The nonlinearities in silicon are diverse. This Review covers the wealth of nonlinear effects in silicon and highlights the important applications and technological solutions in nonlinear silicon photonics. The increasing capability for manufacturing a wide variety of optoelectronic devices from polymer and polymer–silicon hybrids, including transmission fibre, modulators, detectors and light sources, suggests that organic photonics has a promising future in communications and other applications.

Nonlinear silicon photonics

Integrated optical circuits based on silicon-on-insulator technology are likely to become the mainstay of the photonics industry. Over recent years an impressive range of silicon-on-insulator devices has been realized, including waveguides1,2, filters3,4 and photonic-crystal devices5. However, silicon-based all-optical switching is still challenging owing to the slow dynamics of two-photon generated free carriers. Here we show that silicon–organic hybrid integration overcomes such intrinsic limitations by combining the best of two worlds, using mature CMOS processing to fabricate the waveguide, and molecular beam deposition to cover it with organic molecules that efficiently mediate all-optical interaction without introducing significant absorption. We fabricate a 4-mm-long silicon–organic hybrid waveguide with a record nonlinearity coefficient of γ ≈ 1 × 105 W−1 km−1 and perform all-optical demultiplexing of 170.8 Gb s−1 to 42.7 Gb s−1. This is—to the best of our knowledge—the fastest silicon photonic optical signal processing demonstrated. A silicon–organic hybrid slot waveguide with a strong optical nonlinearity is demonstrated to perform ultrafast all-optical demultiplexing of high-bit-rate data streams. The approach could form the basis of compact high-speed optical processing units for future communication networks.

/pdf/all-optical-high-speed-signal-processing-with-silicon-2nxlva6l54.pdf

All-optical high-speed signal processing with silicon–organic hybrid slot waveguides

Optical fibre nanowires and microwires offer a variety of enabling properties, including large evanescent fields, flexibility, configurability, high confinement, robustness and compactness. These distinctive features have been exploited in a wealth of applications ranging from telecommunication devices to sensors, from optical manipulation to high Q resonators. In this paper I will review the fundamentals and applications of nanowires and microwires manufactured from optical fibres.

https://iopscience.iop.org/article/10.1088/2040-8978/12/4/043001/pdf

Optical fibre nanowires and microwires: a review

The propagation of pulses through waveguides with sub-wavelength features, inhomogeneous transverse structure, and high index contrast cannot be described accurately using existing models in the presence of nonlinear effects. Here we report the development of a generalised full vectorial model of nonlinear pulse propagation and demonstrate that, unlike the standard pulse propagation formulation, the z-component of guided modes plays a key role for these new structures, and results in generalised definitions of the nonlinear coefficient gamma, Aeff , and mode orthognality. While new definitions reduce to standard definitions in some limits, significant differences are predicted, including a factor of approximately 2 higher value for gamma, for emerging waveguides and microstructured fibers.

/pdf/a-full-vectorial-model-for-pulse-propagation-in-emerging-1fcomgotnp.pdf

A full vectorial model for pulse propagation in emerging waveguides with subwavelength structures part I: Kerr nonlinearity

Bend resistant multimode optical fibers are disclosed herein. Multimode optical fibers disclosed herein comprise a core region and a cladding region surrounding and directly adjacent to the core region, the cladding region comprising a depressed-index annular portion comprising a depressed relative refractive index.

Bend resistant multimode optical fiber

We report on the progress of bismuth oxide glass holey fibers for nonlinear device applications. The use of micron-scale core diameters has resulted in a very high nonlinearity of 1100 W-1 km-1 at 1550 nm. The nonlinear performance of the fibers is evaluated in terms of a newly introduced figure-of-merit for nonlinear device applications. Anomalous dispersion at 1550 nm has been predicted and experimentally confirmed by soliton self-frequency shifting. In addition, we demonstrate the fusion-splicing of a bismuth holey fiber to silica fibers, which has resulted in reduced coupling loss and robust single mode guiding at 1550 nm.

https://digital.library.adelaide.edu.au/dspace/bitstream/2440/34939/1/hdl_34939.pdf

Bismuth glass holey fibers with high nonlinearity

This paper reports on the recent progress in the design and fabrication of high-nonlinearity lead-silicate holey fibers (HFs). First, the fabrication of a fiber designed to offer close to the maximum possible nonlinearity per unit length in this glass type is described. A value of γ = 1860 W -1 . km -1 at a wavelength of 1.55 μm is achieved, which is believed to be a record for any fiber at this wavelength. Second, the design and fabrication of a fiber with a slightly reduced nonlinearity but with dispersion-shifted characteristics tailored to enhance broadband supercontinuum (SC) generation when pumped at a wavelength of 1.06 μm-a wavelength readily generated using Yb-doped fiber lasers-are described. SC generation spanning more than 1000 nm is observed for modest pulse energies of ∼ 100 pJ using a short length of this fiber. Finally, the results of numerical simulations of the SC process in the proposed fibers are presented, which are in good agreement with the experimental observations and highlight the importance of accurate control of the zero-dispersion wavelength (ZDW) when optimizing such fibers for SC performance.

High-nonlinearity dispersion-shifted lead-silicate holey fibers for efficient 1-μm pumped supercontinuum generation

This paper reports on the recent progress in the design and fabrication of high-nonlinearity lead-silicate holey fibers (HFs). First, the fabrication of a fiber designed to offer close to the maximum possible nonlinearity per unit length in this glass type is described. A value of /spl gamma/=1860 W/sup -1//spl middot/km/sup -1/ at a wavelength of 1.55 /spl mu/m is achieved, which is believed to be a record for any fiber at this wavelength. Second, the design and fabrication of a fiber with a slightly reduced nonlinearity but with dispersion-shifted characteristics tailored to enhance broadband supercontinuum (SC) generation when pumped at a wavelength of 1.06 /spl mu/m-a wavelength readily generated using Yb-doped fiber lasers-are described. SC generation spanning more than 1000 nm is observed for modest pulse energies of /spl sim/ 100 pJ using a short length of this fiber. Finally, the results of numerical simulations of the SC process in the proposed fibers are presented, which are in good agreement with the experimental observations and highlight the importance of accurate control of the zero-dispersion wavelength (ZDW) when optimizing such fibers for SC performance.

/pdf/high-nonlinearity-dispersion-shifted-lead-silicate-holey-cgjjm6plpw.pdf

High-nonlinearity dispersion-shifted lead-silicate holey fibers for efficient 1-/spl mu/m pumped supercontinuum generation

We demonstrate four-wave-mixing based wavelength conversion at 1.55µm in a 2.2 m-long dispersion-shifted lead-silicate holey fiber. For a pump peak power of ~6W, a conversion efficiency of -6dB is achieved over a 3dB bandwidth of ~30nm. Numerical simulations are used to predict the performance of the fiber for different experimental conditions and to address the potential of dispersion-tailored lead silicate holey fibers in wavelength conversion applications utilizing four-wave-mixing. It is shown that highly efficient and broadband wavelength conversion, covering the entire C-band, can be achieved for such fibers at reasonable optical pump powers and for fiber lengths as short as ~2m.

Towards efficient and broadband four-wave-mixing using short-length dispersion tailored lead silicate holey fibers

We report the use of a 2m long Bismuth Oxide fiber with an ultra-high nonlinearity of ~1100 W in a simple 2R regeneration experiment based on self phase modulation and offset filtering. Numerical simulations and experimental results confirm the suitability of this kind of fiber for 2R regeneration. An improvement in receiver sensitivity of more than 5 dB at 10 Gb/s and 2 dB at 40 Gb/s is achieved.

S. Asimakis

Papers

Bismuth glass holey fibers with high nonlinearity

High-nonlinearity dispersion-shifted lead-silicate holey fibers for efficient 1-μm pumped supercontinuum generation

High-nonlinearity dispersion-shifted lead-silicate holey fibers for efficient 1-/spl mu/m pumped supercontinuum generation

Towards efficient and broadband four-wave-mixing using short-length dispersion tailored lead silicate holey fibers

2R regenerator based on a 2-m-long highly nonlinear bismuth oxide fiber