Optical nonlinearity measurement of 4-(N-methyl, N-hydroxyethl)amino, 4'-nitroazobenzene using a transmittance technique with a phase object (T-PO) with top-hat beams at 600-nm wavelength

The transmittance technique with a phase object (T-PO), for measuring optical nonlinear coefficients is proposed with a top-hat beam. The sensitivity of the T-PO with a top-hat beam is a factor of 4 greater than that with a Gaussian beam. The validity of this method is verified by measuring the nonlinearity of a well-characterized liquid, CS₂ at 532-nm wavelength. The ease of use of this method has been proved by measuring a new compound 4-(N-methyl, N-hydroxyethyl)amino, 4'-nitroazobenzene(ANAB) at 600-nm wavelength, indicating that this method can be extended to the measurement of optical nonlinearities in a wide-band spectrum.