Optical Waveguide Theory

Curious wave phenomena that occur in optical fibres due to the interplay of instability and nonlinear effects are reviewed.

/pdf/instabilities-breathers-and-rogue-waves-in-optics-252ilwzt4i.pdf

Instabilities, breathers and rogue waves in optics

Graphene plasmons were predicted to possess ultra-strong field confinement and very low damping at the same time, enabling new classes of devices for deep subwavelength metamaterials, single-photon nonlinearities, extraordinarily strong light-matter interactions and nano-optoelectronic switches. While all of these great prospects require low damping, thus far strong plasmon damping was observed, with both impurity scattering and many-body effects in graphene proposed as possible explanations. With the advent of van der Waals heterostructures, new methods have been developed to integrate graphene with other atomically flat materials. In this letter we exploit near-field microscopy to image propagating plasmons in high quality graphene encapsulated between two films of hexagonal boron nitride (h-BN). We determine dispersion and particularly plasmon damping in real space. We find unprecedented low plasmon damping combined with strong field confinement, and identify the main damping channels as intrinsic thermal phonons in the graphene and dielectric losses in the h-BN. The observation and in-depth understanding of low plasmon damping is the key for the development of graphene nano-photonic and nano-optoelectronic devices.

Highly confined low-loss plasmons in graphene-boron nitride heterostructures

Space-division multiplexing (SDM) uses multiplicity of space channels to increase capacity for optical communication. It is applicable for optical communication in both free space and guided waves. This paper focuses on SDM for fiber-optic communication using few-mode fibers or multimode fibers, in particular on the critical challenge of mode crosstalk. Multiple-input–multiple-output (MIMO) equalization methods developed for wireless communication can be applied as an electronic method to equalize mode crosstalk. Optical approaches, including differential modal group delay management, strong mode coupling, and multicore fibers, are necessary to bring the computational complexity for MIMO mode crosstalk equalization to practical levels. Progress in passive devices, such as (de)multiplexers, and active devices, such as amplifiers and switches, which are considered straightforward challenges in comparison with mode crosstalk, are reviewed. Finally, we present the prospects for SDM in optical transmission and networking.

Space-division multiplexing: the next frontier in optical communication

Optical fiber gratings have developed into a mature technology with a wide range of applications in various areas, including physical sensing for temperature, strain, acoustic waves and pressure. All of these applications rely on the perturbation of the period or refractive index of a grating inscribed in the fiber core as a transducing mechanism between a quantity to be measured and the optical spectral response of the fiber grating. This paper presents a relatively recent variant of the fiber grating concept, whereby a small tilt of the grating fringes causes coupling of the optical power from the core mode into a multitude of cladding modes, each with its own wavevector and mode field shape. The main consequence of doing so is that the differential response of the modes can then be used to multiply the sensing modalities available for a single fiber grating and also to increase the sensor resolution by taking advantage of the large amount of data available. In particular, the temperature cross-sensitivity and power source fluctuation noise inherent in all fiber grating designs can be completely eliminated by referencing all the spectral measurements to the wavelength and power level of the core mode back-reflection. The mode resonances have a quality factor of 105, and they can be observed in reflection or transmission. A thorough review of experimental and theoretical results will show that tilted fiber Bragg gratings can be used for high resolution refractometry, surface plasmon resonance applications, and multiparameter physical sensing (strain, vibration, curvature, and temperature).

Tilted fiber Bragg grating sensors

A novel method utilizing a cantilever beam to tune the center wavelength and the linear chirp of fiber gratings is presented. Based on this method, the center wavelength and the chirp of a 10 cm uniform fiber grating are tuned to compensate for the dispersion of 19 ps pulse width after 133 km transmission. Experimental results show that the effect of dispersion compensation is favorable.

Dispersion compensation experiment on 19 ps pulse width over 133 km single mode fiber with tunable chirp and wavelength gratings

The single-direction, self-healing all optical ring networks with double optical fibers based on the wavelength routing character of fiber gratings is introduced in this paper. The four-node network with ring topology can provide 16×10Gb/s optical transmission. The wavelength-selecting character of chirped fiber gratings is used for wavelength routing, and the function of dispersion compensation and multi-channel add/drop is achieved, too. The SNMP (Simple Network Management Protocol) model is referred to manage this network. Some important parameters are real-time observed to control the network. The results show that, if any optical fiber in the ring is broken down, the interrupted telecommunication service can be recovered automatically in less than 20ms.

Novel optical fiber self-healing network based on wavelength routing of fiber gratings

In this paper, we propose a method of creating plasmons vortex on graphene through cross shape nanoantennas under linearly polarized incidence. For each cross shape antenna, the linearly polarized incidence can be coupled to a near-field plasmons vortex on graphene through antenna resonances. When multiple antennas are arranged into a closed circular array, the sign of topological charge of plasmons vortex can be controlled by the linearly polarized direction of incident light with the distribution of absolute field component exhibiting a non-ideal donut profile. The creating of plasmons vortex on graphene may provide new possibilities in various applications, such as the nanoparticles trapping.

Creation of Graphene Plasmons Vortex via Cross Shape Nanoantennas Under Linearly Polarized Incidence

We present a detailed study on trapping and releasing of light in a graded graphene-silica metamaterial waveguide. By applying proper gate voltages onto the graphene layers, the metamaterial with graded-permittivity has the ability to trap the light due to the vanishing of normalized optical power flow between forward and backward modes. Based on the effective medium theory, the distributions of modes and the transmission characteristics of normalized power flows are investigated. Theoretical investigation shows that the waveguide has the ability to turn on or off the mid-infrared light from 5400 nm to 5800 nm. Moreover, adjusting the voltages on graphene layers can alter the bandwidth of trapped light. The graded metamaterial waveguide can be the candidate for multi-wavelength absorber based on the light trapping effect.

Shuisheng Jian

Papers

Dispersion compensation experiment on 19 ps pulse width over 133 km single mode fiber with tunable chirp and wavelength gratings

Novel optical fiber self-healing network based on wavelength routing of fiber gratings

Creation of Graphene Plasmons Vortex via Cross Shape Nanoantennas Under Linearly Polarized Incidence

Tunable trapping and releasing light in graded graphene-silica metamaterial waveguide

Transient responses to slowly varying input waveforms in backward pumped Raman amplifiers