Steve C. Tidwell

Bio: Steve C. Tidwell is an academic researcher. The author has contributed to research in topics: Beam (structure) & Polarization (waves). The author has an hindex of 2, co-authored 2 publications receiving 601 citations.

Generating radially polarized beams interferometrically.

Abstract: Two interferometric techniques for converting a linearly polarized laser beam into a radially polarized beam with uniform azimuthal intensity are described. The techniques are based on the linear combination of orthogonally polarized beams, which have tailored intensity and phase profiles. Linearly polarized beams with intensity profiles tailored using a modified laser or an apodization filter are combined in separate experiments to produce radially polarized light. A beam with an extinction ratio of −21.7 dB and azimuthal intensity variations of less than ±12% is produced using the modified laser output. The second technique uses circularly polarized light and a unique spiral phase delay plate to produce the required phase profile. When focused, a radially polarized beam has a net longitudinal field useful for particle acceleration and, perhaps, other unique applications.

Efficient radially polarized laser beam generation with a double interferometer.

Abstract: Conversion of a linearly polarized CO2 laser beam into a radially polarized beam is demonstrated with a novel double-interferometer system. The first Mach–Zehnder interferometer converts the linearly polarized input beam into two beams with sin2 θ and cos2 θ intensity profiles, where θ is the azimuthal angle. This is accomplished by using two spiral-phase-delay plates with opposite handedness in the two legs of the interferometer to impart a one-wave phase delay azimuthally across the face of the beams. After these beams are interfered with, the resulting beams are sent directly into the second Mach–Zehnder interferometer, where the polarization direction of one beam is rotated by 90°. The beams are then recombined at the output of the second interferometer with a polarization-sensitive beam splitter to generate a radially polarized beam. The output beam is ≈ 92% radially polarized and contains ≈ 85% of the input power. This system will be used in upcoming laser particle acceleration experiments.

Principles of nano-optics

Abstract: 1. Introduction 2. Theoretical foundations 3. Propagation and focusing of optical fields 4. Spatial resolution and position accuracy 5. Nanoscale optical microscopy 6. Near-field optical probes 7. Probe-sample distance control 8. Light emission and optical interaction in nanoscale environments 9. Quantum emitters 10. Dipole emission near planar interfaces 11. Photonic crystals and resonators 12. Surface plasmons 13. Forces in confined fields 14. Fluctuation-induced phenomena 15. Theoretical methods in nano-optics Appendices Index.

Cylindrical vector beams: from mathematical concepts to applications

Abstract: An overview of the recent developments in the field of cylindrical vector beams is provided. As one class of spatially variant polarization, cylindrical vector beams are the axially symmetric beam solution to the full vector electromagnetic wave equation. These beams can be generated via different active and passive methods. Techniques for manipulating these beams while maintaining the polarization symmetry have also been developed. Their special polarization symmetry gives rise to unique high-numerical-aperture focusing properties that find important applications in nanoscale optical imaging and manipulation. The prospects for cylindrical vector beams and their applications in other fields are also briefly discussed.

Focusing of high numerical aperture cylindrical-vector beams.

Abstract: Cylindrical-vector beams are of increasing recent interest for their role in novel laser resonators and their applications to electron acceleration and scanning microscopy. In this paper, we calculate cylindrical-vector fields, near the focal region of an aplanatic lens, and briefly discuss some applications. We show that, in the particular case of a tightly focused, radially polarized beam, the polarization shows large inhomogeneities in the focal region, while the azimuthally polarized beam is purely transverse even at very high numerical apertures.

Linearly polarized light with axial symmetry generated by liquid-crystal polarization converters

Abstract: Novel liquid-crystal devices are described that generate linearly polarized light with axial symmetry; the beam propagation axis is the symmetry axis. Such light fields can be characterized by a polarization order number P. For example, P = 1 fields represent radially or azimuthally polarized light. The reorientation of the polarization orientation in these polarization converters is due to the twisted nematic effect and the effect of lambda/2 wave plates. A single polarization converter can generate fields of orders 1 and 2. It is shown that one can in principle generate fields of any integral order P by cascading such elements. Devices that generate P = 1 fields are achromatic and can be used as polarization axis finders or as versatile tools for studying birefringent or polarizing materials.