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Background Optical retarders are key elements for the control of the state of polarization of light, and their wavelength dependance is of great importance in a number of applications. Methods We apply a well-known technique for determinig the spectral retardance by measuring the transmission spectra between crossed or parallel polarizers. But we we develop an optical system to perform this measurement...
We propagate partially coherent light through discontinuous surfaces and analyze the optical effects in phase space. The discontinuous surfaces are classified into two types, those with discontinuity in space and those with discontinuity in slope. Results are discussed based on the Wigner function. This approach explains the performance of segmented elements during the transition from the refractive...
The paper presents optical and thermal simulations of two kinds of thermally controlled silicon Photonic Crystal devices: an air hole in silicon slab that switches between two refractive behaviors, and a T-shaped circuit made by silicon rods in air that has an on-off behavior. Both effects have been obtained by increasing the device temperature, then exploiting the thermo-optic effect. Theoretical...
Summary This paper shows the use of a specific type of time series analyses, the so named recurrence plot (RP), for investigations of the outer hull of an imaged and pre-segmented object to derive image features suitable for usage in classificators. Additionally to the features derived by the well documented recurrence quantification analysis (RQA) a new set of features was developed based on closed...
Background In this paper, the impact of the dispersion effect, due to atmospheric pressure and temperature, on NRZ-OOK terrestrial free-space optical transmission system is investigated. An expression for the dispersion parameter in FSO atmospheric channel is derived. Results The results show that the variation of the refractive index along the transmission path induces fluctuations of group velocity...
Background Interests on low-loss terahertz (THz) waveguides are increasing due to their remarkable applications in various fields. Since most the materials are highly absorbent to THz waves therefore it is an ongoing challenge to obtain a low-loss waveguide. This paper presents a novel porous-core square lattice photonic crystal fiber (PCF) for efficient transmission of THz waves. Methods The guiding...
In this study, the used of tapered optical fiber tip as sensors coated with reduced Graphene Oxide (rGO) is investigated. The resultant rGO nanocomposites coated on the tapered fiber sensor were characterized by X-ray Diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy (FESEM). Optimization of the rGO layer and the tapering parameters are found and the sensing capability...
In this paper, we optimized the apodization profile to improve the dispersion compensation performance of the chirped fiber Bragg gratings (CFBGs). Half tanh half uniform (HTHU), half exponential half uniform (HEHU), and half hamming half uniform (HHHU) apodization profiles were evaluated at 2000 nm wavelength. At this wavelength, Hollow-Core Photonic Crystal Fiber (HC-PCF) will be the targeted fiber...
We propose an algorithm to remove a parabolic wavefront from a convergent or divergent beam in the Wigner function. Using this approach we numerically collimate the beam. This avoids a dense sampling in phase space to describe a convergent wavefront. Thereby we reduce the required computer memory, but maintain computational accuracy and physical effects. Furthermore, we compare two algorithms, shearing...
This letter is on the response of gallium arsenide p-i-n diodes to sub-bandgap photons (1.55 μm). We investigate the various regimes of sub-bandgap operation by using different light sources delivering pulses ranging from nanosecond to microsecond durations. We evidence two regimes : a regime of degenerate two-photon absorption, with a clear quadratic dependence with respect to the incident flux,...
Background This study analyses the possibility of optical detection of trace amounts of oil in natural waters. Since petroleum and its derivatives induced by ultraviolet light exhibit a high intensity of fluorescence, this phenomenon can be used to detect petroleum products penetrating both the surface and subsurface waters. The challenge is to discriminate the fluorescence signal originating from...
Background In this work, the experimental behavior observed in the z-scan curves of a sample of bleached photographic film for different incident powers is theoretically modeled. Methods Two models are modified in order to fit the experimental z-scan curves. The Focal Length Dependent on a power of the beam radius (FLD) model and the Nonlocal (NL) model. Results As a result of the fitting, it...
As the number of codewords adopted in phase-coding fringes increases, the solution of fringe orders leads to many mistakes. Consequently, errors of the unwrapped phase occur. Thus, increasing the codeword approach in a phase-coding fringe remains a challenge. In this paper, a modified stair phase-coding fringe is designed, and a new phase unwrapping algorithm based on shifting fringe order is presented...
Background Newton’s ring method is often used to measure many physical parameters. And some measured physical quantity can be extracted by calculating the radius parameter of circular fringes from Newton's ring configuration. Methods The paper presents a new measuring method for radius of circular fringes, which includes three main steps, i.e., determination of center coordinates of circular fringes,...
Background Dual wavelength laser generation has been of constant interest due to their applications in optical communications and teraheartz generation. A novel configuration for Dual-wavelength laser generation based on the use of a couple of multimode interference (MMI) filters is demonstrated in a ring cavity Erbium-doped fibre laser. Methods The MMI filters consist of a segment of no-core fibre...
Mode division multiplexing (MDM) is a promising technology for increasing the aggregate bandwidth of multimode fiber (MMF) in conjunction with wavelength division multiplexing (WDM) in face of the impending capacity crunch in optical fiber networks. This paper investigates the effect of radial and azimuthal mode spacings in a 25-channel MDM-WDM system in MMF using a spatial light modulator-controlled...
We propose an alternative and simple solution to self-referenced digital holographic imaging based on a ring-shaped bifocal lens, without the need of any mirrors, polarizers or spatial light modulators. We discuss the imaging properties of the ring-shaped bifocal lens in self-referenced holography. The easy applicability of this bifocal lens is demonstrated on a realized microscope setup for volumetric...
Background Optical Coherence Tomography OCT is a noninvasive imaging technique that takes pictures of cross sections of human body tissues with a great resolution compared to other techniques. Fourier Domain OCT method provides significant improvement of imaging speed and detection sensitivity but suffers from autocorrelation noise arising as interference signals from reflections of sample layers...
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