The study of DNA nanofibers
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The study of DNA nanofibers Mahi R. Singh Department of Physics and Astronomy, University of Western Ontario, London, Canada N6G 3K7. Abstract: We study the acousto-optic effect on the polaritonic properties of DNA nanofibers which are fabricated by embedding a DNA wire into a polaritonic material. This is a new research area and can be called nanobiopolaritonics. Polaritonic materials have energy gaps in their dispersion relation due to the coupling between optical photons and photons. The bound states of DNA wire are calculated using transfer matrix method. It is found that some of the bound states of the DNA wire lie within the band gap of the polaritonic material. These states do not decay into the polaritonic material since there are not states available for decay process to occur. This means DNA nanofibers has an extremely high Q factor. We have also studied the acousto-optic effect on the photon absorption in DNA nanofibers doped with ensemble of quantum dots. The quantum dots interact with the DNA wire via electron bound polaritons interaction. We have discovered a switching mechanism in DNA nanofibers. When the resonance energy of the quantum dots lies near bound polaritons states, the system becomes transmitting for frequency of a probe field due to the strong electron bound polaritons interaction. This is can be assigned as ‘ON’ of the switch. However, when the strain field is applied the DNA fiber can now absorb the probe beam. This is can be assigned as ‘OFF’ of the switch. Keywords: Nano-biophotonics, DNA fibers, quantum dots, all-optical switching, nano-biooptical devices. PACS: 42.70Qs, 42.55Tv, 78.20.Bh:
INTRODUCTION In this paper we study the acousto-optic effect on the polaritonic properties of DNA nanofibers. The nanofibers are fabricated by embedding DNA wires into a polaritonic material. This is new research area and can be called nano-biopolaritonics. Examples of these materials are semiconductors (i.e. GaP, SiC,), oxide crystals and salts. These materials have energy gaps in their dispersion relation due to the coupling between optical photons and photons [1, 2]. In polaritonic materials the radiation signals are carried out by an admixture of photons and optical phonons rather than electrons or photons. Polaritons propagate with frequencies in the range of hundreds of gigahertz to several terahertz (THz). Therefore, polaritonics lies in an intermediate regime between photonics and electronics.Therefore, this field will bridge the gap between electronics and photonics. Recently there is a considerable interest to study the optical and transport properties of DNA structures [3]. For example, we have developed a theory of charge transport in DNA structures based on polaron hopping [4]. Polarons are nothing but mixture of electron and phonon. A phonon is a quanta of quantized viberational energy present in DNA. Internal motions of the helix due to strain field localized. The unwinding of DNA increases molecular orbital overlap between bases while decreases the base-to-base distance. Phonons are
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