Chirp modulation simulated raman scattering microscopy

A method of imaging a sample, the method comprising:

• a) generating a pump beam and a Stokes beam comprising of a train of short pulses and having a tunable optical frequency difference;
• b) imposing chirped modulation on the pump beam and Stokes beam to achieve a desired spectral resolution, such that each beam is associated with a chirp having a first sign and a second sign;
• and
• c) probing regions of the sample with the pump beam and Stokes beam jointly, said probing comprising switching between the first sign and the second sign for each beam over an optical frequency range, said probing further comprising detecting, for each frequency of said optical frequency range for each of the probed regions, an optical response of the sample resulting from a transfer of said modulation between the pump beam and the Stokes beam when the chirp sign of the pump beam is different from the chirp sign of the Stokes beam, thereby obtaining hyperspectral data of said optical response over said optical frequency range for each of the probed regions.

An imaging system comprising:

• a light source system configured to produce a first set of light pulses in a predefined first wavelength region and a second set of light pulses in a predefined second wavelength region;
• a modulator to positively chirp the first set of light pulses and negatively chirp the second set of light pulses;
• a first optical system coupled to the light source system, the first optical system comprising optics configured to combine the first set of chirped light pulses and the second set of chirped light pulses into a set of combined light pulses, wherein each of the combined light pulses comprises a first pulse from the first set of chirped light pulses and a second pulse from the second set of chirped light pulses;
• a sample holder coupled to the first optical system and configured to hold a sample for analysis, wherein at least a portion of the sample is exposed to a plurality of the combined light pulses;
• a photodetector configured to convert an optical signal resulting from an interaction of the plurality of the combined light pulses with the sample;
• an amplifier configured to remove the second set of chirped light pulses;
• a second optical system configured to collect an interaction light signal resulting from an interaction of the at least one of the combined light pulses with the at least one of the particles;
• an analysis system comprising spectrally dispersive means, the analysis system configured to measure a plurality of spectral components of the interaction light signal.

A modulation method of suppressing noise, the method comprising

• a) generating a first signal having a first train of short pulses having a first frequency, and a second signal having a second train of short pulses having a second frequency, wherein each of the first signal and the second signal is associated with a negative or positive sign;
• b) maintaining a narrow frequency difference between the first frequency and the second frequency;
• c) imposing chirped modulation on the first signal and the second signal to achieve a desired spectral resolution, such that each signal is associated with a chirp having a first sign and a second sign;
• and
• d) switching between the first sign and the second sign for each beam over a frequency range, and detecting for each frequency of said frequency range, a spectral response resulting from a transfer of said modulation between the first signal and the second signal wherein the chirp sign of the first signal is different from the chirp sign of the second signal, thereby obtaining hyperspectral data of said spectral response over said frequency range.