-ray diffraction.
- Item60% Efficient Monolithically Wavelength-Stabilized 970-nm DBR Broad-Area Lasers(New York, NY : IEEE, 2022) Crump, Paul; Miah, M. Jarez; Wilkens, Martin; Fricke, Jorg; Wenzel, Hans; Knigge, AndreaProgress in epitaxial design is shown to enable increased optical output power P opt and power conversion efficiency η E and decreased lateral far-field divergence angle in GaAs-based distributed Bragg reflector (DBR) broad-area (BA) diode lasers. We show that the wavelength-locked power can be significantly increased (saturation at high bias current is mitigated) by migrating from an asymmetric large optical cavity (ASLOC) based laser structure to a highly asymmetric (extreme-triple-asymmetric (ETAS)) layer design. For wavelength-stabilization, 7 th order, monolithic DBRs are etched on the surface of fully grown epitaxial layer structures. The investigated ETAS reference Fabry-Pérot (FP) BA lasers without DBRs and with 200 µm stripe width and 4 mm cavity length provide P opt = 29 W (still increasing) at 30 A in continuous-wave mode at room temperature, in contrast to the maximum P opt = 24 W (limited by strong power saturation) of baseline ASLOC lasers. The reference ETAS FP lasers also deliver over 10% higher η E at P opt = 24 W. On the other hand, in comparison to the wavelength-stabilized ASLOC DBR lasers, ETAS DBR lasers show a peak power increment from 14 W to 22 W, and an efficiency increment from 46% to 60% at P opt = 14 W. A narrow spectral width (< 1 nm at 95% power content) is maintained across a very wide operating range. Consistent with earlier studies, a narrower far-field divergence angle and consequently an improved beam-parameter product is also observed, compared to the ASLOC-based lasers.
- ItemSimulation and analysis of high-brightness tapered ridge-waveguide lasers(Dordrecht [u.a.] : Springer Science + Business Media B.V, 2023) Koester, Jan-Philipp; Wenzel, Hans; Wilkens, Martin; Knigge, AndreaIn this work, a simulation-based analysis of a CW-driven tapered ridge-waveguide laser design is presented. Measurements of these devices delivered high lateral brightness values of 4 W · mm - 1mrad - 1 at 2.5W optical output power. First, active laser simulations are performed to reproduce these results. Next, the resulting complex valued intra-cavity refractive index distributions are the basis for a modal and beam propagation analysis, which demonstrates the working principle and limitation of the underlying lateral mode filter effect. Finally, the gained understanding is the foundation for further design improvements leading to lateral brightness values of up to 10 W · mm - 1mrad - 1 predicted by simulations.
- ItemHybrid integrated mode-locked laser using a GaAs-based 1064 nm gain chip and a SiN external cavity(Washington, DC : Soc., 2022) Vissers, Ewoud; Poelman, Stijn; Wenzel, Hans; Christopher, Heike; Van Gasse, Kasper; Knigge, Andrea; Kuyken, BartExternal cavity mode-locked lasers could be used as comb sources for high volume application such as LIDAR and dual comb spectroscopy. Currently demonstrated chip scale integrated mode-locked lasers all operate in the C-band. In this paper, a hybrid-integrated external cavity mode-locked laser working at 1064 nm is demonstrated, a wavelength beneficial for optical coherence tomography or Raman spectroscopy applications. Additionally, optical injection locking is demonstrated, showing an improvement in the optical linewidth, and an increased stability of the comb spectrum.
- ItemWavelength stabilized high pulse power 48 emitter laser bars for automotive light detection and ranging application(Bristol : IOP Publ., 2020) Klehr, Andreas; Liero, Armin; Christopher, Heike; Wenzel, Hans; Maaßdorf, Andre; Della Casa, Pietro; Fricke, Jörg; Ginolas, Arnim; Knigge, AndreaDiode lasers generating optical pulses with high peak power and lengths in the nanosecond range are key components for light detection and ranging systems, e.g. for autonomous driving and object detection. We present here an internally wavelength stabilized distributed Bragg reflector broad area laser bar with 48 emitters. The vertical structure based on AlGaAs (confinement and cladding layers) and InGaAs (active quantum well) is specifically optimized for wavelength-stabilized pulsed operation, applying a surface Bragg grating with high reflectivity. The bar is electrically driven by a new in-house developed high-speed driver based on GaN transistors providing current pulses with amplitudes of up to 1000 A and a repetition frequency of 10 kHz. The generated 4 ns to 10 ns long optical pulses are nearly rectangular shaped and reach a pulse peak power in excess of 600 Watts at 25 °C. The optical spectrum with a centre wavelength of about 900 nm has a width of 0.15 nm (FWHM) with a side mode suppression ratio > 30 dB. © 2020 IOP Publishing Ltd.