The bandwidth of pulses generated by optical rectification is limited by the laser pulse duration, terahertz absorption in the crystal material, the thickness of the crystal, and a mismatch between the propagation speed of the laser pulse and the terahertz pulse inside the crystal.
12.
Where \ chi ^ { ( 1 ) } is the linear susceptibility, \ chi ^ { ( 2 ) } is the second-order susceptibility ( describing phenomena such as the Pockels effect, optical rectification and second-harmonic generation ), and \ chi ^ { ( 3 ) } is the third-order susceptibility ( describing third-order effects such as the Kerr effect and electric field-induced optical rectification ).
13.
Where \ chi ^ { ( 1 ) } is the linear susceptibility, \ chi ^ { ( 2 ) } is the second-order susceptibility ( describing phenomena such as the Pockels effect, optical rectification and second-harmonic generation ), and \ chi ^ { ( 3 ) } is the third-order susceptibility ( describing third-order effects such as the Kerr effect and electric field-induced optical rectification ).
