Measurement apparatus of wavefront and polarization profile of vectorial optical fields
An apparatus measures the transverse profile of vectorial optical field beams, including both the phase and the polarization spatial profile. The apparatus contains a polarization separation module, a weak perturbation module, and a detection module. Characterizing the transverse profile of vector fields provides an optical metrology tool for both fundamental studies of vectorial optical fields and a wide spectrum of applications, including microscopy, surveillance, imaging, communication, material processing, and laser trapping.
1. A computerized method of transmitting information via an optical vector beam, the method comprising:
encoding the data onto a primary optical beam to form the optical vector beam, wherein the encoding comprises differential spatial phase shift keying (DSPSK) in which the data is represented by physical changes in the optical vector beam across spatially separated portions of the optical vector beam;
decoding the data by identifying respective polarization states and respective phase measurements for the spatially separated portions of the optical vector beam by:
(i) selecting, from the spatially separated portions of the optical vector beam, at least two orthogonally polarized portions of the optical vector beam; and
(ii) identifying the data in the optical vector beam by tracking differences between the respective phase measurements for the at least two orthogonally polarized portions of the optical vector beam;
wherein encoding the data onto the primary optical beam comprises:
directing the primary optical beam to a first spatial light modulator (SLM-1);
using an imprinted hologram on the SLM-1 to receive the primary optical beam and convert the primary optical beam into the optical vector beam comprising spatially separated and orthogonally polarized twin beam portions;
radially separating the twin beam portions such that polarized components of the twin beam portions are non-overlapping;
adjusting the polarized components of the twin beam portions into a common horizontal linear polarization state to adjust the optical vector beam into a spatially-coherent scalar beam of a single polarization.
2. The computerized method of claim 1 , wherein the primary optical beam comprises phase changes across an electrical field, wherein the phase changes represent the data being transmitted.
3. The computerized method of claim 1 , wherein the SLM-1 encodes phase changes into the electrical field of the optical vector beam, wherein the phase changes represent the data being transmitted.
4. The computerized method of claim 1 , wherein decoding the data comprises characterizing the optical vector beam according to a transverse profile of the at least two orthogonally polarized portions of the optical vector beam and measuring relative phase information between the at least two orthogonally polarized portions, wherein the relative phase information is measured for each of the polarized portions simultaneously.
5. The computerized method of claim 4 , wherein characterizing the optical vector beam according to a transverse profile comprises submitting the optical vector beam to a generation module comprising optical components configured for:
directing the optical vector beam from the SLM-1 to a 4-F imaging system with spatial filtering at a focal plane;
using the 4-F imaging system to form, from the optical vector beam, a spatial field for the optical vector beam, wherein the spatial field comprises two transversely separated light beams corresponding to respective left circularly polarized (LCP) and right circularly polarized (RCP) components of the optical vector beam;
defining a generated vector beam comprising the two circular polarization components that correspond to the imprinted hologram on the SLM-1.
6. The computerized method of claim 5 , further comprising directing the generated vector beam to a second spatial light modulator SLM-2, wherein the second SLM-2 applies a polarization perturbation to the generated vector beam to generate a reference electric field beam within the generated vector beam.
7. The computerized method of claim 6 , further comprising imaging the generated vector beam with a polarization resolving camera that converts electric fields of the generated vector beam and the reference field formed by the SLM-2 into decodable left circular polarizations and decodable right circular polarizations.
8. The computerized method of claim 7 , wherein characterizing the optical vector beam further comprises simultaneously measuring a respective horizontal intensity (Ih), vertical intensity (Iv), diagonal intensity (Id), and anti-diagonal intensity (Ia) of the generated vector beam.
9. The computerized method of claim 8 , wherein characterizing the optical vector beam further comprises calculating the Stokes parameters of the generated vector beam from the left and right parts of the generated vector beam to decipher a transverse field profile of the twin beam representing the optical vector beam.
10. A computerized method of transmitting information via an optical vector beam, the method comprising:
encoding the data onto a primary optical beam to form the optical vector beam, wherein the encoding comprises differential spatial phase shift keying (DSPSK) in which the data is represented by physical changes in the optical vector beam across spatially separated portions of the optical vector beam;
decoding the data by identifying respective polarization states and respective phase measurements for the spatially separated portions of the optical vector beam by:
(i) selecting, from the spatially separated portions of the optical vector beam, at least two orthogonally polarized portions of the optical vector beam; and
(ii) identifying the data in the optical vector beam by tracking differences between the respective phase measurements for the at least two orthogonally polarized portions of the optical vector beam;
wherein decoding the data comprises characterizing the optical vector beam according to a transverse profile of the at least two orthogonally polarized portions of the optical vector beam and measuring relative phase information between the at least two orthogonally polarized portions, wherein the relative phase information is measured for each of the polarized portions simultaneously.
11. The computerized method of claim 10 , wherein the primary optical beam comprises phase changes across an electrical field, wherein the phase changes represent the data being transmitted.
12. The computerized method of claim 10 , wherein encoding the data onto the primary optical beam comprises:
directing the primary optical beam to a first spatial light modulator (SLM-1);
using an imprinted hologram on the SLM-1 to receive the primary optical beam and convert the primary optical beam into the optical vector beam comprising spatially separated and orthogonally polarized twin beam portions;
radially separating the twin beam portions such that polarized components of the twin beam portions are non-overlapping;
adjusting the polarized components of the twin beam portions into a common horizontal linear polarization state to adjust the optical vector beam into a spatially-coherent scalar beam of a single polarization.
13. The computerized method of claim 12 , wherein the SLM-1 encodes phase changes into the electrical field of the optical vector beam, wherein the phase changes represent the data being transmitted.
14. The computerized method of claim 10 , wherein characterizing the optical vector beam according to a transverse profile comprises submitting the optical vector beam to a generation module comprising optical components configured for:
directing the optical vector beam from the SLM-1 to a 4-F imaging system with spatial filtering at a focal plane;
using the 4-F imaging system to form, from the optical vector beam, a spatial field for the optical vector beam, wherein the spatial field comprises two transversely separated light beams corresponding to respective left circularly polarized (LCP) and right circularly polarized (RCP) components of the optical vector beam;
defining a generated vector beam comprising the two circular polarization components that correspond to the imprinted hologram on the SLM-1.
15. The computerized method of claim 14 , further comprising directing the generated vector beam to a second spatial light modulator SLM-2, wherein the second SLM-2 applies a polarization perturbation to the generated vector beam to generate a reference electric field beam within the generated vector beam.
16. The computerized method of claim 15 , further comprising imaging the generated vector beam with a polarization resolving camera that converts electric fields of the generated vector beam and the reference field formed by the SLM-2 into decodable left circular polarizations and decodable right circular polarizations.
17. The computerized method of claim 16 , wherein characterizing the optical vector beam further comprises simultaneously measuring a respective horizontal intensity (Ih), vertical intensity (Iv), diagonal intensity (Id), and anti-diagonal intensity (Ia) of the generated vector beam.
18. The computerized method of claim 17 , wherein characterizing the optical vector beam further comprises calculating the Stokes parameters of the generated vector beam from the left and right parts of the generated vector beam to decipher a transverse field profile of the twin beam representing the optical vector beam.