Polarimetry Crystal Electro-optical Performance

Presently, the electro-optical property of the crystal has been greatly applied in the opto-electrical industry. The application of the electro-optical Q-switch, electro-optical mode-locked technology can supply highly powerful and narrow pulse width laser supply. Considered the properties of the crystal, such as high electro-optical coefficient, high transmittance for the work wavelength, high optical quality, high voltage tolerance, low energy loss for the object wavelength, stable refractive index with the temperature changed, stable chemical and mechanism property, easy to get large crystal, only two crystals are the most availably electro-optical crystals: KD P and LiNbO₃, respectively. However, both of the crystals have their own limitations. KD P crystal is grown from aqueous solution, and is readily hygroscopic in air, so the crystal processing and application must be carried out with specific procedures in order to prevent hygroscopic. Furthermore, since KD^*P crystal is grown in a metastable phase, growth is difficult and takes a long time. LiNbO₃ crystal can be grown by the Czochralski method, but the optical damage threshold of LiNbO₃ crystal is low. As a consequence, LiNbO₃ crystal can be only used in low power laser systems.It is traditionally believed that the optically active crystal is not suitable for the electro-optical application. However, the Q-switch with optically active crystal La₃Ga₅SiO₁₄ (or LGS) has been achieved firstly by Institute of Crystal Materials, Shandong University in 2002. The former work of the Q-switch with LGS achieves some good results and obtains two nationals patents. The voltage-increased Q-switch with LGS has been achieved successfully. However, the other method to achieve the Q-switch, voltage-decreased has not been achieved successfully. Then, to achieve the voltage-decreased Q-switch is a big problem for the application of the optically active crystals in the electro-optical property.