Systems and methods for 4-D hyperspectral imaging

1. A hyperspectral imaging system comprising:

a sample holder configured to hold a sample;

a light source configured to emit excitation light having one or more wavelengths;

a two-dimensional (2-D) imaging array; and

an optical system comprising:

a first spectral separator comprising a first dispersive element or a first diffractive element; and

a second spectral separator comprising a second dispersive element or a second diffractive element;

wherein the optical system is configured to (i) structure the excitation light, using the first spectral separator, into a spectrally dispersed two-dimensional excitation pattern at a focal plane in the sample or a conjugate plane of the focal plane; (ii) use the excitation pattern to illuminate the sample with the one or more wavelengths dispersed along a first direction within the focal plane; (iii) collect, from the sample, emission light; (iv) spectrally disperse, using the second spectral separator, the collected emission light; and (v) provide the collected emission light in-focus to the imaging array such that the collected emission light is spectrally dispersed along a second direction.

2. The hyperspectral imaging system of claim 1 , wherein the first spectral separator is configured to modulate a phase of the excitation light.

3. The hyperspectral imaging system of claim 1 , wherein the first spectral separator comprises the first diffractive spectral separator, and the first diffractive element comprises a 2-D array of diffractive lenses.

4. The hyperspectral imaging system of claim 3 , wherein each diffractive lens of the diffractive lenses comprises a zone plate having transparent and nontransparent bands.

5. The hyperspectral imaging system of claim 3 , wherein each diffractive lens of the diffractive lenses comprises a grating.

6. The hyperspectral imaging system of claim 5 , wherein the grating is a subwavelength grating.

7. The hyperspectral imaging system of claim 1 , wherein the first spectral separator comprises the first diffractive element, and the first diffractive element comprises a 2-D lenslet array and a transmissive diffraction grating.

8. The hyperspectral imaging system of claim 1 , wherein the first spectral separator comprises the first diffractive element, and the first diffractive element comprises a linear array of diffractive cylindrical lenslets.

9. The hyperspectral imaging system of claim 1 , wherein the second spectral separator comprises the second diffractive element, and the second diffractive element comprises a 2-D array of diffractive lenses.

10. The hyperspectral imaging system of claim 9 , wherein a diameter of each diffractive lens of the diffractive lenses is approximately a diameter of a diffraction-limited spot of a lens that images the emission light onto the imaging array.

11. The hyperspectral imaging system of claim 1 , wherein a diffraction-limited spot of a lens that images the emission light onto the imaging array covers a plurality of pixels of the imaging array.

12. The hyperspectral imaging system of claim 1 , wherein the optical system further comprises a first polarizer configured to polarize the excitation light.

13. The hyperspectral imaging system of claim 12 , wherein the optical system further comprises at least one of a second polarizer or a polarizing beamsplitter (PBS) configured to reflect light having the same polarization as that of the polarized excitation light.

14. The hyperspectral imaging system of claim 12 , wherein the optical system further comprises a second polarizer having a transmission axis that is rotatable with respect to a vibration orientation of the polarized excitation light.

15. A method for hyperspectral imaging, the method comprising:

providing, from a light source, excitation light having one or more wavelengths;

structuring, by a first spectral separator, the excitation light from the light source into a predetermined two-dimensional excitation pattern at a focal plane in a sample or a conjugate plane of the focal plane;

spectrally dispersing the excitation pattern;

using the excitation pattern to illuminate the sample with the one or more wavelengths dispersed along a first direction within the focal plane;

spectrally dispersing emission light collected from the sample; and

imaging, using a two-dimensional (2-D) imaging array, the spectrally dispersed emission light, wherein the spectrally dispersed emission light is received in-focus by the imaging array such that the spectrally dispersed emission light is spectrally dispersed along a second direction.

16. The method of claim 15 , further comprising:

polarizing, by a first polarizer, the excitation light; and

reflecting, by at least one of a second polarizer or a polarizing beamsplitter (PBS), light having the same polarization as that of the polarized excitation light.

17. The method of claim 15 , wherein the first spectral separator comprises:

a 2-D array of diffractive lenses,

a 2-D lenslet array and a transmissive diffraction grating, or

a linear array of diffractive cylindrical lenslets.

18. The method of claim 15 , further comprising modulating, by the first spectral separator, a phase of the excitation light.

19. The method of claim 15 , further comprising:

illuminating the sample sequentially in a series of excitation patterns that are shifted, within the focal plane within the sample, from each another;

obtaining, using the imaging array, a plurality of 2-D images of the spectrally dispersed emission light, wherein each of the obtained 2-D images corresponds to a respective one of the excitation patterns in the series of excitation patterns; and

reconstructing the obtained plurality of 2-D images to provide a 4-D hyperspectral-imaging dataset.

20. The method of claim 15 , wherein the emission light is spectrally dispersed by a second spectral separator comprising a 2-D array of diffractive lenses.