Efficient second harmonic conversion efficiency through one-dimensional coupled resonator poled nonlinear optical wavegu
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Efficient second harmonic conversion efficiency through one-dimensional coupled resonator poled nonlinear optical waveguide S.M. Hamidi · T. Parvini · M.M. Tehranchi
Received: 29 March 2012 / Accepted: 28 January 2013 © Springer-Verlag Berlin Heidelberg 2013
Abstract In this paper, the second harmonic generation in finite size one-dimensional coupled resonator poled nonlinear optical waveguide has been investigated. To calculate the conversion efficiency, fundamental and second harmonic wave propagation among two proposed structures, we use the transfer matrix method. In the designed nonlinear photonic crystal structure, the linear and nonlinear optical parameters are both periodically modulated, and thus the second harmonic generation efficiency can be several orders of magnitude larger than in a conventional quasi-phasematched nonlinear structure with the same sample length. In fact, due to the presence of a photonic band gap in a slow wave system, the density of states of the electromagnetic fields is large at the photonic band edge and photonic defect modes, and thus the group velocity is small, and the local field is enhanced. All these factors contribute to significant enhancement of the nonlinear optical interactions.
1 Introduction Nonlinear photonic crystals (NPCs) offer unique fundamental ways of enhancing a variety of nonlinear optical processes. One of these processes is the second harmonic generation (SHG) that needs a phase matching condition in the entire of the NPC structure [1]. To satisfy the phase matching condition in periodic structures, the use of the quasiphase matching (QPM) condition, which involves a repeated
S.M. Hamidi () · T. Parvini · M.M. Tehranchi Laser and Plasma Research Institute, Shahid Beheshti University, Evin, Tehran, Iran e-mail: [email protected] Fax: +98-21-22431775
inversion of the nonlinear polarization sign after one coherence length is a common manner [2–4]. This electric poling technique is an effective method to increase the conversion efficiency of SHG [5]. During recent years, enhancements by several orders of magnitude of second-order nonlinear interaction in NPCs have been reported [1, 4, 6–8]. The enhancement is ascribed to the combination of high electromagnetic mode density of states and a slowing down of the optical waves at a frequency near the photonic band gap (PBG) [1] and PBG edge [4], and also is to introduce resonant cavities to achieve better field confinement and enhancement [9–12]. However, reaching to high conversion efficiency and then SHG in defective NPCs based on slow wave systems (SWS) at the PBG edge and at defect modes have not been employed. SWS consists of different configurations such as coupled resonator optical waveguides (CROW) in one, two, or three dimensions [13]. One-dimensional CROWs (1DCROWs) are waveguides based on one-dimensional periodic structures, which consists of high quality factor (Q) cavities that are coupled to each of the nearest neighbor in spatial dimension [14]. By selection of appropriate structural parameter
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