Vertical External Cavity Surface Emitting Lasers (VECSELs) IV, 2014
ABSTRACT We report on the development of a high-efficiency frequency doubled vertical-external-ca... more ABSTRACT We report on the development of a high-efficiency frequency doubled vertical-external-cavity surface-emitting laser with an output power of 20 W and emission spectrum centered at 588 nm. The MBE-grown gain chip incorporated 10 GaInAs quantum wells and emitted in the 1180 nm range. The frequency conversion was achieved using a lithium triborate nonlinear crystal in an intra-cavity configuration. In addition to the nonlinear crystal, the V-shaped cavity also included a birefringent filter and an etalon for linewidth narrowing and wavelength tuning. The maximum optical-to-optical conversion efficiency obtained was ~28 % for 16 W of output power and the VECSEL had a tuning bandwidth of ~26 nm ranging from about 576 to 602 nm. We were also able to generate yellow pulses down to 570 ns duration by directly modulating the VECSEL's pump laser.
2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE/IQEC, 2013
ABSTRACT During the recent years, the wavelength coverage of optically-pumped vertical external-c... more ABSTRACT During the recent years, the wavelength coverage of optically-pumped vertical external-cavity surface-emitting lasers (VECSELs) has expanded significantly and currently reaches from the UV to mid-IR (although not without gaps). This progress has been fuelled by the ability to tailor the VECSELs emission wavelength via bandgap engineering and by the capability to deploy different kinds of semiconductor gain material systems, such as GaAs, InP, GaSb and PbTe, for example. The combination of wavelength flexibility and efficient intra-cavity second-harmonic generation makes these lasers excellent light sources for many applications for which conventional solid-state laser aren't available. In particular, the development of frequency-doubled VECSELs with blue, green and yellow-orange emission has experienced a surge of outstanding achievements.
Lasers, Sources, and Related Photonic Devices, 2012
ABSTRACT We demonstrate a semiconductor disk laser emitting ~0.8 W close to 1120 nm with a short-... more ABSTRACT We demonstrate a semiconductor disk laser emitting ~0.8 W close to 1120 nm with a short-term linewidth <300 kHz without active stabilization. The disk laser gain mirror used strain compensated GaInAs quantum wells.
ABSTRACT We report on the development of an optically-pumped vertical external-cavity surface-emi... more ABSTRACT We report on the development of an optically-pumped vertical external-cavity surface-emitting laser emitting near 1120 nm using strain compensated quantum wells. The development is motivated by the need to achieve narrow linewidth emission at ~280 nm via fourth harmonic generation, which is required to cool Mg+ ions. The gain mirror had a top-emitting geometry, was grown by molecular beam epitaxy and comprised GaInAs/GaAs quantum wells strain compensated by GaAsP layers; the strain compensation was instrumental for achieving a dislocation free epitaxial structure without dark lines. We demonstrate VECSEL operation at a fundamental wavelength close to 1118 nm with a linewidth of less than 300 kHz. Using a lithium triborate crystal we achieved frequency doubling to ~559 nm with an output power of 1.1W.
An output power up to 5 W at 1.48-μm wavelength is achieved from an optically pumped semiconducto... more An output power up to 5 W at 1.48-μm wavelength is achieved from an optically pumped semiconductor disk laser. An active region composed of an AlGaInAs/InP heterostructure grown on an InP substrate was wafer fused with an AlGaAs/GaAs Bragg reflector grown on a GaAs substrate. An intracavity diamond heatspreader bonded to the gain structure surface provides efficient heat removal from the active element. The results further validate that the wafer fusion technique offers a flexible platform for high-power disk lasers in a wide wavelength range.
ABSTRACT We report on the development of a pulsed high-power frequency doubled vertical-external-... more ABSTRACT We report on the development of a pulsed high-power frequency doubled vertical-external-cavity surface-emitting laser (VECSEL) with a peak output power of 14 W and emission spectrum near 588 nm. The semiconductor gain chip was grown by molecular beam epitaxy and comprised 10 GaInAs quantum wells. The gain structure was designed to be antiresonant at 1180 nm. The fundamental wavelength was frequency doubled to the yellow–orange spectral range using a 10-mm long critically phase matched lithium triborate nonlinear crystal, situated at the mode waist of the V-shaped laser cavity. The emission spectrum was narrowed down to FWHM of < 0.2 nm by employing a 1.5 mm birefringent filter and a 100-μm-thick etalon inside the cavity. By directly modulating the pump laser of the VECSEL, we were able to produce pulse widths down to 570 ns with average and peak output power of 81 mW and 14 W, respectively. The repetition rate was kept constant at 10 kHz throughout the measurements. The maximum peak power obtained was pump power limited. In comparison, at the same coolant temperature, a maximum of 8.5 W was achieved in continuous wave. The maximum optical-to-optical conversion efficiency (absorbed peak pump power to peak output power) was calculated to be 20–21 %.
A picosecond GaInP/AlGaInP/GaAs vertical external-cavity surface-emitting laser (VECSEL) at 675 n... more A picosecond GaInP/AlGaInP/GaAs vertical external-cavity surface-emitting laser (VECSEL) at 675 nm is reported. The laser is mode-locked with a GaInP/AlGaInP/GaAs saturable absorber mirror and emitted ~5.1 ps pulses at a 973 MHz repetition rate and an average power of 45 mW. To our knowledge, this is the first demonstration of a passively mode-locked VECSEL emitting fundamental laser radiation at the visible part of the spectrum.
We report on the development of high quality, strain compensated gain mirror for 1120nm vertical ... more We report on the development of high quality, strain compensated gain mirror for 1120nm vertical external-cavity surface-emitting lasers (VECSELs). The gain mirror was grown by molecular beam epitaxy and comprised a total of six Ga0.69In0.31As quantum wells. The effect of the strain compensation has been assessed by measuring the curvature of the wafer and by mapping the photoluminescence to identify
ABSTRACT Optically pumped semiconductor lasers in conjunction with intra-cavity frequency convers... more ABSTRACT Optically pumped semiconductor lasers in conjunction with intra-cavity frequency conversion and tuning elements offer high continuous-wave power, narrow linewidth, and broad tunability. As a result, they are well suited to precision spectroscopic applications. We describe the development and testing of optically pumped semiconductor lasers operating at fundamental wavelengths of 1119 and 1178 nm. The fourth and second harmonic wavelengths are resonant with transitions in Mg II and Na I, respectively. We demonstrate continuously tunable, single-frequency lasers with watt-level average power at 1119, 1178, and 589 nm.
Vertical External Cavity Surface Emitting Lasers (VECSELs) IV, 2014
ABSTRACT We report on the development of a high-efficiency frequency doubled vertical-external-ca... more ABSTRACT We report on the development of a high-efficiency frequency doubled vertical-external-cavity surface-emitting laser with an output power of 20 W and emission spectrum centered at 588 nm. The MBE-grown gain chip incorporated 10 GaInAs quantum wells and emitted in the 1180 nm range. The frequency conversion was achieved using a lithium triborate nonlinear crystal in an intra-cavity configuration. In addition to the nonlinear crystal, the V-shaped cavity also included a birefringent filter and an etalon for linewidth narrowing and wavelength tuning. The maximum optical-to-optical conversion efficiency obtained was ~28 % for 16 W of output power and the VECSEL had a tuning bandwidth of ~26 nm ranging from about 576 to 602 nm. We were also able to generate yellow pulses down to 570 ns duration by directly modulating the VECSEL's pump laser.
2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE/IQEC, 2013
ABSTRACT During the recent years, the wavelength coverage of optically-pumped vertical external-c... more ABSTRACT During the recent years, the wavelength coverage of optically-pumped vertical external-cavity surface-emitting lasers (VECSELs) has expanded significantly and currently reaches from the UV to mid-IR (although not without gaps). This progress has been fuelled by the ability to tailor the VECSELs emission wavelength via bandgap engineering and by the capability to deploy different kinds of semiconductor gain material systems, such as GaAs, InP, GaSb and PbTe, for example. The combination of wavelength flexibility and efficient intra-cavity second-harmonic generation makes these lasers excellent light sources for many applications for which conventional solid-state laser aren't available. In particular, the development of frequency-doubled VECSELs with blue, green and yellow-orange emission has experienced a surge of outstanding achievements.
Lasers, Sources, and Related Photonic Devices, 2012
ABSTRACT We demonstrate a semiconductor disk laser emitting ~0.8 W close to 1120 nm with a short-... more ABSTRACT We demonstrate a semiconductor disk laser emitting ~0.8 W close to 1120 nm with a short-term linewidth <300 kHz without active stabilization. The disk laser gain mirror used strain compensated GaInAs quantum wells.
ABSTRACT We report on the development of an optically-pumped vertical external-cavity surface-emi... more ABSTRACT We report on the development of an optically-pumped vertical external-cavity surface-emitting laser emitting near 1120 nm using strain compensated quantum wells. The development is motivated by the need to achieve narrow linewidth emission at ~280 nm via fourth harmonic generation, which is required to cool Mg+ ions. The gain mirror had a top-emitting geometry, was grown by molecular beam epitaxy and comprised GaInAs/GaAs quantum wells strain compensated by GaAsP layers; the strain compensation was instrumental for achieving a dislocation free epitaxial structure without dark lines. We demonstrate VECSEL operation at a fundamental wavelength close to 1118 nm with a linewidth of less than 300 kHz. Using a lithium triborate crystal we achieved frequency doubling to ~559 nm with an output power of 1.1W.
An output power up to 5 W at 1.48-μm wavelength is achieved from an optically pumped semiconducto... more An output power up to 5 W at 1.48-μm wavelength is achieved from an optically pumped semiconductor disk laser. An active region composed of an AlGaInAs/InP heterostructure grown on an InP substrate was wafer fused with an AlGaAs/GaAs Bragg reflector grown on a GaAs substrate. An intracavity diamond heatspreader bonded to the gain structure surface provides efficient heat removal from the active element. The results further validate that the wafer fusion technique offers a flexible platform for high-power disk lasers in a wide wavelength range.
ABSTRACT We report on the development of a pulsed high-power frequency doubled vertical-external-... more ABSTRACT We report on the development of a pulsed high-power frequency doubled vertical-external-cavity surface-emitting laser (VECSEL) with a peak output power of 14 W and emission spectrum near 588 nm. The semiconductor gain chip was grown by molecular beam epitaxy and comprised 10 GaInAs quantum wells. The gain structure was designed to be antiresonant at 1180 nm. The fundamental wavelength was frequency doubled to the yellow–orange spectral range using a 10-mm long critically phase matched lithium triborate nonlinear crystal, situated at the mode waist of the V-shaped laser cavity. The emission spectrum was narrowed down to FWHM of < 0.2 nm by employing a 1.5 mm birefringent filter and a 100-μm-thick etalon inside the cavity. By directly modulating the pump laser of the VECSEL, we were able to produce pulse widths down to 570 ns with average and peak output power of 81 mW and 14 W, respectively. The repetition rate was kept constant at 10 kHz throughout the measurements. The maximum peak power obtained was pump power limited. In comparison, at the same coolant temperature, a maximum of 8.5 W was achieved in continuous wave. The maximum optical-to-optical conversion efficiency (absorbed peak pump power to peak output power) was calculated to be 20–21 %.
A picosecond GaInP/AlGaInP/GaAs vertical external-cavity surface-emitting laser (VECSEL) at 675 n... more A picosecond GaInP/AlGaInP/GaAs vertical external-cavity surface-emitting laser (VECSEL) at 675 nm is reported. The laser is mode-locked with a GaInP/AlGaInP/GaAs saturable absorber mirror and emitted ~5.1 ps pulses at a 973 MHz repetition rate and an average power of 45 mW. To our knowledge, this is the first demonstration of a passively mode-locked VECSEL emitting fundamental laser radiation at the visible part of the spectrum.
We report on the development of high quality, strain compensated gain mirror for 1120nm vertical ... more We report on the development of high quality, strain compensated gain mirror for 1120nm vertical external-cavity surface-emitting lasers (VECSELs). The gain mirror was grown by molecular beam epitaxy and comprised a total of six Ga0.69In0.31As quantum wells. The effect of the strain compensation has been assessed by measuring the curvature of the wafer and by mapping the photoluminescence to identify
ABSTRACT Optically pumped semiconductor lasers in conjunction with intra-cavity frequency convers... more ABSTRACT Optically pumped semiconductor lasers in conjunction with intra-cavity frequency conversion and tuning elements offer high continuous-wave power, narrow linewidth, and broad tunability. As a result, they are well suited to precision spectroscopic applications. We describe the development and testing of optically pumped semiconductor lasers operating at fundamental wavelengths of 1119 and 1178 nm. The fourth and second harmonic wavelengths are resonant with transitions in Mg II and Na I, respectively. We demonstrate continuously tunable, single-frequency lasers with watt-level average power at 1119, 1178, and 589 nm.
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Papers by Sanna Ranta