Further improvements of an extended Hakki-Paoli method

A modified Hakki-Paoli method, for measuring optical gain in laser diodes, proposed at the past ESREF 2017 conference is here further improved in terms of practical implementation. In particular, averaging both the spectral function and its reciprocal, over an oscillation cycle is shown to lead to the gain function replacing the calculation of maxima and minima, a cumbersome task for noisy spectra at low injection level. The ultimate goal is to get rid of the many constraints that complicate gain measurements for other than the manufacturers, and to provide a new powerful tool for laser diode characterization and diagnostics.