Fiber Optics|3 Article(s)
Analytical formulation for the bend loss in single-ring hollow-core photonic crystal fibers
Michael H. Frosz, Paul Roth, Mehmet C. Günendi, and Philip St.J. Russell
Understanding bend loss in single-ring hollow-core photonic crystal fibers (PCFs) is becoming of increasing importance as the fibers enter practical applications. While purely numerical approaches are useful, there is a need for a simpler analytical formalism that provides physical insight and can be directly used in the design of PCFs with low bend loss. We show theoretically and experimentally that a wavelength-dependent critical bend radius exists below which the bend loss reaches a maximum, and that this can be calculated from the structural parameters of a fiber using a simple analytical formula. This allows straightforward design of single-ring PCFs that are bend-insensitive for specified ranges of bend radius and wavelength. It also can be used to derive an expression for the bend radius that yields optimal higher-order mode suppression for a given fiber structure.
Photonics Research
  • Publication Date: Feb. 23, 2017
  • Vol. 5, Issue 2, 02000088 (2017)
Revisiting the absorption and transmission properties of coupled open waveguides
Lei Chen, and Keng C. Chou
Open waveguides are widely used in modern photonic devices, such as microstructured fiber filters and sensors. Their absorption and transmission spectra are the most important properties in determining the overall performance of the photonic devices. The imaginary parts of their eigenvalues have been commonly used to calculate the absorption and consequently the transmission spectra. Here we show that this formulism is generally incorrect and not consistent with the simulation results obtained by the beam propagation method. We revisit the fundamental theory for the absorption of open waveguides and present a general formulism. We found that parity-time-symmetry transitions, which have been conventionally ignored, play a critical role in the properties of the coupled waveguide. The absorption and transmission are highly dependent on the physical length of the system. On the basis of our findings, optimization criteria for designing photonic sensors and filters are presented.
Photonics Research
  • Publication Date: Oct. 12, 2018
  • Vol. 6, Issue 11, 11001003 (2018)