The subject of this research is to investigating the advantages of a special stable resonator relative to the flat-symetric stable resonator scheme in high power pumped Nd: YAG lasers. At first a discussion about some convetional resonators used in high power Nd: YAG lasers is presented considering the advantages and shortcomes of each resonator scheme. Then by using distributed refractive power model(DRP), for a typical high power side pumped Nd: YAG laser, and investigating the stability regions, a non symmetric resonator scheme is proposed which gives single transverse mode and demonstrates higher fundamental mode volume (12 times greater) compared with flat-symetric scheme. Also misalignment sensivity of the presented resonator has been studied and compared with flat-symetric resonator, using numerical calculation and simulation with GLAD software. The results of this research revealed that in high level of pumped power, it is also possible to achieve high fundamental mode volume and make the resonator stable due to thermal and mechanical disturbance.

One of the most important phenomena to a_ect the motion behavior of Micro Resonators is their thermal dependency. This has recently received the attention of researchers widely. A thermal phenomenon has two main effects, the first is damping, due to internal friction, and the second is softening, due to Young's modulus-temperature relationship. In this research work, some theoretical and experimental reported results are used to make a proper model, including thermal phenomena. Two Lorentzian functions are used to describe the restoring and damping forces caused by thermal phenomena. In order to emphasize the thermal effects, a nonlinear model of the MEMS, considering capacitor nonlinearity and mid-plane stretching, has been used. The responses of the system are developed by employing a multiple time scale perturbation method on a non-dimensionalized form of the equations. Frequency response, resonance frequency and peak amplitude are examined by varying the dynamic parameters of the modeled system. Finally, Fuzzy Generalized Cell Mapping (FGCM) is introduced and applied to the Micro Resonator's dynamical system behavior. It is then concluded as to how the model uncertainties and different initial conditions can affect the working domain of the system and/or make it pull in instabilities. At the end, it can be seen that FGCM is a useful method for monitoring the working regions of Micro Resonators, while varying system parameters.

This paper is devoted to the design and construction of a novel technique for ferrite tuning of dielectric loaded, dual-mode cavity filters. This is dealt with in two specific areas:i) Improving the technique to realize a high -Q , low loss, dielectric-loaded, dual-mode cavity band-pass filter, using the hybrid 11 HEM 11d mode, ii) Developing techniques to obtain a wide range tuning mechanism, using ferrite materials. The designed dual-mode filters offer unloaded Qu of more than 10,000 with an insertion loss less than 1 dB. It is shown that ferrite tuning is possible either at below resonance or at the above resonance state, depending upon the strength of the applied DC magnetic field. Experimental results showed that due to its lower saturation magnetization YIG offers a wider tuning range compared with Nickel ferrite.

Multipactor breakdown analysis is presented in cylindrical dielectric resonator waveguide filter under its dual-mode behavior. The method of effective electron algorithm with combination of Monte-Carlo method is used to perform the simulation and predict multipactor breakdown thresholds. The breakdown thresholds of the proposed structure are presented for different values of frequency-gap product. The results indicate that increasing the radius of filter increases the RF breakdown threshold. The results are compared with the classic parallel plate waveguides.

In this article, we designed a novel monolithic integrated optical transceiver based on the ring resonator structure on semi-insulating In P substrate at 1.55 mm wavelength. To separate the incoming continuous (l2) and modulated (l1) optical waves from the network, an optical ring resonator is utilized. The ring resonator has the p-i-n layer stack that also detects the incoming modulated optical wave (l1). The continuous optical wave (l2) is guided to the ring-resonator based modulator where it is modulated and finally directed toward a pair of ring resonator to reflected back to the network. Channel spacing between l1 and l2 is 200 GHz (1.6 nm) at wavelength ranges of 1520 to 1570 nm. This transceiver can illustrate a 40 GHz bandwidth.

In this study, we present the design and fabrication of a V-shaped resonator that served as an absorption chamber in a laser spectroscopy system for water stable isotope measurement (2H, 17O, 18O) based on optical feedback cavity-enhanced absorption spectroscopy. In the design of a resonator, its length and the radius of curvature of the mirrors guarantee the optical stability of the system. The resonator mirrors are designed considering the condition of stability and based on the desired mode structure of the resonator output. The V-shaped resonator is designed with two arms of 40 cm and inner diameters of 5 mm making an angle of 1.7°. This resonator has an internal volume of 20 cm3 which provides fast response of laser spectrometer. The high reflectivity of mirrors leads to an effective absorption optical path length of 13 km and a high finesse optical resonator of   Ƒ~52،000. These values allow low concentration water vapor isotope analyses and resolution of the absorption spectrum of isotopes for accurate isotope measurements, respectively. Resonator mirrors are designed using Mcleod software to have maximum reflectance at a wavelength of 1.4 micrometers. By making a V-shaped optical resonator for measuring stable isotopes of water and subsequent development for measuring stable isotopes of other elements, the possibility of developing the application of stable isotopes in different areas of research will be provided.

In this article, an X-band low phase noise dielectric resonator oscillator is investigated. For this purpose, a dielectric resonator as a frequency stabilization section at the almost center frequency of 12 GHz is designed. The active device is a packaged GaAs FET (an ATF-36077 pHEMT). Firstly, the ATF36077 microwave transistor has been biased. The substrate of this nonplanar oscillator is Rogers RT/Duroid 5880. Finally, the dielectric resonator oscillator has been introduced as a series feedback structure. This presented X-band dielectric resonator oscillator, operating at nearly 12 GHz, exhibits a phase noise of -71 dBc/Hz and -133 dBc/Hz at 1-kHz and 1-MHz frequency offset, respectively. Also, the output power level of nearly 7 dBm is achieved. The second and third harmonic power levels are more than 50 dB and 30 dB lower than the main harmonic power level.

Piezoelectric Microcantilevers (MCs) are efficient tools in switches of MEMS, AFMs and nano-resonators. Creating maximum vibrating motion with minimum excitation voltage is important in reducing power consumption and noise in this type of MCs. Therefore, investigating the factors affecting the excitability of MCs, as well as the degree of the effect of each of these factors, have an important role in the design and optimal selection of this type of resonators. Therefore, the aim of this paper was to investigate the excitability of this type of MCs. Modeling is conducted according to Hamilton principle and Euler-Bernoulli theory. Equation of motion was solved using Galerkin method with respect to geometrical discontinuities. Finally, eFAST sensitivity analysis was performed on excitability of MCs using statistical methods. Sensitivity analysis results show that the length and thickness of the piezoelectric layer are the most influential parameters on the excitability of MCs. At L1/L=0. 74, the excitability reaches its maximum value.

In this paper, the detector of a moving target in MIMO radar with widely separated antenna in the presence of the a-stable clutter is proposed. Due to the complexity of the unknown parameter estimation in the presence of the target, the Rao test is applied. The a-stable model is a general model that can be applied to different environments with appropriate selection of parameters. The problem with this model is inexistence of a closed form for the probability density function of the distribution. Fortunately, there are models that approximate the distribution by a closed form expression. In the present paper, mixing of Gaussian and Cauchy model is used for expressing clutter. Finally, the performance of the proposed detector is compared with the optimal Gaussian and MiniMax detector by a graph of the probability of detection versus signal-to-clutter ratio. The simulation results, show that the performance of the proposed detector is better than the optimal Gaussian and MiniMax detector.