Active Photonic Crystals Based multiplexer
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0934-I09-15
Active Photonic Crystals Based multiplexer Principia Dardano1,2, Vito Mocella1, Luigi Sirleto1, Luigi Moretti1, and Ivo Rendina1 1 Istituto per la Microelettronica e Micrositemi (IMM), Consiglio Nazionale delle Ricerche (CNR), via Pietro Castellino, 111, Napoli, 80131, Italy 2 Università degli Studi di Napoli 'Federico II', Napoli, 80131, Italy
ABSTRACT In the last years, in order to achieve active tuning of photonic crystals devices, the possibility to use liquid crystal inside photonic crystals has been explored. On this line of argument, in this paper, we numerically investigate a tunable T-shaped waveguide diplexer, based on a two-dimensional square lattice photonic crystal composed of silicon rods in liquid crystals. We prove that complete splitting of the entire input wavelengths range in two sub-ranges symmetrical with respect to the middle (switching) wavelength, and propagating in right and left arms respectively, can be achieved. Moreover, changing the refractive index of liquid crystals by electro-optical effect, a tuning of switching wavelength of about 60 nm can be obtained. INTRODUCTION In order to design filters, diplexers and multiplexers, different kind of defects, and different optimisation approaches have been adopted [1, 2]. A further improvement for such devices is the tuning capability [2]. In order to overcome the lack of mechanism for switching ad filtering in silicon based PhCs, a very promising approach in order to achieve active tuning of the photonic properties can be obtained by using liquid crystal properties inside photonic crystals. This idea goes back to the theoretical predictions by Bush and John [3] and the experimental work by Yoshino et al. [4]. These works considered to fill the liquid crystal into the voids of an artificial opal or an inverted colloidal crystal, respectively. Since, then, many other photonic crystal systems containing liquid crystals were developed [5, 6]. Recently, tuneable Y-shaped waveguides adopting liquid crystals as linear defect in a GaAs substrate [6] has been proposed. In this device the light can propagate on one side or on both sides of Y-shaped waveguides depending on the orientation of liquid crystals. The main drawback of this device is that a significant frequencies range of light is coupled into both output waveguides. In this paper, the design of a T-shaped diplexer based on silicon PhCs in liquid crystals is presented. The aim of our design is to eliminate the wavelength crosstalk between two outputs of T-junction. In other words, to split the entire input wavelengths range in two disjoint sub-ranges propagating in right and left arms of T-shaped PhC waveguide, respectively. Furthermore, we investigate the possibility to tune the switching point by means the electro-optic effect of liquid crystals.
TUNABLE PhC DIPLEXER BASED ON LIQUID CRYSTALS The proposed device is a T-shaped two dimensional square lattice photonic crystal composed by silicon (ε=11,9) rods in E7 nematic liquid crystals (εLC=2.25) (see figure 1). We suppose th
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