Organic materials such as liquid crystals and polymers offer unique optical and electro-optical properties, which make them ideal candidates for the realization of optoelectronic and sensing devices [1-6]. Liquid crystals are rather well assessed and definitely benefit from a mature technology, low cost, low driving voltages, short switching times, low losses and a wide spectral transparency from the visible to the near infrared. Polymers exhibit remarkable properties, among them a refractive index engineerable by varying their chemical composition and their compatibility with other materials, which allow large scale film deposition at low costs. In this Communication I will illustrate several integrated optoelectronic structures which exploit these materials. Among them is a bistable electro-optic switch realized by ion-exchange in glass and employing ferroelectric liquid crystals with polymeric alignment. The device, fully characterized at the wavelength 632.8nm, shows interesting properties ranging from a switching time as short as 300us to an extinction ratio above 14dB for a bias of only 5V applied [7]. Another example is a guided-wave optical switch investigated using ferroelectric liquid crystals and polymers, in which light is confined in two polymeric films and with buffer layers to prevent losses in the near infrared by light absorption in the ITO electrodes. This switch, optimized in terms of extinction ratios and losses for various layers thicknesses, polymer compositions and liquid crystals refractive indices, has an extinction ratio better than 50dB and propagation losses lower than 1dB for a compact structure of just 174um in length [8-9]. An electro-optic router can be obtained based on mode mixing. The design of such configuration, quite promising in terms of crosstalk and versatility [10], is presently under optimization. The device, based on a bi-modal nematic liquid crystal waveguide of an overall length <500um, can be driven to route an optical signal to either one of two output gates by virtue of a small voltage modulation <1V. [1] J. Qi, H. Xianyu, J. Liang, G. P. Crawford, , “Active U-turn electrooptic switch formed in patterned holographic polymer-dispersed liquid crystals”, IEEE Photon. Technol. Lett., Vol. 15, no. 5, pp. 685-687 (2003). [2] D. E. Lucchetta, L. Criante, F. Simoni, “Optical characterization of polymer dispersed liquid crystals for holographic recording”, J. Appl. Phys., Vol. 93, no. 12, pp. 9669-9674 (2003). [3] A. d’Alessandro, R. Asquini, C. Gizzi, R. Caputo, C. Umeton, A. Veltri, A. V. Sukhov, “Electro-optic properties of switchable gratings made of polymer and nematic liquid crystals slices”, Opt. Lett., Vol. 29, 1405-1407, (2004). [4] H. Ren, Y. H. Fan, S. T. Wu, “Polymer network liquid crystals for tunable microlens arrays ”, J. Phys. D – Appl. Phys., Vol. 37, no. 3, pp. 400-403, (2004). [5] D. S. Hermann, G. Scalia, C. Pitois, F. De Marco, K. D’havé, G. Abbate, M. Lindgren, A. Hult, “Novel Passive Polymer Waveguides Integrated with Electro-Optically Active Ferroelectric Liquid Crystals”, Opt. Eng., Vol. 40, no. 10, pp. 2188-2198 (2001). [6] A. d’Alessandro and R. Asquini, “Liquid crystal devices for photonic switching applications: state of the art and future developments, Mol. Cryst. Liq. Cryst., Vol. 398, pp. 207-221 (2003). [7] A. d’Alessandro, R. Asquini, F. Menichella, C. Ciminelli, “Realisation and characterisation of a ferroelectric liquid crystal bistable optical switch”, Mol. Cryst. Liq. Cryst., Vol. 372, pp. 353-363 (2001). [8] R. Asquini and A. d’Alessandro, “BPM analysis of an integrated optical switch using polymeric optical waveguides and SSFLC at 1.55 m” , Mol. Cryst. Liq. Cryst., Vol. 375, pp. 243-251 (2002). [9] R. Asquini, C. Gizzi, R. Beccherelli, A. d’Alessandro, “Performance optimization of optical switches in ferroelectric liquid crystals and polymers operating at 1550nm”, Proc. SPIE 2003 – Liquid Crystals VII, International Symposium on Optical Science and Technology, 48th Annual Meeting, 3-8 August 2003, Vol. 5213, pp. 258-266 (2003). [10] R. Asquini, A. d’Alessandro, G. Assanto, “Electro-optic guided-wave router using nematic liquid crystals”, 11th Europ. Conf. on Integrated Optics ECIO 2003, 2-4 April 2003, Prague, Vol. 1, pp. 249-252 (2003).
Liquid crystals and polymers for novel guided-wave electro-optic devices / Asquini, Rita. - STAMPA. - (2004). (Intervento presentato al convegno Italian Liquid Crystal Society (SICL) 6th National Meeting tenutosi a Ischia - Italy nel July 6-9, 2010).
Liquid crystals and polymers for novel guided-wave electro-optic devices
ASQUINI, Rita
2004
Abstract
Organic materials such as liquid crystals and polymers offer unique optical and electro-optical properties, which make them ideal candidates for the realization of optoelectronic and sensing devices [1-6]. Liquid crystals are rather well assessed and definitely benefit from a mature technology, low cost, low driving voltages, short switching times, low losses and a wide spectral transparency from the visible to the near infrared. Polymers exhibit remarkable properties, among them a refractive index engineerable by varying their chemical composition and their compatibility with other materials, which allow large scale film deposition at low costs. In this Communication I will illustrate several integrated optoelectronic structures which exploit these materials. Among them is a bistable electro-optic switch realized by ion-exchange in glass and employing ferroelectric liquid crystals with polymeric alignment. The device, fully characterized at the wavelength 632.8nm, shows interesting properties ranging from a switching time as short as 300us to an extinction ratio above 14dB for a bias of only 5V applied [7]. Another example is a guided-wave optical switch investigated using ferroelectric liquid crystals and polymers, in which light is confined in two polymeric films and with buffer layers to prevent losses in the near infrared by light absorption in the ITO electrodes. This switch, optimized in terms of extinction ratios and losses for various layers thicknesses, polymer compositions and liquid crystals refractive indices, has an extinction ratio better than 50dB and propagation losses lower than 1dB for a compact structure of just 174um in length [8-9]. An electro-optic router can be obtained based on mode mixing. The design of such configuration, quite promising in terms of crosstalk and versatility [10], is presently under optimization. The device, based on a bi-modal nematic liquid crystal waveguide of an overall length <500um, can be driven to route an optical signal to either one of two output gates by virtue of a small voltage modulation <1V. [1] J. Qi, H. Xianyu, J. Liang, G. P. Crawford, , “Active U-turn electrooptic switch formed in patterned holographic polymer-dispersed liquid crystals”, IEEE Photon. Technol. Lett., Vol. 15, no. 5, pp. 685-687 (2003). [2] D. E. Lucchetta, L. Criante, F. Simoni, “Optical characterization of polymer dispersed liquid crystals for holographic recording”, J. Appl. Phys., Vol. 93, no. 12, pp. 9669-9674 (2003). [3] A. d’Alessandro, R. Asquini, C. Gizzi, R. Caputo, C. Umeton, A. Veltri, A. V. Sukhov, “Electro-optic properties of switchable gratings made of polymer and nematic liquid crystals slices”, Opt. Lett., Vol. 29, 1405-1407, (2004). [4] H. Ren, Y. H. Fan, S. T. Wu, “Polymer network liquid crystals for tunable microlens arrays ”, J. Phys. D – Appl. Phys., Vol. 37, no. 3, pp. 400-403, (2004). [5] D. S. Hermann, G. Scalia, C. Pitois, F. De Marco, K. D’havé, G. Abbate, M. Lindgren, A. Hult, “Novel Passive Polymer Waveguides Integrated with Electro-Optically Active Ferroelectric Liquid Crystals”, Opt. Eng., Vol. 40, no. 10, pp. 2188-2198 (2001). [6] A. d’Alessandro and R. Asquini, “Liquid crystal devices for photonic switching applications: state of the art and future developments, Mol. Cryst. Liq. Cryst., Vol. 398, pp. 207-221 (2003). [7] A. d’Alessandro, R. Asquini, F. Menichella, C. Ciminelli, “Realisation and characterisation of a ferroelectric liquid crystal bistable optical switch”, Mol. Cryst. Liq. Cryst., Vol. 372, pp. 353-363 (2001). [8] R. Asquini and A. d’Alessandro, “BPM analysis of an integrated optical switch using polymeric optical waveguides and SSFLC at 1.55 m” , Mol. Cryst. Liq. Cryst., Vol. 375, pp. 243-251 (2002). [9] R. Asquini, C. Gizzi, R. Beccherelli, A. d’Alessandro, “Performance optimization of optical switches in ferroelectric liquid crystals and polymers operating at 1550nm”, Proc. SPIE 2003 – Liquid Crystals VII, International Symposium on Optical Science and Technology, 48th Annual Meeting, 3-8 August 2003, Vol. 5213, pp. 258-266 (2003). [10] R. Asquini, A. d’Alessandro, G. Assanto, “Electro-optic guided-wave router using nematic liquid crystals”, 11th Europ. Conf. on Integrated Optics ECIO 2003, 2-4 April 2003, Prague, Vol. 1, pp. 249-252 (2003).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
