Efficient third harmonic generation in photonic nanowires

In a photonic nanowire the strong optical confinement allows for the phase matching of nonlinear interactions that would not normally be phase matched, while the large longitudinal component of the electric field serves to further enhance the effective nonlinearity. Thus such waveguides are good choices for studying nonlinear effects such as third harmonic generation. In this paper we analyse third harmonic generation analytically and present the criteria for optimal harmonic generation. In addition we analyse the inverse process of 1/3 harmonic generation and show that efficient parametric amplifiers can be made which would be a high brightness source of entangled photons for producing GHZ states

Efficient low-threshold lasers based on an erbium-doped holey fiber

We report experimental results on the continuous-wave lasers based on a small core erbium-doped holey fiber. In a simple Fabry-Perot-type cavity with high output coupling, we demonstrate low-threshold (0.55 mW) high slope-efficiency (57.3%) operation confirming both the quality and exceptionally high gain efficiency of the fiber. In an all-fiber ring cavity where the cavity loss is reduced, we show that it is possible to achieve a low-threshold laser with extremely wide tunability (>100 nm around 1550 nm). Our results illustrate some of the unique opportunities provided by active small core holey fibers

The role of confinement loss in highly nonlinear silica holey fibers

Small-core holey fibers (HFs) can offer tight mode confinement, and are, therefore, attractive for highly nonlinear fiber applications. However, we show here that confinement loss can significantly degrade the performance of devices based on such small core fibers. We also identify a range of fiber designs that result in high fiber nonlinearity and low confinement loss. In particular, we show that pure silica HFs can exhibit effective nonlinearities more than 50 times higher than conventional fibers, and that the confinement loss can be lowered below the loss of standard fiber types

A holey fiber based Brillouin laser

We demonstrate for the first time a Brillouin laser based on a Holey Fiber (HF). Using a simple Fabry-Perot resonator scheme containing a 75m long highly nonlinear HF with an effective area of 2.85µm2 we obtain a threshold of 125mW and a slope efficiency of ~70%

The quick and the dead: when reaction beats intention

Everyday behaviour involves a trade-off between planned actions and reaction to environmental events.Evidence from neurophysiology, neurology and functional brain imaging suggests different neural bases for the control of different movement types. Here we develop a behavioural paradigm to test movement dynamics for intentional versus reaction movements and provide evidence for a ‘reactive advantage’ in movement execution, whereby the same action is executed faster in reaction to an opponent. We placed pairs of participants in competition with each other to make a series of button presses. Within subject analysis of movement times revealed a 10 per cent benefit for reactive actions. This was maintained when opponents performed dissimilar actions, and when participants competed against a computer, suggesting that the effect is not related to facilitation produced by action observation. Rather, faster ballistic movements may be a general property of reactive motor control, potentially providing a useful means of promoting survival

Fundamental properties of small core holey fibres

We explore some of the fundamental limits in small core silica holey fibres that have a direct bearing on nonlinear device applications. In particular, we examine issues related to coupling and polarization in these fibres

Air-clad holmium-doped silica fiber laser

Date of Publication : 10 December 2015We report the design, fabrication, and operation of an air-clad holmium-doped fiber laser that was manufactured by directly milling the rare-earth-doped preform. This silica fiber laser operates at 2.1 μm with a slope efficiency of 49.7%, and is in-band pumped with a 1.94-μm thulium fiber laser. To the best of our knowledge, this is the first demonstration of an air-clad holmium-doped fiber laser.Sebastian W. S. Ng, David G. Lancaster, Tanya M. Monro, Peter C. Henry, and David J. Ottawa

SOHO (SOlid HOley) fiber

We report the first successful fabrication of an all-solid microstructured fiber based on large index contrast glasses. High effective nonlinearity 230 W at 1550nm has been predicted and measured

Towards new fiber optic sensors based on the vapor deposited conducting polymer PEDOT:Tos

Conducting polymers are widely researched in terms of both their electrical and optical properties. These optical properties are typically observed on the macroscopic (mm2- cm2) scale using techniques such as UV-Vis-NIR spectroscopy. To broaden their application, fabrication and characterization of conducting polymers on the microscale (μm2) are required. In this paper, microscale poly(3,4-ethylenedioxytiophene)-tosylate (PEDOT:Tos) layers were vapor deposited at the tip of a single mode optical fiber. This was done without the need for intermediate layers such as Indium Tin Oxide commonly used in electropolymerization. The optical properties and behavior of PEDOT:Tos below thicknesses of 500 nm were investigated. Laser-induced damage (LID) behavior of the PEDOT:Tos layer was observed for different intensities of CW or pulsed near infrared light (primarily at 1550 nm). A mathematical model based on energy deposition and the laser-induced damage threshold (LIDT) for low intensity light radiation was developed. It was shown that LID can be avoided by applying irradiance below 31.8 W/mm2 for both CW and pulsed laser. Understanding of LIDT has implications for the use of conducting polymers in new optical fiber sensing applications.Soroush Shahnia, Junaiz Rehmen, David G. Lancaster, Tanya M. Monro, Heike Ebendorff-Heidepriem, Drew Evans and Shahraam Afshar V

An ultra-stable 2.9 mu m guided-wave chip laser and application to nano-spectroscopy

We present a configurable guided-wave planar glass-chip laser that produces low-noise and high-quality continuous-wave laser emission tunable from 2.82 to 2.95 µm. The laser has a low threshold and intrinsic power and mode stability attributable to the high overlap of gain volume and pump mode defined by an ultrafast laser inscribed waveguide. The laser emission is single transverse-mode with a Gaussian spatial profile and M²x,y ∼ 1.05, 1.10. The power drift is ∼0.08% rms over ∼2 h. When configured in a spectrally free-running cavity, the guided-wave laser emits up to 170 mW. The benefit of low-noise and stable wavelength emission of this hydroxide resonant laser is demonstrated by acquiring high signal-to-noise images and spectroscopy of a corroded copper surface film with corrosion products containing water and hydroxide ions with a scattering-scanning near-field optical microscope.D.G. Lancaster, D.E. Otten, A. Cernescu, N. Bourbeau Hébert, G.Y. Chen, C.M. Johnson, T.M. Monro, and J. Genes