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Dynamical Behaviour of Policryps Gratings

Francesco Vita ,Antigone Marino ,Volodymyr Tkachenko ,Roberto Caputo ²,Cesare Umeton ²,Alessandro Veltri ²,Giancarlo Abbate
INFM Unità di Napoli and Università di Napoli Federico II INFM Unità di Napoli and Dip. di Scienze Fisiche - Università di Napoli Federico II ²Liquid Crystal Italian Laboratory LICRYL, Dipartimento di Fisica - Università della Calabria and INFM Unità di Cosenza
We have studied the dynamical response of a new polymer-liquid crystal composite, realised in a form of a thick grating. This structure, named POLICRYPS, consists in an alternate sequence of homogeneous polymer slides and liquid crystal stripes. Optimisation of response time is an important factor to propose POLICRYPS as basic element in different photonic devices for telecom applications. We analyse the response dependence on the pulse duration and amplitude: we show that both ON and OFF switching times are depending on the applied electric field and propose a phenomenological explanation for this unexpected behaviour. Moreover we outline the possibility to get response times of the order of 100 us by properly choosing the pulse shape. Results are very interesting for applications and induce to a deeper analysis of the microscopic interaction between liquid crystal and polymer interfaces in POLICRYPS gratings.

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