Browsing by Author "Anand, V."

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Anisotropic 3D columnar micro-film coating for applications in infrared and visible spectral ranges
(Elsevier B.V., 2022) Hu, J.; Han, M.; Grineviciute, L.; Ng, S.H.; Anand, V.; Katkus, T.; Ryu, M.; Morikawa, J.; Tobin, M.J.; Vongsvivut, J.; Tolenis, T.
Polarisation analysis of thin (∼1 μm) SiO2 films deposited via evaporation at a glancing angle of 70◦ to the normal on resist pillar arrays was carried out using synchrotron-based Fourier transform infrared (s-FTIR) microspectroscopy in reflection mode. Changes in intensity of absorption bands were observed to follow the angular dependence of ∼ cos2 𝜃, consistent with the absorption anisotropy. The strongest absorption was found to be the sharp Si–O–Si stretching vibrational mode at 1040 ± 20 cm−1, which can be used for sensor applications, as well as radiative cooling in the atmospheric transparency window, within the range of 8-13 μm (i.e. 1250-769 cm−1). Anisotropy of IR absorbance is correlated with retardance/birefringence of the same patterns in the visible spectral range. Larger period patterns of 3D columnar SiO2 films of ∼1 μm in thickness deposited on polymer/resist pillar arrays provide the possibility to control anisotropy of the form-birefringent 3D columnar films.
Optical anisotropy of glancing angle deposited thin films on nano-patterned substrates
(Optica Publishing Group, 2022) Grineviciute, L.; Moein, T.; Han, M.; Ng, S.H.; Anand, V.; Katkus, T.; Ryu, M.; Morikawa, J.; Tobin, M.J; Vongsvivut, J.; Tolenis, T.
This study has demonstrated that 3D columnar micro-films/coatings can be deposited over pre-patterned surfaces with sub-micrometer periodic patterns. Four-angle polarisation analysis of thin (0.4 − 1~μm) Si and SiO2 films, evaporated via glancing angle deposition (GLAD) at 70° to the normal, was carried out in reflection mode using synchrotron infrared microspectroscopy at the Australian Synchrotron. The angular dependence of absorbance followed A(θ) ∝ cos 2θ, confirmed for Si substrates patterned by electron beam lithography and plasma etching, which were used to make checkerboard patterns of Λ = 0.4~μm period on Si. Retardance control by birefringence of a patterned SiO2 substrate coated by columnar SiO2 is promising for UV-visible applications due to the use of the same material to endow polarisation control.
Review of engineering techniques in chaotic coded aperture imagers
(Light: Advanced Manufacturing, 2022) Anand, V.; Rosen, J.; Juodkazis, S.
Coded aperture imaging (CAI) is a technique to image three-dimensional scenes with special controlled abilities. In this review, we survey several recently proposed techniques to control the parameters of CAI by engineering the aperture of the system. The prime architectures of these indirect methods of imaging are reviewed. For each design, we mention the relevant application of the CAI recorders and summarize this overview with a general perspective on this research topic.
Roadmap on chaos-inspired imaging technologies (CI2-Tech)
(Springer Nature, 2022) Rosen, Joseph; de Aguiar, H.B.; Anand, V.; Baek, Y.; Gigan, S.; Horisaki, R.; Hugonnet, H.; Juodkazis, S.; Lee, K.; Liang, H.; Liu, Y.
In recent years, rapid developments in imaging concepts and computational methods have given rise to a new generation of imaging technologies based on chaos. These chaos-inspired imaging technologies (CI2-Tech) consist of two directions: non-invasive and invasive. Non-invasive imaging, a much older research direction with a goal of imaging through scattering layers, has reached faster, smarter, and sharper imaging capabilities in recent years. The invasive imaging direction is based on exploiting the chaos to achieve imaging characteristics and increase dimensionalities beyond the limits of conventional imagers. In this roadmap, the current and future challenges in invasive and non-invasive imaging technologies are presented.
Three-Dimensional Incoherent Imaging Using Spiral Rotating Point Spread Functions Created by Double-Helix Beams [Invited]
(Springer Nature, 2022) Anand, V.; Khonina, S.; Kumar, R.; Dubey, N.; Reddy, A.N.K.; Rosen, J.; Juodkazis, S.
In recent years, there has been a significant transformation in the field of incoherent imaging with new possibilities of compressing three-dimensional (3D) information into a two-dimensional intensity distribution without two-beam interference (TBI). Most incoherent 3D imagers without TBI are based on scattering by a random phase mask exhibiting sharp autocorrelation and low cross-correlation along the depth axis. Consequently, during reconstruction, high lateral and axial resolutions are obtained. Scattering based-Imaging requires a wasteful photon budget and is therefore precluded in many power-sensitive applications. This study develops a proof-of-concept 3D incoherent imaging method using a rotating point spread function termed 3D Incoherent Imaging with Spiral Beams (3DI2SB). The rotation speed of the point spread function (PSF) with displacement and the orbital angular momentum has been theoretically analyzed. The imaging characteristics of 3DI2SB were compared with a direct imaging system using a diffractive lens, and the proposed system exhibited a higher focal depth than the direct imaging system. Different computational reconstruction methods such as the Lucy–Richardson algorithm (LRA), non-linear reconstruction (NLR), and the Lucy–Richardson–Rosen algorithm (LRRA) were compared. While LRRA performed better than both LRA and NLR for an ideal case, NLR performed better than both under real experimental conditions. Both single plane imaging, as well as synthetic 3D imaging, were demonstrated. We believe that the proposed approach might cause a paradigm shift in the current state-of-the-art incoherent imaging, fluorescence microscopy, and astronomical imaging.
White Light Correlation Holography Using a Random Lens for Astronomical Imaging Applications
(2022 Photonics & Electromagnetics Research Symposium (PIERS), 2022) Anand, V.; Ng, S. H.; Katkus, T.; Juodkazis, S.