The methods of nonlinear optics are widely applied to the study of changes in structure of large biomolecules.1'2 The information obtained by these methods may be used for the investigation of relationship between structural changes of the biomolecules and their specific activity. Molecular left-right asymmetry is an origin of nonvanishing even order optical nonlinear susceptibilities of non-racemic solutions of chiral molecules. New nonlinear optical spectroscopic schemes based on three-and five-wave interactions in chiral homogeneous isotropic media (symmetry forbidden in centrosymmetric racemic solutions) are investigated with the aim to develop a novel technique to clearly distinguish between left and right mirror isomers of biological molecules and to measure their individualnonlinearopticalhyperpolarizabilities, and vibrational spectra.3Though second harmonic generation (SHG) due to quadratic dipolar nonlinearity is still symmetryforbidden in optically active liquids yet we have succeeded in experimental observation, for the first time, of noncollinear SHG due to five-mixing process according to a scheme 2 cv = 3cv -w, governed by a fourth order susceptibility tensor 4"• SHG signal is found to be well collimated and quasi phase-matched, it shows theoretically predicted polarization, spectral and temporal properties. 1.INTRODUCTION.An optically active isotropic liquid (for instance, non-racemic solution of mirror-asymmetric molecules) lacks the center of inversion and, hence, possesses non-vanishing even order dipolar nonlinear optical susceptibilities:(2)D (4)D 3-5 . .(2)D ... .x , x etc . Optical sum-frequency generation due to x in an optically active arabinose solutions was observed for the first time by Rentzepis et al.6 in a non-collinear, phase-mismatched geometry. However, second harmonic generation (SHG) due to dipolar quadratic nonlinearity is still forbidden in such liquids because of permutationsymmetryreason4.Some time ago, one of us (N.I.K.) has shown that higher order nonlinearity (namely, fourth-order one) does allow the SHG process to occur in phase-matched non-collinear scheme5. Is presented hereafter a Theory of interaction of strong laser field with mirror-asymmetric isotropic mediums, theory of five-wave interaction in chiral homogeneous isotropic media and new experimental results on observation of five-wave mixing 2w= 3w -cv 0-8194-1 155-8/93/$6.00 SPIE Vol. 1922 Laser Study of Macroscopic Biosystems (1992)129 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/16/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

We report on the results of experimental studies of the photocurrent (PC) of photodiodes based on GaAs p-i-n structures with InAs/GaAs(001) double asymmetric quantum dot (DAQD) arrays obtained by self-assembling in the process of low-pressure metal-organic vapor phase epitaxy (LP-MOVPE). Three peaks were observed in the dependence of the PC on the reverse bias, measured under photoexcitation with a photon energy equal to the energy of the interband ground state transition in larger InAs QDs. These peaks were attributed to photoexcitation of electrons from the ground hole states in larger QDs into the ground electron states followed by resonant dissipative (with absorption or emission of optical phonons) and conservative tunneling into the GaAs conduction band via the ground electron states in smaller QDs. The PC dependence on the bias voltage agrees qualitatively with the theoretical field dependence of the probability of 1D dissipative tunneling between the QDs.

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