Photonic Research Articles

Theoretical study and demonstration of photonic asynchronous first-order delta-sigma modulator for converting analog input to NRZ binary output

Fil: Costanzo Caso, Pablo Alejandro. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico La Plata. Centro de Investigaciones Opticas (i); Argentina. Rose-Hulman Institute of Technology. Physics and Optical Engineering Department; Estados Unidos

Preparation and field emission property of silicon nanotip arrays

Laser devices used in the field of optical-electronics are made of GaAs, InP and so on, which are expensive and hard to be integrated into Si-chip. If a laser device can directly made from silicon, the problems can be solved. A novel strategy for preparing large-area, vertically aligned silicon nanotip arrays at near room temperature by combining silver mirror reaction with metal-catalyzed electroless etching (MCEE) has been developed. It has been demonstrated that the silicon nanotips arrays with a length among 4~7 m and a middle part diameter ranging from 100 to 300 nm have been successfully fabricated on silicon wafers. This method is considerably simple, efficient, nontoxic, controllable and low-cost. Moreover it does not need high temperature, complicated equipments and demanding conditions of environment. At last, the field emission property of the Si nanotip array is primarily tested. The conclusions are as follows: effective electron emission can be obtained by the Si nanotip array; the turn-on field is 2.7 V/m (the current density is 10 A/cm2). The field enhancement factors determined using the F-N curve is 692, the resultant large-area vertically aligned Si nanotips arrays on Si substrate can be expected to be used on field-emitting applications in the future and it will have broad prospects for development.

Acknowledgement to Reviewers of Photonics in 2014

Acknowledgement to Reviewers of Photonics in 2014

4.3 μm低损耗硫系空芯光子带隙光纤结构设计及性能研究

运用平面波展开法分析As2S3、Ge20Se65Sb15和As2Se3硫系玻璃光纤在不同空气填充率下的带隙分布图, 分析结果表明三种材料在空气填充率提高到0.75时, 光子带隙与空气线均出现交汇模式, 且带隙宽度大, 纤芯空气孔中适宜进行激光传输.运用有限元法分析不同纤芯孔直径的Ge20Se65Sb15硫系玻璃空芯光子带隙光纤的基模限制损耗和有效模场面积, 结果表明纤芯直径9.2 μm时限制损耗最低, 模场面积较小.通过优化光纤的结构参量, 适合于4.3 μm波长处高功率中红外激光传输的空芯光子带隙光纤, 其限制损耗为0.00472 dB/m, 有效模场面积为58.046 μm2.

Soft glass spiral photonic crystal fiber for large nonlinearity and high birefringence

This paper presents a soft glass spiral photonic crystal fiber with circular air holes for achieving high birefringence, large nonlinearity and large negative dispersion. The material used here for designing the fiber is soft glass (SF-57). A central defect air hole is being introduced in the core for achieving high birefringence and for different ellipticity ratios the effect of various optical properties of a photonic crystal fiber are studied. The structure proposed has a high birefringence in the order of 10 –2 , high nonlinearity of 5828 W –1 km –1 and high negative dispersion of –1546.6 ps/nm·km at 0.850 μm. A numerical approach based on the finite element method is used for the design and simulation of the structure. Due to the optimization in the cladding air holes, the fiber can be used as polarization maintaining fibers, in dispersion compensation and other nonlinear applications.

A novel approach to photonic generation of periodic triangular radio frequency waveforms

A novel approach to photonic generation of triangular radio frequency waveforms with a tunable repetition rate is proposed and analyzed. In the proposed system, a continuous-wave light is modulated by a reference microwave signal through a polarization modulator, and then its output optical sidebands are manipulated by a microwave photonic filter with a negative tap. By properly adjusting the system parameters, full-duty-cycle triangular radio frequency waveforms can be generated after optical-to-electrical conversion, and its repetition rate (frequency) can be tuned in a wide range. A model describing the proposed system is derived, which is verified via computer simulations.

Polarity-reversed ultra-wideband monocycle pulse generation with dual-channel multicasting in a photonic crystal fiber

This paper proposes and demonstrates a novel scheme of a two-channel-output ultra-wideband monocycle pulse generator consisting of a 100 m dispersion-flattened highly nonlinear photonic crystal fiber and two optical bandpass filters. Based on the cross-phase modulation effect in a dispersion-flattened highly nonlinear photonic crystal fiber, two polarity-reversed ultra-wideband monocycle pulses simultaneously output from two different channels are successfully achieved by appropriately locating the probe wavelength at the left linear slope and the right linear slope of the two optical bandpass filters transmission spectra, respectively. The full width at half-maximum and a fractional bandwidth of 24 ps and 260% for a positive pulse, 24 ps and 251% for a negative pulse are obtained. Moreover, the influences of input signal powers, the polarization misalignment between the data light and the continuous wave probe light, and probe wavelength variation on the double output ultra-wideband signals quality are also investigated. The results show that the system has some tolerance to both the input signal power fluctuation and the slight polarization mismatch and even can efficiently operate with a widely tunable wavelength range. This makes it very attractive for engineering applications in future multiuser ultra-wideband-over-fiber communication systems.

Investigation on the spectrum of complex self-organized plasma photonic crystal

A complex plasma photonic crystal (PPC) was obtained by self-organization of filaments in air dielectric barrier discharge using two planar water electrodes. The PPC structure consists of many square sublattices, and each sublattice is composed of large spots, two kinds of small spots and lines, corresponding to thick plasma columns, two kinds of thin plasma columns, and plasma slices, respectively. By using the optical emission spectrum method, the electron densities and molecular vibration temperatures at different positions of the PPC were studied. The electron densities were compared by comparing the broadenings of Ar I (2P2-->1S5) spectrum line, and the molecular vibration temperatures were calculated by the spectrum line of nitrogen band of second positive system (C3Πu-->B3Πg) . It was found that the electron densities and molecular vibration temperatures at different positions are both different, showing that the plasma states at different positions are different. The descending order of the electron density is: thin plasma columns around the thick plasma columns, thick plasma columns, plasma slices, and thin plasma columns at junction of plasma slices. The descending order of the molecular vibration temperature is: thin plasma columns at junction of plasma slices, plasma slices, thick plasma columns, and thin plasma columns around the thick plasma columns, which is opposite to that of the electron density. So, the electron densities and the molecular vibration temperatures in different positions of the PPC show the opposite changing trend. As the refractive index of plasma is dependent upon the electron density, the thick plasma columns, two kinds of thin plasma columns and plasma slices in this PPC have different refractive indexes. Together with the surrounding area where no discharges occur, in which the refractive index is also different from the discharging areas, the complex PPC can be seen as a self-organized periodic structure with five different refractive indexes. The PPC has the advantages of being obtained easily, having structural diversity, and being analyzed simply, which may lead to wide applications in many scientific and technical areas.

Photonic delay systems as machine learning implementations

Nonlinear photonic delay systems present interesting implementation platforms for machine learning models. They can be extremely fast, offer great degrees of parallelism and potentially consume far...

Fertile ground for photonics

Fertile ground for photonics

Photonics is a Nobel cause

Photonics is a Nobel cause

Measurement of pressure sensitivity of modal birefringence of birefringent optical fibers using a Sagnac interferometer

The paper presents a method of measuring the sensitivity of modal birefringence to pressure in birefringent optical fibers, based on a Sagnac interferometer with a birefringent fiber. In this method, the pressure sensitivity of modal birefringence of the optical fiber is determined on the basis of the measurement of the pressure sensitivity of the Sagnac interferometer including the fiber being measured, and the measurement of the group modal birefringence of that fiber, which is also performed by using the Sagnac interferometer. Utilizing the above method, measurements were performed of the pressure sensitivity of modal birefringence of birefringent optical fibers: a photonic crystal fiber and a bow-tie fiber, in the wavelength range 1460–1600 nm. Presented are the results of these measurements and their comparison with the results obtained by using different methods for the same types of fibers.

Effect of Mobile Phone-Induced Electromagnetic Field on Brain Hemodynamics and Human Stem Cell Functioning: Possible Mechanistic Link to Cancer Risk and Early Diagnostic Value of Electronphotonic Imaging.

The mobile phones (MP) are low power radio devices which work on electromagnetic fields (EMFs), in the frequency range of 900-1800 MHz. Exposure to MPEMFs may affect brain physiology and lead to various health hazards including brain tumors. Earlier studies with positron emission tomography (PET) have found alterations in cerebral blood flow (CBF) after acute exposure to MPEMFs. It is widely accepted that DNA double-strand breaks (DSBs) and their misrepair in stem cells are critical events in the multistage origination of various leukemia and tumors, including brain tumors such as gliomas. Both significant misbalance in DSB repair and severe stress response have been triggered by MPEMFs and EMFs from cell towers. It has been shown that stem cells are most sensitive to microwave exposure and react to more frequencies than do differentiated cells. This may be important for cancer risk assessment and indicates that stem cells are the most relevant cellular model for validating safe mobile communication signals. Recently developed technology for recording the human bio-electromagnetic (BEM) field using Electron photonic Imaging (EPI) or Gas Discharge Visualisation (GDV) technique provides useful information about the human BEM. Studies have recorded acute effects of Mobile Phone Electromagnetic Fields (MPEMFs) using EPI and found quantifiable effects on human BEM field. Present manuscript reviews evidences of altered brain physiology and stem cell functioning due to mobile phone/cell tower radiations, its association with increased cancer risk and explores early diagnostic value of EPI imaging in detecting EMF induced changes on human BEM.

The year of light for enlightening photonics and cytometry‐ start of new year's note

The year of light for enlightening photonics and cytometry‐ start of new year's note

WDM optical access network for full-duplex and reconfigurable capacity assignement based on Polmux technique

This work was supported by the national project TEC2011-26642 funded by the Ministerio de Economia y Competitividad. Also, The authors wish to acknowledge the financial support given by the Generalitat Valenciana under the Research Excellency Award Program GVA PROMETEO 2013/012 Next Generation Microwave Photonic technologies.

Photonics: general discussion.

Photonics: general discussion.

Call for papers - Announcing issue on Attoseconds Photonics

Call for papers - Announcing issue on Attoseconds Photonics

Call for papers - Announcing issue on Attoseconds Photonics

Call for papers - Announcing issue on Attoseconds Photonics

Scatterings

Bake and Print Your Own Microscope: Gravity shapes inexpensive lenses for applications in education and medicine; Tracking the Eye’s Quivering Crystalline Lens; Better Polymer IR Lenses from Waste Sulfur; A Look at Intracellular Signaling; Deformable Mirror Corrects Itself; Solar Roadways; Cuomo Decrees US$1 Billion for Solar Development in NY; NIST Funds Two Grants for Photonics Industry Roadmaps; Photonic IC Market to See Big Growth Through 2019; Trapped Atom; Collider Could Turn Light into Matter.

SPIE Photonics Europe shines light on photonics markets, novel research

SPIE Photonics Europe shines light on photonics markets, novel research