相位共轭光腔的热稳性

使用传播矩阵方法推导出了相位共轭腔的热稳条件,指出仅满足G_1G_2=(1/2)并不意味着相位共轭腔一定是热稳的.因此,为得到高质量的输出激光束,需进行相位共轭腔的最佳设计.用本文所得结果还能解释利用相位共轭技术消除畸变的定域性现象.     

G波段500 W带状注扩展互作用速调管设计研究

针对太赫兹频段实现高功率面临物理机制上的难题,设计了一个G波段带状注速调管,展示了基于非相对论带状电子注和扩展互作用技术所能达到的功率水平以及影响性能的物理因素。文中设计基于电压24.5 kV、电流0.6 A,1 mm×0.15 mm的椭圆电子注,以及与之相匹配的互作用系统,即横向过尺寸哑铃型多间隙谐振腔,可以实现高功率和高增益。三维PIC仿真结果显示,在考虑实际腔体损耗的情况下,能够获得超过500 W的功率,电子效率和增益分别达到3.65%和38.2 dB。研究发现,输出功率和效率的提升很大程度上受到多间隙腔模式稳定性以及电路欧姆损耗的制约;输出腔的欧姆损耗对输出功率影响尤为显著,工程设计需要特别考虑。本文的研究为高频段带状注扩展互作用器件的研发打下了良好的基础。     

对史密斯-帕塞尔自由电子激光光栅的研究

为了研究史密斯-帕塞尔自由电子激光的输出频率和光栅槽深、光栅槽长、光栅槽宽的关系,对于基于矩形光栅的史密斯-帕塞尔自由电子激光利用粒子模拟软件进行模拟和理论分析。首先,利用粒子模拟软件模拟对于基于矩形光栅的史密斯-帕塞尔自由电子激光进行了研究,发现史密斯-帕塞尔自由电子激光的输出频率随光栅槽深、光栅槽长、光栅槽宽的增大而减少。接着,对史密斯-帕塞尔自由电子激光的光栅槽进行了理论分析,发现每个光栅槽都可以等效为一个LC谐振电路,并发现在史密斯-帕塞尔自由电子激光中存在两种辐射,一种是史密斯-帕塞尔辐射,另一种是LC振荡辐射。最后,对光栅槽的LC振荡辐射进行了估算,发现史密斯-帕塞尔自由电子激光输出频率的模拟值与光栅槽的LC振荡辐射估算值的数量级均为102 GHz,且变化规律上一致。据此推测决定史密斯-帕塞尔自由电子激光输出频率的应该是光栅槽,而不是谐振腔。     

Mixed Fano-SP resonant absorption of THz electromagnetic waves in a photonic resonator contacting with a metal film

In terahertz frequency region, we have investigated theoretically the correlation between spectra of a free photonic structure and that deposited on a metal for several models of metal. It was found that for quasi-normal incidence of p-polarized electromagnetic field the presence of metal generates narrow spectral wells in the middle of reflection windows existing in a free photonic crystal. Quite another manifestation of metal-resonator inter-influence takes place at incident angles exceeding the Brewster angle when reflection spikes coincide with modes of photonic crystal resonator and they are absent throughout the stopband areas. The effects are strongly depended on polarization, number of periods and angle of incidence.     

Influence of the torsional vibration of the periodically attached perpendicular beam resonator on the flexural band of a Euler-Bernoulli beam

The bending and torsional vibration of the periodic perpendicular cantilever beam-mass resonators (PCBMR) is idealized as translational and rotational oscillators attached to the main beam. In this paper, the effect of that torsional vibration of the PCBMR on the dynamics of an infinitely long Euler-Bernoulli beam is evaluated. The band-structure is explored by implementing the transfer matrix method in conjunction with Bloch-Floquet's theorem. The combination of the translational and rotational oscillator modifies the relative position of the coupling coefficient in the transfer matrix, which plays a pivotal role in the band-gap formation. The flexural band-structure is highly sensitive to the torsional vibration while the radius of gyration of the tip mass is considerably higher than the length of the PCBMR. Ill-tuning leads to split and reduction of attenuation band to 50%; whereas, around 38% elongation of the attenuation band in the low frequency regime can be achieved by proper tuning.     

Ground state cooling of magnomechanical resonator in PT-symmetric cavity magnomechanical system at room temperature

We propose to realize the ground state cooling of magnomechanical resonator in a parity–time (PT)-symmetric cavity magnomechanical system composed of a loss ferromagnetic sphere and a gain microwave cavity. In the scheme, the magnomechanical resonator can be cooled close to its ground state via the magnomechanical interaction, and it is found that the cooling effect in PT-symmetric system is much higher than that in non-PT-symmetric system. Resorting to the magnetic force noise spectrum, we investigate the final mean phonon number with experimentally feasible parameters and find surprisingly that the ground state cooling of magnomechanical resonator can be directly achieved at room temperature. Furthermore, we also illustrate that the ground state cooling can be flexibly controlled via the external magnetic field.     

光子晶体微环插分滤波器的理论分析与数值模拟

设计了基于二维正方晶格光子晶体微环的插分滤波器的基本结构,对其进行了时域耦合模理论分析,得到了输出端口的归一化透射率表达式。利用时域有限差分法对滤波器进行数值仿真,仿真结果与时域耦合模理论分析结果一致。结果显示,经过合理的参数调节,滤波器的传输效率可达到98％。这一分析方法同样可以适用于其他光子晶体结构。     

Indirect strong coupling regime between a quantum emitter and a cavity mediated by a mechanical resonator

Achieving strong coupling between light and matter is usually a challenge in Cavity Quantum Electrodynamics (cQED), especially in solid state systems. For this reason is useful taking advantage of alternative approaches to reach this regime, and then, generate reliable quantum polaritons. In this work we study a system composed of a quantized single mode of a mechanical resonator interacting linearly with both a single mode cavity and a quantum two-level system. In particular, we focus on the behavior of the indirect light-matter interaction when the phonon mode interfaces both parts. By diagonalization of the Hamiltonian and computing the density matrix in a master equation approach, we evidence several features of strong coupling between photons and matter excitations. For large energy detuning between the cavity and the mechanical resonator it is obtained a phonon-dispersive effective Hamiltonian which is able to retrieve much of the physics of the conventional Jaynes–Cummings model (JCM). In order to characterize this mediated coupling, we make a quantitative comparison between both models and analyze light-matter entanglement and purity of the system leading to similar results in cQED.     

Characteristics of Add Drop Filter using single and dual PCRR in square lattice

A Photonic Crystal Ring Resonator (PCRR) based Add Drop Filter is designed using two dimensional (2D) square lattice PC silicon rods in air host. The normalized transmission spectra for a single-ring and dual-ring configurations have been investigated using 2D Finite Difference Time Domain (FDTD). The filter characteristics such as coupling efficiency, dropping efficiency, resonant wavelength and Q factor are numerically analyzed for single ring and dual ring PCRR. It is noted that the coupling efficiency, dropping efficiency and Q factor of single ring circular PCRR with scatterer rod are 100%, 100% and 186.75, respectively. The backward dropping is observed in single ring PCRR whereas forward dropping are noticed in dual ring PCRR based ADF. The Photonic Band Gap (PBG) with respect to structural parameters such as the radius of the rod, lattice constant and refractive index difference, and propagation modes in periodic and nonperiodic structure are calculated by Plane Wave Expansion (PWE) method.     

环程光程随机扰动时光纤环形腔的有效带宽

对由环境引起的环程光程扰动对光纤环形腔的影响作了详细的理论分析,在扰动为各态历经扰动假设下的理论分析表明：小的慢与快变化扰动的影响是不同的。慢变化扰动影响与人射光时间相干性相同,使有效带宽增大;而快变化扰动对有效带宽的影响很小。然而对大的慢或快变化扰动,都会使环形腔失去它的带通和带阻特性。实验结果证实了一结论。