Continuously coupled unstable resonators: problem of large output beam divergence

A problem which arises when one considers continuously coupled unstable resonators is that the beam divergence due to geometrical effects is usually large. This note describes a simple remedy which can be applied in most cases.     

Investigation and applications of all-fiber brillouin ring resonator lasers

We examine the theoretical and experimental behavior of Brillouin ring resonator lasers (BRRL), highlighting differences between Brillouin scattering in ring resonators and long fiber lengths. The theory, which assumes that the nonlinear interaction is welldescribed by two coupled equations for the optical waves, agrees well with measured data. We examine the single and multimode behavior of BRRL and show how this may be usefully implemented in microwave signal generation, in Stimulated Brillouin Scattering gain studies, and to realize a new form of all-fiber frequency shifter.     

An optical technique to measure the frequency and mode emission of tunable lasers

Summary To use mode tunable lasers it is necessary to measure the laser frequency and the mode emission. This problem is very important when waveguide lasers are used. Normally this information is obtained by a heterodyne technique, but there are some difficulties to perform this method in a large electrical noise environment, when pulsed or radiofrequency lasers are used. We have obtained this laser information by using an alternative low-cost optical system. With this apparatus we have measured the cavity pulling and roughly estimated an upper limit for the linewidth of a radiofrequency, high pressure, line and mode-tunable, CO₂ laser.

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Riassunto Nell'impiego di lasers accordabili in modo è necessario misurare la frequenza. Normalmente questa misura è derivata da tecniche eterodina, ma ci sono grosse difficoltà in presenza di un grosso rumore elettromagnetico di fondo, come quando viene usata una eccitazione a radiofrequenza. Le stesse informazioni possono essere ottenute con metodi ottici; per esempio con questa tecnica noi abbiamo misurato lo spostamento di cavità e la larghezza di banda di un laser ad alta pressione a CO₂ alimentato a RF accordabile 500 MHz in modo.

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Резюме Для использования настроенных лазеров необходимы измерения частоты и моды излучения. Зта проблема является очень важнои, когда используются волноводные лазеры. Обычно зта информция получается с помощью гетеродинной техники, но возникает ряд трудностей при применении этого метода из-за высокого злектрического шума скружающей среды, когда используются импульсные или радиочастотные лазеры. Мы предлагаем получать зту информацию о лазерах, используя альтернативную оптич ческую систему с низкой стоимостью. С помощью этой аппаратуры мы измеряем резонатор и грубо оцениваем верхний предел длины волны радиочастотного настроенного CO₂ лазера с высоким давлением.

     

A simple technique for the alignment of a ring resonator

A simple technique for the alignment of a ring resonator is presented. The positional and the directional alignments are obtained by the movements of independent mirrors. The effects of alignment inaccuracies on the performance of a ring resonator are discussed.     

谐振频率可调的环状开口谐振器结构及其效应

理论和实验研究表明，开口谐振环(SRRs)中可以激励磁谐振从而实现负磁导率.通过在SRRs结构中引入与其开口边平行的金属短杆设计并制备了新的磁谐振单元，采用波导法系统研究了短杆对SRRs和左手材料的微波透射特性以及左手效应的影响.实验和数值模拟表明：金属短杆和SRRs开口边形成附加电容，导致SRRs开口电容增大从而引起谐振频率降低.随短杆长度l和短杆与SRRs间距d的增大，SRRs谐振频率也随之减小和增加.短杆的加入不影响SRRs的负磁导率特性，改变短杆与SRRs间距d< 关键词： 开口谐振环 金属短杆 调控 左手材料     

Transient and steady state analysis of micro ring resonator array based photodetector in optical communication wavelength (linear and nonlinear operation)

Array of micro ring resonators based optical photodetectors is introduced and evaluated in this paper to operate in optical communication windows for broad band situation. In this work, we introduced an array of resonators to engineer the transfer function of the detector for broad band operation as well as very sharp edges. The electron and photon transport in the proposed structure is modeled based on rate equation and then transient and steady state behavior are extracted. Finally nonlinear operation added to the model and its effect on spectral behavior as well as transient operation is investigated.     

A Lotus shaped acoustofluidic mixer: High throughput homogenisation of liquids in 2 ms using hydrodynamically coupled resonators

This paper presents an acoustically actuated microfluidic mixer that uses an array of hydrodynamically coupled resonators to rapidly homogenise liquid solutions and synthesise nanoparticles. The system relies on 8 identical oscillating cantilevers that are equally spaced on the perimeter of a circular well, through which the liquid solutions are introduced. When an oscillatory electrical signal is applied to a piezoelectric transducer attached to the device, the cantilevers start resonating. Due to the close proximity between the cantilevers, their circular arrangement and the liquid medium in which they are immersed, the vibration of each cantilever affects the response of its neighbours. The streaming fields and shearing rates resulting from the oscillating structures were characterised. It was shown that the system can be used to effectively mix fluids at flow rates up to 1400 µl.min⁻¹ in time scales as low as 2 ms. The rapid mixing time is especially advantageous for nanoparticle synthesis, which is demonstrated by synthesising Poly lactide-co-glycolic acid (PLGA) nanoparticles with 52.2 nm size and PDI of 0.44.     

自由空间中左手材料传输特性的仿真研究

 研究了左手材料的传输和反射特性,介绍了所仿真的样品形式和测量系统,并采用高频构造仿真方法(HFSS)在已有自由空间宽频测量的基础上进行理论仿真。结果表明：S参量的数字仿真与实验测量结果在宽频条件下达到了较好的一致性;测量中产生的损耗主要归因于铜线结构有限的电导率;理论上左手材料的最佳无损工作频段应高于谐振环的谐振频率。     

Dielectric-Based Electromagnetically Induced Transparency Metamaterial in the Microwave Band

An electromagnetically induced transparency metamaterial (EITM) based on dielectric resonators is presented in this paper, which consists of a cut wire (CW) and ten dielectric columns. Destructive interference between the CW, which is a branch of the microstrip line, and the dielectric resonators causes the EIT phenomenon. The simulation results show that the dielectric-based EITM designed can obtain a transmission peak of 0.938 at 2.17 GHz, and the two-oscillator model is utilized to verify the effectiveness of the structure. In addition, samples of the dielectric-based EITM are also fabricated and the effectiveness of the metamaterial is experimentally verified. The proposed metamaterial has several advantages, including high efficiency, low loss, a simple structure, and ease of manufacture, which has good prospects for application in the fields of electromagnetic switches, sensors, and nonlinear metamaterials.