Waveguide two-point differential-excitation method for quantitative absorption measurements of nanostructures

To establish a new useful quantitative absorption measurement method for nanostructures, we investigated quantitative accuracy of a recently developed waveguide two-point differential-excitation method, which combines Fabry-Pé rot fringe analysis and attenuated internal emission analysis for differential-path-length excitations. Quantitative absorption spectra of an 8-nm-thick GaAs quantum well at various temperatures consistent with theoretical predictions are demonstrated within 5% relative accuracy and a high dynamic range of 0-210 cm-1 in modal absorptions. The results were also compared with conventional photoluminescence excitation spectra of the same sample, which turned out to underestimate the absorption peak intensity of the lowest exciton at low temperatures.