Abstract
Mode-locked (ML) lasers are extensively used in many areas of physics such as nonlinear optics and time-resolved spectroscopy. ML operation of high-power high-repetition-rate lasers is usually achieved by acoustooptic modulators. Our aim is to demonstrate that an electrooptic ring modulator (EORM),1 shown in Fig. 1 within the dashed line, allows achieving efficient ML of cw Nd:YAG lasers both in Q-switching (QS) and cavity-dumping (CD) modes. Our EORM consists of two dichroic high-reflectivity plane mirrors M2 and M3, a LiNbO3 Pockels cell (PC), and a McNeille polarizer P. In Fig. 1 is shown our cw Nd:YAG laser that uses as an output coupler an EORM acting as ML, QS, and CD. The ¼-×¾-in. Nd:YAG rod is continuously pumped within a gold-plated elliptical reflector. The laser resonator that has a cavity round-trip time equal to 6,3 ns is terminated in a total reflecting convex 1-m radius-of-curvature mirror to compensate the rod lens effect. By using the Jones formalism we find that the field reflection coefficient of the EORM is, except for a constant phase factor, given by (1) where rs, rp are the electromagnetic field complex reflection coefficients for s and p polarizations, respectively, and ϕ(t) is the ratio between the applied PC voltage V(t) and V(λ/2). By evaluating Eq. (1) for the values of our EORM optical component coefficients we find that the intensity field reflectivity varies from 10 to 0.9 when the PC applied voltage varies from zero to V(λ/2) = 2700 V. EORMs, because of their polarization flipping behavior, can reflect s- and p-polarized electromagnetic fields only as p and s, respectively.
© 1986 Optical Society of America
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