(c) Dr Paul Kinsler. [Acknowledgements & Feedback]
LOCATION: IQEC, Moscow, Russia, 2002: oral presentation.
WORK DONE AT:
Physics Department,
Imperial College.
SIZE: various
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AUTHORS: P Kinsler, G.H.C. New
We present both a comprehensive framework for treating the nonlinear interaction of few-cycle pulses and a range of simulation results. These demonstrate how the effect of the nonlinearity differs between the many-cycle and few-cycle cases.
Optical parametric oscillators (OPOs) based on aperiodically-poled lithium
niobate (APPLN) have generated 53 fs idler pulses at 3m that are nearly
transform limited, and contain only five optical cycles[1]; laser pulses with
less than three optical cycles have been generated in other contexts[2].
This means the slowly-varying envelope approximations
traditionally used to model such processes are no longer
valid.
We present a theory for modelling few-cycle pulses that includes diffraction, dispersion, multiple fields, and a wide range of nonlinearities. We build upon the work of Brabec and Krausz[3] and Porras[4], but a characteristic feature of our approach is that no approximations are made until the final stage when a particular problem is considered: it is left entirely to choice which terms in the exact solution to retain, and to what order approximations should be applied. We can now rigorously study what combination of approximations affords the most efficient method for treating a given nonlinear interaction involving few-cycle pulses.
We apply this to an OPO, using dispersion, multiple fields and its second-order nonlinearity. We show numerical simulations involving pulses with different numbers of cycles, including idler pulses containing as few as two cycles. The characteristic differences between the results under various levels of approximation are discussed in detail. Other nonlinear optical processes are also discussed.
[1] T. Beddard, M. Ebrahimzadeh, T.D. Reid, W. Sibbett,
Opt.Lett. 25, 1052 (2000).
[2] A. Baltuska, Z. Wei, S. Pshenichnikov and D. Wiersma,
Opt.Lett. 22, 102 (1997).
[3] T. Brabec, F. Krausz,
Phys. Rev. Lett. 78, 3282 (1997).
[4] M.A. Porras,
Phys. Rev. A60, 5069 (1999).
These are in fact the updated and slightly corrected slides for the later talk I gave at Photon'02, which was the same except for some additional content -- notably the Super-Scaled OPO slide.
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Date=1010 20020619 Author=P.Kinsler