Passive Q-Switch Cr4+:YAG

Saturable Absorber Passive Q-Switch - Cr4+YAG - CR:YAG

General Information

Cr4+:YAG has become the solid-state passive Q-switch material of choice for 1 micron laser systems, offering several significant advantages over active acousto-optic and electro-optic devices, including:

  • Eliminates the need for a high voltage power supply
  • Reduce packaging size and weight
  • Improved reliability and a longer lifetime in 1064 nm Nd:YAG lasers.
  • Readily fabricated into high optical quality OEM components.

A small fraction of the chromium ions in YAG can be induced to change valence from the normal Cr3+ to Cr4+ with the addition of charge compensating impurities such as Mg2+ or Ca2+. The best measure of the Cr4+ concentration is the low power absorption coefficient alpha at 1064 nm. The typical values of alpha vary from 1-7 cm-1 for passive Q-switch applications.

Contact us with your specific requirements or for availability and pricing.

Standard Componet Specifications

Orientation <100> standard, <110> optional
Surface Flatness < λ/10
Surface Finish 10-5 Scratch-Dig (Per MIL-O-13830A)
Absorption Coefficient ( λ specific) 1.0 cm-1 — 7 cm-1
Coating AR @ 1064 nm (<0.2%)

Customer Supplied Specifications (Typical)

Diameter / Cross section <10 mm
Thickness 1-5 mm (+/- 1.0)mm
Specify Either:
Optical Density
Absorption Coeficient
% Transmission
0.1 to 0.8

1.0 cm-1 — 7 cm-1

10% to 90%

Material Properties

Charge compensating ion Ca2+
Crystal Structure Cubic
Molecular Weight 593.7 g mol-1
Melting Point 1965°C
Density 4.56 g cm-3
Thermal Expansion Coefficient 6.14 x 10-6 K-1
Thermal Conductivity 11.2 W m-1 K-1
Specific Heat (Cp) 0.59 J g-1 K-1
MOHS Hardness 8.2
Young’s Modulus 335 GPa
Tensile Strength 2 GPa
Thermal Shock Resistant 800 W m-1
Host Refractive Index @ 632.8 nm 1.83


1) Some fundamental theory is given by, A.E. Siegman, "Lasers", University Science Books, Mill Valley, CA (1986), Chapter 26

2) Practical devices are described by, W. Koechner, "Solid State Laser Engineering", Springer-Verlag, New York (1988). Chapter 8

3) A review article "Cr4+-doped crystals: their use as lasers and passive Q-switches" is given by, Y. Kalisky, Progress in Quantum Electronics 28 (2004) 249-303

4) A comprehensive reference for the optical properties of Cr4+ in YAG is given in A.G. Okhrimchuk and A.V. Shestakov, Optical Materials 3, 1-13 (1994)

Absorption Coefficient Chart

passive q-switch

Absorption Coefficient Calculator

Enter component thickness and your target small signal transmission.

Small Signal Transmission (%)

Thickness min (mm) =

Thickness max (mm) =

alpha Min (cm-1)

alpha Max (cm-1)

Data Sheet Downloads