Studies on Genotoxic Effects of Mobile Phone Radiation on A375 Cells

Introduction: Radiation from cell phones has been associated with an increased risk of cancer. The literature has reported evidence of certain biological effects resulting from exposure to various wavelengths, doses, and intensities of radiofrequency radiation. The present study aimed to evaluate the possible adverse effects of radiation from a GSM mobile phone operating at 900 MHz on human melanoma A375 cells. Material and Methods: Cellular morphology was observed under an inverted phase contrast microscope. Cell viability was determined through trypan blue dye exclusion and clonogenic assay. Moreover, flow cytometry was applied to detect DNA damage, cell cycle arrest, and reactive oxygen species (ROS) production. Cellular reduced glutathione (GSH) content was estimated by measuring the total soluble thiol. In addition, the physico-chemical changes were assessed using spectrophotometer and viscometer. Results: This study revealed that there was no change in cellular morphology and necrotic cell killing; although a small effect was observed on delayed cell death. Depletion in GSH content was noted, but ROS generation was not significantly different from that of the control group. No DNA damage was found during such exposure and there was no alteration in cell cycle distribution. In vitro evaluation of radiation effect on calf thymus DNA showed a slight perturbation in absorption spectra that was completely reversible with time. On the other hand, viscometric analysis showed no changes. Conclusion: From the findings, it can be concluded that this range of mobile phone radiation for 60 min of continuous exposure has no genotoxic impact on A375 cells

Efficient Spectral Broadening in the 100-W Average Power Regime Using Gas Filled Kagome HC-PCF and Pulse Compression

We present nonlinear pulse compression of a high-power SESAM-modelocked thin-disk laser (TDL) using an Ar-filled hypocycloid-core Kagome Hollow-Core Photonic Crystal Fiber (HC-PCF). The output of the modelocked Yb:YAG TDL with 127 W average power, a pulse repetition rate of 7 MHz, and a pulse duration of 740 fs was spectrally broadened 16-fold while propagating in a Kagome HC-PCF containing 13 bar of static Argon gas. Subsequent compression tests performed using 8.4% of the full available power resulted in a pulse duration as short as 88 fs using the spectrally broadened output from the fiber. Compressing the full transmitted power through the fiber (118 W) could lead to a compressed output of >100 W of average power and >100 MW of peak power with an average power compression efficiency of 88%. This simple laser system with only one ultrafast laser oscillator and a simple single-pass fiber pulse compressor, generating both high peak power >100 MW and sub-100-fs pulses at megahertz repetition rate, is very interesting for many applications such as high harmonic generation and attosecond science with improved signal-to-noise performance

Picosecond Fiber MOPA Pumped Supercontinuum Source With 39 W Output Power

We report a picosecond fiber MOPA pumped supercontinuum source with 39 W output, spanning at least 0.4-2.25 µm at a repetition rate of 114.8 MHz. The 2m long PCF had a large, 4.4 µm diameter core and a high-delta design which led to an 80% coupling efficiency, high damage threshold and rapid generation of visible continuum generation from the picosecond input pulses. The high and relatively uniform power density across the visible spectral region was ~31.7 mW/nm corresponding to peak power density of ~12.5 W/nm for the 21 ps input pulses. The peak power density was increased to 26.9 W/nm by reducing the repetition rate to 28 MHz. This represents an increase in both average and peak power compared to previously reported visible supercontinuum sources from either CW pumped or pulsed-systems

Polarization Properties of Selectively Gold-filled Suspended Core Microstructured Optical Fibers

We study the polarization properties of suspended core microstructured optical fibers (SC-MOFs) with hexagonal lattice structure and high air-filling fraction having a single gold-filled hole along the horizontal axis. The interaction between the core-guided light and metal leads to surface plasmon resonance (SPR) at particular frequencies where the phase-matching condition is satisfied. We observe from the modal analysis that MOFs with high air-filling fraction offer the possibility of coupling of the fundamental mode with the first-order surface plasmon polariton (SPP) mode. With the increase in the suspension factor (SF), the fundamental mode couples with higher order SPP modes and the coupling strength also enhances. It also leads to an increase in modal birefringence. Reduction in beat length by an order of magnitude compared to the reported values is being reported for the first time to our knowledge. We have achieved the lowest beat length of 0.0105 mm at 1 μm wavelength for the structure having d/Λ = 0.85 and SF = 1.65. The results show that such plasmonic SC-MOFs may perform as efficient in-fiber polarizers and polarization filters

Suspended core microstructured optical fibers with diverse arrangements of gold-filled holes: study of the polarization characteristics and resonance strength

We study the dispersion and polarization properties as well as the coupling characteristics of suspended core microstructured optical fibers (SC-MOFs) having constant pitch and air-filling fraction with a varying suspension factor (SF) and diverse arrangements of gold-filled holes. The interaction between the core-guided fundamental mode and the surface plasmon polaritons (SPPs) generated on the surface of the gold-filled hole creates surface plasmon resonance (SPR) at the phase-matching wavelengths. It is observed that such plasmonic SC-MOF designs exhibit very high birefringence and an increased number of complete coupling points for high SF values. In addition, for all the arrangements of gold-filled holes, the coupling occurs for a higher order of the SPP for structures having greater SF. The resonance strength of such SC-MOFs is significantly enhanced and considerable reduction in full width at half maximum(FWHM) bandwidth of the SPR peak is achieved for the x-axis with suitable arrangement of gold-filled holes. The values of the coupling strength and FWHM achieved for the proposed SC-MOF structures are better compared to all the data reported until now to the best of our knowledge. The results suggest that such SC-MOF structures may be beneficial for developing polarizers or in-fiber polarization splitters with improved performance. (C) 2019 Optical Society of Americ

Strong infrared radiation through passive dispersive wave generation and its control

We observe strong infrared (IR) radiation as a result of passive dispersive wave generation for a realistic microstructured fiber having two zero-dispersion wavelengths. The IR radiation frequency can be suitably controlled by varying the operational wavelength, which falls in the first normal dispersion regime. The amplitude of the radiation can be significantly increased by introducing a suitable amount of chirp in the input pulse. This strong phase-matching radiation can be considered as an alternative solution for the IR laser for different applications. (C) 2011 Optical Society of Americ

Determination of modal effective indices and dispersion of microstructured fibers with different configurations: a variational approach

A simple semi-analytical model based on the variational method is developed for determining the effective indices of the fundamental modes and consecutively the dispersion properties of microstructured optical fibers (MOFs) with different lattice geometries without resorting to any numerical tool. We consider an equivalent step-index (ESI) profile of the MOF and the fundamental mode shape is approximated as a simple Gaussian function in the core. Effective index data and dispersion obtained from the proposed variational method offer reasonable agreement with numerically derived data using the Finite Element Method (FEM). The proposed model offers an alternative and swift way for reasonably precise determination of the effective index of the fundamental mode and dispersion properties of MOF designs with different lattice geometries. Finally, as a major application, the dispersion property of a fabricated MOF, derived through the proposed variational method, is directly used in order to model experimental supercontinuum (SC) spectra with satisfactory agreement

Supercontinuum Generation in Microstructured Silica Optical Fibers : The Formation of Artificial White Light

The inherent feature of nonlinear optics is the modification of the optical properties of the medium due to the interaction of the propagating high intensity light with the medium ultimately leading to the generation of new frequencies. An ultra-short optical pulse experiences spectral broadening when it is passed through a nonlinear medium such as high purity silica fiber and eventually generates artificial white light with unique spectral properties, controlled time duration and high spectral brightness. Owing to its wide and continuous spectra, such phenomenon is generally called supercontinuum (SC) generation. A variety of nonlinear processes governed by the associated pulse duration are involved in such spectral broadening. For femtosecond pump pulses, soliton dynamics plays a pivotal role whereas self-phase modulation (SPM), four wave mixing (FWM) etc are important for wider pump pulses. The generation of white light is an interesting physical phenomenon and it opens up new possibilities in the field of optical communication, optical metrology, nonlinear spectroscopy, microscopy and laser biomedicine. In the present review particular attention is paid to the description of the formation of white light in different operational conditions in highly nonlinear waveguides like photonic crystal fiber (PCF)

Efficient supercontinuum sources based on suspended core microstructured fibers

We fabricate uniform silica microstructured optical fibers (MOFs) having very simple geometry with only three rings of air holes in order to generate efficient supercontinuum (SC). The fabricated MOFs possess suspended core with comparatively larger pitch and are the most active component in a SC source. We use the suspension factor as a design parameter which significantly influences the nonlinear and dispersion properties of the MOFs. It is experimentally shown that our fabricated MOFs generate efficient SC both in femtosecond and picosecond pumping domain. We also numerically model the nonlinear dynamics for SC sources in order to identify the nonlinear processes and illustrate the spectral broadening mechanisms