Dispersion-modulation by high material loss in microstructured polymer optical fibers

Abstract

Abstract:The influence of strong loss peaks on the dispersion (through the Kramers-Kronig relations) of a nonlinear waveguide is investigated theoretically. It is found specifically for degenerate four-wave mixing in a poly(methyl methacrylate) microstructured polymer optical fiber that the loss-induced dispersion significantly modifies the wavelengths for which there is phase-match. Depending on the pump wavelength, the waveguide dispersion, and the loss peaks, it is possible for the output spectrum to either be unaffected by the loss-induced dispersion modulation, or to show an increase in the efficiency of nonlinear spectral broadening, compared to the expected efficiency when ignoring the loss-induced dispersion modulation.

Highly birefringent microstructured polymer fibers optimized for a preform drilling fabrication method

“…A He-Ne laser wavelength (633 nm) was selected as a reference to compare the results of simulations conducted for different geometrical parameters of the investigated fibers. Our goal was to find a fiber geometry that assures single mode operation, phase modal birefringence at 633 nm greater than 1 × 10 −4 , and confinement loss of the fundamental mode significantly lower than the material loss of bulk PMMA [24] in the whole spectral range of 500-1100 nm. As a practical criterion for a cut-off of the higher order modes (single mode operation), we considered a loss level exceeding 30 dB m −1 .…”

Highly sensitive and simple method for refractive index sensing of liquids in microstructured optical fibers using four-wave mixing

“…The resulting fit was found to agree to within ±4 · 10 −4 (∼ 0.03%) for data from (4) because of an absorption peak centered around 3342 cm −1 (2.99 µm) [23], which causes a strong drop in the real part of n from ∼ 2.4 µm to 2.87 µm, followed by a sharp increase in n. Since we find, both experimentally and from the calculations, that the FWM Stokes peak with methanol in the holes is located at 2.6 µm, we assume that we do not need reliable data for n above 2.9 µm; also it seems reasonable to neglect the imaginary part of n when calculating β (λ ) for the waveguide, as long as β (λ ) does not need to be calculated too close to the absorption peak at 2.99 µm. We note that pumping close to an absorption peak causes a shift in the FWM peaks, because the Kramers-Kronig relation links together dispersion modulation and absorption [25]. The refractive index of silica was found using the Sellmeier expression (p. 92 in Ref.…”