Open Z-scan analytical model for multiphoton absorption

Abstract

We present an open-aperture elliptic Gaussian beam Z-scan theory for thin nonlinear optical material possesses simultaneous $$ \left( {N - n} \right) $$ nonlinear absorption processes with residual linear absorption. We show that an approximate analytical but closed-form expression for the normalized energy transmittance is possible by means of the weak nonlinearities approximation. The elaborate theory can be used to fit the open Z-scan traces allowing the determination of material’s nonlinear absorption coefficients and incident Gaussian beam parameters. The contribution of absorptions of distinct order can also be identified, separated and compared.