Tilted-pulse time-resolved off-axis digital holography

In this Letter we present an improvement of time-resolved off-axis digital holography by the use of tilted femtosecond laser pulses. The pulse front tilting of the reference beam with respect to the phase front allows larger crossing angles to be used for recording of digital holograms without significant reduction of pulse interference area (typically limited by low temporal coherence of ultrashort pulses). Such approach increases the area of interference fringes, thus enabling the higher resolution of the reconstructed image as well as better separation of dc term. Temporal resolution is not deteriorated by this method, as only the reference pulse is tilted. The proposed technique was applied for direct intensity clamping observations of light filaments in water using the laser pulses of 30 fs duration.