摘要
Herein we report a highly sensitive filter-less fluorescence detection method using an APD （avalanche photodiode）. Experimental measurements using the proposed APD-based highly sensitive fluorescence detection method exhibits the sensing capability to detect an excitation light and a fluorescence light without band pass filter or grating. The principle of this APD-based highly fluorescence detection method is used the varying multiplication ratio that is decided by wavelength. The wavelength controls running distance of photo-excited carrier by absorption coefficients, and this element decide multiplication ratio on fixed high electrical field. In fluorescence detection, they use two types of light： excitation light and fluorescence light. These lights have different wavelengths and make different multiplication ratio as well. Thus this method can separate two types of light easily by using multiplication ratios of APD without band pass filters/gratings. In this experiment, the excitation light is LED （light emitting diode） and fluorescence light occurs from FITC （fluorescein isothiocyanate） with ethanol. The FITC concentration changes from 0.1 μmol/L to 10 mmol/L. In this measurement circuit, we employ APD （S2385）, power supply voltage, and pico ampere current meter. As a result, these lights are correctly separated by using multiplication ratio with calculation at every concentration FITCs.
