Intracavity pumped Yb: SFAP crystal emitting at 985 nm and second harmonic generation [6871-56]
Oxxius Yb:SFAP intracavity laser sources today
Presented at SPIE Photonics West 2008 (proceedings reference 6871-56), this paper reports Yb:SFAP 985 nm intracavity pumping in a co-lasing Nd:YVO₄ cavity, combined with second harmonic generation to produce compact blue-green output at 492.5 nm. This SPIE conference paper is the companion contribution to the Optics Letters 2008 journal paper on the same architecture, providing additional experimental characterization of the Yb:S-FAP crystal performance under intracavity pumping conditions.
The Yb:S-FAP (Ytterbium-doped Strontium Fluorapatite) crystal is an unusual gain medium for this wavelength range: its three-level transition at 985 nm is normally difficult to reach efficiently due to strong reabsorption at room temperature. The intracavity pumping scheme overcomes this barrier by exposing the Yb:SFAP crystal to the intense intracavity field of a co-lasing Nd:YVO₄ source at 914 nm — effectively providing a pump intensity orders of magnitude higher than what an external diode could deliver at the crystal facet. This enables efficient 985 nm oscillation, which is then frequency-doubled in a nonlinear crystal to yield 492.5 nm output.
Significance for compact visible laser design
The 492.5 nm wavelength is of direct interest for fluorescence microscopy and flow cytometry, where it provides an alternative excitation line to the standard 488 nm argon source with slightly better spectral separation from GFP emission. The intracavity co-lasing architecture demonstrated here — combining Nd:YVO₄ and Yb:SFAP in a single cavity with an intracavity SHG crystal — represents one of the most compact paths to this wavelength. This research contributes to Oxxius’s broader expertise in nonlinear frequency conversion and underpins the CW & Modulated Laser product line covering the blue-green spectral range.
Abstract
We present what is, to the best of our knowledge, the first experiment of intracavity pumping at 914 nm of an
Yb:SFAP crystal emitting at 985 nm on the three-level laser transition. This configuration enabled us to indirectly
diode-pump this ytterbium doped crystal, and to obtain 1.4 W output power at 985 nm for 20 W of incident pump
power at 808 nm. Intracavity second harmonic generation has also been demonstrated in a KNbO3 crystal with a
total of 120 mW linearly polarized output power at 492.5 nm on two output beams.
Keywords: Diode-pumped lasers, Neodymium lasers, Ytterbium lasers, visible lasers