Polymer‐free,low tension graphene mechanical resonators

Graphene resonators are fabricated using a polymer‐free, direct transfer method onto metal reinforced holey carbon grids. The resonators are distinguished by the absence of organic residues and excellent crystallinity. The normal mode frequencies are measured using a Fabry–Perot technique; resonance curves indicate highly linear behaviour but very little built‐in strain, which is consistent with device geometry examined by atomic force microscopy. We conclude that the oscillators' restoring force is due instead to graphene's intrinsic bending rigidity; our measurements indicate a value of approximately 1.0 eV, consistent with previous theoretical and experimental work. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Systematical research on the characteristics of a vertical coupled Fabry–Perot plasmonic filter

A nanometric surface plasmon polariton (SPP) filter based on a vertical coupled metal–insulator–metal (MIM) Fabry–Perot resonator is proposed and analyzed. The transmission characteristics of the SPP filter are analyzed in detail by using the finite difference time domain method. And the resonance condition derived by the numerical method is consonant with the analytic model based on the Fabry–Perot model, which includes the metal loss and dispersion effects. And the simulation results show that multiple transmission dips can be formed and the resonance wavelengths of the transmission dips can be altered by the Fabry–Perot cavity length and width. Also the extinction ratio and the quality factor of the filter are affected by the barrier thickness of the coupling region. The proposed nanometric plasmonic filter is simple and very promising for the SPP waveguides platform.     

Sapphire hard X‐ray Fabry–Perot resonators for synchrotron experiments

Hard X‐ray Fabry–Perot resonators (FPRs) made from sapphire crystals were constructed and characterized. The FPRs consisted of two crystal plates, part of a monolithic crystal structure of Al₂O₃, acting as a pair of mirrors, for the backward reflection (0 0 0 30) of hard X‐rays at 14.3147 keV. The dimensional accuracy during manufacturing and the defect density in the crystal in relation to the resonance efficiency of sapphire FPRs were analyzed from a theoretical standpoint based on X‐ray cavity resonance and measurements using scanning electron microscopic and X‐ray topographic techniques for crystal defects. Well defined resonance spectra of sapphire FPRs were successfully obtained, and were comparable with the theoretical predictions.     

Broadband efficient light absorbing in the visible regime by a metananoring array

The broadband efficient light‐absorbing property of a metamaterial‐based subwavelength nanoring array in visible regime is reported. The nanoring array can absorb light efficiently with an average absorptivity of 0.97 over the whole visible waveband. In addition, it is found that this kind of super light‐absorbing capability is independent of the incoming light polarization state and can maintain an average of 0.9 for an incident angle as large as ±60° under TM illumination. The perfect absorbing property of the metamaterial‐based nanoring array is attributed to the synergetic effect of the Fabry–Perot resonance and the localized surface plasmon resonance enhancement.     

Effect of Fabry‐Perot resonances in disordered one‐dimensional array of alternating dielectric bi‐layers

We study numerically and analytically the role of Fabry‐Perot resonances in the transmission through a one‐dimensional finite array formed by two alternating dielectric slabs. The disorder consists in varying randomly the width of one type of layers while keeping constant the width of the other type. Our numerical simulations show that localization is strongly inhibited in a wide neighborhood of the Fabry‐Perot resonances. Comparison of our numerical results with an analytical expression for the average transmission, derived for weak disorder and finite number of cells, reveals that such expression works well even for medium disorder up to a certain frequency. Our results are valid for photonic and phononic one‐dimensional disordered crystals, as well as for semiconductor superlattices.     

A high-finesse fiber optic Fabry–Perot interferometer based magnetic-field sensor

A high-finesse extrinsic Fabry–Perot interferometric sensor for the measurement of weak dc magnetic fields is demonstrated. The Fabry–Perot cavity is formed by aligning the fiber end-face and the TbDyFe rod end-face, and each end-face is coated by a mirror with a micro-lens. The length of the TbDyFe rod is changed by the variation of an applied dc magnetic field, leading a change of the Fabry–Perot cavity length. By interrogating the white-light interferometric spectrum, the wavelength of the resonant peak is tracked and the length of the Fabry–Perot cavity is obtained. The sensor exhibits a high sensitivity of 1510 nm/mT with a magnetic resolution of 25 nT.     

一维金属光栅的透射光学特性

利用时域有限差分法模拟了一维金属光栅的透射光场的分布及光栅厚度等因素对透射光谱的影响.结果表明:特定波长的光通过金属光栅中的亚波长狭缝时有异常大的透过率增强.分析其物理起源,认为是类FabryPerot(FP)腔作用的结果.基底介电常量对类FP腔长度的调制导致了对透射光谱的影响.金属光栅表面激发的表面等离子体激元波与多缝干涉一样,对透射光谱有一定的影响,但不是形成增强的原因 关键词： 金属光栅 透射光学特性     

Extraordinary light transmission through a metal film perforated by a subwavelength hole array

It is shown that, depending on the incident wave frequency and the system geometry, the extraordinary transmission of light through a metal film perforated by an array of subwavelength holes can be described by one of the three mechanisms: the “transparency window” in the metal, excitation of the Fabry–Perot resonance of a collective mode produced by the hybridization of evanescence modes of the holes and surface plasmons, and excitation of a plasmon on the rear boundary of the film. The excitation of a plasmon resonance on the front boundary of the metal film does not make any substantial contribution to the transmission coefficient, although introduces a contribution to the reflection coefficient.     

An Extrinsic Fabry–Perot Optical Fiber Sensor Based on Nano-Magnetic Fluid

Abstract

An extrinsic Fabry–Perot optical fiber sensor based on nano-magnetic fluid and a Fabry–Perot interference is presented for magnetic field measurement. The sensing fiber end is coated with a thin film of SU-8 photoresist; immersing it into a nano-magnetic fluid forms a magnetic-field-dependent extrinsic Fabry–Perot interference. The relationship between the fringe contrast and magnetic field is analyzed in different concentrations of the magnetic fluid, and the concentration of 25% is most suitable for the measurement of the magnetic field intensity. The stability of the sensor is also addressed.     

III‐V/silicon photonics for on‐chip and intra‐chip optical interconnects

In this paper III‐V on silicon‐on‐insulator (SOI) heterogeneous integration is reviewed for the realization of near infrared light sources on a silicon waveguide platform, suitable for inter‐chip and intra‐chip optical interconnects. Two bonding technologies are used to realize the III‐V/SOI integration: one based on molecular wafer bonding and the other based on DVS‐BCB adhesive wafer bonding. The realization of micro‐disk lasers, Fabry‐Perot lasers, DFB lasers, DBR lasers and mode‐locked lasers on the III‐V/SOI material platform is discussed.     

Polarization-insensitive surface plasmon resonance sensor by cross-slit metallic periodic arrays

We propose a plasmonic structure to obtain polarization-insensitive localized surface plasmon resonance (LSPR) sensor, which consists of cross-slit metallic periodic arrays embedded in the background material. Numerical simulation illustrates that the mechanism of the LSPR sensor is based on the shift of the Fabry–Perot cavity mode resonance peak in the spectrum as the change of the dielectric material properties for the near fields. And one of the transmission dips of the structure is very sensitive to the background materials; the structure could gain the sensitivity (nm/RIU) more than 500 nm/RIU. Meanwhile, the structure holds great potential to achieve high-performance sensors in practical application due to polarization-insensitive virtue.     

Continuous wave tunable fiber optical parametric oscillator with double-pass pump configuration

We demonstrate a continuous wave tunable fiber optical parametric oscillator in a Fabry–Perot cavity consisting of a 500-m highly nonlinear fiber. In this work, the pump propagates in both directions together with the signal, thus making full use of its parametric gain. The resultant laser peak power is uneven across the wavelength range of interest due to wavelength-dependent phase modulation by the single-mode fiber sections in the cavity. This can be solved by filtering the idler spectral component from the oscillating cavity.     

Highly Enhanced Emission of Visible Light from Core–Dual‐Shell‐Type Hybridized Nanoparticles

Core–dual‐shell‐type hybridized nanoparticles (NPs) having Au‐core/dye‐doped silica inner shell/Au outer shell are successfully fabricated by developing a biphasic process that is a kind of so‐called “one‐pot” method. The resulting hybridized NPs exhibit evidently about 20‐fold enhancement of fluorescence intensity, increase in fluorescence quantum yield, and decrease in fluorescence lifetime. These effects depend on the metal nanostructure being optimized, compared with the reference hybridized NPs with neither a Au‐core nor a Au outer shell, due to the gap‐mode effect induced by localized surface plasmon resonance in the core–dual‐shell‐type MIM‐like nanostructure. More detailed elucidation concerning the enhancement mechanism will provide the possibility of photonic device application, for example as a high‐performance point light source, nanolaser, or sensor for bioimaging in the visible region in the near future.     

Design of multi-layer mirrors for measuring optical phase modulation at 1300 nm

A theoretical design and experimental realization of multi-layer mirrors for Fabry–Perot interferometry and optical telecommunications is described in this work. The mirrors were designed and fabricated by 13 successive thin layers to achieve very high reflectance at optical wavelengths around 1300 nm. Thin layers are ZnS and MgF₂ presenting high and low refractive index, respectively. Layer thickness λ_o/2 at λ_o=656 nm. Experimental results include characterization of transmittance of mirrors around 1300 nm. Additionally, the mirrors were integrated in a Fabry–Perot interferometer to characterize optical sources emitting at 1300 nm. Finally to show a practical application, optical phase modulation was analyzed, using the fabricated mirrors through a scanning Fabry–Perot interferometer acting as high-resolution optical spectrum analyzer (OSA).     

Wideband frequency tunable optoelectronic oscillator based on a dispersion compensated microwave photonic filter

A wideband tunable optoelectronic oscillator (OEO) based on a dispersion compensated phase modulated microwave photonics filter (MPF) is proposed and experimentally demonstrated. The MPF, consisting of a tunable laser source (TLS), a phase modulator, a fiber Bragg grating Fabry–Perot filter and a photodetector, is used as the oscillating mode selection device. Dual-loop configuration is employed to make sure the OEO operates at a single oscillating mode. Theoretically analysis is carried out to demonstrate the tuning range limitation due to the phase-modulation to intensity-modulation conversion caused by long single mode fiber (SMF). To overcome this disadvantage and expand the signal tuning range, a dispersion compensation fiber is introduced followed by the SMF to compensate the fiber dispersion. By simply adjusting the wavelength of the TLS, an ultra-wideband tunable microwave signal with the frequency tuning range from 2 to 44 GHz is obtained. The phase noise is also investigated and measured to be less than ? 110 dBc/Hz at an offset of 10 kHz within the whole frequency range.     

Spin accumulation in the semi classical and quantum regimes

We consider spin accumulation at a ferromagnet-normal metal interface in the presence of magnetic scattering in the normal metal. In the classical regime, we discuss the inverse Drude scaling of the conductance as a function of the interface transparencies. We present a treatment based on an exact solution of the Boltzmann equation. In the quantum regime, we solve a single impurity “spin-flip Fabry Perot interferometer” for quantum coherent multiple scatterings, in which we find a resonance in the spin flip channels. This resonance appears to be the quantum analog of the semi classical inverse Drude scaling of the conductance.     

Thermal noise computation in gravitational wave interferometers from first principles

We propose a universal method of computation of thermal noise in mirrors of gravitational wave interferometers based on first principles. We imagine a situation where a mirror is part of a Fabry–Perot cavity. The movement of the mirror's surface produces variation of the eigen frequency of the cavity, which is computed by evaluating the variation of the energy stored in cavity. We consider two particular examples: first, the thermal noise from a dielectric slab inside the Fabry–Perot cavity, and second, the polarization-dependent thermal noise in the folded cavity.     

Optical properties of Fabry–Perot microcavity with organic light emitting materials

We investigated the optical properties of the tris(8-hydroxyquinoline)aluminum (Alq₃) organic film with Fabry–Perot microcavity by measuring photoluminescence (PL) and transmittance. We have simulated the phase change on reflection as a function of wavelength. The Fabry–Perot microcavity structures were designed according to the simulation results and the resonant wavelength corresponding to the maximum of PL spectrum of a bare Alq₃ film. These structures were fabricated in three types of microcavities, such as type A [air|metal|Alq₃|metal|glass], type B [air|dielectric|Alq₃|dielectric|glass], and type C [air|metal|Alq₃|dielectric|glass]. A bare Alq₃ layer on glass, [air|Alq₃|glass], showed a PL peak around 514 nm and its full width at half maximum (FWHM) was about 80 nm. The broad FWHM of the bare Alq₃ film was reduced to 15–27.5, 7–10.5 and 16–16.6 nm for three types by cavity effects. Also, the control of the resonant wavelength can be achieved by the spacer length as well as the phase change on reflection on mirror.     

Effect of surface plasmons at the Al/alumina interface on the formation of nanopores in Al anodization

We investigated the formation mechanism of nanoporous alumina in the electrochemical reaction of aluminium with oxalic acid solution in terms of the pinning effect of Fermi level at the metal–oxide interface. On the Al metal surface, the image potential state pins the standing mode of collectively excited surface electrons and the evanescent wave forms the plasmon mode, which can be reflected in oxide barrier formation. A nanoporous alumina thin film with an amorphous phase oxide layer on the Al surface can enhance light absorption at a shorter wavelength than 382 nm and provide strong Fabry–Perot oscillation in photoreflectance. The cathodoluminescence spectra show the surface plasmon mode as a consequence of the self-ordered oxide nanopores. The Kretschmann configuration of an attenuated total reflection set-up for prism/oxalic solution/Al interface, which also provides a prism-coupled surface plasmon and forms oxide nanopores on the Al surface via a laser-enhanced anodization process.     

Simple air-gap fiber Fabry–Perot interferometers based on a fiber endface with Sn-microsphere overlay

This study presents a simple, cost-effective and sensitive air-gap fiber Fabry–Perot interferometer (AG-PPFI) which is based on a metal Tin (Sn)-overlaying fiber technique. An extremely small drop of metallic Sn was heated and then melted to shrink into a microsphere owing to the cohesion of the material. When a fiber was inserted into the melting Sn microsphere, an air gap was naturally formed between the fiber endface and the metal Sn during the cooling process. By carefully controlling the reaction time, various air-gaps can be formed as the Fabry–Perot interferometric cavities for the proposed AG-PPFIs. Measurements reveal that a smaller length of air-gap and heavier mass of Sn-microsphere are associated with higher sensitivity of temperature, but the former is dominated. A best temperature sensitivity of wavelength shift with +4.3 nm/°C is achieved when the air-gap is about 5 μm with mass of Sn-microsphere of about 10 μg. The variation of the wavelength shift is equivalent to sensitivity for a change in the cavity length of +14.83 nm/°C.