LiNbO3(LN) Electro-Optical Q-Switch Crystal

22 May 2019

Description

LiNbO3 crystal has been widely used in optical waveguide and optical communication technology because of its excellent electro-optical properties. It is an ideal substrate material for many integrated optoelectronic devices. Because of the large electro-optic coefficient of LiNbO3, the half-wave voltage is low. The electro-optic effect of LiNbO3 crystal is usually used to modulate the optical signal. Electro-optic modulation is divided into longitudinal and transverse, and LiNbO3 is mainly used in transverse modulation. It has been widely used in medium and low power solid-state lasers.

Parameter

Physical and optical properties

Chemical formula	LiNbO3
Crystal structure	trigonal
Space group	R3C
Density	4.64 g/cm3
Mohs hardness	5
Optical homogeneity	~ 5 x 10-5 / cm
Transparency range	420 – 5200 nm
Absorption coefficient	~ 0.1 % / cm @ 1064 nm
Refractive indices at 1064 nm	ne = 2.146, no = 2.220 @ 1300 nm
	ne = 2.156, no = 2.232 @ 1064 nm
	ne = 2.203, no = 2.286 @ 632.8 nm
Sellmeier equations (λ, μm)	no2 = 4.9048 + 0.11768 / (λ2 – 0.04750) – 0.027169λ2
Sellmeier equations (λ, μm)	ne2 = 4.5820 + 0.099169 / (λ2 – 0.04443) – 0.021950λ2
Thermal expansion coefficient @ 25 °C	//a, 2.0 x 10-6 / K
Thermal expansion coefficient @ 25 °C	//c, 2.2 x 10-6 / K
Thermal conductivity	~ 5 W/m/K @ 25 °C
Thermal optical coefficient	dno/dT = -0.874 x 10-6 / K at 1.4 µm
Thermal optical coefficient	dne/dT = 39.073 x 10-6 / K at 1.4 µm

LiNbO3 General specification for Q-Switch

Refractive retardation	Γ=лLnr22V/λd
Electro-optic coefficients	R33=32pm/V
	R31=10pm/V
	R22=6.8 pm/V
Aperture	4x4mm ~ 9x9mm
Length	15~25mm
Tolerance of size	+/-0.1mm
Chamfer
Accuracy of orientation
Parallelism
Flatness	l/8 at 632.8 nm
Wavefront Distortion	<l/4 at 632.8 nm
Extinction Ratio	>400:1 @ 633nm, dia 6mm beam

LiNbO3 specification for Optical waveguide

Operating wavelength range	1.525-1.605μm
Extinction ratio	＜20dB
Half wave voltage	＜6V
DC bias voltage	＜8V
Input characteristic impedance	50Ω
Light reflection	≤-50dB
Maximum input electric power	20dBm
Maximum input optical power	10-100mW
Storage temperature	-40-85℃
Operating temperature	-40-70℃

piezoelectric property

Elastic stiffness coefficient cij/(1010N/m2)	c11	c12	c13	c14	c33	c44
Elastic stiffness coefficient cij/(1010N/m2)	20.3	5.3	7.5	0.9	24.5	6.0
Elastic compliance coefficient sij/(10-12m2/N)	S11	S12	S13	S14	S33	S44
Elastic compliance coefficient sij/(10-12m2/N)	5.78	-1.01	-1.47	-1.02	5.02	17.0
piezoelectric strain constant dij/(10-11C/N)	d11	d15	d22	d31	d33
piezoelectric strain constant dij/(10-11C/N)	8	7.4	2.04	-0.086	1.62
dielectric constant	εT11/ε0	εT11/ε0
dielectric constant	78	32
Electromechanical coupling coefficient kij(%)	k15	k31
Electromechanical coupling coefficient kij(%)	68	50

Nonlinear Optical Properties

NLO Coefficients	d33 = 34.4 pm/V
	d31 = d15 = 5.95 pm/V
	d22 = 3.07 pm/V
Efficiency NLO Coefficients	deff =5.7 pm/V or ~14.6 x d36 (KDP) for frequency doubling 1300 nm;
	deff =5.3 pm/V or ~13.6 x d36 (KDP) for OPO pumped at 1064 nm;
	deff =17.6 pm/V or ~45 x d36 (KDP) for quasi-phase-matched structure.
Electro-Optic Coefficients	gT33 = 32 pm/V, gS33 = 31 pm/V,
	gT31 =10 pm/V, gS31=8.6 pm/V,
	gT22 = 6.8 pm/V, gS22= 3.4 pm/V,
Half-Wave Voltage, DC Electrical field\|\|z, light ^z: Electrical field\|\|x or y, light\|\|z:	3.03 KV
	4.02 KV

Damage Threshold	100 MW/cm2 (10 ns, 1064nm)

Standard Specifications of laser grade LiNbO3 crystals

Transmitted wavefront distortion	better than l/4 @ 633nm
Dimension tolerance	(W±0.1mm) x (H±0.1mm) x (L±0.2mm)
Clear aperture	over 90% central diameter
Flatness	l/8 @ 633nm
Surface quality	20 /10 Scratch/Dig
Parallelism	better than 20 arc sec
Perpendicularity	5 arc min
Angle tolerance	Dq < 0.5o, Df < 0.5o
AR-coating	dual wave band AR coating at 1064/532 nm on both surfaces, with R < 0.2% at 1064 nm and R < 0.5% at 0.532 nm per surface