Blue-pumped photorefractive optical transient detection with low-power femtosecond laser pulses

We demonstrate optical transient detection (OTD) via photorefractive two-wave mixing using visible femtosecond pulses. This technique utilizes a nonlinear crystal to perform OTD directly in the blue spectrum by employing second-harmonic generation (SHG) of high-repetition-rate infrared pulses. The approach enables measurement of phase variations in dynamic signals by using conventional Si-based detectors, while effectively minimizing stationary background fluctuations. Results show a correlation between input phases and output intensities, and condition for enhanced phase sensitivity under weak phase modulation. Additionally, we demonstrate that synchronization of blue pulses results in low-average-power requirement for OTD using a single nonlinear crystal.