Optical Limiting Within Capillary Waveguides

Abstract

_______________________________________ _________________REPORT Public reporting burder for this collection of information is estibated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burder SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING AGENCY REPORT NUMBER US Naval Academy Annapolis, MD 21402Trident Scholar project report no. (2002) SUPPLEMENTARY NOTES 12a. DISTRIBUTION/AVAILABILITY STATEMENTThis document has been approved for public release; its distribution is UNLIMITED. 12b. DISTRIBUTION CODE ABSTRACT:A study of the optical limiting characteristics of capillary waveguides containing highly nonlinear cores is reported. Nonlinear waveguides prove useful, both for the study of fundamental physical phenomena they display and for practical applications (such as optical limiting) they may fulfill. Work presented here strives to use nonlinear waveguides as optical limiting elements, incorporating the waveguides into geometries that may integrate into modern optical fiber systems. Multi-mode and single-mode nonlinear waveguides, with core diameters ranging from 3.2 to 200 µm, were filled with solutions of silicon naphthalocyanine (SiNc). SiNc displays large absorptive and refractive index nonlinearity. The transmission characteristics of these nonlinear waveguides were measured as a function of incident energy from two different pulsed, frequency-doubled Nd:YAG lasers (producing 7 ns and 5 ns pulses at 532 nm). For the multimode waveguides, nonlinear effects are observed at input energies as low as 1.0 x 10 -10 J and a transmission of 5% or less was observed for input energies as low as 1.0 x 10 -7 J. For the single-mode waveguide, a limiting response was stimulated at input pulse energies < 20 pJ. Multi-mode waveguide data were compared with a three-level sequential absorption model, which modeled the nonlinear behavior of SiNc. . NUMBER OF PAGES AbstractA study of the optical limiting characteristics of capillary waveguides containing highly nonlinear cores is reported. Nonlinear waveguides prove useful, both for the study of fundamental physical phenomena they display and for practical applications (such as optical limiting) they may fulfill. Work presented here strives to use nonlinear waveguides as optical limiting elements, incorporating the waveguides into geometries that may integrate into modern optical fiber systems.Multi-mode and single-mode nonlinear waveguides, with core diameters ranging from 3.2 to 200 µm, were filled with solutions of silicon naphthalocyanine (SiNc). SiNc displays large absorptive and refractive index nonlinearity. The transmission characteristics of these nonlinear waveguides were measured as a function of incident energy from two different puls...

Optical Limiting in a Single Mode Waveguide System

“…Thus, the two groups much be treated individually when expressing the overall coefficient of absorption of the material. 5 The coefficient of absorption related to the ground-state molecules is given by 7 :…”

“…In the excited-state, energy is dissipated by collisions with other molecules and various other processes. 5…”

“…These Bessel functions describe the electric and magnetic fields propagating through a waveguide. 5 However, different Bessel functions model the behavior of light inside and outside the core of capillary.…”

“…The fact that one mode corresponds to one value of β, enables one to find the number of modes that propagate in a waveguide core by solving this boundary condition problem. 5 As the difference in index of refraction between the waveguide's core and cladding decreases, fewer modes are allowed to propagate in the waveguide core. When this difference is less than 1 percent, the set of allowed modes is called the linearly polarized modes.…”

“…Solving the boundary conditions of this set leads to a transcendental equation that can be solved for the propagation constants of the allowed modes. This equation is 5 :…”