Intensity dependent residual amplitude modulation in electro-optic phase modulators.
Residual amplitude modulation (RAM) mechanisms in electro-optic phase modulators are detrimental in applications that require high purity phase modulation of the incident laser beam. While the origins of RAM are not fully understood, measurements have revealed that it depends on the beam properties of the laser as well as the properties of the medium. Here we present experimental and theoretical results that demonstrate, for the first time, the dependence of RAM production in electro-optic phase modulators on beam intensity. The results show an order of magnitude increase in the level of RAM, around 10 dB, with a fifteenfold enhancement in the input intensity from 12 to 190  mW/mm2. We show that this intensity dependent RAM is photorefractive in origin.
Applied Optics and Nanotechnology Group, School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, PO Box 2434, Brisbane, Queensland 4001, Australia. juna.sathian@qut.edu.au
Juna
J
Sathian
Esa
E
Jaatinen