Surface Plasmon Interference Lithography Assisted by a Fabry-Perot Cavity Composed of Subwavelength Metal Grating and Thin Metal Film

A surface plasmon interference lithography assisted by a Fabry-Perot （F-P） cavity composed of subwavelength metal gratings and a thin metal fihn is proposed to fabricate high-quality nanopatterns. The calculated results indicate that uniform straight interference fringes with high contrast and high electric-field intensity are formed in the resist under the F-P cavity. The analyses of spatial frequency spectra illuminate the physical mechanism of the formation for the interference fringes. The influence of the F-P cavity spacing is discussed in detail. Moreover, the error analyses reveal that all parameters except the metal grating period in this scheme can bear large tolerances for the device fabrication.

An Ultraviolet Fiber Fabry-Perot Cavity for Florescence Collection of Trapped Ions

We demonstrate a fiber Fabry-Pérot cavity in the ultraviolet range, which covers the florescence wavelength for the 2P to 2S transition of Yb and is designed in the bad cavity limit for florescence collection. Benefiting from both the small cavity mode volume and the large atom dipole, a cavity with moderate finesse and high transmission still supports a good cooperativity, which is made and tested in experiment. Based on the measured experimental parameters, simulation performed on the cavity and ion shows a Purcell factor better than 2.5 and a single-mode fiber collection efficiency over 10%. This technology can support ultra-bright single photon sources based on trapped ions and can provide the possibility to link remote atoms as a quantum network.

Improved Directivity of an OAM Antenna by a Fabry-Perot Cavity: An Experimental Study

The circular phased antenna array is commonly used for generating waves bearing Orbital Angular Momentum (OAM) in the radio frequency band, but it achieves a relatively low directivity. To overcome this drawback, we present here a method to improve the directivity of an OAM circular phased antenna array by embedding it inside a Fabry-Perot cavity. The Fabry-Perot cavity contains three main parts: a partially reflecting surface (PRS), an air cavity and a ground plane. Simulation data show that the directivity of this new OAM antenna achieves an improvement of 8.2 dB over the original array. A prototype is realized and characterized. The simulated and measured characteristics are in good agreement.

Quantifying non-classical correlations under thermal effects in a double cavity optomechanical system

We investigate the generation of quantum correlations between mechanical modes and optical modes in an optomechanical system,using the rotating wave approximation.The system is composed of two Fabry-Pérot cavities separated in space;each of the two cavities has a movable end-mirror.Our aim is the evaluation of entanglement between mechanical modes and optical modes,generated by correlations transfer from the squeezed light to the system,using Gaussian intrinsic entanglement as a witness of entanglement in continuous variables Gaussian states,and the quantification of the degree of mixedness of the Gaussian states using the purity.Then,we quantify nonclassical correlations between mechanical modes and optical modes even beyond entanglement by considering Gaussian geometric discord via the Hellinger distance.Indeed,entanglement,mixdness,and quantum discord are analyzed as a function of the parameters characterizing the system(thermal bath temperature,squeezing parameter,and optomechanical cooperativity).We find that,under thermal effect,when entanglement vanishes,purity and quantum discord remain nonzero.Remarkably,the Gaussian Hellinger discord is more robust than entanglement.The effects of the other parameters are discussed in detail.

Low insertion loss silicon-based spatial light modulator with high reflective materials outside Fabry–Perot cavity

The extinction ratio and insertion loss of spatial light modulator are subject to the material problem, thus limiting its applications. One reflection-type silicon-based spatial light modulator with high reflective materials outside the Fabry-Perot cavity is demonstrated in this paper. The reflectivity values of the outside-cavity materials with different film layer numbers are simulated. The reflectivity values of 6-pair Ta2O5/SiO2 films at 1550 nm are experimentally verified to be as high as 99.9%. The surfaces of 6-pair Ta2O5/SiO2 films are smooth: their root-mean-square roughness values are as small as 0.53 nm. The insertion loss of the device at 1550 nm is only 1.2 dB. The high extinction ratio of the device at 1550 nm and 11 V is achieved to be 29.7 dB. The spatial light modulator has a high extinction ratio and low insertion loss for applications.

弹体在内摩擦介质中的斜侵彻深度计算

考虑介质处于内摩擦状态下,利用球腔膨胀理论及内摩擦介质侵彻近区运动方程求得刚性弹体在侵彻过程中的阻力。在此基础上,考虑自由表面对弹体斜侵彻的影响,将斜侵彻分为3个阶段,推导了斜向侵入弹体表面上任一点的应力公式,进而得出了新的刚性弹体的斜侵彻解析解。该解与别列赞公式在形式上一致,计算结果也符合较好,从而在理论上对别列赞经验公式进行了解释。

Dual-band simultaneous lasing in MOFs single crystals with Fabry-Perot microcavities

Multi-band microlasers based on single microcrystalline materials with Fabry-Perot(F-P) cavities are critically and technologically essential. Here, we demonstrate simultaneous dual-band lasing output(615 and 685 nm) in metal-organic frameworks(MOFs) and organic dyes hybrid single crystals, which support F-P resonances. Through a two-step assembly strategy, two different types of cationic pyridinium hemicyanine dye molecules can be encapsulated into the channel pores of anionic bioMOF-1-2 Me successfully. In addition, the employment of the host-guest system significantly increases the dye loading, enhances luminescent efficiency, and diminishes the aggregation-caused quenching(ACQ) effect in the resultant MOFs/dye composites.This finding not only combines the characteristic of MOFs materials with excellent luminescent properties of organic dyes, but also points out a simple and promising strategy to design multi-band microlasers based on F-P mechanism, opening a low-cost avenue for the rational design of miniaturized lasers in the future.

Design of Fiber Magnetic Field Sensor Based on Fiber Bragg Grating Fabry-Perot Cavity Ring-Down Spectroscopy

A novel fiber magnetic sensor based on the fiber Bragg grating Fabry-Perot （FBG-FP） cavity ring-down technique with pulse laser injection is proposed and demonstrated theoretically. A general expression of the intensity of the output electric field is derived, and the effect of the external magnetic field on the ring-down time is discussed. The results show that the output light intensity and the ring-down time of the FBG-FP cavity are in the inverse proportion to the magnitude of the external magnetic field. Our results demonstrate the new concept of the fiber magnetic sensor with the FBG-FP cavity ring-down spectroscopy and the technical feasibility.

Loss Measurement of High-Finesse Fabry-Perot Cavities

The loss of a high-finesse Fabry-Perot cavity was measured using frequency scan and cavity ring-down techniques.Different transverse modes were examined by sweeping the frequency of the laser across the corresponding resonances.In addition,cavity ring-down technique was used to measure the loss of the Fabry-Perot cavity and a simple model was employed to remove the influence of finite response time of the optical switch and the detection circuit.

Analysis of Focusing Orbital Angular Momentum Wave Using Fabry-Perot Cavity

One of the biggest obstacles to the application of orbital angular momentum(OAM)in the microwave field is its divergence problem.This paper presents a full analysis of generating and focusing OAM waves using original and improved Fabry-Perot(F-P)cavities.Utilizing combination of microstrip antenna and original F-P cavity,the gain of the OAM antenna is enhanced from 4.0 dBi to 9.3 dBi and the corresponding divergence angle is decreased from 41to 24.To further improve the performance of the OAM antenna,the improved F-P cavity is introduced.The simulated results show that the gain is further enhanced to 12.0 dBi and the divergence angle is further decreased to be 15.

THE NEW BEHAVIOR OF BIFURCATION AND CHAOS IN A NONLINEAR FABRY-PEROT CAVITY

Ⅰ. INTRODUCTION In a Fabry-Perot cavity, there exist two electric fields, which propagate in the counter direction and interact with each other via the absorber, so that the theoretical analysis of the Fabry-Perot system is very complicated. On account of this, many authors had focused their attention on the ring cavity, a considerably simple system. It was proposed as a

Ultrasensitive monolayer-MoS_(2) heterojunction photodetectors realized via an asymmetric Fabry-Perot cavity

Two-dimensional(2D)materials have attracted significant attention as a promising candidate for electronic and optoelectronic devices.However,low absorption impairs the performance of few-layer 2D material-based photodetectors(PDs).Herein,we purpose an asymmetric Fabry-Perot cavity consisting of a dielectric layer and metallic film to enhance the interactions between light and monolayer molybdenum disulfide(MoS_(2)).The external quantum efficiency of the monolayer MoS_(2)heterojunction PD is enhanced by more than two orders of magnitude via optimizing the thickness of the dielectric layer.The monolayer-MoS_(2)/nickel oxide heterojunction PD exhibits a large on/off ratio of 2×10^(5),a responsivity of 703 A W^(-1),and an ultrahigh detectivity of 1.31×10^(15)Jones.The detectivity is the best value ever reported for monolayer-MoS_(2)heterojunction PDs.Our results may pave the way for high-performance 2D materialbased PDs.

High-sensitivity refractive index sensors based on Fano resonance in a metal-insulator-metal based arc-shaped resonator coupled with a rectangular stub

A metal-insulator-metal(MIM)-based arc-shaped resonator coupled with a rectangular stub(MARS) structure is proposed. This structure can generate two tunable Fano resonances originating from two different mechanisms. The structure has the advantage of being sensitive to the refractive index, and this feature makes it favorable for application in various microsensors. The relationship between the structural parameters and Fano resonance is researched using the finite element method(FEM) based on the software COMSOL Multiphysics 5.4. The simulation reveals that the sensitivity reaches1900 nm/refractive index unit(RIU), and the figure of merit(FOM) is 23.75.

Theoretical analysis of transmission characteristics for all fiber,multi-cavity Fabry-Perot filters based on fiber Bragg gratings

The characteristics of transmission spectra for the all fiber, multi-cavity Fabry- Perot （FP） configuration based on fiber Bragg gratings （FBG） are theoretically analyzed and modeled. The general transmission matrix function for the structure with any number of cavities is derived, and explicit expression of the power trans- mission coefficient for symmetrical two-cavity FP is presented. The general condi- tions for flat-top single resonant peak at the central wavelength in FBG stop band are derived and verified in the numerical simulation section. The transmission peaks of single-cavity and two-cavity FP structures are compared and discussed, and results show that compared to the single-cavity FP, flatness of the top and steepness at the edge of transmission peak can be improved by introducing one more cavity. The resonant transmission peak properties of two-cavity structure are investigated in detail for various values of cavity length and FBGs with different reflection characteristics, and the design guidelines for transmission-type filters are presented. The results show that the steepness of peak slope can be improved by increase of FBG reflectivities, and these kinds of filters can be used as nar- row-band single-channel selectors and multi-channel wavelength de-multiplexing by properly choosing the length of cavities and reflectivities of FBGs.

A Novel Analytical Approach for Multi-Layer Diaphragm-Based Optical Microelectromechanical-System Pressure Sensors

An optical microelectromechanical-system （MEMS） pressure sensor based on multi-layer circular diaphragm is described and analysed by using the proposed novel analytical approach and the traditional transfer matrix method. The analytical expressions of the deflection of multi-layer diaphragm and absolute optical reflectance are derived respectively. The influence of residual stress on the deflection of diaphragm is also analysed. Simulation results given by the finite element method are consistent with the ones which are analysed by using the analytical approach. The analytical approach will be helpful to design and fabricate the optical MEMS pressure sensors with multi-layer diaphragm based on Fabry-Perot interferometry.

Highly Angular Tolerant Transmission Filters for Narrow-Band Image Sensors

A dielectric transmittance filter composed of subwavelength grating sandwiched between two few-layers distributed Bragg reflectors (DBRs) is proposed with the aim of being compatible with CMOS technology and to be tunable by lithographic means of the grating pattern without the need of thickness changes, in the broad spirit of metamaterials. The DBR mirrors form a Fabry-Perot (FP) cavity whose resonant frequency can be tuned by changing the effective refractive index of the cavity, here, by tailoring the in-plane filling factor of the grating. The structure has been studied and designed by performing numerical simulations using Fourier Modal Method (FMM). This filter proves to have high broad angular tolerance up to ±30˚. This feature is crucial for evaluating the spectral performance of narrow-band filters especially the so-called Ambient light sensors (ALS). By analyzing the transmittance spectral distributions in the band diagram, it is found that the angular tolerance is due to coupling between the FP and the guided mode inside the cavity in analogy to resonances occurring within multimode periodic waveguides in a different context.

Parameter Optimization of Digital Locking of an Optical Cavity

The combination of an optical cavity and a proportional-integral(PI)controller is commonly used in experimental quantum optical fields.In this study,an optimal PI controller for an optical cavity was designed based on the average-squared value of the error signal.The controller was implemented using a field-programmable gate array(FPGA)data acquisition board and LabVIEW software.The overall gain of the controller is optimized by adopting the cavity transmission as an optical power reference,such that the cavity locking performance does not degrade as the optical power varies.

Ultra-compact lithium niobate photonic chip for high-capacity and energy-efficient wavelength-division-multiplexing transmitters

Recently,high-performance thin-film lithium niobate optical modulators have emerged that,together with advanced multiplexing technologies,are highly expected to satisfy the ever-growing demand for high-capacity optical interconnects utilizing multiple channels.Accordingly,in this study,a compact lithium-niobate-on-insulator(LNOI)photonic chip was adopted to establish four-channel wavelength-division-multiplexing(WDM)transmitters,comprising four optical modulators based on ultracompact 2×2 Fabry-Perot cavities and a four-channel WDM filter based on multimode waveguide gratings.The fabricated chip with four wavelength channels has a total footprint as compact as 0.3×2.8 mm^(2),and exhibits an excess loss of~0.8 dB as well as low inter-channel crosstalk of<–22 dB.Using this LNOI photonic chip,high-capacity data transmissions of 320 Gbps(4×80 Gbps)on-off-keying signals and 400 Gbps(4×100 Gbps)four-level pulse amplitude signals were successfully realized with the ultra-low power consumption of 11.9 fJ/bit.

呼吸过程胸膜腔内压和肺泡壁压强的产生与变化规律

生理学教科书都论及胸膜腔压强、肺泡壁压强和肺内压,但都未阐明清楚。本研究揭示胸膜腔内压、肺泡壁压强和肺泡内压的产生及变化规律。结果表明,胸膜腔内压是肺胸膜所受扩张力或压缩力的压强产生。平静吸气时,胸廓扩张,胸膜腔负压增大。平静呼气时,胸廓缩小,但胸廓、肺仍处于扩张状态,胸膜腔内仍为负压。随着胸廓缩小,负压减小。在用力呼气时肺胸膜、壁胸膜挤压胸膜腔,其内才产生正压。肺泡壁压强是胸膜腔内压、肺组织内的压强与肺泡壁附加压强的代数和。肺泡壁附加压强用球形弹性膜拉普拉斯公式计算。肺泡内压取决于肺泡壁张缩运动快慢和气道阻力大小。

判断PICC导管异位的一种新方法

目的 探讨一种PICC导管异位的新方法.方法 对252例行PICC患者采用一种新的判定导管异位方法——咳嗽动作对滴速影响观察法,观察其效果.结果 判定准确率达100.00％(252/252),252例患者首次置管成功率为100.00％(252/252).结论 咳嗽动作对滴速影响观察法对于PICC导管异位的判断有效、方便,对于置管过程中及后期继发性异位的判断具有很好的应用价值.