(c) Dr Paul Kinsler. [Acknowledgements & Feedback]

Few-cycle optical pulses (2001-)

This work was done in conjunction with Prof. GHC New in the Department of Physics at Imperial College.

This description is under construction

Optical parameric ocillators (OPO's) based on aperiodically poled lithium niobate (APPLN) can generate 53fs nearly transform limited pulses at 3 $3\mu$m corresponding to only five optical cycles[1]. Such short pulses are usually modelled by traditional slowly varying envelope approximations (SVEA), but in order to obtain a more accurate picture a new approach is needed. Ultrashort pulses have applications in areas ranging from precision spectroscopy (THz to VUV), optical atomic clocks, and fundamental tests of physical theories.

I have derived a general equation for treating (short) few-cycle pulses based on the approach of Brabec and Krausz [2] (see also [3]). We allow for diffraction, multiple fields, and also the $3\chi^{(2)}$ nonlinearity present in an OPO. The results of numerical simulations of an OPO using this new method will be compared to the SVEA solution, and the characteristic differences between the two are discussed. We also aim to compare results with a modified SVEA method, which attempts to simulate few-cycle effects by the addition of a variable phase adjustment to the pulse envelope.

My derivation has been done in such a way as to avoid approximation until the final step, and this allows a rigorous investigation of exactly {\em what} approximations need to made in order to obtain a convenient method for solving these types of few-cycle-pulse problems. It also allows the choice of which approximations to make, and a decision as to what order of approximation to use to be made. I plan to make to make my full step-by-step derivation publically available, as well as a suitable version of my pulse simulation code.

Background References:
1. T. Beddard, M. Ebrahimzadeh, T.D. Reid, W. Sibbett, Opt. Lett. 25, 1052 (2000).
2. T. Brabec, F. Krausz, Phys. Rev. Lett. 78, 3282 (1997).
3. M.A. Porras, Phys. Rev. A60, 5069 (1999).

( Research homepage; )
Date=18 20011117 Author=P.Kinsler Created=20011117

LOGBUG