Ultrathin femtometer for few-cycle pulses

The easy yet precise measurement of ultra-short intense femtosecond pulses is essential for a wide range of applications including attosecond physics, ultrafast material processing, and bioimaging. We present an in-line, attosecond-stable, ultrathin glass plate autocorrelator, which is capable of measuring few-cycle femtosecond (fs) pulses with ease using a phone camera. The ultrathin autocorrelator consists of a pair of micrometer thin identical glass plates that split the incident wavefront of femtosecond pulses with attosecond-resolved time delay between them over about an 80 fs delay range. Its performance is validated by accurate measurement of two kinds of femtosecond pulses: (i) 25±1fs pulses having about 0.3 mJ energy per pulse and (ii) 11±1fs pulses having 2 nJ energy using a phone camera and homemade software in agreement with the commercial specifications of the laser pulses. Our compact device can readily measure femtosecond pulses over a broad spectral range from visible to IR. Additionally, it is also useful to characterize few-cycle pulses entering space-constrained or alignment-sensitive situations such as ultrafast microscopy and attosecond pump-probe spectroscopy setups.