Chr. P. Wyss

Emission properties of an optimised 2.8 μm Er3+:YLF laser

Abstract A Ti:sapphire-pumped Er 3+ :YLF laser is built. The samples are grown at our institute and are compared with a commercially available Er 3+ :YLF. The dopant concentration and the polarisation of the pump beam is optimised. Slope efficiencies up to 50% and thresholds as low as 42 mW are achieved. The emission properties of the laser are studied. The cw laser emission is linearly polarised. More than 90% of the output power is emitted on a single Stark transition.

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%.

Energy transfer in Yb3+:Er3+:YLF

Abstract Yb 3+ as codopant in Er 3+ doped laser hosts is interesting due to the broad absorption band and the high absorption cross-section around 940 nm wavelength in Yb 3+ . We report on measurements to determine the cross-relaxation parameter W 1b for the energy transfer from excited Yb 3+ to ground-state Er 3+ and W a3 for the inverse process in LiYF 4 (YLF). The micro-parameters, describing the electric dipole-dipole interaction between a donor and an acceptor ion are determined for the normal and the inverse process. Furthermore, the micro-parameters for the energy migration between the Yb 3+ -ions and between the Er 3+ -ions are determined.

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.

Modulation and single-spike switching of a diode-pumped Er/sup 3+/:LiYF/sub 4/ laser at 2.8 /spl mu/m

An Er/sup 3+/:YLF laser at 2.8 /spl mu/m pumped with two polarization-coupled diode lasers is built. The emission properties of the laser are studied. The threshold is 107 mW and the slope efficiency is 33%. The laser output is modulated by either chopping the pump beam or by chopping the resonator mode. Single-spike switching using a rotating mirror is demonstrated for the first time in bulk material lasers at 2.8 /spl mu/m. Single spikes (pulse duration: 200-500 ns) are emitted with repetition rates up to 137 Hz. The temporal shape of the spikes is nearly Gaussian. Pulse duration and repetition rates are ideal for micro surgical applications. Rotating-mirror Q-switching was employed as other standard switching devices, such as acoustooptic or electrooptic modulators that were presently available to us introduce lasses to the cavity that cannot be compensated with the highest achievable gain in our system.

A diode-laser pump source with small focus diameter for end-pumped systems

A pump source with eight angular multiplexed laser diodes is built. The diode laser emission is collimated and focused using relatively inexpensive aspherical lenses. The maximum output power is 6.3W at 970nm. The overall transmittance of the beam shaping optics is T=85%. The electrical, temporal and spectral properties are studied. The variances of the spatial intensity distribution are Δr0x=99m and Δr0y=85m. The beam propagation factors are M2x=38 and M2y=112. The high intensity in the focus makes this system ideal for end pumping of solid state lasers.

Excitation of the thulium /sup 1/G/sub 4/ level

Summary form only given. Infrared pumped upconversion lasers in the visible wavelengths range are of great interest. We have found an excitation scheme for diode pumping laser action has not yet been reached but we have measured spectral properties of crystal and glass samples with various thulium concentration in the range from 300 nm to 2300 nm. Ytterbium is needed sensitise the excited state absorption and to enable efficient diode pumping at 940 nm or 790 nm. Lifetimes of the /sup 1/G/sub 4/ level of thulium are presented for several host materials.

Microchip laser based on an Nd{sup 3+}:GdVO{sub 4} crystal

A diode-pumped microchip laser based on an Nd3+:GdVO4 crystal was investigated. A maximum output power of about 4 W with a differential efficiency of 22% was obtained.A diode-pumped microchip laser based on an Nd{sup 3+}:GdVO{sub 4} crystal was investigated. A maximum output power of about 4 W with a differential efficiency of 22% was obtained. (lasers)