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Recently some of us have shown that the use of a correct ab initio approach to nonlinear pulse propagation simulations during nonlinear optical device designing can result in threefold efficiency increase with respect to the efficiency of existing solutions [1]. In that work we have focused on small beam size, and thus, high divergence regime where the effects of diffraction, spatial and temporal walk-off are difficult to separate and thus require numerical approach. Our collinear model of pulse propagation enabled modelling and optimization of a cascade third harmonic generation in a single element tripler. Herewith, we present the results of expanding our model to treatment of non-collinear optical configurations and the model application to our OPCPA design [2,3]. To the best of our knowledge this is a first propagation model that enables non-collinear configurations while in minimal assumptions regime: unidirectionality and paraxial approximation.
By definition the non-collinear propagation is required when interaction of two or more beams is considered. In this case the use of not necessarily slowly varying envelope for each interacting beam is justified from both physical and computational reasons. In case of 3D non-collinear propagation the above conclusion leads to the concept of reference wavevector. Our model is based on unidirectional pulse propagation equation (UPPE [4]) in a rotated frame of reference. Rotation by a different angle has to be, however, performed separately for each of the interacting beams. Apparently even for quite high mutual beam angles it is enough to solve scalar, rather than vectorial, version of UPPE and sustain accuracy. Finally the initial conditions (rotated optical pulses) can be prepared through arbitrary 3D rotation through Fourier Transform shear operations. The idea, realization and advantages of the above mentioned, novel concepts: reference wavevector, rotated UPPE and arbitrary Fourier rotation will be discussed in the presentation.
The real life examples of model results for the usage will be presented: an LBO based chirped pulse non-collinear optical parametric amplifier working in “exotic” (off major plane) phase matching conditions and the redesigned multiterawatt BiBO based OPCPA system [2].
1. T. M. Kardaś, M. Nejbauer, P. Wnuk, B. Resan, C. Radzewicz, and P. Wasylczyk, "Full 3D modelling of pulse propagation enables efficient nonlinear frequency conversion with low energy laser pulses in a single-element tripler," Scientific Reports 7, 42889 (2017).
2. P Wnuk, Y Stepanenko, C Radzewicz “Multi-terawatt chirped pulse optical parametric amplifier with a time-shear power amplification stage”, Optics Express 17(17), 15264 (2009)
3. Y. Stepanenko, "On the efficiency of a multiterawatt optical parametric amplifier: numerical model and optimization," JOSA B 28, 2337–2346 (2011).
4 M. Kolesik and J. V. Moloney, "Nonlinear optical pulse propagation simulation: From Maxwell’s to unidirectional equations," Phys. Rev. E 70, (2004).
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