LGS(La3Ga5SiO14 )is a multifunctional intraocular crystal that can be used as an electro-optic crystal after considering and studying the interaction between electro-optic effect and optical rotation in functional crystals. The LGS electro-optic Q switch passes light along the Z direction of the crystal and applies an electric field along the X direction, which can make full use of the lateral electro-optic effect of the crystal to realize the Q-switch function of the LGS crystal. The electro-optic Q-switch made by LGS is actually a new kind of rotation-electro-optical Q-switch. Because of the effect of optical rotation, it can be used as a practical switch and a good Q-modulation result can be obtained. LGS crystal widens the new direction of exploring and discovering new electro-optic crystals from optically active crystals.
| Point group | 32 |
| Airborne group | P32I |
| specific resistance | 4.0×1012Ω/cm-1 |
| Thickness | 0.13-0.5mm |
| Diameter | 50mm |
| Length | 90-100mm |
| Melting point | 1470℃ |
| Density | 5.67g/cm3 |
| Mohs hardness | 5.5 |
| Thermal expansion coefficient | aa=16×10-6/K, ac=4×10-6/K |
| Photo damage threshold | 670MV/cm2 |
| Cell Parameters | a=b=0.8162nm,c=0.5087nm |
| Dielectric constant | ε11=18.27 |
| ε33=55.26 | |
| Electro-optical coefficients | γ11=2.3×10-12m/V |
| γ33=1.8×10-12m/V | |
| Piezoelectric strain constant (10-12)C/N | d11=6.3 |
| d14=-5.4 | |
| Phase velocity,m/s | 2750～2850 |
| Electromechanical coupling coefficient, K[ %] | 0.28～0.46 |
| Solubility | None |
| Coefficient of thermal expansion | α11=5.15×10-6K-1 |
| α33=3.65×10-6K-1 |
| Maximum operating frequency | 50KHz | |
| Maximum output power | 7.5W | |
| Pulse width | 46ns | |
| Energy output -40℃ | 155mJ | |
| Energy output +50℃ | 163mJ | |
| Room temperature energy output | 167mJ | |
| Electro-optic conversion efficiency | 1.26% | |
Comparative properties of piezoelectric crystals
| Propertie | ||||
| Quartz | LGS | Li2B4O7 | LiTaO3 | |
| Electromechanical Coupling Factor K, %(BAW) | 7 | 15.8 | 24 | 47 |
| Frequency Spacing Δf, % | 0.25 | 0.9 | 4 | 7 |
| Q-Factor Q, ×103 | 100 | 50 | 10 | 2 |
| Temperature Frequency Coefficient TFC,×10-6/℃ | 0.5 | 1.6 | 6 | 4 |
SAW properties of langasite and Quartz
Properties | Quartz | LGS |
| Density, g/cm³ | 2.65 | 5.746 |
| SAW Velocity Vef, m/s | (0°, 132.75°, 0°) 3157 | (0°, 140°, 25°) 2756 |
| Electromechanical coupling factor K2emc, %(SAW) | 0.14 | 0.36 |
| Second order temp. coef.α2, ×10-8/℃ | -3.2 | -6.8 |
| Temp. Coef. TTO, ℃ | 25 | 23 |
| Dielectric Constant e | 4.92 | 27 |
| Power flow angle , ° | 0 | 0.5 |
| Constant | Relative Dielectric Constant | Piezoelectric Constant （pC/N） | Elastic Stiffness（1011 Pa） | |||||||
| ε11 | ε33 | d11 | d14 | c11 | c12 | c13 | c14 | C33 | C44 | |
| Value | 18.96 | 50.19 | 5.66 | -5.48 | 1.898 | 1.058 | 1.022 | 0.144 | 2.626 | 0.535 |
| First Order Temp. Coef.（10-6·K-1） | 150 | -760 | 329 | -342 | -66 | 204 | -75 | -335 | -94 | -63 |
High damage threshold
Good optical rotation
Can withstand high and low temperature changes
Stable physical and chemical properties
High electromechanical coupling coefficient (3 times of quartz)
Low equivalent series resistance
electro-optic Q-switch
SAW device
BAW device
Sensor
High power high repetition rate all solid state laser
High and low temperature change laser