混合微球谐振腔热非线性效应的增强方法（英文）

提出并实现了一种可增强微球谐振腔热非线性效应的方法。通过在微球谐振腔表面涂覆低折射率紫外胶形成并制备了混合谐振腔。通过分析混合谐振腔结构的热光系数,从理论和实验论证了混合谐振腔结构可获得更大的热非线性效应,同时验证了混合谐振腔的品质因素对热非线性的影响。应用此混合谐振腔结构于温度传感实验,结果表明通过增强方法制备的谐振腔其检测灵敏度提高了2.8倍。因此,此方法在传感应用、生物化学检测、通讯等领域也有广泛的应用前景。     

在纤式回音壁模式微球谐振腔及其传感特性

提出一种在纤式回音壁模式微球谐振腔，并对其温度和折射率传感特性进行研究。首先，分析了不同尺寸的微球腔与光纤结构耦合时的相位匹配情况，以锥形光纤为探针来拾取并移动钛酸钡微球，将其嵌入空心光纤，形成在纤式谐振腔结构，从而在微球中激发回音壁模式，并与空心光纤端面的反射光相互作用，产生法诺共振。实验结果表明，激发的法诺共振峰曲线的斜率高达-99.3 dB/nm。另外，通过实验证明了此结构对温度和折射率均具有较好的传感特性，灵敏度分别为26.8 pm/℃和-244.97 dB/RIU。该谐振腔性能稳定、结构紧凑、加工简单，在纤式的反射结构使其有望在复杂的传感环境中发挥作用。     

高Q光学微球腔角速度传感效应验证

根据角速度传感的基本原理,搭建了以高Q光学微球腔为核心敏感部件的角速度传感实验测试系统。实验中通过调制、解调技术得到了光学微球腔的谐振曲线及其相对应的解调曲线,并采用PID反馈控制电路实现了微球腔谐振点的实时跟踪锁定,谐振点锁定精度约为10 kHz。通过对系统提供低、高2组不同的旋转角速度进行实验测试,并对数据进行处理分析,得到系统输出信号幅度的变化趋势与测试转台提供的旋转角速度变化情况相对应的结果。初步验证了高Q光学微球腔的角速度传感效应,为后续深入研究高Q光学微谐振腔角速度传感器件奠定了基础。     

毛细管内嵌微球谐振腔的温度传感特性研究

对基于毛细管的微球谐振腔耦合器件的耦合机理与温度传感特性进行了研究。微球支持较多的高阶模式,易与石英毛细管模式满足相位匹配条件,因此微球回音壁模式会被激发。使用钛酸钡微球进行了温度传感实验,为进一步提升传感的灵敏度,采用聚甲基丙烯酸甲酯（polymethyl methacrylate,PMMA）微球进行了温度传感实验。实验结果表明,PMMA微球温度传感灵敏度可达83.9 pm/℃,约为钛酸钡微球温度传感灵敏度的8倍,在提升温度传感灵敏度方面具有重要作用。     

纳流通道-谐振腔耦合结构测量荧光物质微位移

本文提出了一种纳流通道-谐振腔耦合结构,用于实现对荧光物质微位移的检测。在本文中,首先,使用时域有限差分法,研究了量子点偏振态及结构参数对荧光与结构耦合效果的影响,进而对结构进行优化;然后,通过测量耦合结构输出光功率的变化,实现对荧光物质微位移的检测;最后,对影响传感灵敏度的因素进行研究。结果表明,相比传统方法,纳流通道-谐振腔耦合结构的折射率处于2.8~3.3之内时,该结构都可以实现对荧光物质微位移的高精度准确传感,并且通过减小纳流通道与谐振腔的间距可进一步提高传感灵敏度。     

无源Ge_(28)Sb_(12)Se_(60)硫系玻璃微球谐振腔的制备及其光学回廊模式表征

为了对硫系玻璃微球谐振腔在中短红外波段的光学回廊模式进行理论研究和实验表征,用熔融淬冷法制备了组分为Ge28Sb12Se60的无砷环保型硫系玻璃,并在此基础上采用漂浮粉末熔融法批量制备出直径分布为50~200μm的微球谐振腔.在显微镜下挑选出直径分别为112.01μm和57.63μm的一大一小两颗微球与自制石英微纳光纤锥进行近场耦合实验,以窄带宽可调谐激光器为泵浦源测试此耦合系统在1 530~1 560nm波段的光谱.光谱中明显观测到由微球回廊模式谐振引起的等间距分布的光谱吸收峰.小球、大球的吸收峰间距分别为5.22nm和2.60nm,与米氏散射理论计算得出的一阶TE回廊模谐振峰间距基本相符.实验结果表明新型Ge28Sb12Se60硫系玻璃有望在红外微球光子器件如窄带滤波器、微球喇曼激光器、高灵敏度传感器等领域获得重要应用.     

CaF2光学微谐振腔中基于光热振荡的热耗散率测量

通过测量光热振荡周期可以检测出CaF_2光学微谐振腔腔体与环境之间的热耗散率,然而多个振荡周期与热耗散率呈非线性关系,无法利用某个振荡周期值有效测量热耗散率。使用一种基于反向传播人工神经网络的传感数据测量模型,通过测量振荡周期值,实现了热耗散率的有效测量,优化了神经网络参数,提高了热耗散率测量精度。数值仿真结果表明,该方法可有效测量CaF_2光学微谐振腔的热耗散率,对实现基于光学微腔的热参量探测具有重要意义。     

Si基双环级联光学谐振腔应变检测研究

绝缘衬底上的硅材料制备的光学微环谐振腔结构具有高灵敏度、结构尺寸小和极低模式体积等特性,被广泛应用到光信息传递、惯性导航领域,但极少被应用到力学信号的测试,为此,研究了一种基于硅基光学微环谐振腔结构的悬臂梁式应力/应变敏感计,利用微环谐振腔环形波导径向形变量作为感应应力的中间物理量,在外界应力作用下,环形波导的半径将发生改变,使结构的光学谐振参数产生变化,从而使光学微环谐振腔谐振谱线发生明显红移,体现出良好的应力/应变敏感特性;通过设计双环级联光学微腔,并采用MEMS光刻、ICP腐蚀工艺制备了嵌入式光学微腔应变计结构,结合理论计算了悬臂梁结构的应力应变敏感特性,经仿真及实验得到,应变计结构的应力/应变灵敏度分别为0.185 pm·kPa-1,18.04 pm·microstrain-1,与单环微腔结构相比,线性量程增加了近50.3%,应力灵敏度提高了近10.6%,初步验证了嵌入式光学微腔结构进行高灵敏度应力/应变检测的可行性,有望实现新型光学力敏传感器件的微型化、集成化。     

空心微瓶谐振腔的封装及折射率传感特性研究北大核心CSCD

为提高传感器的稳定性和便携性,提出一种基于空心微瓶谐振腔的折射率传感器,对系统进行封装并对其折射率传感特性进行研究。仿真分析不同壁厚下空心微瓶谐振腔径向回音壁模式的光场分布,光场在微瓶内部的占比随着器件壁厚的减少而增加,有利于提高传感灵敏度。为减小空心微瓶谐振腔的壁厚,利用氢氟酸对石英毛细管进行腐蚀,使用光纤熔接机制备了薄壁空心微瓶谐振腔。采用紫外胶将耦合系统封装固定在载玻片上,器件稳定性和便携性得到提升。研究了封装器件在不同折射率匹配液下的传感特性,器件传感灵敏度为26.50 nm/RIU。该传感器具有稳定性强、灵活性高、损耗小等优点,在光微流控折射率检测方面拥有很大的应用潜力。     

纳米银溶胶和微腔型光纤SERS基底的制备及其性能比较

通过化学法制备了纳米银溶胶基底和微腔型光纤表面增强拉曼散射(SERS)基底,其中光纤SERS基底的微腔结构是通过氢氟酸(H F)腐蚀得到的.实验采用湿法检测,首先将纳米银溶胶基底与罗丹明6G(R6 G)混合,找到增强效果最强时的裸光纤微腔结构,在此结构的基础上采用溶胶自组装法制备银纳米颗粒包覆的光纤SERS基底,通过控...     

Hybrid temperature effect on a quartz crystal microbalance resonator in aqueous solutions

The quartz crystal microbalance(QCM) is an important tool that can sense nanogram changes in mass. The hybrid temperature effect on a QCM resonator in aqueous solutions leads to unconvincing detection results. Control of the temperature effect is one of the keys when using the QCM for high precision measurements. Based on the Sauerbrey's and Kanazawa's theories, we proposed a method for enhancing the accuracy of the QCM measurement, which takes into account not only the thermal variations of viscosity and density but also the thermal behavior of the QCM resonator. We presented an improved Sauerbrey equation that can be used to effectively compensate the drift of the QCM resonator. These results will play a significant role when applying the QCM at the room temperature.     

Thermal effects on mass detection sensitivity of carbon nanotube resonators in nonlinear oscillation regime

A mass sensor using a nano-resonator has high detection sensitivity, and mass sensitivity is higher with smaller resonators. Therefore, carbon nanotubes (CNTs) are the ultimate materials for these applications and have been actively studied. In particular, CNT-based nanomechanical devices may experience high temperatures that lead to thermal expansion and residual stress in devices, which affects the device reliability. In this letter, to demonstrate the influence of the temperature change (i.e., thermal effect) on the mass detection sensitivity of CNT-based mass sensor, dynamic analysis is carried out for a CNT resonator with thermal effects in both linear and nonlinear oscillation regimes. Based on the continuum mechanics model, the analytical solution method with an assumed deflection eigenmode is applied to solve the nonlinear differential equation which involves the von Karman nonlinear strain–displacement relation and the additional axial force associated with thermal effects. A thermal effect on the fundamental resonance behavior and resonance frequency shift due to adsorbed mas, i.e., mass detection sensitivity, is examined in high-temperature environment. Results indicate a valid improvement of fundamental resonance frequency by using nonlinear oscillation in a thermal environment. In both linear and nonlinear oscillation regimes, the mass detection sensitivity becomes worse due to the increasing of temperature in a high-temperature environment. The thermal effect on the detection sensitivity is less effective in the nonlinear oscillation regime. It is concluded that a temperature change of a mass sensor with a CNT-based resonator can be utilized to enhance the detection sensitivity depending on the CNT length, linear/nonlinear oscillation behaviors, and the thermal environment.     

Generating Squeezed States of Nanomechanical Resonator via a Flux Qubit in a Hybrid System

We propose a scheme for generating squeezed states based on a superconducting hybrid system.Our system consists of a nanomechanical resonator,a superconducting flux qubit,and a superconducting transmission line resonator.Using our proposal,one can easily generate the squeezed states of the nanomechanical resonator.In our scheme,the nonlinear interaction between the nanomechanical resonator and the superconducting transmission line resonator can be implemented by the flux qubit as 'nonlinear media' with a tunable Josephson energy.The realization of the nonlinearity does not need any operations on the flux qubit and just needs to adiabatically keep it at the ground state,which can greatly decrease the effect of the decoherence of the flux qubit on the squeezed efficiency.     

Hybrid photonic surface-plasmon-polariton ring resonators for sensing applications

We introduce a hybrid photonic surface plasmon ring resonator which consists of a silicon nitride (Si₃N₄) dielectric traveling-wave ring resonator vertically coupled to a thin layer of metallic strip ring resonator made of Silver (Ag) on top. The cladding is assumed to be porous alumina on top of the metal layer, which provides more surface area for the adsorption of target molecules and their efficient interaction with the surface plasmon wave excited at the metal-cladding interface. Simulations show that this hybrid structure has a large refractive index sensitivity due to the excitation of surface plasmon waves and also a relatively narrow resonance linewidth due to the large quality factor of the photonic ring resonator. The Finite Element method is used to systematically design the hybrid structure and to investigate the performance of the hybrid resonator as a refractive index sensor. The proposed structure is very compact and can be implemented on a chip in an integrated platform. Thus, it can be used for lab-on-a-chip sensing applications and is capable of being spectrally and spatially multiplexed for muti-analyte sensing.     

Wave propagation in deep-subwavelength mode waveguides

This Letter proposes a dielectric waveguide with deep-subwavelength mode sizes. Results of both frequency domain and time domain analysis show that the effective mode area is below λ(0)(2)/400 and can even reach λ(0)(2)/1000 (λ(0) is the wavelength in vacuum). The effective electrical mode area can be comparable to that of a hybrid plasmonic subwavelength confinement waveguide, with reduced optical absorption. In contrast to slot waveguides, which guide light in low-index materials, the proposed structure guides light in high-index materials. Results obtained in this Letter show that the losses are sensitive to the surface roughness on the tens of nanometers scale. The structure can be used to design ring resonators with a quality factor comparable to that of a diffraction-limited dielectric ring resonator with the same standing wave numbers. The property can be applied in nonlinear effect enhancement or laser design with ultralow threshold.     

All-optical scheme for detecting the possible Majorana signature based on QD and nanomechanical resonator systems

Majorana fermions(MFs) are exotic particles that are their own anti-particles. Currently, the search for MFs occurring as quasiparticle excitations in condensed matter systems has attracted widespread interest, because of their importance in fundamental physics and potential applications in topological quantum computation based on solid-state devices. Motivated by recent experimental progress towards the detection and manipulation of MFs in hybrid semiconductor/superconductor heterostructures, in this review, we present a novel proposal to probe MFs in all-optical domain. We introduce a single quantum dot(QD), a hybrid quantum dot-nanomechanical resonators(QD-NR) system, and a carbon nanotube(CNT) resonator implanted in a single electron spin system with optical pump-probe technology to detect MFs, respectively. With this scheme, a possible Majorana signature is investigated via the probe absorption spectrum and nonlinear optical Kerr effect, and the coupling strength between MFs and the QD or the single electron spin is also determined. In the hybrid QD-NR system, vibration of the NR will enhance the nonlinear optical effect, which makes the MFs more sensitive for detection. In the CNT resonator with a single electron, the single electron spin can be considered as a sensitive probe, and the CNT resonator behaved as a phonon cavity is robust for detecting of MFs. This optical scheme will provide another method for the detection MFs and will open the door for new applications ranging from robust manipulation of MFs to quantum information processing based on MFs.     

Measurements of the thermodiffusion ratio in a binary solution using an acoustic resonator

The nonlinear acoustic resonator filled with a layered solution is studied. The possibility of its application to measure liquid parameters is shown. The proposed acoustic method is based on the dependence of the speed of sound in a solution on its concentration which varies due to thermal diffusion in the beam propagation region. An analysis of the relations describing the resonator transmittance showed that, having measured the steady-state and minimum resonator transmittances, the thermodiffusion ratio in a binary solution filling the resonator can be determined.     

The intensity distribution and thermal stability of InnoSlab laser

Partially end-pumped slab laser is an innovative solid state laser, namely InnoSlab. Combining the hybrid resonator with partially end-pumping, the output power can be scaled with high beam quality. In this paper, the output intensity distributions are simulated by coordinate transformation fast Fourier transform(FFT) algorithm, comparing the thermal lens influence. As the simulated curves showed, the output mode is still good when the thermal lens effect is strong, indicatingthe good thermal stability of InnoSlab laser.Such a new kind of laser can be designed and optimized on the base of this simulation.     

Optical bistability in a single-bus InGaAs micro-ring resonator array

In this paper, we investigate the optical bistability induced by optical nonlinearity in a compact parallel array of micro-ring resonators with radius of 5 μm. Due to the nature of perfect light confinement in this structure, resonance and accumulation process in a ring resonator and optical nonlinear effects, are observable even at small optical power (a few milliwatts). Different optical applications such as all-optical switching, optical memory devices, logic gates and modulators are possible, due to optical bistability in a ring resonator. Using alternative semiconductor compounds, instead of silicon that have weak nonlinear optical properties, we improve the performance of ring-resonator based devices. Here we use a polymer cladding layer with negative thermo-optic coefficient. Using this structure we can eliminate the temperature created nonlinearity which is a very slow process. Therefore, the switching speed increases from a few MHz to several tens of GHz. By plotting the transfer function of the resonator, a hysteresis loop is observed in a few milliwatts. Although, using a ring resonator array the bandwidth reduces, however, the width of the hysteresis loop and resolution between both steady state increases.     

激光二极管端面抽运Nd:YVO4板条激光器及其热效应

激光器中激光介质采用板条状几何结构可以极大地降低它的热效应,但仍然需要进一步分析其影响,进而优化激光器效率.利用有限元分析方法分析了部分端面抽运的混合腔板条激光器中激光介质的热效应,计算的热透镜焦距与实测结果基本相符.分析了热效应对模式匹配的影响,分析结果对于优化激光器效率、改进谐振腔设计具有一定的参考价值.并在分析的基础上进行了混合腔实验,抽运功率为110 W时,获得连续输出激光功率41.5 W,光光转换效率约38%,斜效率达58.8%,M2因子为非稳腔方向M2x＝1.59,稳定腔方向M2y＝1.55.