Low-loss hollow-core silica/air photonic bandgap fibre

Abstract

Photonic bandgap structures use the principle of interference to reflect radiation. Reflection from photonic bandgap structures has been demonstrated in one, two and three dimensions and various applications have been proposed. Early work in hollow-core photonic bandgap fibre technology used a hexagonal structure surrounding the air core; this fibre was the first demonstration of light guided inside an air core of a photonic bandgap fibre. The potential benefits of guiding light in air derive from lower Rayleigh scattering, lower nonlinearity and lower transmission loss compared to conventional waveguides. In addition, these fibres offer a new platform for studying nonlinear optics in gases. Owing largely to challenges in fabrication, the early air-core fibres were only available in short lengths, and so systematic studies of loss were not possible. More recently, longer lengths of fibre have become available with reported losses of 1,000 dB km(-1). We report here the fabrication and characterization of long lengths of low attenuation photonic bandgap fibre. Attenuation of less than 30 dB km(-1) over a wide transmission window is observed with minimum loss of 13 dB km(-1) at 1,500 nm, measured on 100 m of fibre. Coupling between surface and core modes of the structure is identified as an important contributor to transmission loss in hollow-core photonic bandgap fibres.

Coherent-state-induced transparency

“…(15), where the function 1 F 1 and the exponential factor tend to unity for |α| 2 /N 2 < 1, while for the transparency one needs D ≪ 1 as seen from Eqs. (17). For large N 2 this strongly weakens the interaction of the control field with atoms, so that the maximum transparency is expected in the case of single-mode coherent state or CW control field, when the transparency in fact perfectly coincides with that induced by the classical control field (Fig.2a, red line).…”

“…This behavior results from the modification of the photon statistics in the coherent state, where the increase of mode number shifts the * Electronic address: agogyan@gmail.com maximum of photon distribution to the Fock states with small number of photons provided that the total intensity of the control field remains unchanged. To enhance the atom-photon interaction and cancel the Doppler broadening, we consider propagation of a weak probe pulse in a cold atomic ensemble, such as the atoms inside a hollow-core photonic crystal fiber (HC-PCF) of a few microns in diameter, which can tightly confine both atoms and photons transversely over long interaction lengths [11,12,[17][18][19][20][21]. Of course, different dissipative effects are significant for coherent states with different mode numbers, however, we ignore these complications to concentrate on more fundamental issues.…”

Air-guiding photonic bandgap fiber with improved triangular air-silica photonic crystal cladding

“…3(a) stay further apart as compared to the fiber reported in. 2 This means the coupling between the two mode groups is smaller. With careful excitation, we can achieve single-mode operation for applications like laser beam delivery, in which severe fiber bending can be purposely avoided.…”

“…1(a)] explicitly uses air-silica photonic crystal (PC) made from a bundle of thin silica tubes (triangular placement) in its cladding. 2 Such fiber has two main disadvantages: surface-mode interference and multimode operation. Though theoretically, there does exist some design which eliminates the surface-mode problem, 3 such fiber hasn't been fabricated, largely due to difficulties in preform preparation and maintaining the core shape during drawing.…”

Fabrication of functional microstructured optical fibers through a selective-filling technique

“…1 More recently, microstructured optical fibers (MOFs) inspired by photonic band-gap research have been extensively investigated, leading to many interesting optical phenomena. [2][3][4] A hollow-core MOF can achieve air guiding by using the Bragg reflection from the periodic fiber cladding structure, 1 which can potentially lead to ultralow propagation loss 5 and have a significant impact on long-distance optical communications. In addition, hollow-core MOFs are an attractive medium for the study of nonlinear optical phenomena in gas phase materials.…”