After a brief examination of known insulating laser crystals and the stimulated emission channels of their generating activator ions, this article reviews recent advances in the development of novel lasing crystals and ceramics, as well as inorganic and organic nonlinear-laser crystals for χ(3) and cascaded χ(3) ↔ χ(2) frequency converters Several new modern attractive technologies in the physics and techniques of crystalline lasers are also discussed

https://onlinelibrary.wiley.com/doi/pdf/10.1002/lpor.200710008

Laser crystals and ceramics: recent advances

The quasi-three-level 912 nm continuous-wave laser emission under direct diode laser pumping at 880 nm into emitting level 4F3/2 of Nd:GdVO4 have been demonstrated. An end-pumped Nd:GdVO4 crystal yielded 8.1 W of output power for 13.9 W of absorbed pump power. The slope efficiency with respect to the absorbed pump power was 0.679. To the best of our knowledge this is the first demonstration of such a laser system. Comparative results obtained for the pump with diode laser at 808 nm, into the highly-absorbing 4F5/2 level, are given in order to prove the advantages of the 880 nm wavelength pumping.

https://iopscience.iop.org/article/10.1002/lapl.200910082/pdf

Highly efficient continuous-wave 912 nm Nd:GdVO4 laser emission under direct 880 nm pumping

https://iopscience.iop.org/article/10.1088/1361-6463/ab31d5/pdf

A review of terahertz detectors

We review the physical properties, linear and nonlin- ear optical characteristics, and phase-matching configurations of BiB3O6 (BIBO), the first low-symmetry (monoclinic) inor- ganic nonlinear crystal that has found broad applications for frequency conversion of laser sources from the UV, across the visible, to the near-IR based on three-wave interactions. We describe in detail the most relevant optical properties that make this material an attractive candidate for nonlinear frequency con- version of laser light in general, and ultrafast femtosecond laser sources in particular. With special focus on ultrafast frequency conversion, characteristics such as group-velocity mismatch and spectral acceptance, parametric gain bandwidth, group-velocity dispersion, as well as angular acceptance and spatial walk-off are evaluated and optimum configurations for the attainment of maximum conversion efficiency, minimum pulse duration, and highest spatial beam quality are identified and compared with the most widely established alternative borate crystal, β-BaB2O4. Experimental results are presented on both parametric up- and down-conversion of femtosecond pulses, from the high-energy, low-repetition-rate (1 kHz) to the low-energy, high-repetition- rate (56-76 MHz) regime, demonstrating the unique versatility of BIBO for efficient frequency conversion of femtosecond pulses with broad tunability from 250 nm in the UV, throughout the visible, up to ∼ 3000 nm in the IR. Photograph of a femtosecond synchronously pumped optical parametric oscillator (SPOPO) based on BiB3O6 emitting in the yellow region of the spectrum. Pumped near 400 nm in the blue by the second harmonic of a Kerr-lens mode-locked Ti:sapphire laser, the SPOPO can generate femtosecond pulses across the full visible range of 480-710 nm, from the blue-green, through to yellow, orange and red.

/pdf/femtosecond-nonlinear-frequency-conversion-based-on-bib3o6-3z7ng4rkvm.pdf

Femtosecond nonlinear frequency conversion based on BiB3O6

We describe the output performances of the 916 nm 4F3/2 → 4I9/2 transition in Nd:LuVO4 under in-band pumping with diode laser at the 880 nm wavelength, directly into the 4F3/2 emitting level. An end-pumped Nd:LuVO4 crystal yielded 11.7 W of continuous-wave output power for 23.5 W of absorbed pump power. The slope efficiency with respect to the absorbed pump power was 66.6%. Furthermore, 5.9 W 458 nm deep-blue light was acquired by frequency doubling, resulting in an optical-to-optical efficiency with respect to the absorbed pump power of 25.1%. Comparative results obtained for the pump with diode laser at 809 nm, into the highly-absorbing 4F5/2 level, are given in order to prove the advantages of the in-band pumping.

Quasi‐three‐level Nd:LuVO4 laser under diode pumping directly into the emitting level

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.

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

We present what we believe to be the first true three-level laser based on a Nd-doped crystal. From the 4F3/2-4I9/2 laser transition, the lower laser level being the ground state, emission at 879nm in NdGdVO4 has been obtained with diode pumping. Up to 0.8W of power has been achieved in cw operation and 24μJ per pulse (35ns) in the Q-switched regime. Intracavity second-harmonic generation in the pulsed regime is also demonstrated with 178mW of average output power at 439.5nm, corresponding to an energy of 17μJ per pulse.

/pdf/nd-gdvo4-as-a-three-level-laser-at-879-nm-47zyt2qa9r.pdf

Nd:GdVO4 as a three-level laser at 879 nm

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.

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

We present for the first time a Nd:YVO(4) laser emitting at 1064 nm intracavity pumped at 912 nm by a Nd:GdVO(4) laser. We carried out a model to design the system properly, and laser performance was experimentally investigated. Intracavity sum-frequency mixing at 912 and 1064 nm was then realized in a BiBO crystal to reach the blue range. We obtained a cw output power of 155 mW at 491 nm with a pump laser diode emitting 20 W at 808 nm.

/pdf/1064-nm-nd-yvo4-laser-intracavity-pumped-at-912-nm-and-sum-hdt7c1gk0f.pdf

1064 nm Nd:YVO4 laser intracavity pumped at 912 nm and sum-frequency mixing for an emission at 491 nm.

We present what is, to the best of our knowledge, the first diode-pumped Nd:YAG laser emitting at 899 nm and below, based on the 4F3/2 - 4I9/2 transition, generally used for a 946 nm emission. A power of 630 mW at 899nm has been achieved in cw operation and 16 mW at 884 nm with a fiber-coupled laser diode emitting 9 W at 808 nm. Intracavity second-harmonic generation in cw mode has also been demonstrated with a power of 100 mW at 450 nm by using a LiB3O5 nonlinear crystal.

/pdf/diode-pumped-nd-yag-laser-emitting-at-899-nm-and-below-2x5mexkytd.pdf

Emilie Hérault

Papers

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

Nd:GdVO4 as a three-level laser at 879 nm

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

1064 nm Nd:YVO4 laser intracavity pumped at 912 nm and sum-frequency mixing for an emission at 491 nm.

Diode-pumped Nd:YAG laser emitting at 899 nm and below.