Dataset for S. Blundell et al., Ultracompact Programmable Silicon Photonics Using Layers of Low-Loss Phase-Change Material Sb2Se3 of Increasing Thickness Dataset DOI: 10.5258/SOTON/D3353 Dataset consists of text files with data for the figure subpanels organised in folders for each figure \figure 1 Raw SEM/EDX outputs bitmaps and CSV text files for different elements and bands \figure 2abc Output E-fields directly exported from Lumerical FDTD, containing separate Y and Z scales and YZ maps python scripts to directly generate figure 2a and 2b,c from these data are included \figure 2d,e Origin file and text files with columns of data, first column contains x-axis scale \figure 2f Origin file with data for figure 2f on log-log scale with linear fit, and corresponding text file with values \figure 3 text file with maps and spectra for figure 3a, first column contains x-axis scale text files with data for figure 3b,c, first column contains x-axis scale \figure 4 text files with patterns, transmission t/t0 and contrast values \figure 5 text files with patterns, transmission t/t0 and contrast values \figure 6 text files with contrast values \figure S2 text file with data points, first column contains x-axis scale \figure S3 text file with XY map, first row and first column contains x and y-axis scales \figure S4 text file with data points, first column contains x-axis scale \figure S7 text file with maps and spectra for figure S7a, first column contains x-axis scale text files with data for figure S7b,c,d first column contains x-axis scale \figure S8 text file with maps and spectra for figure S8a, first column contains x-axis scale text files with data for figure S8b,c,d first column contains x-axis scale \figure S9 text file with maps and spectra for figure S9a, first column contains x-axis scale text files with data for figure S9b,c,d first column contains x-axis scale \figure S10 text file with data points, first column contains x-axis scale \figure S13 text files with patterns text file with columns of data points for experimental and simulated values