Efficient time-to-space conversion of femtosecond optical pulses

Abstract

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Femtosecond pulse shaping for synthesis, processing, and time-to-space conversion of ultrafast optical waveforms

“…This can be also be performed approximately by spatial filtering or simply by placing an iris after the pulseshaping setup. In any case, if one takes the filter function to be the coefficient of the lowest Hermite-Gaussian mode in the expansion of , one arrives at the following expression [1], [56]: (4) Equation (4) shows that the effective filter in the frequency domain is the mask function convolved with the intensity profile of the beam. The main effect of this convolution is to limit the full-width at half-maximum (FWHM) spectral resolution of the pulse shaper to .…”

“…Note that in our treatment above we assume that the output Gaussian mode which is selected is matched to the input mode. The case where the input and output mode sizes are not matched is analyzed in [60]; in some cases this can give improvement in spectral resolution compared to that expected from (4).…”

“…nonlinear) medium. We have adopted this approach in our laboratory and have investigated how to optimize the conversion efficiency of the second-harmonic generation (SHG) based time-to-space converter [4]. We have recently achieved greater than 50% second conversion efficiency, which constitutes more than two orders of magnitude improvement compared to the original experiments.…”

Quantum-noise measurements in high-efficiency single-pass second-harmonic generation with femtosecond pulses

“…In this system the spectral prof ile of the input femtosecond pulses (with a typical bandwidth of 12 nm at 857.6 nm) is much broader than the phase-matching bandwidth (ϳ0.7 nm for a crystal length of 6.7 mm) of the KNbO 3 crystal. 13 The conversion eff iciency from fundamental pulses (centered at 857.6 nm) to bluelight pulses (at 428.8 nm) can be greater than 60%, which is in the strong depletion region for the fundamental field. The quantum noise on the blue light was observed to be 1.0 dB below the shot-noise limit in certain conditions and to be highly sensitive to the center wavelength of the input pulses.…”

“…12 In a femtosecond pulsed TW SHG a slope efficiency of 300% nJ 21 for harmonic conversion was observed with a 3-mm long crystal. 13 Thus, single-pass SHG in KNbO 3 crystal with femtosecond pulses promises to be a simple system for the study of quantum noise.…”