In-line and off-axis polarization-selective holographic lenses recorded in azopolymer thin films via polarization holography and polarization multiplexing

Abstract

Polarization-selective diffractive in-line and off-axis lenses are recorded in azopolymer thin films using polarization holography. A simple, yet efficient, and to the best of our knowledge, new method is used to suppress the surface relief grating formation and to improve the polarization properties of the lenses. The in-line lenses are converging for right circularly polarized (RCP) light and diverging for left circularly polarized (LCP) light. Bifocal off-axis lenses are recorded by polarization multiplexing. By rotating the sample at 90° between the exposures, the two focal points of these lenses are located in orthogonal directions O x and O y , so we can refer to these novel lenses as 2D bifocal polarization holographic lenses. The light intensity in their focuses depends on the reconstructing light polarization. According to the recording scheme, they can either reach maximum intensities simultaneously (for LCP or RCP), or alternatively, one of them can be at maximum for LCP, while the other for RCP. These lenses may be used as polarization controllable optical switches, in the field of self-interference incoherent digital holography or for other photonics applications.

Polarization Diffraction Gratings in PAZO Polymer Thin Films Recorded with Digital Polarization Holography: Polarization Properties and Surface Relief Formation

“…The recording is performed either through the substrate side (case 1 in Figure 1), or from the azopolymer film side of the sample (case 2). As shown by our earlier studies [18,33], in case 1, the intensity of the recording beam is significantly reduced before reaching the free surface of the azopolymer film (due to the absorbance within the film itself), and this allows us to suppress the formation of the surface relief grating. In contrast, in case 2, the intensity of the recording beam is maximal on the free surface of the azopolymer layer, and this results in high amplitude surface relief grating.…”

“…In recent decades, there has been increasing scientific interest in polarization-sensitive photoanisotropic materials, due to their unique applications in polarization holography, and in photonics, as a media for the reversible optical storage of information and polarization multiplexing [14,15], for creating polarization-selective optical elements [16][17][18], for structures with surface modulation with high spatial frequency [19,20], to create optical switches [21,22], and more. Azobenzene-containing materials are commonly used organic materials for polarization holographic recording due to the high values of photoinduced anisotropy upon illumination with polarized light [10].…”

“…A widely investigated azopolymer is poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt], commonly denoted as PAZO, which is commercially available. PAZO is often the preferred material for polarization holography by many research groups, due to the high values of the photoinduced birefringence and large amplitude of the surface relief gratings [18,20,[35][36][37][38][39][40]. Another important advantage of the azopolymer PAZO is that it is water soluble, thus toxic organic solvents, which are usually required for the film deposition of other azopolymers, can be avoided.…”

Highly efficient polarization and angular multiplexed vector hologram

“…Earlier, diverse holographic methods have been employed to store large amounts of data, utilizing various multiplexing schemes such as angular multiplexing, wavelength multiplexing, polarization multiplexing, depth multiplexing, frequency multiplexing, etc. [14][15][16][17][18][19][20][21] Within these, polarization holograms play a pivotal role in polarization hologram multiplexing, offering accessible demultiplexing of recorded holograms through the utilization of polarization filtering. The polarization hologram multiplexing can be added with another multiplexing scheme to increase the data storage capabilities.…”

Two-Dimensional Polarization Holographic Gratings in Azopolymer Thin Films: Polarization Properties in the Presence or Absence of Surface Relief

“…In fact, for some applications, the properties of the polarization grating are more important, and the SRG has an adverse effect, deteriorating the polarization characteristics of the optical element. Examples of such applications are optical switches [23], a circular polarization beam splitter [24], bifocal polarization lenses [25], and a reconfigurable fiber Bragg filter [26], all based on azo-containing materials. In these cases, it is essential to find an efficient method to suppress the formation of the surface relief grating or to evaluate its influence on the polarization properties of the obtained holographic optical element.…”