Surface Plasmon Polariton (SPP) modes have attracted many minds for over 100 years. Confining light to dimensions
smaller than its propagating wavelength, point towards technological possibilities, such as optical circuitry within ultra
small computer processors or, small biochemical sensors. As for other lasers, surface plasmon lasers (SPL) require gain
and feedback. Yet, quenching of the fluorescence and induced current losses by the metal interface almost proved SPL to
be unattainable. Such impediments were circumvented by a periodic design on the nano scale, which reduced the losses
and maintained gain of a few ten thousands per cm.
Fiber optic sensor technology offers the possibility of implementing low weight, high performance and cost effective health and damage assessment for infrastructure elements. Common fiber sensors are based on the effect of external action on the spectral response of a Fabry-Perot or a Bragg grating section, or on the modal dynamics in multimode (MM) fiber. In the latter case, the fiber itself acts as the sensor, giving it the potential for large range coverage. We were interested in this type of sensor because of its cost advantage in monitoring structural health. In the course of the research, a new type of a rugged modal filter device, based on off-center splicing, was developed. This device, in combination with a MM fiber, was found to be a potential single point-pressure sensing device. Additionally, by translating the pressing point along a MM sensing fiber with a constant load and speed, a sinusoidal intensity modulation was observed. This harmonic behavior, during load translation, is explained by the theory of mode coupling and dispersion. The oscillation period, L~0.43. mm, obtained at 980 nm in a Corning SMF-28 fiber, corresponds to the wavevector difference, Db, between the two-coupled modes, by L = 2p/Db. An additional outcome of the present research is the observation that the response of the loaded MM fiber is strongly dependent on the polarization state of the light traveling along the MM fiber due to different response of the modes to polarization active elements. Our main conclusions are that in MM fiber optic sensor design, special cautions need to be taken in order to stabilize the system, and that the sensitivity along a MM fiber sensor is periodic with a period of ~ 0.4 - 0.5 mm, depending on various fiber parameters and excited modes.
Single-Wall Carbon Nanotubes (SWCNT) have stimulated extensive attention due to their extraordinary electronic properties. Unlike past studies of SWCNT where the tubes were agglomerated in bundles, or, suspended in a solution only recently, we were able to grow well-separated individual SWCNT in a controlled fashion. Moreover, unlike their counterparts, these SWCNT are strongly chiral and semiconductive. Ordered arrays of nano-size spheres (photonic crystals) attracted the attention of many researchers for their linear and nonlinear properties. For example, one is able to design and realize imaging elements thinner than the propagating wavelength or, use these highly dispersive structures to compress or, broaden ultra-short pulses. The optically confining environment of these three-dimensional, periodic structures is particularly attractive when it is imbedded with nonlinear material such as, SWCNT. In this talk I will review experimental results obtained for SWCNT. These tubes were encapsulated in polymers, suspended in solutions or, grown within the voids of photonic crystals. The experiments were conducted at the visible, near IR and THz frequency range using CW, nanosecond and femptosecond pulsed lasers. Overall, SWCNT exhibited a large nonlinear characteristic, which is associated with very short-lived photo-induced carriers.
We have conducted visible pump-THz probe experiments on single wall carbon nanotubes (SWCNTs) deposited on quartz substrates. Our results suggest that the photoexcited nanotubes exhibit localized transport due to Lorentz-type photo-induced localized states. These experiments were repeated for ion-implanted, 3-4nm Si nanoclusters in quartz for which a similar behavior was observed.
We have conducted visible pump-THz probe experiments on single wall carbon nanotubes (SWCNTs) on quartz substrates. Our results suggest an upper limit to the carrier-lifetime, which is on the order 1.5ps, limited only by the THz pulse duration. These experiments were repeated for ion-implanted, 3-4nm Si nanoclusters in quartz for which the carrier lifetime was also assessed at 1.5ps. THz time-domain spectroscopy (THz-TDS) of SWCNTs revealed that the THz pulse peak transmission changed under optical illumination.
We present a new type of planar optical interconnects; the transverse holograms. With this type of interconnect, one dimensional, input light distribution is converted into a one dimensional output light distribution via holographic pattering along the direction of the optical wave propagation.
Artificial dielectric materials are dielectrics in which other dielectrics or conductors are embedded to achieve different, effective dielectric properties. In the experiment, transmission lines embedded with suspended GaAs crystallites were used. The effective dielectric constant was changing upon illuminating the strip-line with light.
Easy to make, potentially high efficient Schottky type solar cells are presented. Patterning of the cells of Si wafers was achieved by photo-ablation using a UV Excimer laser. We have found that the patterned cells were as much as 15% more efficient than non-patterned cells.
Novel dielectric properties are achieved when semiconductor crystallites are emedded in polymeric, passive host material. Upon illumination which photon energy above the semiconductor band-gap, a dielectric constant change will be observed for a below band-gap, propagating photon.
Based on a non-linear coupling between the etchant species and the photo-induced carriers during photo-electrochemical etching of semiconductor surfaces, we propose that the reaction residue, the oxide layer, regulates the reaction.