Table 1.

Comparison between experimentally obtained second-order nonlinear susceptibility and theoretically calculated values, along with prior results obtained at other frequency³⁶.

Frequency	χ(2) (m/V, LN, extraordinary light)
	Theorya (ions)	Experimentb	Theorya (phonon polariton)
Visible light	4.0 × 10−11
THz wave	8.0 × 10−11	>1.58 × 10−6	~1.7 × 10−5
Microwave	6.7 × 10−9

^a Theoretical value (ions) is calculated by Lorentz model of ions, and theoretical value (phonon polariton) is calculated by nonlinear Huang equations, Eq. (1).

^b Experimental values for visible light and microwave are quoted from³⁶.