Abstract

A ${\mathrm{LiNbO}}_3$-loaded microwave cavity pumped with weakly AM-modulated 30 fs optical pulses was used as a platform to investigate AM-to-PM conversion in the optical rectification process. Theoretical treatment of AM-to-PM conversion (i.e., peak-induced electrical phase deviation ${\beta }_i$ due to optical power modulation with index $m$) suggests that the dominant mechanism is self-group-velocity modulation due to ${\chi }^{(3)}$ and cascaded ${\chi }^{(2)}$ processes with a value of $\delta ={\beta }_i/m=-151\mathrm{dB}$, linearly dependent on the optical power at intensities of $6\times {10}^{10}\mathrm{W}/{\mathrm{m}}^2$ in a 40 mm long ${\mathrm{LiNbO}}_3$ crystal. This is in stark contrast to p-i-n photodiodes which can exhibit an AM-to-PM conversion gain $\delta >0\mathrm{dB}$. In this experiment, we measured values of $\delta$ for a resonant optical rectification detector using typical mode-locked Ti:sapphire laser pulses (100 MHz, 30 fs, $P_{\mathrm{avg}}\approx 100\mathrm{mW}$) and found an instrumentation-limited lower bound of $\delta \approx -43.5\mathrm{dB}$, independent of the optical power.

© 2017 Optical Society of America

Self-group-velocity modulation and AM-to-PM conversion in optical rectification

Brian H. Kolner and Lanbing Kang
J. Opt. Soc. Am. B 34(2) 307-314 (2017)

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