Stimulated Raman scattering tomography system and method

1 . A stimulated Raman scattering tomography system comprising:

a laser light source configured to provide a first output and a second output,

wherein the first output is configured to generate a first input light beam,

wherein the first input light beam is phase-modulated;

wherein the second output is configured to generate a second input light beam, wherein the second input light beam is amplitude-modulated; and

wherein the first input light beam and the second input light beam are configured to be form collinear Bessel beams, the collinear Bessel beams configured to generate an axial optical beating pattern comprising a plurality of axial spatial-frequency components along an axial direction;

an objective configured to direct the collinear Bessel beams onto a sample, wherein depth information of the sample is encoded into the plurality of axial spatial-frequency components of the optical beating pattern;

a condenser configured to collect an output light beam from the sample;

a detector configured to detect at least a portion of the output light beam corresponding to the first input light beam; and

a lock-in amplifier configured to demodulate the detected portion of the output light beam from the sample for forming a depth-resolved image of the sample from the detected portion of the output light beam, wherein the depth-resolved image is formed based on the encoded axial spatial-frequency components without scanning a focal spot of the first or second input light beam across a depth direction of the sample.

2 . The system as claimed in claim 1 , wherein the laser light source comprises a broadband femtosecond laser light source.

3 . The system as claimed in claim 1 , wherein the first input light beam comprises a pump beam and the second input light beam comprises a Stokes beam.

4 . The system as claimed in claim 3 , further comprising a spatial light modulator for phase-modulating the pump beam based on a predetermined phase pattern, wherein the predetermined phase pattern defines an axial beating profile configured to generate the plurality of axial spatial-frequency components of the collinear Bessel beams.

5 . The system as claimed in claim 3 , further comprising an electro-optic modulator for amplitude-modulating the Stokes beam at a predetermined frequency.

6 . The system as claimed in claim 1 , further comprising a bandpass filter set positioned after the condenser and configured to spectrally isolate the portion of the output light beam corresponding to the first input light beam.

7 . The system as claimed in claim 1 , wherein the lock-in amplifier is configured to extract a modulated signal from the detected portion of the output light beam, and wherein the extracted signal is demodulated using an inverse fast Fourier transform to obtain depth-resolved information, and wherein the inverse fast Fourier transform is applied to the plurality of axial spatial-frequency components encoded in the optical beating pattern.

8 . The system as claimed in claim 1 , wherein the output light beam comprises a reflected beam portion and a transmitted beam portion from the sample, wherein the transmitted beam portion is detected.

9 . A stimulated Raman scattering tomography method comprising:

generating a first input light beam, wherein the first input light beam is phase-modulated;

generating a second input light beam, wherein the second input light beam is amplitude-modulated;

forming the first input light beam and the second input light beam into collinear Bessel beams, the collinear Bessel beams configured to generate an axial optical beating pattern comprising a plurality of axial spatial-frequency components along an axial direction;

directing the collinear Bessel onto a sample, wherein depth information of the sample is encoded into the plurality of axial spatial-frequency components of the optical beating pattern;

collecting an output light beam from the sample;

detecting at least a portion of the output light beam corresponding to the first input light beam; and

forming a depth-resolved image of the sample from the detected portion of the output light beam, wherein the depth-resolved image is formed based on the encoded axial spatial-frequency components without scanning a focal spot of the first or second input light beam across a depth direction of the sample.

10 . The method as claimed in claim 9 , wherein the first input light beam comprises a pump beam and the second input light beam comprises a Stokes beam.

11 . The method as claimed in claim 10 , wherein the pump beam is phase-modulated based on a predetermined phase pattern using a spatial light modulator, wherein the predetermined phase pattern defines an axial beating profile configured to generate the plurality of axial spatial-frequency components of the collinear Bessel beams.

12 . The method as claimed in claim 10 , wherein the Stokes beam is amplitude-modulated at a predetermined frequency using an electro-optic modulator.

13 . The method as claimed in claim 9 , wherein forming the depth-resolved image of the sample comprises extracting a modulated signal from the detected portion of the output light beam from the sample using a lock-in amplifier and applying an inverse fast Fourier transform to reconstruct the depth-resolved image of the sample, and wherein the inverse fast Fourier transform is applied to the plurality of axial spatial-frequency components encoded in the optical beating pattern.

14 . A three-dimensional volumetric imaging method comprising the method as claimed in claim 9 .

15 . The three-dimensional volumetric imaging method as claimed in claim 14 , wherein the sample is label-free.