Development of an optical pulsing by using pockels effect

Abstract

Laser produced from active medium is normally in continuous mode. The beam can be modulated by inserting switching mechanism. An electro-optic mechanism is one of the techniques used to alter the operation of laser beam from continuous into pulse mode. Hence, the objective of this project is to develop an optical switch system by using Pockels effect. Helium-Neon (He-Ne) laser was used as continuous light source in the project. Calcite and quartz crystals were employed as natural birefringent materials. While a synthetic birefringent material, lithium niobate was used as a Pockels cell. The lithium niobate crystal can become birefringent only through the application of electric field. Therefore, several pulse generators were developed and used to trigger an electrooptic driver to electrify the lithium niobate crystal. A Pockels cell house was designed and fabricated by using perspex. The Pockels cell house was completed with electrodes. The performance of the fabricated Pockels cell was compared to the commercial Pockels cell. Both of the Pockels cells exhibited similar characteristic, whereby the linear polarization state of laser light was turned into circular state when it entered the electrified Pockels cells with a : b ratio of 1.0 : 1.0 (2 kV and 3 kV voltage applied) and 1.1 : 1.0 (4 kV voltage applied). This converts the continuous He-Ne beam into pulse mode. The generation of the laser pulse can be operated either in a single or repetitive mode. It depends on the frequency of the pulse generator. The amplitude of the produced laser pulse was increased by increasing the voltage supplied to electrify the lithium niobate crystal. The amplitude of the produced laser pulse by using transverse Pockels cell was 500 mV, 700 mV and 1000 mV at 2 kV, 3 kV and 4 kV applied voltage. While the result obtained by using commercial Pockels cell was 700 mV, 900mV and 1200 mV.