A particle detector includes a housing, a light source, and a photo-responsive material. The housing includes a sample inlet and a sample outlet, and encloses a detection cavity. The light source directs irradiating light along a longitudinal axis to particles of a sample fluid flowing in the detection cavity. The photo-responsive material surrounds at least a portion of the detection cavity, and receives measurement light propagating from the particles in a plurality of measurement light paths angled relative to the longitudinal axis. The particle detector may be utilized to measure scattered light and/or light emitted due to autofluorescence. Fluids sampled may include aerosols, bio-aerosols, and liquids.