Holography is a technique for recording and reconstructing the complete wavefront of light, including its amplitude and phase. This allows for the creation of three-dimensional images, or holograms, that appear lifelike and can be viewed from different angles. Polarization holography is a unique technique that harnesses the polarization state of light to record and reconstruct information, enabling the creation of vector holograms. Unlike traditional intensity-based holography, this approach encodes not only the amplitude and phase but also the polarization state of the incident light. This multidimensional encoding unlocks new opportunities for applications in high-density optical data storage, advanced display technologies, and structured light manipulation.

Recent developments in polymer science have highlighted azo-carbazole copolymer-based composite films as exceptional materials for polarization holography. These films exhibit remarkable photo-induced anisotropy and high polarization sensitivity, making them ideal for the development of rewritable vector holograms. Notably, the azo-carbazole copolymer film demonstrates outstanding optical properties, including high diffraction efficiency, excellent stability, and the capability to support multiple rewrites. These features lay a solid foundation for innovative techniques such as hybrid multiplexing, which combines spatial, angular, and polarization degrees of freedom to optimize data storage capacity and holographic performance. For more details, read the papers.

1. Azo-carbazole copolymer-based composite films for rewritable vector holograms

2. High-density polarization multiplexed holograms using azo-carbazole films for diverse applications

Computer-generated holography (CGH) is a technique that utilizes digital computing to generate and simulate holograms, allowing for the creation of three-dimensional (3D) images or patterns. In CGH, a digital model of an object or scene is transformed into a hologram using algorithms, such as Fourier transform or phase retrieval methods. The process involves encoding both amplitude and phase information of the light wave scattered by the object into a digital format. CGH offers several advantages, including flexibility, precision, and the ability to generate complex light patterns without the need for physical setups. It has applications in various fields, such as display technology, optical data storage, microscopy, and beam shaping. One key benefit of CGH is its capacity to create holograms for reconstructing 3D images from a flat surface, providing an efficient way to generate high-quality, realistic visualizations of objects.

Structured light beams are optical fields whose phase, amplitude, or polarization are engineered to exhibit nontrivial spatial properties, such as orbital angular momentum (OAM), self-healing, or non-diffracting behavior. These beams go beyond conventional Gaussian beams, allowing for applications in optical communication, microscopy, imaging, and laser trapping.

Structured Light Beams in Different Coordinate Systems

Cartesian (x, y, z): Airy beams, Hermite-Gaussian beams

Cylindrical (r, φ, z): Laguerre-Gaussian beams, Bessel beams

Elliptical (ξ, η, z): Mathieu beams, Ince-Gaussian beams

Parabolic (u, v, z): Weber beams

Properties of Structured Light Beams

1. Orbital Angular Momentum (OAM): Beams like LG and Bessel beams carry OAM, which is useful in optical tweezers and communication.

2. Non-Diffracting Nature: Bessel, Mathieu, and Airy beams maintain their intensity profile over large distances.

3. Self-Healing Ability: Bessel, Airy, and Mathieu beams can reconstruct their profiles after encountering obstacles.

4. Polarization Control: Vector beams provide tailored polarization distributions for applications in microscopy and quantum optics.

5. Topological Robustness: Beams with phase singularities or skyrmionic structures show resilience to perturbations.

Vortex beams are characterized by a helical phase front and a phase singularity at the center, resulting in a donut-shaped intensity profile. They carry Orbital Angular Momentum (OAM), which is distinct from the spin angular momentum associated with circular polarization.

Properties of Vortex Beams

• Phase Singularity: At the center of the beam, the phase is undefined, leading to a point of zero intensity (dark core).

• Orbital Angular Momentum (OAM): Each photon in a vortex beam carries an OAM.

• Intensity Profile: The intensity distribution is typically ring-shaped (donut-shaped) due to the phase singularity.

• Topological Charge (l): Determines the number of intertwined helices in the phase front and the amount of OAM carried by the beam.

Vector beams are characterized by a non-uniform polarization distribution across their cross-section. Unlike scalar beams (e.g., scalar vortex beams), the polarization state of a vector beam varies spatially.

Properties of Vector Beams

• Spatially Variant Polarization: The polarization state changes across the beam profile, often forming patterns such as radial, azimuthal, or higher-order polarization structures.

• Polarization Singularities: Points or lines where the polarization state is undefined (e.g., C-points or L-lines).

• Non-Separable States: The spatial and polarization degrees of freedom are coupled, making vector beams non-separable in these dimensions.

Comparison of Vortex Beams and Vector Beams

    Property                                 Vortex Beams                                     Vector Beams                          

Phase Structure                    Helical phase front                         Uniform or structured phase          

Polarization                          Uniform polarization                     Spatially varying polarization       

Intensity Profile                   Donut-shaped (dark core)             Can vary (e.g., donut, Gaussian)     

Angular Momentum                  Carries OAM                               carry SAM and OAM                 

Singularities                        Phase singularity (dark core)               Polarization singularities           

Applications of Vortex and Vector Beams

1. Optical Communication: OAM beams enable multiplexing, increasing data transmission capacity.

2. Optical Trapping and Manipulation: Vortex beams can trap and rotate particles due to their OAM.

3. Quantum Optics: OAM states are used in quantum entanglement and encoding quantum information.

4. Imaging and Microscopy: Vector beams improve resolution and contrast in imaging systems.

5. Material Processing: Vortex beams are used in laser machining and microfabrication.

Generation and Detection

Vortex Beams: Generated using spiral phase plates, SLMs, or metasurfaces. Detected using interferometric techniques or OAM sorters.

Vector Beams: Generated using q-plates, polarization converters, Polarization Holography, or SLMs. Detected using polarimetry or spatial polarization analyzers.

For more details, read the papers.

1. Tailoring arbitrary large vectorial structured light beam array utilizing the tensor theory of multiplexed polarization hologram.

2. Generation of arbitrary vector vortex beams on a higher-order Poincaré sphere using a double-exposure polarization-multiplexed hologram.

3. Tricomi–Gauss beam and its propagation characteristics.

4. Tailoring Large Asymmetric Laguerre–Gaussian Beam Array Using Computer-Generated Holography.

5. Generation of Ince–Gaussian beams using Azocarbazole polymer CGH.