Emilie Herault

491 nm generation by sum-frequency mixing of diode pumped neodymium lasers.

We present three different dual-wavelength laser architectures to obtain cw blue radiations. They are based on diode-pumped Nd-doped crystals lasing on the 4F3/2-4I11/2 and 4F3/2-4I9/2 transitions. Blue radiations were achieved by intracavity sum frequency operation in a BiB3O6 crystal. We report a maximum output blue power of 303 mW at 491 nm for a pump power of 10 W.

Thermal conductivity measurements of laser crystals by infrared thermography. Application to Nd:doped crystals.

We present a thermal conductivity measurement method for laser crystals based on thermal mapping of the crystal face by an infrared camera. Those measurements are performed under end-pumping of the laser crystal and during laser operation. The calculation of the fraction of pump power converted into heat is therefore simplified, and it is possible to link easily the temperature in the crystal to the thermal conductivity. We demonstrate the efficiency of this measurement method with a Nd:YAG crystal, before using it to compare Nd:YVO(4) and Nd:GdVO(4) crystals.

Highly efficient broadband double-sided Fresnel lens for THz range

Modern passive THz setups require effective optical elements with a large numerical aperture. Here we propose a new type of the optical element for THz applications, which is a broadband double-sided Fresnel-like lens with an optimized thickness. The optimization is performed to obtain a very low attenuation, low material cost, and small weight in the element media. It also provides achromatic properties for the assumed wavelength range. The experimental evaluation of the proposed diffractive lens by means of time-domain spectroscopy is presented and discussed.

Off-axis metallic diffractive lens for terahertz beams

A diffractive optical element for off-axis focusing of terahertz radiation is presented. It was designed in a nonparaxial regime and manufactured in a metal slab by laser cutting of curved stripes. The optical function of the structure includes focusing and deflecting the illuminating beam of a chosen frequency in a particular place. Therefore, the element acts as both a spatial and a spectral filter; hence it is especially suitable for separating the terahertz signal from a broadband thermal load in passive detection devices. The experimental evaluation of the proposed diffractive lens by means of time-domain spectroscopy is presented and discussed.

Observation of terahertz beam diffraction by fabrics

The structure of most of fabrics is an almost periodic network of interlaced yarns or threads, whose periodicity is of the order of the terahertz wavelength. We report here on the diffraction of terahertz electromagnetic waves by the yarn network in common cloths. In the case of linen, this effect could lead to overestimating (by a factor as large as 3) the absorption when determined from the classical terahertz time-domain experiment. Our results are confirmed by a HFSS numerical simulation.

Pulsed blue laser at 491nm by Nonlinear Cavity Dumping

A nonlinear cavity dumping process is applied for the first time to generate kW peak power pulses at 491 nm. The system is based on efficient sum-frequency mixing of 1063 nm and 912 nm radiations in a BiBO nonlinear crystal placed inside a Nd:GdVO4 laser oscillator with a high finesse cavity at 912 nm. The nonlinear cavity dumping process is triggered by high peak power nanosecond pulses from a 1063 nm Q-switched Nd:GdVO4 laser operating at 10 kHz. To reach the kW range at 491 nm a key point is to Q-switch the high finesse 912 nm cavity instead of continuous wave operation. Thus, the peak power (9.3 kW for 3 ns pulses) and the average power (280 mW) obtained at 491 nm are 14 times higher than the one obtained when the 912 nm laser operated in continuous wave.

First Demonstration of Neodymium True Three Level Laser Emitting at 879 nm

We present the first true three-level-laser based on an Nd-doped crystal. Emission at 879-nm in NdGdVO4 was studied in cw and pulsed regime. SHG was realized to reach blue range at 439.5-nm.

1064 nm oscillation under 914 nm intracavity pumping in Nd:YVO 4 and sum-frequency mixing to reach blue range

We present for the first time a Nd:YVO4 laser emitting at 1064-nm intracavity pumped by a 914-nm diode-pumped Nd:YVO4 laser. Intracavity sum-frequency operation is realized to reach blue range. We obtained 67-mW at 492-nm.

Generation of continuous-wave blue light by sum-frequency mixing of diode pumped dual-wavelength lasers

Simultaneous emissions were demonstrated with a Nd:GdVO/sub 4/ crystal (912-nm and 1063-nm) and with two crystals: Nd:YLF (1047-nm) and Nd:GdVO/sub 4/(912-nm). Blue light was generated by sum-frequency mixing up to 93-mW at 487-nm.

Gain competition in a dual-wavelength Nd:GdVO 4 laser at 1063 nm and 912 nm and intracavity sum-frequency

Simultaneous emissions were demonstrated with a Nd:GdVO4 crystal (912-nm and 1063-nm) and with two crystals: Nd:YLF (1047-nm) and Nd:GdVO4 (912-nm). Blue light was generated by sum-frequency mixing up to 93-mW at 487-nm.