Nanoscale photonics

Inverse opals are formed by the use of micro- or nanospheres to template a structure containing spherical cavities. One way of doing this is to use monodisperse latex spheres. These latex spheres are prepared by slow addition of an aqueous precursor solution into a reservoir of hydrophobic silicone liquid, forming emulsion droplets. The size of the droplets is controlled by the concentration of the aqueous latex, the speed at which the suspension is stirred and ratio between the silicone liquid and latex. Polymerisation results in latex spheres of well defined size of the order of a few hundred nanometers, and spherical shape. As the concentration of the latex spheres increases to its critical concentration 

---

Gudiksen, M. S. Lauhon, L. J. Wang, J. Smith, D. Lieber, C. M. 2002. Growth of nanowire superlattice structures for nanoscale photonics and electronics. Nature 415 617-620. 

J.-M.Loutrouz et al., Photonic Crystals Towards Nanoscale Photonic Devices (Springer, Berlin, 2005). 

Conventional photonic components are at the micrometer scale, while electronic elements have reached the nanometer scale in size. Nanoscale photonic circuits due to size-compatibility are crucial. Plasmonic switch is a novel example which takes the advantage of resonance coupling between single gold nanorods and photochromic dye molecules, and by controlling the plasmon resonance properties of the gold nanorods, the objective of a Plasmonic switch is achieved [29]. 

Among the variety of morphologies, nanowires are emerging as a powerful class of materials that, through controlled growth and organization, are opening up substantial opportunities for novel nanoscale photonic and electronic devices [352]. 

J.-M. Lourtioz, H. Benisty, V. Berger, J.-M. Gerard, D. Maystre, A. Tchelnokov, Photonic Crystals Towards Nanoscale Photonic Devices, 2nd edn. (Springer-Verlag, Berlin, 2008)... 

Milic TN, Chi N, Yablon DG, Flynn GW, Batteas JD, Drain CM (2002) Controlled hierarchical self-assembly and deposition of nanoscale photonic materials. Angew Chem Int Ed 41(12) 2117-2119... 

A nano-light-source generated on the metallic nano-tip induces a variety of optical phenomena in a nano-volume. Hence, nano-analysis, nano-identification and nanoimaging are achieved by combining the near-field technique with many kinds of spectroscopy. The use of a metallic nano-tip applied to nanoscale spectroscopy, for example, Raman spectroscopy [9], two-photon fluorescence spectroscopy [13] and infrared absorption spectroscopy [14], was reported in 1999. We have incorporated Raman spectroscopy with tip-enhanced near-field microscopy for the direct observation of molecules. In this section, we will give a brief introduction to Raman spectroscopy and demonstrate our experimental nano-Raman spectroscopy and imaging results. Furthermore, we will describe the improvement of spatial resolution... 

However, as Raman scattering is a two-photon process, the probability of the Raman scattering process is lower than that of fluorescence and IR absorption processes. The cross section of Raman scattering is 10 cm, which is much smaller than that of fluorescence ( 10 cm ) and IR absorption ( 10 °cm ). When we detect Raman scattering at the nanoscale, the number of photons obtained is less than with the usual micro-Raman spectroscopy due to reduction in the detection area or the number of molecules. To overcome this problem, we need to devise a method for amplification of Raman scattering. 

To summarize, we have shown here that enhanced electric-field distribution in metal nanoparticle assemblies can be visualized on the nanoscale by a near-field two-photon excitation imaging method. By combining this method and near-field Raman imaging, we have clearly demonstrated that hot spots in noble metal nanoparticle assemblies make a major contribution to surface enhanced Raman scattering. 

The creation of nanoscale sandwiches of compound semiconductor heterostructures, with gradients of chemical composition that are precisely sculpted, could produce quantum wells with appropriate properties. One can eventually think of a combined device that incorporates logic, storage, and communication for computing—based on a combination of electronic, spintronic, photonic, and optical technologies. Precise production and integrated use of many different materials will be a hallmark of future advanced device technology. 

UE provides an important potential advantage beyond small size. The excited states in Si-based electronics decay by phonons, and thus a huge heat dissipation problem faces nanoscale inorganic electronics at DR = 3 nm. In contrast, UE devices may be able to decay from their excited states by photon emission [15]. If the photon decay channel can be maximized, UE devices will have a great heat advantage over inorganic ones. 

Hayden, O. Agarwal, R. Lieber, C. M. 2006. Nanoscale avalanche photodiodes for highly sensitive and spatially resolved photon detection. Nature Mater. 5 352-353. 

McAlpine, M. C. Friedman, R. S. Lieber, C. M. 2005. High-performance nanowire electronics and photonics and nanoscale patterning on flexible plastic substrates. Proc. IEEE 93 1357-1363. 

Fig. 16.2 Nanoscale optofluidic sensor arrays (NOSA). (a) 3D illustration of a NOSA sensing element. It consists of a ID photonic crystal microcavity, which is evanescently coupled to a Si waveguide, (b) The electric field profile for the fundamental TE mode propagating through an air clad Si waveguide on SiOi. (c) SEM of a NOSA device array. It illustrates how this architecture is capable of two dimensional multiplexing, thus affording a large degree of parallelism, (d) Actual NOSA chip with an aligned PDMS fluidic layer on top. Reprinted from Ref. 37 with permission. 2008 Optical Society of America...

Hybrid polymer silica nanocomposites formed from various combinations of silicon alkoxides and polymers to create a nanoscale admixture of silica and organic polymers constitute a class of composite materials with combined properties of polymers and ceramics. They are finding increasing applications in protective coatings (Figure 7.1), optical devices, photonics, sensors and catalysis.1... 

Micelles have internal cavities of the order of 1-3 nm diameter, which allow them to act as nanoscale photochemical reactors for incarcerated guest molecules. Photons absorbed by the guest provide the necessary activation to break covalent bonds in the guest molecule, while the resulting reaction intermediates are themselves constrained to remain in the micelle cavity. 

This chapter shows that zeolite L is a very suitable host for the arrangement of a wide variety of chromophores. The structure of zeolite L is such that the formation of non-fluorescent dimers inside the channels can be prohibited and chromophores can be aligned in a certain direction. We have shown that this host-guest system can be used to make very efficient nanoscale two-directional photonic antenna systems. A broad spectral absorption range can be achieved by using several different cationic and neutral dyes. 

Three-dimensional (3D) structuring of materials allows miniaturization of photonic devices, micro-(nano-)electromechanical systems (MEMS and NEMS), micro-total analysis systems (yu,-TAS), and other systems functioning on the micro- and nanoscale. Miniature photonic structures enable practical implementation of near-held manipulation, plasmonics, and photonic band-gap (PEG) materials, also known as photonic crystals (PhC) [1,2]. In micromechanics, fast response times are possible due to the small dimensions of moving parts. Femtoliter-level sensitivity of /x-TAS devices has been achieved due to minute volumes and cross-sections of channels and reaction chambers, in combination with high resolution and sensitivity of optical con-focal microscopy. Progress in all these areas relies on the 3D structuring of bulk and thin-fllm dielectrics, metals, and organic photosensitive materials. 

---