Temporal optics is an emerging field in which optical signals are considered similarly to objects in spatial optics. Indeed, temporalmagnifications, temporal Fourier transform, and temporal signal processing have been demonstrated by adopting optical schemes from space to time. However, temporal imaging has so far focused on the equivalent of two-dimensional spatial imaging schemes, while ignoring the depth of the input. Here we adopt the concept of threedimensional (3D) imaging into the time domain, providing a new dimension in temporal optics. We developed the concept of temporal 3D objects and demonstrated temporal depth imaging. First, we define signals with temporal depth as signals where each point in time has a different dispersion value. Next, we demonstrate how to measure these signals with a moving time lens. Finally, we present a time lens array and use it to realize temporal depth imaging with a single measurement. Our temporal depth imaging concept will enable measurements of ultrafast nonperiodic phenomena, such as optical rogue waves and the evolution of ultrafast pulses in fiber lasers, with temporal resolution that was not possible until now.
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© 2017 Optical Society of America.