CLBO Crystal: The Optical Heart of Deep Ultraviolet Lasers

CLBO: the optical heart of deep-UV lasers

Deep-UV (DUV) solid-state lasers — sources below ~300 nm — are enabled by the nonlinear crystal that performs the final, hardest conversion step. For high-power 266 nm (the fourth harmonic of Nd:YAG) and shorter wavelengths, that crystal is almost always CLBO (CsLiB₆O₁₀), earning it the description of the "optical heart" of DUV systems.

Why CLBO is central to DUV

Generating 266 nm by fourth-harmonic generation demands a crystal that transmits deep into the UV, phase-matches at 266 nm, tolerates intense DUV flux, and accepts a tight focus. CLBO meets all four: it transmits to ~180 nm, has wide angular/spectral acceptance, small walk-off, and a high damage threshold — together delivering more DUV output at higher average power than BBO in the same role.

Where it is used

CLBO-based DUV sources power semiconductor inspection, finescale micromachining, UV Raman/fluorescence spectroscopy, and research DUV. For background see the CLBO deep-UV article and the CLBO product page.

Frequently asked questions

Why CLBO and not BBO for high-power 266 nm? CLBO's wider acceptance and higher DUV damage threshold give more 266 nm at high average power.

What limits CLBO? Its hygroscopic nature — it needs a dry, temperature-stabilised environment.