Polarizing and spectrally selective photonic device based upon dielectric nanorods Sophia Buhbut a , Arkady Rudnitsky b , Michael Rosenbluh c , Arie Zaban a , Zeev Zalevsky b, * a Chemistry Department, Institute of Nanotechnology, Bar-Ilan Univ., 52900 Ramat-Gan, Israel b School of Engineering, Institute of Nanotechnology, Bar-Ilan Univ., 52900 Ramat-Gan, Israel c Physics Department, Institute of Nanotechnology, Bar-Ilan Univ., 52900 Ramat-Gan, Israel article info Article history: Received 8 September 2009 Received in revised form 13 December 2009 Accepted 14 December 2009 Available online 22 December 2009 Keywords: Dielectric nanorods Optical waveguides Polarizing device Spectral selective device abstract In this paper, we present a simple fabrication technique for growing dielectric nanorods and their imple- mentation in integrated photonic devices having polarizing or spectrally selective capabilities. Prelimin- ary experimental characterization results of the fabricated chips are presented. Ó 2009 Elsevier B.V. All rights reserved. 1. Introduction Integrated photonic devices having polarizing or spectrally selective capabilities may be very applicable as part of a photonic chip to be used for optical communication applications where con- trolling and modifying the spectral [1,2] and especially the polari- zation state of light [3,4] plays a major role. Nanostructures have been intensively studied in the last few dec- ades due to their great potential and applicability for electronic and photonic devices. In recent years, ZnO nanostructures [5] have been of particular focus, because of their special properties. ZnO is an n- type semiconductor with a wide band-gap of 3.3 eV, a high refrac- tive index of 2.3, optical transparency, electrical conductivity and piezo electricity [6]. The nanostructure has a diameter and length which can be much smaller than a wavelength of visible light. Such a configuration has useful optical, chemical and electrical properties while being nontoxic, inexpensive and chemically stable [7]. In this paper, we present a simple approach for fabricating dielectric ZnO nanorods having controllable dimensions, which can be easily adapted for mass production. An air slit can be used as an optical waveguide since the beam propagating in the slit will be bounced back from the nanorods surrounding the slit. The rods surrounding the slit act as an optical waveguide cladding, confin- ing the light in the slit. The confined light is reflected with a known polarization as well as spectral selectivity. The dimension of the nanorods surrounding the air gap waveguide determines the polar- ization and spectral properties of the light that remains guided. Thus, the main contribution of this paper is in introducing a novel approach for realizing on chip photonic devices that can be used as a waveguide polarizer or spectral filter. 2. Fabrication process The ZnO nanorods were prepared on three different types of substrates: bare glass, fluorine doped tin oxide (FTO) and indium tin oxide (ITO). The substrate was rinsed with deionized water, acetone and ethanol. Then a thin layer of ZnO was deposited on the substrate by radio frequency (RF) magnetron-sputtering. The sputtering condition consisted of 100 W RF power and 15 mTorr pressure of argon for 10 min. After the sputtering, there was no change in the optical transparency of the substrate. For subsequent growth of highly oriented ZnO nanorods the coated substrate im- mersed in baths of two different concentrations. The baths con- sisted of a solution of 0.01 M zinc nitrate hexahydrate Zn(NO 3 ) 2 6H 2 O (Sigma–Aldrich) and 0.4 M sodium hydroxide NaOH (Sigma–Aldrich) which we ‘‘call” high concentration, or a solution of 0.001 M zinc nitrate Zn(NO 3 ) 2 6H 2 O and 0.01 M sodium hydroxide NaOH which we ‘‘call” low concentration. In both cases the solvent was deionized water at 70 °C [8]. During the deposition, the solution was stirred on a hot plate. The resulting films were rinsed with deionized water and then with ethanol for 10 min in a sonicator bath [9]. After each 60 min of deposition, the solution was replaced by a fresh one. The indica- tion that showed the end of the reaction in a given solution was that the solution changed its color from transparent into white. 0167-9317/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.mee.2009.12.055 * Corresponding author. E-mail address: zalevsz@eng.biu.ac.il (Z. Zalevsky). Microelectronic Engineering 87 (2010) 1319–1322 Contents lists available at ScienceDirect Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee