Single-shot optical recorder with sub-picosecond resolution and scalable record length on a semiconductor wafer

We demonstrate a novel, single-shot recording technology for transient optical signals. A resolution of 0.4 ps over a record length of 54 ps was demonstrated. Here, a pump pulse crossing through a signal samples a diagonal "slice" of space-time, enabling a camera to record spatially the time content of the signal. Unlike related χ⁽²⁾-based cross-correlation techniques, here the signal is sampled through optically pumped carriers that modify the refractive index of a silicon wafer. Surrounding the wafer with birefringent retarders enables two time-staggered, orthogonally polarized signal copies to probe the wafer. Recombining the copies at a final crossed polarizer destructively interferes with them, except during the brief stagger window, where a differential phase shift is incurred. This enables the integrating response of the rapidly excited but persistent carriers to be optically differentiated. This sampling mechanism has several advantages that enable scaling to long record lengths, including making use of large, inexpensive semiconductor wafers, eliminating the need for phase matching, broad insensitivity to the spectral and angular properties of the pump, and overall hardware simplicity.