Abstract
We introduce a spectral-interferometry (SI) technique for measuring the complete intensity and phase of relatively long and very complex ultrashort pulses. Ordinarily, such a method would require a high-resolution spectrometer, but our method overcomes this need. It involves making multiple measurements using SI (in its SEA TADPOLE variation) at numerous delays, measuring many temporal pulselets within the pulse, and concatenating the resulting pulselets. Its spectral resolution is the inverse delay range--many times higher than that of the spectrometer used. Our simple proof-of-principle implementation of it provided 71 fs temporal resolution and a temporal range of 100 ps using a few-cm low-resolution spectrometer.
Highlights
The version of MUD TADPOLE that we discuss here is a multi-shot technique, we believe that the long temporal range, or equivalently its high spectral resolution, provides a substantial improvement to the field of arbitrary waveform metrology
Instead of using a high-resolution spectrometer, we introduce a technique that uses a delay stage to scan the unknown pulse in time, resulting in multiple SEA TADPOLE measurements at different delays
Each SEA TADPOLE trace combined with a frequency-resolved optical gating (FROG) measurement of the reference pulse determines the spectral phase of the unknown pulse, φunk(ω), yielding the entire electric field, Ei (ω) = Si (ω)eiφi (ω)
Summary
There is great interest in the generation of arbitrary complex ultrafast waveforms in time, typically ~1 ns long with ~100 fs substructure, for telecommunications [1], frequency combs [2,3], coherent control, and spectroscopy [4]. Weiner and coworkers demonstrated a modified version of DQSI using spectral shearing and a periodically poled LiNbO3 (PPLN) waveguide called dual quadrature spectral shearing intereferometry to measure complex frequency combs up to 30 ps in length [21] All of these variations of SI retain the alignment issues of standard SI. Using a simple Fourier-filtering algorithm, MUD TADPOLE directly retrieves both the intensity and phase of the unknown pulse It can in principle be extended to measure extremely complex nanosecond long pulses with fs resolution, achieving temporal range-to-temporal resolution ratios of ~ 210,000, while measuring complex pulses with time-band-width products of ~ 70,000. The version of MUD TADPOLE that we discuss here is a multi-shot technique, we believe that the long temporal range, or equivalently its high spectral resolution, provides a substantial improvement to the field of arbitrary waveform metrology. We are working on a single-shot version and will report on it in a future publication
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