Low-snr optical detection technique using destructive interference

Abstract

At least one sample parameter of a sample (16) is measured by means of probe light. The probe light is split to into sample probe light and reference probe light. The sample probe light interacts with the sample (16), which generates modified probe light having a phase and/or intensity depending on the sample parameter. The modified probe light and the reference probe light are overlapped to interfere, thereby generating signal light, and the intensity of the signal light is measured. A tuning parameter (t1, t2, t1′, t2′, t1″, t2″) is determined from the intensity of the signal light and used to control a phase and/or intensity tuner (20, 32, 52, 70′, 70″) in order to make the interference destructive, thereby minimizing or at least reducing the measured intensity. The sample parameter is determined using the intensity parameter and/or the tuning parameter. This technique reduces shot noise. It can be used in a plurality of applications, but a particularly preferred application is in stimulated Raman scattering or NIR reflection/absorption spectroscopy.

Dependencies are inferred from the claim text.