You are here: Home » Products » Nonlinear and Laser Crystals » Passive Q-Switches

Passive Q-Switches

Passive Q-switches (saturable absorbers) provide high power laser pulses without electro-optic Q-switches, thereby reducing the package size and eliminating high voltage power supply.

EKSMA OPTICS offers few passive q-switching crystals: Co2+:MgAl2O4, Cr4+:YAG.

Co2+:MgAl2O4 (Co2+:Spinel or Co:MALO) is a relatively new material for passive Q-switching in lasers emitting from 1.2 to 1.6 µm, in particular, for eye-safe 1.54 µm Er:glass laser, but also works at 1.44 µm and 1.34 µm wavelengths. High absorption cross section (3.5 × 10-19 cm2) permits Q-switching of Er:glass laser without intracavity focusing both with flash-lamp and diode-laser pumping. Negligible excited-state absorption results in high contrast of Q-switch, i.e. the ratio of initial (small signal) to saturated absorption is higher than 10 (Figure 1).

Cr4+:YAG (Cr:YAG) is one of the best passive Q-switching crystal for high power lasers emitting at ~1 µm wavelength. Standard diameter apertures – 5, 8, 9.5 mm and various initial transmission (or optical density) are available upon request. Also Cr4+:YAG laser rods for ultra-short pulse solid-state lasers are available.

Finally, excellent optical, mechanical and thermal properties of the crystals give an opportunity to design compact and reliable laser sources with these passive q-switches.
Co2+:MgAl2O4 Cr4+:YAG
Working wavelength range, µm
 1.2-1.6 0.8–1.2
Absorption cross-section, cm2
 3.5×10-19
 (at 1.54 µm) 		5×10-18
(at 1.06 µm)
Initial transmittance, %
 30-99 20-99
Aperture, mm
 5-12 5, 8, 9.5
Thickness, mm
 1-5 1-5
Coatings*
 AR@1.54 µm, R<0.2% AR@1.06 µm, R<0.15%

Fe:ZnSe, Cr:ZnSe, Co:ZnS solid-state saturable absorbers are also available upon request.

Back