R. Winfield

73.7 Tb/s (96 x 3 x 256-Gb/s) mode-division-multiplexed DP-16QAM transmission with inline MM-EDFA

Transmission of a 73.7 Tb/s (96 x 3 x 256-Gb/s) DP-16QAM mode-division-multiplexed signal over 119 km of few-mode fiber transmission line incorporating an inline multi mode EDFA and a phase plate based mode (de-)multiplexer is demonstrated. Data-aided 6 x 6 MIMO digital signal processing was used to demodulate the signal. The total demonstrated net capacity, taking into account 20% of FEC-overhead and 7.5% additional overhead (Ethernet and training sequences), is 57.6 Tb/s, corresponding to a spectral efficiency of 12 bits/s/Hz.

20 × 960-Gb/s Space-division-multiplexed 32QAM transmission over 60 km few-mode fiber

We show transmission of 20 wavelength-division-multiplexed (WDM) × 960-Gb/s space-division-multiplexed 32QAM modulated channels (spectral efficiency (SE) of 15 bits/s/Hz) over 60 km of few-mode fiber (FMF) with inline few-mode EDFA (FM-EDFA). Soft-decision FEC was implemented and used to achieve error-free transmission.

Three mode Er3+ ring-doped fiber amplifier for mode-division multiplexed transmission

We successfully fabricate three-mode erbium doped fiber with a confined Er(3+) doped ring structure and experimentally characterize the amplifier performance with a view to mode-division multiplexed (MDM) transmission. The differential modal gain was effectively mitigated by controlling the relative thickness of the ring-doped layer in the active fiber and pump launch conditions. A detailed study of the modal gain properties, amplifier performance in a MDM transmission system and inter-modal cross-gain modulation and associated transient effects is presented.

Refractive femtosecond laser beam shaping for two-photon polymerization

Three dimensional microstructure fabrication by two-photon polymerization is an established technique that normally uses single beam serial writing. Recently the use of a micro-optical element, to give multipoint beam delivery, was reported to give a degree of parallel processing. The authors describe an alternative approach to parallel processing using an axicon lens. This is a refractive element that, in combination with a high power microscope objective, efficiently transforms the laser beam from a Gaussian spot to an annulus. The authors demonstrate that the beam can polymerize a three dimensional shape, with nanoscale resolution. The use of more sophisticated refractive beam shaping is also discussed.

Novel approaches to direct search algorithms for the design of diffractive optical elements

The implementation of direct search schemes for the design of multi-level diffractive optical elements is investigated. In particular, simulated annealing with an estimated temperature is shown to yield improvements in iteration time over simple simulated annealing. A cost function for the formation of greylevel diffraction patterns is suggested. An efficient method of finding an appropriate initial temperature for simulated annealing is presented.

Nonlinear effects on pulsed laser propagation in the atmosphere

Nonlinear effects on the propagation of a high power pulsed laser beam through the earths atmosphere are modeled. Stimulated Raman scattering in relatively modest power laser beams is estimated to be very significant when extremely long path lengths are considered. Whole beam self-focusing may also seriously affect beam propagation. The observation of these phenomena is likely to be enhanced by wavefront compensation techniques to remove linear refractive-index atmospheric effects such as beam steering and scintillation. Examples of space to ground and ground to space beam propagation are presented.

Graphene-doped photo-patternable ionogels: tuning of conductivity and mechanical stability of 3D microstructures

This work reports for the first time the development of enhanced-conductivity, graphene-doped photo-patternable hybrid organic-inorganic ionogels and the effect of the subsequent materials condensation on the conductivity and mechanical stability of three-dimensional microstructures fabricated by multi-photon polymerisation (MPP). Ionogels were based on photocurable silicon/zirconium hybrid sol–gel materials and phosphonium (trihexyltetradecylphosphonium dicyanamide) [P6,6,6,14][DCA] ionic liquid (IL). To optimise the dispersion of graphene within the ionogel matrices, aqueous solutions of graphene were prepared, as opposed to the conventional graphene powder approach, and employed as catalysts of hydrolysis and condensation reactions occurring in the sol–gel process. Ionogels were prepared via a two step process by varying the hydrolysis degree from 25 to 50%, IL content between 0–50 w/w%, and the inorganic modifier (zirconate complex) concentration from 30 to 60 mol.% against the photocurable ormosil and they were characterised via Raman, Electrochemical Impedance Spectroscopy and Transmission Electron Microscopy. MPP was performed on the hybrid ionogels, resulting in three-dimensional microstructures that were characterised using scanning electron microscopy. It is clearly demonstrated that the molecular formulation of the ionogels, including the concentration of graphene and the zirconate network modifier, plays a critical role in the conductivity of the ionogels and influences the resulting mechanical stability of the fabricated three-dimensional microstructures. This work aims to establish for the first time the relationship between the molecular design and condensation of materials in the physico-chemistry and dynamic of ionogels.

Capacitance and

This paper presents a method for measuring the complex permittivity of a dielectric material on a dielectric/metal stack without etching the dielectric layer. A series of circular capacitor test structures were designed and fabricated. For the first time, the unwanted capacitance Cp, which is formed by the oxide layer between the bottom metal layer and the silicon substrate, was defined and systematically investigated. The technique is shown to be suitable for characterization of a lead magnesium niobate-lead titanate (PMNT) material on the complex cross sections involved in the development of a novel high-k material. An extremely high- k of 1115 (high capacitance density of 26 fF/μm2) for a PMNT metal-insulator-metal (MIM) capacitor was achieved. In addition, low leakage current density of 2 × 10-10 A/cm2 and low loss tangent were also obtained. These results clearly showed that the PMNT MIM capacitors are very promising for both decoupling and more general RF and mixed-signal applications until the year 2020, according to the International Technology Roadmap for Semiconductors (ITRS).

S

High-performance metal-insulator-metal (MIM) capacitors using novel Pb(Mg_0.33Nb_0.67)_0.65Ti_0.35O₃ (PMNT) thin films were fabricated and investigated. The dielectric properties of the PMNT capacitors were characterized at both dc and radio frequencies. A significant high-κ of 1115 (high capacitance density of 26 fF/μm²) for a PMNT MIM capacitor has been achieved. In addition, small leakage current density of 2 × 10^-10 A/cm² and low loss tangent of 0.0188 are also obtained. The results indicate that high-κ PMNT is a promising candidate material for high-performance MIM capacitors.

-Parameter Techniques for Dielectric Characterization With Application to High-

An analysis is made of the possible methods of liberation of electrons from atomic negative halide ions in the context of providing sufficient preionization for discharge‐pumped rare‐gas‐halide excimer lasers. Some previous treatments of collisional detachment are shown to be in error by several orders of magnitude. Ion and electron impact detachment of electrons is found to produce a negligible preionization electron number density. Photodetachment is shown to be the dominant electron liberation mechanism, and to be capable of producing electron densities adequate for preionization of the excimer laser discharge.