Technical Testing of Deep-UV Solid-State Sources for Fluorescence Lifetime Measurements in the Frequency Domain

摘要

Recently, deep-ultraviolet light emitting diodes were developed basing on AlGaN materials system. These LEDs emit milliwatt fluxes at wavelengths short enough for excitation of fluorescence in basic biological fluorophores and bacterial agents. In particular, deep-UV LEDs can be used for excitation of aromatic amino acids, whereas near-UV LEDs are suitable for excitation of autofluorescent coenzymes. The SUVOS AlGaN LEDs as well as commercial InGaN near-UV LEDs were tested for spectral purity and the possibility of high-frequency modulation up to 200 MHz and applied in frequency- domain measurements of fluorescence lifetime on the nanosecond scale. Applicability of such measurements for real-time characterization of fluorescence was evaluated using an optimized automated laboratory facility for frequency-domain measurements of fluorescence lifetime. The output of the LEDs was harmonically modulated at frequencies up to 200 MHz and the phase difference between the waveforms of the excitation emission and fluorescence was measured as a function of frequency.