Stefan Bjurshagen

Modeling of energy-transfer upconversion and thermal effects in end-pumped quasi-three-level lasers

An analytical model of cw quasi-three-level lasers that includes the influence of energy-transfer upconversion (ETU) has been developed. The results of the general output modeling were applied to a laser with Gaussian beams, and rigorous numerical calculations have been made to study the influence of ETU on threshold, output power, spatial distribution of population-inversion density, and fractional thermal loading. The model was applied to a laser operating at 946 nm in Nd:YAG, where the dependence of laser-beam size on laser performance was investigated in particular. A simple model for the degradation of laser-beam quality from a transversally varying saturated gain is proposed that is in good agreement with measurements of the laser in a plane-plane cavity.

Fluorescence dynamics and rate equation analysis in Er3+ and Yb3+ doped double tungstates

The fluorescence dynamics in Er3+ and Yb3+ doped KGd(WO4)2 and KY(WO4)2 has been investigated. Lifetimes have been measured for the Yb (2F(5/2)), Er (4I(13/2)), and Er (4S(3/2)) levels around 1, 1.5, and 0.55 microm, respectively. The Yb (2F(5/2)) lifetimes show a decreasing trend toward the limiting Er (4I(11/2)) lifetime with increasing Er-to-Yb concentration ratio, whereas the Er (4I(13/2)) lifetimes are mostly unaffected by the doping concentrations. A rate equation analysis has been performed to explain the observed behavior and gain is calculated for a continuous-wave laser at 1.53 microm to find the optimum doping concentrations for high gain.

Crystal growth, spectroscopic characterization, and eye-safe laser operation of erbium- And ytterbium-codoped KLu(WO4)2

Erbium (Er)- and Ytterbium (Yb)-codoped monoclinic KLu(WO4)2 single crystals were grown by top seeded solution growth-slow cooling method for several different doping concentrations. Growth parameters have been optimized to obtain macrodefect-free single crystals. Er energy levels involved in the 4I13/2-->4I15/2 were determined by 6 K polarized optical absorption. The maximum emission cross section for this electronic transition has been evaluated, being 2.85x10(-20) cm2 for E||Nm at 1535 nm. Laser oscillation in the 1.5 microm range was obtained by pumping the Yb ion at 980 nm and sensitizing Er. The maximum output power achieved was 152 mW, with 1.2% slope efficiency.

An all solid-state UV source based on a frequency quadrupled, passively Q-switched 946 nm laser.

We report a 236 nm light source with 20 mW of average power based on critically phase-matched second-harmonic generation in a beta-barium borate crystal at room temperature. The fundamental light source was a passively Q-switched 946 nm Nd:YAG laser tunable from 10 - 38 kHz and with a pulse length of 16 ns. In the generation of 473 nm light, periodically poled KTP and BiBO was compared in terms of conversion efficiency and stability.

946-nm Nd:YAG laser under ground-state direct diode-pumping at 869 nm

We have demonstrated, what we believe is for the first time, direct diode-pumping at 869 nm into the emitting level of a quasi-three-level Nd:YAG laser operating at 946 nm

Polymer encapsulated diode pumped Nd:YAG lasers

We have previously reported on the development of a novel and versatile design concept for diode-pumped solid-state lasers (DPSSL) utilising microstructured silicon carriers. This concept enables compact assembly and passive alignment of all the optical components, passive and active. The carrier also provides a reliable and efficient thermal management. We here present, to the best of our knowledge, the first report on a polymer encapsulated diode-pumped solid-state laser, based on our previous design concept. This technology could enable extremely low-cost DPSSL devices for high-volume market applications.

200 mW of blue light generated by intracavity frequency doubling of a diode-pumped Nd:YAG laser operating at 938.5 nm

Summary form only given. We report efficient room-temperature operation of a compact diode-pumped Nd:YAG laser at 938.5 nm with a maximum continuous wave (cw) output power of 3.9 W. The laser rod is a transversally water-cooled composite rod with a 5 mm long doped middle section. A high-brightness fiber-coupled laser diode array served as the pump.

Novel design for diode-pumped miniature lasers using microstructured silicon carriers

A new design concept for compact diode-pumped solid-state lasers is presented. The design is based on a microstructured silicon carrier with etched v-grooves. This silicon microbench provides efficient thermal management at 10W pumping level, as well as compact integration and alignment of all active and passive optical components of compact diode-pumped solid-state lasers. In initial experiments, a Nd:YAG laser built on the microbench delivered a continuous-wave output of 3W.

Crystal Growth, Spectroscopic Characterisation and Eye-Safe Laser Operation of Er and Yb Doped KLu(WO4)2

High quality Er:Yb:KLu(WO4)2have been grown using TSSG method and spectroscopically investigated . The laser performance is compared with that in Er:Yb:KY(WO4)2. Role of upconversion processes and optimum doping concentrations have been estimated.

NaLa(WO 4 ) 2 and NaY(WO 4 ) 2 Raman Converters for Picosecond Pulses

Quasi-steady state SRS with 1.7 ps pulses is investigated in tetragonal NaY(WO₄)₂ and NaLa(WO₄)₂ crystals in the regimes of collinear and noncollinear SRS-assisted four-wave-mixing. Single-pass conversion efficiency of 31% is reported.