Single-shot diagnostics of femtosecond bright squeezed vacuum pulses

Bright squeezed vacuum (BSV) is taking the squeezed quantum vacuum state of light to extreme intensities. With the use of an ultrashort pump laser and spontaneous parametric down conversion process, a super bright, squeezed quantum light source is produced, reaching 1010 - 1012 photons per pulse. However, due to the fact that each pulse of BSV is different in intensity and spectrum, conventional pulse characterization tools have struggled to measure BSV accurately. Here we report, for the first time, a full single-shot characterization of the temporal properties of BSV (amplitude and phase), revealing an ultrashort, broadband pulse. Using a fully characterized coherent reference pulse and spectral analysis, we perform single-shot interferometry measurements, retrieving the BSV spectrum and spectral phase. We report a nearly-transform limited single-mode BSV with roughly 40fs pulse duration, almost 4 times shorter than the original driving pump. Single-shot-resolved BSV has the potential to enable attosecond spectroscopy measurements near or above the conventional damage threshold of materials. 

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