READ ME File For 'Data set for: Limits of Coupling Efficiency into Hollow-core Antiresonant Fibres' Dataset DOI: https://doi.org/10.5258/SOTON/D2636 Date that the file was created: May, 2023 ------------------- GENERAL INFORMATION ------------------- ReadMe Author: Viktor Zuba, University of Southampton Date of data collection: 2021-2023 Information about geographic location of data collection: University of Southampton, U.K. Related projects: Programme Grant 'Airguide Photonics' (EPSRC) -------------------------- SHARING/ACCESS INFORMATION -------------------------- Licenses/restrictions placed on the data, or limitations of reuse:CC-BY Recommended citation for the data: This dataset supports the publication: AUTHORS: V. Zuba, H. C. H. Mulvad, R. Slavik, H. Sakr, F. Poletti, D. J. Richardson, and E. Numkam Fokoua TITLE: Limits of Coupling Efficiency into Hollow-core Antiresonant Fibres JOURNAL: Journal of Lightwave Technology (accepted for publication) PAPER DOI IF KNOWN: %%*****%% -------------------- DATA & FILE OVERVIEW -------------------- This dataset contains: Data files for Figure 2, 3, 4, 5, 6, 7, and 9 in the main article The corresponding figure legends are included below the file names. Figure2.xslx Fig. 2. [...] (c) Corresponding coupling loss values of the respective mode group, as a function of the beam-core ratio w/a, where w is the beam waist of a Gaussian beam. In case of ideal coupling (marked with vertical dashed line for a 0.7 beam-core ratio), most of the field is coupled into the LP_01 (blue curve) mode, while the other higher order modes receive only a fraction of it, -20dB, -50dB, -110dB for the LP_02, LP_21 and LP_11 modes, (red, black and green curves) respectively. Figure3.xslx Fig. 3. Coupling between free space Gaussian beam into the fundamental mode of a 6-tube NANF as a function of normalized frequency: (a) incident beam waist to core size ratio w/a for which coupling loss is minimized as a function of the normalized frequency f , (b) corresponding minimum coupling loss as the function of the normalized frequency f . Regions highligthed in blue, red and gray colours correspond to the 1st, 2nd and 3rd order antiresonant windows, respectively. (c) Coupling loss versus normalized incident between waist at selected normalized frequencies within the first (blue), second (red) and third (black) anitiresonant windows. Note how the best coupling is achieved at around w/a ~0.7, highlighted by the vertical dashed line. Figure4.xslx Fig. 4. Normalized electric field distribution of the fundamental LP01 mode of a typical 6-tube NANF. Highlighted are the curves of the x-component of the electric fields of different wavelengths, corresponding to different f normalized frequencies or optical windows, along the marked cut of the fibre cross-section. It can be seen that the electric field changes sign an m-number of times inside the cladding membrane (illustrated by the light-blue section), where m is the order of the respective transmission window. These curves show an increased overlap with a strictly-positive Gaussian distribution for the case of even-numbered windows, with the best fit correlated to the 2nd order. Figure5.xslx Fig. 5. Impact of the (a) inter-tube distance d and (b) number of cladding tubes on the coupling loss and the ideal beam-core ratio w/a. While both figures show a clear trend of the examined parameters on the coupling loss and beam-core ratio, they can also influence other properties of the HCF, e.g. the attenuation (see text). Note the different scaling of the y-axes for the two simulations � both performed in the first optical transmission window, corresponding to the normalized frequency of f = 0.74. Figure6.xslx Fig. 6. Cutback measurements of the NANF samples used for the experiments. Following the colour convention, the blue and red curves show the attenuation of the 1st (NANF-1) and the 2nd (NANF-2) window fibres including the error bars covering the 900?1700 nm wavelength range, respectively. The dashed vertical line marks the central wavelength ?0 = 1064 nm of the laser source, while the SEMs of the fibre samples are presented on the right. Figure7-NANF1.xslx, and Figure7-NANF2.xslx Fig. 7. [...] (b) Corresponding coupling loss values of the respective mode groups, as a function of the beam-core ratio w/a. Compared to the ideal case (shown in Figure 2), the ideal coupling (marked with vertical dashed line) is slightly increased to a 0.72 beam-core ratio from 0.7. However, similar to the ideal simulations, under ideal coupling conditions, the coupling loss into the FM is ~2 order of magnitude lower when compared to the HOMs. Figure9.xslx Fig. 9. Histogram representation of measured transmission efficiency values into NANF-1 and NANF-2. Each bin aggregates a range of 0.15 %. The y-axis covers the counts of transmission efficiency recorded for given bins for each fibre piece, blue and red for NANF-1 and NANF-2, respectively. The different colour shades illustrate the results from independent experimental conditions. The average across all measurements and confidence interval is highlighted with thick black lines and shaded backgrounds, while the corresponding numerical values are shown above the respective histograms. The uncertainties arise from the power fluctuations of the source.