Ultra-Thin BBO for Ultrafast Lasers

For frequency conversions of ultrafast lasers with femtosecond ( fs ) pulsewidth, one of the the main concerns is pulse broadening induced by group velocity ( Vg ) mismatch or group velocity dispersion of NLO crystal. In order to avoid pulse broadening, the thickness of the crystal should not exceed the maximum length ( Lmax) as defined by the pulsewidth divided by the inversed group velocity mismatch ( IGVM = ΔVg-1 ). The table below lists the Lmax for 10 fs pulses at the wavelength range of a Ti:Sapphire laser,
the most popular ultrafast laser. Check BBO orientation here

Type I PM in BBO Crystals	SHG @ 700 nm	SHG @ 800 nm	SHG @ 900 nm	SFG @ 700 nm + 350nm	SFG @ 800 nm + 400 nm	SFG @ 900 nm + 450nm
IGVM (ps/cm)	2.721	1.922	1.401	8.497	5.676	4.079
Lmax @ 10fs (µm)	40	50	70	10	18	25

Apparently a thickness of sub-100 µm ( 0.1 mm) is desired. In particular, crystals as thin as 10-20 µm may be needed for reaching short wavelengths.

Newlight Photonics Inc. can provide BBO crystals as thin as 10 µm (0.01 mm) for frequency conversion of ultrafast pulses.

We also supply birefringent calcite plates and alpha-BBO plates for temporal walkoff ( time delay ) compensation, please contact us for details.

Standard Products

Part No.	Width x Height x Thickness	Coating	Application
BTC2511	5 x 5 x 0.01 mm	P-coating	SHG @ 800 nm
BTC2512	5 x 5 x 0.02 mm	P-coating	SHG @ 800 nm
BTC2515	5 x 5 x 0.05 mm	AR@800/400nm or P-coating	SHG @ 800 nm
BTC2521	5 x 5 x 0.1 mm	AR@800/400nm or P-coating	SHG @ 800 nm
BTC2522	5 x 5 x 0.2 mm	AR@800/400nm or P-coating	SHG @ 800 nm
BTC2525	5 x 5 x 0.5 mm	AR@800/400nm or P-coating	SHG @ 800 nm
BTC2531	5 x 5 x 1.0 mm	AR@800/400nm or P-coating	SHG @ 800 nm
BTC3511	5 x 5 x 0.01 mm	P-coating	SFG @ 800nm + 400nm
BTC3512	5 x 5 x 0.02 mm	P-coating	SFG @ 800nm + 400nm
BTC3515	5 x 5 x 0.05 mm	AR@800/400/267nm or P-coating	SFG @ 800nm + 400nm
BTC3521	5 x 5 x 0.1 mm	AR@800/400/267nm or P-coating	SFG @ 800nm + 400nm
BTC3525	5 x 5 x 0.5 mm	AR@800/400/267nm or P-coating	SFG @ 800nm + 400nm
BTC3531	5 x 5 x 1.0 mm	AR@800/400/267nm or P-coating	SFG @ 800nm + 400nm

Coating

We provide protective coatings or AR coatings @ 800nm and its harmonics. Please specify your requirement if coatings at the other wavelengths are needed.

Substrate

Crystals of thickness less than 100 µm are supplied optically contacted on UV fused silica substrates with a typical thickness of 1.5mm. It is recommended that the ultrafast pulses are incident on the crystal side.

Mount

For customer convenience and protection of ultrathin crystals, all ultrathin crystals are pre-mounted on a 1" ( 25.4 mm ) anodized aluminum (Al) holder. A standard 1" mirror mount may be conveniently used to tune the crystals for optimized frequency conversions.
( Mirror mount and post are not included)

Specifications on finished ultrathin BBO

Wavefront distortion:	less than λ/8 @ 633 nm
Clear aperture:	> 90% central area
Flatness:	λ/8 @ 633 nm
Surface quality:	10/5 Scratch/Dig per MIL-O-13830A
Parallelism:	better than 20 arc seconds
Perpendicularity:	15 arc minutes
Angle tolerance:	Δθ < 0.25o, Δφ < 0.25o