Second Harmonic Generation

The Sirah Frequency Conversion Unit (FCU) is designed to frequency double a dye laser beam. Typically, the dye laser is operated in the visible spectral range. This frequency is doubled by a BBO crystal followed by a compensator. The crystal’s angle is tuned to maintain phase matching inside of the crystal. An arrangement of 2 or 4 Pellin-Broca prisms (WS-2 or WS-Auto, please order separately) separates the UV from the fundamental beam. The FCU may be integrated into the laser housing (not possible for the Cobra model) or attached externally to the laser (add FC-EXH housing). All crystals, compensators and Pellin-Broca prisms are fully adjustable, making the unit easy to use.

Optical Layout


Tuning Range

Tuning curves for the frequency doubled dye laser. Left: Dye laser pumped with 375 mJ @ 355 nm. Right: Dye laser pumped with 650 mJ @ 532 nm. At a given wavelength full energy is only obtained if resonator configuration is suited.

Wavelength Range

Crystal Material Separation Tuning Range 1)
1) Tuning range of crystal, further limitation due to resonator configuration is possible
2) Absorption losses of UV energies are lower for WS-2 (two Pellin-Broca prisms). WS-Auto may be converted to WS-2 by removing 2 prisms.
SHG-280 BBO WS-2 / WS-Auto 280 .. 450 nm
SHG-250 BBO WS-2 / WS-Auto 250 .. 380 nm
SHG-215 BBO WS-2 / WS-Auto 215 .. 280 nm
SHG-XXL BBO WS-2 / WS-Auto 220 .. 300 nm
SHG-206 BBO WS-22) ~206 .. 220 nm

Energy Output

UV Wavelength Pump Laser Output Energy  
353 nm 650 mJ @ 532 nm 14.6 mJ  
308 nm 650 mJ @ 532 nm 39.0 mJ  
283 nm 650 mJ @ 532 nm 39.0 mJ  
226 nm3) 375 mJ @ 355 nm 6.75 mJ  
214 nm3) 375 mJ @ 355 nm 6.56 mJ  
3) Using WS-2
See tuning curves for energies at other wavelengths.

General Characteristics

Repetition Rate 10 – 50 Hz recommended, contact Sirah for specifications at higher rates
Crystal Tuning Mode Look-up table (Autotracking optional)
Temperature Stabilization Crystal temperature stabilisation is recommended for systems with repetition rate above 20 Hz, or pump energies greater 500 mJ @ 532 nm / 250 mJ @ 355 nm
Compensators C-BBOL for all BBO crystals
UV Beam Polarization Horizontal, >98%
UV Beam Diameter (typical) 3 – 6 mm, depending on amplifier cell type
UV Beam Divergence < 0.5 mrad
Linewidth < 1.5 x Dye Laser Linewidth / cm-1

Dimensions External Housing (FC-EXH)

All Dimensions in mm. Specifications are subject to change without notice.

Literature & Downloads

Datasheet SHG