Long-term and wideband laser intensity stabilization with an electro-optic amplitude modulator

This paper aims at two practical design issues encountered with electro-optic amplitude modulators, namely (1) the long-term optical power drift when a single electro-optic crystal is used and (2) the mechanical resonances of the crystal that limit the control bandwidth. We investigated an active control scheme using a single crystal to offset the drifts of different origins such as polarization, crystal birefringence, and electronics. The control system worked continuously for at least 15 h without interruption and a power instability of 8 x 10(-4) was achieved in a 3-h measurement. This technique can be employed in electro-optic applications where two matched crystals are usually used to compensate the birefringence-related drifts. Meanwhile, mechanical resonances in two crystals (LiNbO3 and KTiOPO4) were mapped out and their influences on the control bandwidth were quantitatively investigated. Residual noises of two intensity-stabilized lasers (a Helium-Neon laser and a dye laser) were analyzed in detail. (c) 2012 Elsevier Ltd. All rights reserved.