Sanna Ranta

High-efficiency 20 W yellow VECSEL

A high-efficiency optically pumped vertical-external-cavity surface-emitting laser emitting 20 W at a wavelength around 588 nm is demonstrated. The semiconductor gain chip emitted at a fundamental wavelength around 1170-1180 nm and the laser employed a V-shaped cavity. The yellow spectral range was achieved by intra-cavity frequency doubling using a LBO crystal. The laser could be tuned over a bandwidth of ~26 nm while exhibiting watt-level output powers. The maximum conversion efficiency from absorbed pump power to yellow output was 28% for continuous wave operation. The VECSELs output could be modulated to generate optical pulses with duration down to 570 ns by directly modulating the pump laser. The high-power pulse operation is a key feature for astrophysics and medical applications while at the same time enables higher slope efficiency than continuous wave operation owing to decreased heating.

Raman fiber laser pumped by a semiconductor disk laser and mode locked by a semiconductor saturable absorber mirror

A 1.6µm mode-locked Raman fiber laser pumped by a 1480nm semiconductor disk laser is demonstrated. Watt-level core pumping of the single-mode fiber Raman lasers with low-noise disk lasers together with semiconductor saturable absorber mirror mode locking represents a highly practical solution for short-pulse operation.

Mode-locked VECSEL emitting 5 ps pulses at 675 nm

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.

Femtosecond mode-locked holmium fiber laser pumped by semiconductor disk laser

We report on a 2085 nm holmium-doped silica fiber laser passively mode-locked by semiconductor saturable absorber mirror and carbon nanotube absorber. The laser, pumped by a 1.16 μm semiconductor disk laser, produces 890 femtosecond pulses with the average power of 46 mW and the repetition rate of 15.7 MHz.

Narrow linewidth 1118/559 nm VECSEL based on strain compensated GaInAs/GaAs quantum-wells for laser cooling of Mg-ions

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.

High-Power 1.48-

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.

\mu

A high-power dual-wavelength AlGaInAs / GaAs laser operating in a vertical external-cavity surface emitting geometry, grown by molecular beam epitaxy, is reported. The active regions of the laser are separated by an optical long-wave-pass filter to prevent absorption of short-wavelength radiation in the long-wavelength gain area. The maximum output power achieved at 15 degrees C was 0.75 W at lambda approximately 966 nm and 1.38 W at lambda approximately 1047 nm for the pump power of 21.2 W.

m Wafer-Fused Optically Pumped Semiconductor Disk Laser

We report high power operation of a vertical external-cavity surface-emitting laser (VECSEL) operating around 1180 nm. The gain chip of the VECSEL comprises 10 strain-compensated GaInAs/GaAs quantum wells in a top-emitting configuration. A maximum output power of 23 W was achieved with a mount temperature of about 0 ‡C, and 20.5 W with the mount temperature of about 12 °C. By introducing a birefringent filter inside the laser cavity we demonstrate a tuning range of 67 nm. The gain chip was also used to construct a VECSEL for single-frequency operation. In this configuration, a maximum output power of about 11 W was recorded.

Dual-wavelength generation by vertical external cavity surface-emitting laser

The 1550nm wavelength region is critical to the development of next generation eye safe military applications such as range finding and friend or foe identification (FOE). So far the relatively low laser external efficiency was a strong limiting factor favoring shorter wavelength diode lasers. We report on the development of a new monolithic multiple junction pulsed laser diode offering an external efficiency of more than one Watt per Amp with high brightness. Peak optical output power of more than 37 Watts has been achieved from a single multi-junction diode laser. Divergence is narrow with less than 35 degrees (FWHM) in the fast axis direction. Starting from an AlGaInAs quantum well laser structure, we show the criticality of the design of InP based tunnel junctions to the growth of the three layer epitaxial monolithic laser. We then report on trenches employed to confine carriers under the contacting stripe and on growth strategies used to decouple the multiple light sources resulting from the multi-junction design. A full set of characterization data is presented concluding with a discussion on performance limitations and their potential causes.

High power (23W) vertical external cavity surface emitting laser emitting at 1180 nm

Distributed feedback lasers with third-order surface gratings obtained by lateral corrugations of the ridge waveguide have been fabricated using low-cost nanoimprint lithography. The lasers, emitting in the 980 nm wavelength range exhibited stable single-longitudinal-mode operation with side-mode suppression ratios up to 50 dB.