Berlin 2014 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 30: Poster: Photonics, laser development and applications, ultrashort laser pulses, quantum effects

Q 30.15: Poster

Dienstag, 18. März 2014, 16:30–18:30, Spree-Palais

Modification of frequency-resolved optical gating setup improves signal-to-noise ratio — •Sven Kraft, Philipp Rohrmann, Alexander Hause und Fedor Mitschke — Universität Rostock, Institut für Physik, Universitätsplatz 3, 18051 Rostock

Frequency-resolved optical gating (FROG) is one of the most popular techniques to assess the entire amplitude-and-phase structure of ultrashort light pulses. In this contribution we show that a modification can vastly improve the signal-to-noise ratio, thereby enabling measurements on weak pulses as they emerge from experiments, rather than strong pulses straight from the laser. In the standard version a camera is exposed line by line in sequence whereas noise accumulates in all lines, for the entire exposure time. We avoid the unnecessary noise accumulation by using a nanopositioning stage and a fast and sensitive line camera, operating under computer control for smooth operation.

Time to obtain a FROG trace is limited by the camera readout time; for a 512x512 pixel format our setup takes ≈ 470 ms. With extended exposure time sensitivity is increased. We tested this with a single line exposure time of 6 s on weak anti-phase double pulses with energies of E≈ 350 fJ and peak powers of only P0≈ 590 mW emerging from a fiber-optic transmission experiment. A full field reconstruction with acceptable noise was achieved.

In comparison to the standard FROG we find a significant signal-to-noise improvement of 35.9 dB. Moreover, the refined version is designed to make additional calibrations of scan linearity etc. unnecessary.

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