The single-beam Z-scan thermal lens technique is
conducted to evaluate the fluorescence quantum yield of various
solutions in the case of high-moderate absorption, considering both
scenarios: solutions with substantial fluorescence and solutions with
high thermal efficiency but low fluorescence. An analytical
calculation is performed to determine the uncertainties associated
with the random errors introduced by optical detectors. The results
reveal that solutions with low fluorescence lead to a significant
error, whereas higher fluorescence can help in decreasing the
uncertainty. Additionally, the issue of random errors arising when
multiple measurements are needed to accurately estimate the
fluorescence of a solution will be discussed in different
situations.