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25 pages, 8379 KiB

Open AccessArticle

An Intriguing Interpretation of 1D and 2D Non-Diffracting Modes in Cosine Profile

by Allam Srinivasa Rao

Photonics 2023, 10(12), 1358; https://doi.org/10.3390/photonics10121358 - 8 Dec 2023

Cited by 2 | Viewed by 1497

We provide a simple analysis based on ray optics and Dirac notation for 1D (one-dimensional) and 2D (two-dimensional) non-diffracting modes in the cosine profile, which are often called Cosine beams. We explore various kinds of structured modes formed by the superposition of two 1D Cosine beams. We then went on to understand the properties of the Bessel beams in terms of Cosine beams. For the first time, we report on the generation of three-dimensional tunable needle structures based on the interference of 1D Cosine beams. These size-tunable optical needles can have multiple advantages in material processing. Also, we report, for the first time, on the Talbot effect in Cosine beams. Straightforward mathematical calculations are used to derive analytical expressions for Cosine beams. The present method of demonstrating Cosine beams may be utilized to understand other structured modes. The Dirac notation-based interference explanation used here can provide new researchers with an easy way to understand the wave nature of light in a fundamental aspect of interferometric experiments as well as in advanced-level experiments such as beam engineering technology, imaging, particle manipulation, light sheet microscopy, and light–matter interaction. We also provide an in-depth analysis of similarities among Cosine, Bessel, and Hermite–Gaussian beams. Full article

(This article belongs to the Special Issue Research in Computational Optics)

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17 pages, 3744 KiB

Open AccessArticle

Long-Focusing Device for Broadband THz Applications Based on a Tunable Reflective Biprism

by Giancarlo Margheri and Tommaso Del Rosso

Micromachines 2023, 14(10), 1939; https://doi.org/10.3390/mi14101939 - 18 Oct 2023

Cited by 1 | Viewed by 1442

Abstract

THz radiation has assumed great importance thanks to the efforts in the development of technological tools used in this versatile band of the electromagnetic spectrum. Here, we propose a reflective biprism device with wavelength-independent long-focusing performances in the THz band by exploiting the high thermo-mechanical deformation of the elastomer polydimethylsiloxane (PDMS). This deformation allows for achieving significant optical path modulations in the THz band and effective focusing. The surface of a PDMS layer is covered with a gold thin film acting as a heater thanks to its absorption of wavelengths below ~500 nm. An invariance property of the Fresnel integral has been exploited to experimentally verify the THz performances of the device with an ordinary visible laser source, finding excellent agreement with the theoretical predictions at 1 and 3 THz. The same property also allowed us to experimentally verify that the reflective biprism focus has a longitudinal extension much greater than that exhibited by a benchmark convex cylindrical mirror with the same optical power. The device is thermo-mechanically stable up to a heating power of 270 mW, although it might be potentially exploited at higher powers with minor degradation of the optical performances. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in 'Engineering and Technology' 2023)

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12 pages, 3520 KiB

Open AccessArticle

Single-Shot 3D Topography of Transmissive and Reflective Samples with a Dual-Mode Telecentric-Based Digital Holographic Microscope

by Ana Doblas, Charity Hayes-Rounds, Rohan Isaac and Felio Perez

Sensors 2022, 22(10), 3793; https://doi.org/10.3390/s22103793 - 17 May 2022

Cited by 3 | Viewed by 5700

Abstract

Common path DHM systems are the most robust DHM systems as they are based on self-interference and are thus less prone to external fluctuations. A common issue amongst these DHM systems is that the two replicas of the sample’s information overlay due to self-interference, making them only suitable for imaging sparse samples. This overlay has restricted the use of common-path DHM systems in material science. The overlay can be overcome by limiting the sample’s field of view to occupy only half of the imaging field of view or by using an optical spatial filter. In this work, we have implemented optical spatial filtering in a common-path DHM system using a Fresnel biprism. We have analyzed the optimal pinhole size by evaluating the frequency content of the reconstructed phase images of a star target. We have also measured the accuracy of the system and the sensitivity to noise for different pinhole sizes. Finally, we have proposed the first dual-mode common-path DHM system using a Fresnel biprism. The performance of the dual-model DHM system has been evaluated experimentally using transmissive and reflective microscopic samples. Full article

(This article belongs to the Special Issue Three-Dimensional (3D) Biophotonics Sensing and Reconstruction towards Biomedical Research)

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