We present a novel Lotus shaped negative curvature antiresonant hollow core fiber with the potential for low loss and very wide bandwidth. A minimum loss of ~10 dB/km at 1550 nm and less than 100 dB/km over a bandwidth of ~650 nm is demonstrated, with effectively single mode behaviour over lengths of a few tens of meters. We demonstrate power penalty free 10.5-Gbit/s data transmission through an 85 m length of fiber at both O and C telecom bands. The fiber macro bend sensitivity has also been tested, which is relevant for telecom as well as for other applications including beam delivery and gas based sensing. The bend loss is found to be below 0.2 dB/m for bend radii down to 8 cm at wavelengths away from the short wavelength edge of the transmission band.Index Terms-Fiber optics communications, hollow core optical fibers, low latency, microstructured optical fibers.

In microelectromechanical systems (MEMS), parallel plate structures with sub-micron separation have been of much use in various types of sensors and actuators. As the separation distance in these devices reaches down to hundreds of nm, it gets difficult to control the gap due to parasitic charging and the Casimir force. The Casimir force and its dependence on the boundary conditions of electromagnetic fields is a phenomenon that is mostly avoided rather than explored. In this paper, we present a methodology involving a micromachined parallel-plate geometry to measure the Casimir force at sub-micron separation. The new feature in this setup is the micromechanical means of parallelism control to measure the force at extremely small separation distances. A fabrication process for the micromachined parallel-plate structure is also given.

We review and compare recent hollow core photonic crystal fibers, both bandgap-guiding and antiresonant, which were designed and fabricated for high power laser delivery applications.High power lasers are routinely used across a wide range of applications including welding, metal cutting and surgery. A wide range of laser sources are deployed and different parameters such as pulse length, beam quality and wavelength define their application space. Within these laser sources there are a growing range of ultra-high average power lasers, as well as ultra-short pulse lasers, which have a wide spectral bandwidth and a very high peak power. Ideally, the laser output will be delivered to the point of need via a flexible and versatile beam delivery system, which is able to maintain or even improve the beam quality, while transporting the laser light with minimal attenuation.

We present a novel negative curvature antiresonant hollow core fibre design with the potential for low loss and very wide bandwidth. A low loss of 10.5 dB/km at 1550 nm is demonstrated, showing its potential for use in data transmission and high power beam delivery applications.

The project was financially supported by the Smartmix MEMPHIS program of the Dutch Ministry of Economic A↵airs. Cover Design by: R. Kottumakulal Jaganatharaja Front cover: Two hands acting as parallel plate boundary and the waves as the quantum vacuum fluctuations that fits within the boundary. Back cover: Clockwise from left (top): SEM image of bonded parallel plate structures for Casimir force measurement; Red light propagating through the TripleX waveguide; and the SEM image showing the top view of waveguide with anti-stiction bumps. Printed by Wöhrmann