Variable repetition frequency asynchronous optical sampling method without a feedback loop

The ultrafast pump–probe measurement represents a key technique to study fs–ps dynamics. asynchronous optical sampling (ASOPS) method realizes fast and long time-range with high time resolution using different repetition frequency light pulses. difference Δ f is an important parameter, as it dictates the resolution. However, usual ASOPS measurements require complex precise stabilizer control or difficult change f. In this study, we use two free-running titanium/sapphire pulse lasers develop variable (VRF-ASOPS) without feedback loop, where can easily alter by changing cavity length of probe laser. To detect coincidences pulses, cause instantaneous reflectivity in 100 nm platinum film irradiating pump observe light. We signal trigger directly determine f, which enables us average convert measured responses loop. Using VRF-ASOPS system, obtain echo signals GHz Brillouin oscillations, are equivalent those mechanical delay line method, confirming validity our developed method.