deletions | additions       diff --git a/section_Four_wave_mixing_Bragg__.tex b/section_Four_wave_mixing_Bragg__.tex  index f36d171..7f42b05 100644  --- a/section_Four_wave_mixing_Bragg__.tex  +++ b/section_Four_wave_mixing_Bragg__.tex 
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$$    In the straightforward case of $\epsilon  = 0, 0$,  the $\beta^{(3)}$  term (as well as all the other odd terms) terms of $\kappa$)  cancels out, leaving only smaller the  contribution from higher order dispersion. In the approximation $\Delta\Omega \gg \Delta\omega \gg \epsilon  we obtain the simple a simpler  expression (2) for the process momentum conservation  $$ \kappa(\epsilon) * L =  in which we can identify the process acceptance-bandwidth $\delta\omega_{bs}$,  and the frequency shift of the optimal conversion separation  from the symmetry symmetric  point $\delta\epsilon = \frac{\beta^{(4)}}{3 \beta^{(3)}} \Delta\Omega^2$  due to higher-order dispersion [Machin10]. \cite{Provo_2010}.  One prominent feature of FWM-BS, already noticed in [Inoue94,Marhic96] is highlighted by equation (2), that is translation for any given pair of signal and idler frequency can be exacly phasematched by choosing the appropriate pumps: this gives the flexibility of tuning the parameters of the interaction without the modifing the dispersion of the nonlinear medium.