We report the realization of precise spatial polarization control of light via a priori optimization of the polarization ratio and retardation modulation in a vectorial optical field generator. For the polarization ratio calibration, we generate 45° linearly polarized light, measure the intensities of the vertical and horizontal components of the output beam and calculate the ratio of them to obtain the modification coefficient. After several iterations, the corresponding coefficient converges to an optimized value based on the criterion that the measured intensities are equal to each other. As for the retardation calibration, circularly polarized light is generated and letting the modulated beam propagate through a circular polarization analyzer. The modification value is adjusted by dichotomy until the detected intensity of the output beam from the circular polarization analyzer approaches extinction. Several typical kinds of vectorial optical beams are generated with the obtained modification parameters and the measured Stokes parameters demonstrate that this method is practicable and beneficial for the performance improvement of the vectorial optical field generator.
Theoretically, we propose an investigation of the vectorial light field interacting with the isotropic Kerr medium. We obtain the analytical expression of the focal field of the hybrid polarized beam based on the vectorial Rayleigh-Sommerfeld formulas under the paraxial condition. Then we numerically simulate the far-field vectorial self-diffraction behavior and nonlinear ellipse rotation of a hybrid polarized beam by isotropic Kerr nonlinearity. Experimentally, we observe the vectorial self-diffraction behavior of the femtosecond-pulsed hybridly polarized beam in carbon disulfide at 800 nm, which is in agreement with the theoretical predictions. Our results demonstrate that the self-diffraction intensity pattern and the distribution of state of polarization (SoP) of a hybridly polarized beam could be manipulated by tuning the magnitude of the isotropic optical nonlinearity, which may find interesting applications in nonlinear mechanism analysis, nonlinear characterization technique, and spin angular momentum (SAM) manipulation.
We demonstrate the design, fabrication and testing of miniature steerable optical sources that are capable of beaming photons with spin and orbital angular momentum through coupling nanoscale emitters to plasmonic waveguide and antenna structures.
Photolithography is widely used to transfer a geometric pattern from a mask to a photoresist film, but the minimum
feature sizes are limited by diffraction through the mask. Focused ion beam and electron beam lithography can be used
when higher resolution is desired, but the write times are long and costly. Deep ultraviolet interference lithography,
which is a maskless technique, can be used as an alternative to produce high resolution patterns with feature sizes as
small as 100 nm. Since double negative metamaterial superlenses can be used for super-resolving and imaging subwavelength
objects, there is a need for fabricating such objects to characterize the performance of these metamaterials.
In this paper, simulations using standard finite element methods are first used to verify super-resolution and near-field
imaging at 405 nm for such objects using a metamaterial superlens previously fabricated from silver and silicon carbide
nanoparticles. Thereafter, results of fabrication and characterization of sub-wavelength objects using molybdenum of
typical thickness 50 nm initially sputtered on a glass substrate is presented. A deep ultraviolet laser source at 266 nm is
used. An anti-reflection layer followed by a high resolution negative tone photoresist is coated on the top of the
molybdenum film. The cross-linked photoresist created after the development and bake processes is used as a mask for
etching. Fabrication of the sub-wavelength object is completed using reactive ion etching in fluorinated plasma. Both
1D and 2D patterns are fabricated. The quality of the sub-wavelength objects during fabrication is checked using
scanning electron microscopy, and the 1D object is characterized using TE and TM polarized illumination.
In this invited paper, we review some of our latest works on plasmonic antennas and their interactions with photonic
angular momentum. As receiving antennas, both theoretical and experimental results reveal that spiral plasmonic
antenna responds differently to photons with left-hand circular polarization and right-hand circular polarization. This
spin degeneracy removal finds many potential applications including extremely small circular polarization analyzer for
polarimetric imaging, parallel near field probes for optical imaging and sensing, nano-lithography and high density heat assisted magnetic recording. On the transmitter side, through coupling quantum dot nano-emitters to spiral plasmonic antenna, nano-scale spin photon sources with high directivity and circular polarization extinction ratio is demonstrated. Numerical modeling and experimental evidences also indicate that the emitted photons can be imprinted with the photonic spin angular momentum and orbital angular momentum information simultaneously via the interactions between photonic angular momentum and plasmonic antennas. These findings not only are useful for the fundamental understanding of the interaction between plasmonic antennas and photonic angular momentum but also illustrate the versatility of plasmonic antennas as building blocks for practical spin optics and quantum optics devices and systems.