525 research outputs found
Linear Rotary Optical Delay Lines
I present several classes of analytical and semi-analytical solutions for the
design of high-speed rotary optical delay lines that use a combination of
stationary and rotating curvilinear reflectors. Detailed analysis of four
distinct classes of optical delay lines is presented. Particularly, I consider
delay lines based on a single rotating reflector, a single rotating reflector
and a single stationary reflector, two rotating reflectors, and two rotating
reflectors and a single stationary reflector. I demonstrate that in each of
these cases it is possible to design an infinite variety of the optical delay
lines featuring linear dependence of the optical delay on the rotation angle.
This is achieved via optimization of the shapes of rotating and stationary
reflector surfaces. Moreover, in the case of two rotating reflectors a
convenient spatial separation of the incoming and outgoing beams is possible.
For the sake of example, all the blades presented in this paper are chosen to
fit into a circle of 10cm diameter and these delay lines feature in excess of
600ps of optical delay
Non-perturbative approach to high-index-contrast variations in electromagnetic systems
We present a method that formally calculates \emph{exact} frequency shifts of
an electromagnetic field for arbitrary changes in the refractive index. The
possible refractive index changes include both anisotropic changes and boundary
shifts. Degenerate eigenmode frequencies pose no problems in the presented
method. The approach relies on operator algebra to derive an equation for the
frequency shifts, which eventually turn out in a simple and physically sound
form. Numerically the equations are well-behaved, easy implementable, and can
be solved very fast. Like in perturbation theory a reference system is first
considered, which then subsequently is used to solve another related, but
different system. For our method precision is only limited by the reference
system basis functions and the error induced in frequency is of second order
for first-order basis set error. As an example we apply our method to the
problem of variations in the air-hole diameter in a photonic crystal fiber.Comment: Accepted for Opt. Commu
Liquid-core low-refractive-index-contrast Bragg fiber sensor
We propose and experimentally demonstrate a low-refractive-index-contrast
hollow-core Bragg fiber sensor for liquid analyte refractive index detection.
The sensor operates using a resonant sensing principle- when the refractive
index of a liquid analyte in the fiber core changes, the resonant confinement
of the fiber guided mode will also change, leading to both the spectral shifts
and intensity changes in fiber transmission. As a demonstration, we
characterize the Bragg fiber sensor using a set of NaCl solutions with
different concentrations. Strong spectral shifts are obtained with the sensor
experimental sensitivity found to be ~1400nm/RIU (refractive index unit).
Besides, using theoretical modeling we show that low-refractive-index-contrast
Bragg fibers are more suitable for liquid-analyte sensing applications than
their high-refractive-index-contrast counterparts.Comment: 3 pages, 4 figure
Diagrammatic Explanation of the Reverse Doppler Effect in Space-Time Modulated Photonic Crystals
An inverse Doppler shift occurs in a photonic crystal (PC) bounded by a
moving wall. The interpretation of this result has stirred some controversy. In
this paper, we address the problem using a diagrammatic approach. This visual
representation provides immediate insight into the phenomenon, and is a
powerful tool for the design of time-varying PCs.Comment: Submitted to 2016 AP-S Symposium. 2 pages, 2 figure
- …