AC detection of directivity of fluorescence from a minute particle using TAS chip incorporated with radially arranged light-waveguides

In this paper, we attempt to drastically improve the S/N ratio of detected fluorescence signals from the resin-based optical TAS chip by applying AC-modulated laser power for irradiation on a fluorescent substance attached micro-particles at a frequency of approximately 1 MHz. We also try to precisely optimize both the drive frequency and voltage of the optical scanner (light switch) which utilizes optical fiber’s resonance characteristics, in order to completely suppress variation of apparent transmittance of radially arranged light waveguides for laser power irradiation. Through these countermeasures, we successfully obtained high-quality fluorescence signal waveforms corresponding to angular scanning irradiation on 5-μm diameter resin particles. The high-quality signal waveforms also ensured that “directivities” of fluorescence with high reproducibility were obtained under conditions of a wider range of particle running velocity in a TAS chip.