CLBO Crystal for Deep Ultraviolet Solid-State Lasers

CLBO (cesium lithium borate, CsLiB₆O₁₀) is a nonlinear crystal built specifically for the deep ultraviolet (DUV). It efficiently generates the fourth harmonic of Nd:YAG at 266 nm and, through further sum-frequency mixing, reaches shorter DUV wavelengths that are difficult or inefficient with BBO and LBO. Its combination of short-wavelength transparency, wide angular acceptance and high damage threshold makes CLBO the crystal of choice for high-power DUV solid-state lasers.

Why DUV systems need CLBO

Producing DUV light by frequency conversion is hard because most crystals become absorptive or phase-match poorly below ~300 nm, and because DUV photons damage the crystal. CLBO addresses both: it transmits down to roughly 180 nm, supports phase matching for 266 nm fourth-harmonic and 236/199 nm mixing, has a large angular and spectral acceptance bandwidth (so tight focusing and angle tolerance are less critical), a small walk-off, and a high laser-damage threshold — together giving more DUV output at higher average power than BBO in the same role.

Application areas

CLBO-based DUV lasers serve semiconductor inspection and metrology, finescale micromachining and marking (where the short wavelength enables tiny feature sizes), UV resonance Raman and fluorescence spectroscopy, and research sources needing compact, high-brightness DUV. For the 1064→532/355 nm stages that feed a CLBO 4th-harmonic stage, designers typically use LBO and BBO — see our BBO vs LBO vs KTP comparison.

CLBO vs BBO for the deep UV

BBO can reach 266 nm but with a smaller angular acceptance, larger walk-off and lower conversion at high average power. CLBO's wider acceptance and higher damage threshold give it the edge for high-power 266 nm and shorter wavelengths. The trade-off is that CLBO is more hygroscopic and must be kept dry and temperature-stabilized, and is softer mechanically — so handling and packaging matter more.

Frequently asked questions

Which crystal for 266 nm? CLBO is preferred for high-power 266 nm fourth-harmonic generation; BBO works at lower power where its narrower acceptance is manageable.

Is CLBO hard to handle? It is hygroscopic, so it needs a dry, temperature-controlled cell — AOG supplies CLBO with suitable coating and can advise on packaging.

Can CLBO go below 266 nm? Yes — via further sum-frequency mixing it can reach ~236 nm and shorter, supporting advanced DUV sources.

For CLBO cut and coated for your DUV wavelength, contact sales@aogcrystal.com — see also the CLBO product page.