J.-F. Bisson

Highly efficient continuous-wave operation at 1030 and 1075 nm wavelengths of LD-pumped Yb3+:Y2O3 ceramic lasers

Room-temperature cw laser oscillations at 1030 and 1075 nm wavelengths were demonstrated for the TEM00 mode with Yb3+:Y2O3 ceramics by LD-pumping. A maximum extraction efficiency of 72% at 1075 nm lasing wavelengths and of 45% at 1030 nm lasing wavelengths were observed.

Yb3+:Sc2O3 ceramic laser

A solid-state laser material based on highly transparent Yb3+-doped scandia (Sc2O3) ceramic was developed using nanocrystalline technology and the nonpress vacuum sintering method. Continuous wave laser oscillations were obtained at around 1041 and 1094 nm using a 2.5 at. % Yb3+:Sc2O3 ceramic plate. Broadband lasing spectra were observed.

Role of undoped cap in the scaling of thin-disk lasers

The optimum design of a powerful thin-disk laser implies a compromise between amplified spontaneous emission (ASE), overheating, and the round-trip losses. The power enhancement of a composite thin-disk laser made of an undoped layer bonded over a thin active layer to reduce ASE losses is estimated analytically. Scaling laws for the parameters of a disk laser are suggested for cases both with and without an anti-ASE cap. Predictions of the maximal power achievable for a given laser material are compared to the published experimental data. The anti-ASE cap allows an increase of the maximal output power proportional to the square of the logarithm of the round-trip loss.

Surface loss limit of the power scaling of a thin-disk laser

We show that the general limit of power scaling of thin-disk lasers comes not only from the overheating and amplified spontaneous emission (ASE) but also from the surface loss. Overheating or thermal fracture increases the transverse size at the scaling, whereas ASE limits the gain-size product. The gain coefficient should decrease at the scaling. However, the round-trip gain should remain larger than the background loss; hence, the thickness should increase at the scaling. The limit of the output power per single active element occurs when the medium becomes too thick and cannot work efficiently without overheating. The maximum output power scales inversely with the cube of the surface loss coefficient. In the quasi-continuous regime, the average power scales inversely to the product of the duration of pulses to the repetition rate.

Switching of emissivity and photoconductivity in highly doped Yb3+:Y2O3 and Lu2O3 ceramics

Reversible jump of thermal emission accompanied with jump of photocurrent is observed in highly doped Yb3+:Y2O3 and Lu2O3 bulk ceramics pumped at 940nm wavelength. In contrast, when these materials are heated with a CO2 laser at 10.6μm wavelength, only a gradual increase of thermal emission and photoconductivity are observed up to the melting point. These results are interpreted as a ytterbium mediated, photoassisted avalanche of thermal emission.

Thermal effects in quasi-continuous-wave Nd3+:Y3Al5O12 nanocrystalline-powder random laser

We report an experimental investigation on the thermal effects in a Nd3+:Y3Al5O12 nanocrystalline-powder random laser with a one-mirror structure by quasi-continuous-wave laser diode pumping. Extremely low thermal conductivity in powder and significant temperature dependence of the narrow emission spectrum of Nd3+:Y3Al5O12 leads to a laser line redshift and gain reduction with a higher heat deposit. Mode drifting induced by the temperature dependence of the refractive index is also discussed.

Nonequilibrium acoustic phonons in Y3Al5O12-Based nanocrystalline ceramics

The phonon transport processes in high-transparency nanocrystalline laser ceramics based on cubic Y3Al5O12 garnet oxide were investigated by the heat-pulse technique. The propagation kinetics of nonequilibrium acoustic phonons was studied in the range of helium temperatures (1.7–3.8 K). The structural model is suggested for the intergrain layers, and their thickness is estimated.

High-power single-mode solid-state laser with a short, wide unstable cavity

A wide, short unstable cavity laser design is proposed for high-power, single-longitudinal, single-transverse-mode emission from a solid-state laser. Such a laser combines the single-mode master oscillator and the single-mode amplifier in a single piece. Design formulas are suggested; the efficiency and conditions of the single-longitudinal-mode operation are analyzed. Examples with Nd:YAG and Yb:YAG are considered. For a device of a few millimeters wide, the slope efficiency of approximately 50% and the threshold of a few watts are predicted.

Ridged atomic mirrors and atomic nanoscope

Recent results on the reflection of waves from ridged mirrors are discussed. Numerical calculations, analytical estimates and the direct measurements of coefficient of specular reflection of atomic waves from solid-state mirrors are combined. The reflectivity is approximated as an elementary function of period L of ridges, their width l, wavenumber K, grazing angle θ and effective depth w of the van der Waals potential. In a special case L = l, the fit reproduces the reflectivity of flat surfaces. Our approximation allows us to optimize the L at given l and estimate the maximum performance of a ridged mirror. Such a mirror is suggested as a focusing element for the nano-scale imaging system.

99% Diffraction Efficiency Leaky Mode Sustained Resonant Gratings and Susceptibility to Laser Damage

A resonant diffraction grating comprising a mirror, a dielectric layer and a corrugation at the layer-air interface is shown to exhibit a record diffraction efficiency of more than 99% in the – 1streflected order at 1064 nm wavelength. The leaky mode field enhancement in the high index grating raises the issue of laser damage.