Tomi Leinonen

High power CW red VECSEL with linearly polarized TEM00 output beam

High-power, continuous-wave operation at red wavelengths has been achieved with a vertical external cavity surface emitting laser based on the GaInP/AlGaInP/GaAs material system. Output power of 0.4W was obtained in a linearly polarized, circularly symmetric, diffraction-limited beam. A birefringent filter inserted in the cavity allowed tuning of the laser output spectrum over a 10nm range around 674nm.

Vertical external-cavity surface-emitting laser for dual-wavelength generation

We report an optically pumped vertical external-cavity surface-emitting laser that is designed for emission at two wavelengths simultaneously. Single transverse mode continuous-wave (CW) operation is demonstrated at the wavelengths of 984 and 1042 nm. The device produces a CW optical power of 140 mW for the 984-nm component and 115 mW for the 1042-nm component, exhibiting over 10% efficiency. At a high pump power, self-pulsation of the components appeared on top of the CW-mode components. The maximum total output of 1 W was obtained at the pump power of 9 W.

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.

11 W single gain-chip dilute nitride disk laser emitting around 1180 nm

We report power scaling experiments of a GaInNAs/GaAs-based semiconductor disk laser operating at ~1180 nm. Using a single gain chip cooled to mount temperature of ~10 °C we obtained 11 W of output power. For efficient thermal management we used a water-cooled microchannel mount and an intracavity diamond heat spreader. Laser performance was studied using different spot sizes of the pump beam on the gain chip and different output couplers. Intracavity frequency-doubling experiments led to generation of ~6.2 W of laser radiation at ~590 nm, a wavelength relevant for the development of sodium laser guide stars.

SESAM mode-locked red praseodymium laser.

We present the first semiconductor saturable absorber mirror (SESAM) mode-locked praseodymium solid-state laser. The laser is based on a Pr(3+):LiYF(4) crystal as gain medium and a GaInP-quantum well-based SESAM. Self-starting continuous-wave mode-locked laser operation with an average output power of 16 mW is achieved at a center wavelength of 639.5 nm. The laser operates at a repetition rate of ∼85.55  MHz and emits pulses with a duration of ∼18  ps.

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.

Simultaneous Dual-Wavelength Emission From Vertical External-Cavity Surface-Emitting Laser: A Numerical Modeling

The analysis of novel vertical external-cavity surface-emitting laser (VECSEL) designed for simultaneous dual-wavelength emission is presented. Inhomogeneous optical pumping of the nonidentical quantum wells of the active region has been studied. The novel rate equations description of our VECSEL is presented taking into account a strong time-delayed feedback. Steady-state stability conditions and the dynamics of dual-wavelength lasing have been investigated. It appears that tendency to self-pulsation due to Q-switching at high pump power is avoidable by accurate modeling and epitaxial growth of the active region of the laser

High-power disk lasers based on dilute nitride heterostructures

We report the development of InGaAsN-based gain mirrors for high-power optically pumped semiconductor disk lasers with direct emission at wavelengths around 1180nm. The gain mirrors were fabricated by molecular beam epitaxy. They consist of 10 dilute nitride quantum wells, which were placed within a GaAs micro-cavity on top of a GaAs/AlAs distributed Bragg reflector. We demonstrated laser operation at 1180nm with record high output power ( 7W). The differential efficiency was 30% for operation at 5 C and 28% when operating at 15 C. The lasers exhibited excellent tuning characteristics, delivering an output power of more than 5W in a narrow spectrum and providing over 30nm tuning band. These features represent significant progress towards demonstration of practical high-power lasers with frequency-doubled yellow emission required for laser guide stars, life sciences and spectroscopy. At the same time the results emphasize the importance of dilute nitride heterostructures in the development of novel optoelectronic devices.

3 nJ, 100 ps laser pulses generated with an asymmetric waveguide laser diode for a single-photon avalanche diode time-of-flight (SPAD TOF) rangefinder application

An asymmetric waveguide laser diode with a thick active layer operated with enhanced gain switching is shown to be able to produce ?100 ps, ?25 W optical pulses in fundamental transverse mode with ?15 A, ?1.5 ns injection current pulses. A pulsed time-of-flight distance measurement demonstration utilizing this laser diode and a SPAD detector indicates centimetre-level precision and compensated accuracy from uncooperative targets at tens to hundreds of metres in a measurement time of a fraction of a second.