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

Crump, P.; Schultz, C. M.; Wenzel, H.; Erbert, G.; Tränkle, G.

doi:10.1088/0022-3727/46/1/013001

Cited by 18 publications

(7 citation statements)

References 65 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…First, for the same overall chip dimension, the DBR lasers have a shorter pump length (here L pump = L -L DBR = 3 mm) compared to the reference lasers (L pump = 4 mm), leading to (4/3)× higher R s (also thermal resistance R th ) for higher voltage and ∼ 1.4× higher mirror loss α m = (0.5/L pump )ln(R r ×R f ) for higher threshold current. The introduction of the monolithic grating stabilization also leads to higher threshold current and more rapid thermal rollover due to detuning effects [22]: the gain wavelength varies with temperature at 0.34 nm/K and the grating (DBR) wavelength at 0.077 nm/K, meaning that gain and grating can only overlap at one operating point. Here, gain and grating coincide at around P opt = 15 W, threshold current is increased and thermal rollover is exaggerated due to reduced gain away from this point.…”

Section: Resultsmentioning

confidence: 99%

“…DEVICE STRUCTURE We investigate and compare BA lasers, both with and without DBRs, that use two different epitaxial layer structures. We use an asymmetric large optical cavity (ASLOC) epitaxial layer design from [4], [21] as a baseline, that is established in previous studies as being suitable for realizing highly efficient diode with monolithically integrated gratings [22]- [23]. We next introduce gratings into an improved extreme-triple-asymmetric (ETAS) laser structure from [21], which achieves higher power and conversion efficiency.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

60% Efficient Monolithically Wavelength-Stabilized 970-nm DBR Broad-Area Lasers

et al. 2022

View full text Add to dashboard Cite

Progress 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.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

60% Efficient Monolithically Wavelength-Stabilized 970-nm DBR Broad-Area Lasers

et al. 2022

View full text Add to dashboard Cite

show abstract

“…From the data in Figure 8 and Table 3, it can be seen that DFB LDs with the same ridge width and a lower grating period exhibited lower slope efficiency because of the higher value of ĸL compared to those with high order gratings [26]. In addition, the slope efficiency of DFB LDs with sidewall gratings was slightly higher than that of the DFB LDs with surface gratings but smaller than F–P LDs because of the scatter losses and diffraction losses from the gratings.…”

Section: Resultsmentioning

confidence: 99%

InGaN/GaN Distributed Feedback Laser Diodes with Surface Gratings and Sidewall Gratings

Deng

Liao

et al. 2019

Micromachines

View full text Add to dashboard Cite

A variety of potential applications such as visible light communications require laser sources with a narrow linewidth and a single wavelength emission in the blue light region. The gallium nitride (GaN)-based distributed feedback laser diode (DFB-LD) is a promising light source that meets these requirements. Here, we present GaN DFB-LDs that share growth and fabrication processes and have surface gratings and sidewall gratings on the same epitaxial substrate, which makes LDs with different structures comparable. By electrical pulse pumping, single-peak emissions at 398.5 and 399.95 nm with a full width at half maximum (FWHM) of 0.32 and 0.23 nm were achieved, respectively. The surface and sidewall gratings were fabricated alongside the p-contact metal stripe by electrical beam lithography and inductively coupled plasma etching. DFB LDs with 2.5 μm ridge width exhibit a smaller FWHM than those with 5 and 10 μm ridge widths, indicating that the narrow ridge width is favorable for the narrowing of the line width of the DFB LD. The slope efficiency of the DFB LD with sidewall gratings is higher than that of surface grating DFB LDs with the same ridge width and period of gratings. Our experiment may provide a reliable and simple approach for optimizing gratings and GaN DFB-LDs.

show abstract

“…Spectral stabilization of BA lasers reduces both Δλ 95% and δλ/δT so is therefore preferred for wavelength-based power scaling. BA lasers stabilized using internal distributed Bragg gratings have recently demonstrated reliable powers and efficiencies (η E = 58% at P out = 10 W [13,14]) close to that of un-stabilized devices, and reduce the channel spacing to < 2 nm, due to their narrow spectrum and reduced temperature sensitivity (Δλ 95% < 1 nm and δλ/δT ~ 0.08 nm/K [13,14]). Wavelength stabilization of BA lasers using external gratings is also in wide use [7][8][9][10][11][15][16][17][18][19][20][21], and extremely narrow, highly temperature stable spectra are possible, even in high power systems (a linewidth of < 100 GHz and δλ/δT < 0.01 nm/K have been demonstrated).…”

Section: Introductionmentioning

confidence: 99%

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

View full text Add to dashboard Cite

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.

show abstract

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

Cited by 18 publications

References 65 publications

60% Efficient Monolithically Wavelength-Stabilized 970-nm DBR Broad-Area Lasers

60% Efficient Monolithically Wavelength-Stabilized 970-nm DBR Broad-Area Lasers

InGaN/GaN Distributed Feedback Laser Diodes with Surface Gratings and Sidewall Gratings

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

Contact Info

Product

Resources

About