"SPRINT-AC" TECHNIQUE FOR FS-PULSE RETRIEVAL
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Anatoly Masalov
Scientific Center 'Ultratekh', 141700, Dolgoprudny, Moscow dist., Institutsky per. 9, Russia
Sergei Nikitin and Qiang Fu
Quantronix Corporation, 41 Research Way, East Setauket, New York 11733, USA
The progress in techniques for measuring fs-pulse amplitude and phase is associated nowadays with implementation of "optical oscilloscope" to be used for real-time pulse shaping, phase control and other applications. This paper describes a new method of fs-pulse diagnostics - SPRINT-AC (spectrally resolved interference), which can be considered as a step to build such an oscilloscope. The diagnostic is based on a single-shot SHG autocorrelation technique [1] combined with a spectrograph, as in SHG-FROG method [2], and modified as shown in the Figure below. Two identical input pulses A(t)exp(-iw0t) generate sum-frequency
and two harmonic beams in a thin nonlinear crystal. One of two harmonic beams is allowed to interfere with the sum-frequency beam at the entrance slit of a spectrograph. The intensity of this asymmetric interference pattern contains a contribution, which depends on spatially varying relative optical delay t as IINT(t) =  A2(t)A*(t)A*(t+t)exp(iw0t)dt + c.c. Under assumption |A(t)|3  d(t), this function approximately coincides with the pulse field: IINT(t) A*(t)exp(iw0t) + c.c. By using the last relation as initial guess, an accelerated pulse-field retrieval can be accomplished.
An experimental test of the SPRINT-AC technique has been done using a commercial 1kHz/1mJ/30fs multipass amplifier seeded with 15-fs pulses from a 150 mW Ti:Sapphire oscillator. An ordinary spectrum of the pulses can be simultaneously registered in this device to aid retrieval and to perform cross-check of resulting data.
[1] R.N.Gyuzalian, S.B.Sogomonian and Z.G.Horvath. Opt. Commun 29, 239 (1979).
[2] D.J. Kane and R. Trebino. Opt.Lett. 18, 823 (1993).
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