System and methods for fluorescence detection

A method for detecting fluorescence comprising:

• emitting excitation light from a light source through a first optical fiber to a sample in a sample unit;
• and
• receiving, by a avalanche photodiode array detector, through a second optical fiber, fluorescent light generated by the sample when the sample is irradiated with the excitation light;
• wherein the second optical fiber has a numerical aperture of equal to or greater than about 0.15 and is positioned such that a longitudinal axis of the second optical fiber is orthogonal to a longitudinal axis of the first optical fiber;
• and
• wherein the fluorescence detection system has a fluorescence detection limit of equal to or greater than about one fluorescent particle per microliter for fluorescent particles having an average diameter of about two micrometers.

A computer-implemented method for detecting fluorescence comprising:

• emitting, by a processor of a computer system, excitation light from a light source to a sample in a sample unit through a first optical fiber;
• receiving, by an avalanche photodiode array detector, through a second optical fiber, fluorescent light generated by the sample when the sample is irradiated with the excitation light, wherein the second optical fiber has a numerical aperture of equal to or greater than about 0.15 and is positioned such that a longitudinal axis of the second optical fiber is orthogonal to a longitudinal axis of the first optical fiber, and wherein the avalanche photodiode array detector has a fluorescence detection limit of equal to or greater than about one fluorescent particle per microliter for fluorescent particles having an average diameter of about two micrometers;
• receiving, by the processor of the computer system, sample information from the avalanche photodiode array detector;
• and
• storing, by the processor of the computer system, the sample information in a memory.