Tsz Chun Wong

Coherent artifact in modern pulse measurements

All optical pulse cmeasurement techniques necessarily fail in multi-shot measurements of unstable pulse trains because the measurement can only provide a single result, despite of the presence of many different pulse shapes. At the very least, however, the technique should provide a reasonable estimate of a typical pulse in the train and indicate the trains stability. While frequency-resolved optical gating (FROG, [1]) and spectral phase interferometry for direct electric-field reconstruction (SPIDER, [2]) naturally operate single-shot, multi-shot variants are very common, so it is important to understand the effects of instability on multi-shot measurements.

Single-shot measurement of the complete temporal intensity and phase of supercontinuum

We demonstrate the first technique for the complete temporal measurement of a single supercontinuum pulse. We achieve large ranges and high resolutions using polarization gating, a tilted gate pulse, and the cancellation of geometrical smearing.

Simultaneously measuring two ultrashort laser pulses on a single-shot using double-blind frequency-resolved optical gating

We demonstrate a simple self-referenced single-shot method for simultaneously measuring two different arbitrary pulses, which can potentially be complex and also have very different wavelengths. The method is a variation of cross-correlation frequency-resolved optical gating (XFROG) that we call double-blind (DB) FROG. It involves measuring two spectrograms, both of which are obtained simultaneously in a single apparatus. DB FROG retrieves both pulses robustly by using the standard XFROG algorithm, implemented alternately on each of the traces, taking one pulse to be “known” and solving for the other. We show both numerically and experimentally that DB FROG using a polarization-gating beam geometry works reliably and appears to have no nontrivial ambiguities.

Measuring many-picosecond-long ultrashort pulses on a single shot using XFROG and pulse-front tilt

We demonstrate the use of pulse-front tilt in cross-correlation frequency-resolved optical gating (XFROG) to measure complex many-picosecond-long pulses on a single shot.

Simultaneous measurement of two different-color ultrashort pulses on a single shot

We experimentally demonstrate the ability of double blind frequency-resolved optical gating to simultaneously measure two independent pulses at very different wavelengths on a single shot. Our device uses polarization-gate geometry, allowing pulses at any two wavelengths and unlimited operating bandwidth. The retrieval algorithm is robust and is capable of ignoring most forms of noise in the measured spectrograms.

Single-shot Measurement of the Complete Temporal Intensity and Phase of Supercontinuum

We demonstrate the first technique for the complete temporal measurement of a single supercontinuum pulse. We achieve large ranges and high resolutions using polarization gating, a tilted gate pulse, and the cancellation of geometrical smearing.

Simultaneous measurement of two ultrashort pulses at different wavelengths using double blind polarization-gate frequency-resolved optical gating

We demonstrate the use of Double-Blind Frequency-Resolved Optical Gating implemented in Polarization-Gate geometry to measure two pulses at very different center wavelength (400nm and 800nm) simultaneously on a single-shot. Complex pulse pair with Time-Bandwidth-Product of 1.1 and 6.2 are measured and retrieved.

Complete Measurement of Supercontinuum on a Single Shot

We demonstrate the first single-shot technique for measuring the complete intensity and phase of a complex supercontinuum pulse. We use pulse-front tilt in polarization-gating cross-correlation frequency-resolved optical gating to cancel out all geometrical smearing effects.

The Coherent Artifact in Modern Pulse Measurements

We simulate multi-shot FROG and SPIDER measurements of unstable pulse trains, finding that FROG yields the approximate average duration, with disagreement between measured and retrieved traces, while SPIDER significantly under-estimates it, yielding only the coherent artifact.

Measuring Two Different-Color Ultrashort Pulses by Double Blind Polarization Gate Frequency-Resolved Optical Gating

Two independent ultrashort pulses at very different center wavelengths (400nm and 800nm) are measured simultaneously on a single shot using Double Blind Polarization Gate Frequency-Resolved Optical Gating.