A light amplifying structure 100 for Raman spectroscopy includes a a resonant cavity 108. A distance between a first portion 102B and a second portion 102A of the structure 100 forming the resonant cavity 108 is used to amplify excitation light emitted from a light source 420 into the resonant cavity 108 at a first resonant frequency of the resonant cavity 108. Also, the resonant cavity 108 amplifies radiated light radiated from a predetermined molecule excited by the excitation light in the resonant cavity at a second resonant frequency of the resonant cavity 108.