Ivan A. Shcherbakov

Spectroscopic characterization and laser performance of diode-laser-pumped Nd: GdVO4

We have carried out a detailed spectroscopic characterization of Nd: GdVO4, a new laser crystal with high effective absorption and emission cross sections. The accidental degeneracy of the upper4F3/2 laser level decreases the number of emission lines and creates -together with the anisotropic crystal field - high emission cross sections (7.6 × 10−19 cm2 at 1.06 µm and 300 K). In addition, the lines are strongly homogeneously broadened (1.6 nm for the 808.4 nm diode-laser pump transition). The temperature dependences of lifetime, linewidths, and cross sections have been determined. Slope efficiencies up to 57% with respect to the absorbed diode-laser pump power and output powers up to 0.8 W have been achieved at 1.06 µm from a 2 mm long crystal. Intracavity second-harmonic generation, using a KTP crystal, is demonstrated.

Efficient Cr3+ sensitized Nd3+: GdScGa-garnet laser at 1.06 μm

Room-temperature cw lasing at 1.061 μm has been obtained in Cr,Nd: GdScGa-garnet. Threshold powers as low as 7 mW and slope efficiencies up to 41% have been measured. Cross pumping of Nd3+ via Cr3+ is nearly as efficient as direct pumping. Time-resolved measurements of the transfer rate yield a transfer efficiency of 0.86 and an average transfer time of 17 μs. An improvement in pulsed broad band pumping can also be expected.

Acoustooptic Q-switching of erbium lasers

Experiments were performed on Q switching of erbium lasers at 3 mu m with an acoustooptical modulator. Different laser crystals of YAG:Er and YSGG:Cr:Er have been investigated. The highest fraction of single pulse Q-switch energy to free-running mode energy was 1%. Pulse durations of 50 ns were obtained. Multiple switching with up to 14 Q-switch peaks per flashlamp pulse could be generated, containing up to 19% of the energy of the free-running mode. >

Performance of a Tm3+:GdVO4 microchip laser at 1.9 μm

Abstract GdVO 4 as a host for thulium has several advantages for diode pumping. The absorption cross section of thulium in GdVO 4 is considerably stronger and broader than in YAG and YLF, and the spectrum is shifted closer to the emission wavelength of commercially available AlGaAs laser diodes. In our paper we compare the 2 μm transition in Tm:GdVO 4 with the one in Tm:Ho:GdVO 4 . The population dynamics in the two crystals is discussed. Furthermore, we report on the optimisation of a Tm 3+ (6.9 at.%):GdVO 4 microchip laser with respect to high efficiency. CW lasing is established at room temperature in a wavelength range around 1.95 μm. The lowest threshold achieved is 310 mW and the highest slope efficiency is 21%.

Diode-pumped passively Q-switched self-frequency-doubling Nd:YAB laser

We report on a diode-pumped 531-nm self-frequency-doubling Nd:YAB laser passively Q switched by a Cr4+:YAG saturable absorber. Pumped by 1.4 W of 807-nm GaAlAs diode laser radiation, the Nd:YAB laser system generates 5.6-ns-long TEM00 light pulses with an energy of 1.0 µJ at a repetition rate of 45 kHz. The experimental data are compared with the results of a numerical analysis based on rate equations that consider the optical properties of the Nd:YAB crystal and of the Cr4+:YAG saturable absorber.

Spectroscopic properties and lasing of Nd:Gd0.5La0.5VO4 crystals

Abstract We report on the synthesis and spectroscopic characterization of new neodymium doped disordered laser crystals of Gd0.5La0.5VO4 for diode laser pumping. The neodymium 4 F 3 2 lifetime is 100 μs and the crystals have a broad (2 nm) absorption band at 808 nm and a high emission cross section (3 × 10−19 cm2) at 1.06 μm. Under diode pumping 550 mW of output power at 1.06 μm has been achieved at a slope efficiency of 41%.

Femtosecond solid-state lasers using Nd 3+ -doped mixed scandium garnets

The mode-locking features of a series of Nd3+-doped solid solutions of aluminum and gallium garnets are investigated, and the influence of multiline gain spectra on mode-locking performance is discussed. With an additive-pulse nonlinear Michelson interferometer used to mode lock the laser passively, pulses as short as 260 fs are obtained. The effect of interferometer detuning on the pulse characteristics is studied.

Laser operation and spectroscopy of Tm: Ho: GdVO4

Abstract Laser operation on the Ho 5 I 7 - 5 I 8 2 μm transition in Tm: Ho: GdVO 4 is described, to our knowledge for the first time. This material has very strong and broad absorption bands, α = 19.1 cm -1 at 797 nm with a fwhm of 7 nm, which is very desirable for diode pumping. The fluorescence spectrum is continuous from 1.9 to 2.07 μm with two closely spaced peaks at 2.04 and 2.05 μm. A 0.7 mm long Tm: Ho: GdVO 4 sample was pumped by a titanium sapphire laser using the active mirror geometry to achieve 90% pump absorption efficiency. Room temperature lasing was achieved at 2.049 μm.

A diode-pumped 1.4-W Tm/sup 3+/:GdVO/sub 4/ microchip laser at 1.9 /spl mu/m

GdVO/sub 4/ as a host for thulium has several advantages for diode pumping in comparison with other crystals. The absorption cross section of thulium in GdVO/sub 4/ is considerably stronger and broader than in YAG and YLF, and the spectrum is shifted closer to the emission wavelength of commercially available AlGaAs laser diodes. In our paper, we report on a diode-pumped monolithic Tm/sup 3+/(6.9 at.%):GdVO/sub 4/ microchip laser at 1.9 /spl mu/m. A maximum output power of 1.4 W is achieved. Two different arrangements for cooling the crystal are discussed. Furthermore, the input-output curves under Ti:sapphire pumping are compared for different pump wavelengths. Slope efficiencies of 58%, clearly exceeding the Stokes limit of 41%, are achieved.

2.79 /spl mu/m YSGG:Cr:Er laser pumped at 790 nm

2.79 /spl mu/m quasi-CW laser operation at room temperature was achieved from a YSGG:Cr:Er crystal. The output from the crystal, which was longitudinally pumped with a Ti:sapphire laser at 790 nm, was self-terminating. Under quasi-CW pumping, the length of the emitted pulses decreased exponentially with increasing pump power. The self-terminating behavior is explained by thermal effects with a computer simulation of the population mechanisms in the crystal. This simulation considers not only the common cross-relaxation and up-conversion processes, but also the inverse processes. They turn out to be of the same importance as the normal processes. The YSGG:Cr:Er crystal depends so critically on the laser parameters that it is an ideal candidate for testing the system of rate equations. >