We demonstrate generation of broadband high‐intensity picosecond pulses using a non‐collinear optical parametric amplifier, seeded with a broadband cavity‐less dye laser and pumped using the second harmonic of a picosecond Nd:YAG laser. With appropriate choice of the pump‐seed non‐collinearity angle, we observed energy conversion from the pump to the signal wave of around 15%, with the bandwidth of the amplified radiation around 445 cm−1 (20.7 nm) centered around 680 nm. An energy of 1.2 mJ per pulse of duration around 26 ps has been achieved. A light source with such parameters could be suitable for use in time‐resolved broadband picosecond Coherent anti‐Stokes Raman scattering. Copyright © 2014 John Wiley & Sons, Ltd.

A cascade mechanism of the emerging of a radiation in blue and red spectral ranges in the KTP crystal—combined non‐collinear parametric down‐ and up‐conversion—was discovered and experimentally investigated. To become observable this mechanism needs to be accompanied by a process of parametric amplification of the seeding wave. The non‐collinear optical parametric amplifier based on the KTP crystal, pumped by 532 nm picosecond pulses, was exploited to study combined noncollinear down‐conversion and up‐conversion processes. Narrowband seeding was provided by radiation of a picosecond optical parametric generator pumped by 355‐nm picosecond pulses synchronized with 532‐nm pulses. The corresponding phase matching conditions for both down‐ and up‐conversion stages were found out on the basis of the tuning curves calculated for the type II phase matching in the XOZ plane of the KTP crystal. When the wavelength and noncollinearity angle of the seeding matched any signal wave of the down‐conversion stage, the seeding was amplified. Along with this, a radiation appeared in the visible part of the spectrum, which was not observed without seeding amplification. The wavelengths and spatial patterns of the radiation arisen, corresponded to some phasematched processes of sum frequency generation between the signal and idler waves existing in the crystal at the down‐conversion stage. Being very weak, these processes are usually unobserved. Thus, injection seeding allows from plenty possible processes to reveal and highlight only those, which correspond to the noncollinearity angle and the wavelength of the seeding. This phenomenon potentially can be exploited to control light at the outlet of a nonlinear crystal.

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We measured small Faraday polarization rotation in nanopolyacetylene in a magnetic field -150 Oe. We found that -4 % polyacetylene nanoparticles increase up to 50% the polarization rotation angle of the transparent matrix containing them when probed near and at the NPA absorption band. The rotation angles were in the range 1-15 irad.

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