Potassium titanyl phosphate crystal (KTiOPO₄, KTP) is a well-known nonlinear optical material for efficient frequency conversion of laser radiation in the near- and mid-infrared range. The popularity of KTP originates in its high laser-induced damage threshold of up to 30 GW/cm²(single-shot measurement with 8.5 ns pulses at the wavelength of 1.064 µm), wide transparency range of 0.35−4.5 µm, sufficiently high nonlinear optical coefficients of d31 = 2.2 pm/V, d32 = 3.7 pm/V and d33 = 14.6 pm/V, and possibilities of manufacturing periodically poled structures in the crystal. Presently, KTP is considered a promising material for converting infrared (IR) laser radiation to terahertz waves.

Transmitting Range:	350nm ~ 4500nm
Phase Matching Range:	984nm ~ 3400nm
Refractive Index:	@1064nm	1.7377(n_x)	1.7453(n_y)	1.8297(n_z)
	@532nm	1.7780(n_x)	1.7886(n_y)	1.8887(n_z)
Sellmeier Equations:(l in µm)	N_x² = 3.0065 + 0.03901 / ( l² - 0.04251) - 0.01327l²
	N_y² = 3.0333 + 0.04154 / ( l² - 0.04547) - 0.01408l²
	N_z² = 3.3134 + 0.05694 / ( l² - 0.05658) - 0.01682l²
Therm-Optic Coefficient:(10^-5/°C)	dn_x/dT=1.1		dn_y/dT=1.3	dn_z/dT=1.6
Absorption Coefficient:	a<1%/cm @1064nm and 532nm
Nonlinear Optical Coefficients and Equation:	@1064nm	d₃₁=2.54pm/V	d₃₂=4.35pm/V	d₃₃=16.9pm/V
		d₂₄=3.64pm/V	d₁₅=1.91pm/V
	d_eff(II)=(d₂₄-d₁₅)sin2f sin2q - (d₁₅sin²f +d₂₄cos²q )sinq
Electro-optic coefficients:	Low Frequency(pm/V)		High Frequency(pm/V)

Reference

1. Terahertz Optical Properties of KTiOPO4 Crystal in the Temperature Range of (−192)–150 ◦C, Crystals 2021, 11(2), 125

2. Flux Growth and External Morphology of KTiOPO4 Crystals, Cryst. Growth Des. 2009, 9, 2, 1190–1193