The electro-optic (EO) coefficients r 22 of a congruent LiTaO 3 bulk crystal, with dimensions of 6 × 5 × 20 mm 3 ,havebeen measured over a wide frequency range (from dc up to 150 MHz) using the novel and elaborate step-voltage time-response method (TRM). At low frequencies, these results are compared with those obtained with the frequency-doubling EO-modulation (FDEOM) method. From these measurements, the clamped and unclamped EO coefficients, r S ,respectively, have been derived and the acoustic contribution r a 22 to the EO effect has been deduced and compared with theoretically calculated values. Also, using the values of acoustic contribution, r a ,thetrue value of the EO coefficient r 22 has been extracted. Lastly, the above results are compared with those obtained for a pure congruent LiNbO 3 crystal in the framework of a typical intensity-modulation (IM) EO system.

No abstract

Abstract. The multifactor optical encryption authentication method [Opt. Lett., 31, 721-3 (2006)] reinforces optical security by allowing the simultaneous authentication of up to four factors. In this work, the photon-counting imaging technique is applied to the multifactor encrypted function so that a sparse phase-only distribution is generated for the encrypted data. The integration of both techniques permits an increased capacity for signal hiding with simultaneous data reduction for better fulfilling the general requirements of protection, storage and transmission. Cryptanalysis of the proposed method is carried out in terms of chosen-plaintext and chosen-ciphertext attacks. Although the multifactor authentication process is not substantially altered by those attacks, its integration with the photon-counting imaging technique prevents from possible partial disclosure of any encrypted factor, thus increasing the security level of the overall process. Numerical experiments and results are provided and discussed.

No abstract

No abstract