In this paper the polarized optical spectra (absorption and fluorescence) of the Nd 3+ ion in the YAl 3 (BO 3 ) 4 nonlinear crystal have been systematically investigated at low (10 K) and room temperature. Most energy levels of Nd 3+ in this crystal ( 103) have been identified and conveniently labelled with their crystal field quantum numbers, µ = 1/2 and µ = 3/2. The radiative emitting states have been identified. Analysing the optical absorption spectra with the anisotropic Judd-Ofelt theory, the radiative lifetimes and branching ratios from the metastable state 4 F 3/2 have been calculated. Then, relevant spectroscopic parameters (quantum efficiency and emission cross sections) for laser applications have been estimated. Infrared to visible up-conversion is reported for the first time in this host crystal.

Laser radiation corresponding to the three fundamental colors (red, green, and blue) has been generated from the same Nd:YAl3(BO3)4 crystal, operating on a fundamental laser wavelength of 1338 nm in an end-pumping configuration. Continuous wave generation was obtained by pumping with a tunable Ti: sapphire laser. Red (669 nm) has been obtained by self-frequency doubling of the fundamental laser line. Green (505 nm) and blue (481 nm) have been obtained by self-sum-frequency mixing of the fundamental laser radiation at 1338 nm and the pump radiation (807 nm for green and 755 nm for blue).

Stable continuous-wave laser action in the near-infrared and in the green spectral region has been obtained in a self-frequency doubling solid-state laser, the Yb3+:MgO:LiNbO3 nonlinear crystal. By pumping with a Ti:sapphire laser and using a nearly concentric cavity, laser action at 1.06 μm was achieved with an absorbed power threshold of 101 mW and efficiency around 47%. As much as 60 mW of self-frequency-doubled radiation at 530 nm was also obtained with absorbed pump powers of 800 mW in critical cavity alignment. Efficient laser action was also obtained in the near-infrared region under pumping with diode laser.

Simultaneous generation of red, green, and blue continuous-wave laser radiation in a Nd3+-doped aperiodically poled lithium-niobate crystal is reported. Red (686 nm) and green (542 nm) are obtained by self-frequency-doubling fundamental infrared laser lines at 1084 and 1372 nm oscillating simultaneously. Blue (441 nm) is obtained by self-sum-frequency mixing of end-pump laser radiation at 744 nm and the fundamental laser line at 1084 nm. Other laser lines at 605 nm (orange) and 482 nm (blue) are simultaneously obtained by self-sum-frequency mixing of both infrared fundamentals and by self-sum-frequency mixing of pump laser radiation with the remaining fundamental line at 1372 nm, respectively. A weaker violet (372 nm) laser emission results from frequency doubling of the pump radiation.

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