基于同轴TM812模谐振腔的毫米波多注速调管

 研究了群聚电子注穿越同轴TM₈₁₂模谐振腔的换能效率和同轴TM₈₁₂模谐振腔中微波能量的提取方法,论证了其作为毫米波多注速调管的输出腔的可行性。研究结果表明:理想群聚电子注穿越同轴TM₈₁₂模谐振腔的换能效率可达3.29%,一般群聚电子注穿越同轴TM₈₁₂模谐振腔的换能效率可达1.86%;采用同轴TM₈₁₂模谐振腔与沿轴向的同轴线耦合可以实现微波能量的提取;在输出腔工作频率为100.945 GHz,外观品质因数为2 243情形下,根据估算,最大输出功率可达15 kW。     

CONCEPTUAL DESIGN STUDIES OF AN 84 GHz, 500 kW, CW GYROTRON

The feasibility of an 84 GHz, 500 kW, CW gyrotron for ECRH on an experimental tokamak will be presented in this paper. Mode competition and mode selection procedures are carefully investigated by considering various candidate modes and the TE_10,4 mode is chosen as the operating mode. A conventional cylindrical cavity resonator with weak input and output tapers and parabolic roundings is considered for interaction studies. Self-consistent, both single mode and time-dependent, calculations are carried out and power and efficiencies are computed for a typical set of beam parameters. The results show that an output power of well over 500 kW, CW and efficiency around 40% can be reached without a depressed collector.     

Well-designed rectangular cavity resonator for FMR experiment

The unloaded quality factor of the cavity resonator is the ratio between the stored energy of the cavity resonator to the power loses in the cavity resonator. The homemade rectangular cavity resonator in X-band shows higher unloaded quality factor compare with standard cavity resonator in the TE₁₀₂ mode. Because the inner walls of rectangular cavity resonator are treated through high quality polishing and high purity Au plating. Also the inner walls are made by printed circuit board which has thin Cu foil, two problems such as mechanical vibration and thermal expansion can be solved by minimizing unwanted eddy current. Through the ferromagnetic resonance measurement by using our rectangular cavity resonator, we can be obtained reasonable values of resonance frequency and linewidth by using NiFe thin film. As a result, the Gilbert damping constant from the experimental result is in good agreement with the typical value of damping parameter of the NiFe thin film.     

High-power Q-switched laser with high-order Laguerre–Gaussian modes: application for extra-cavity harmonic generations

We present a compact efficient scheme for generation of high-order Laguerre–Gaussian TEM _p,0 modes in a diode-pumped actively Q-switched Nd:YVO₄ laser. The resonator is composed of two plane mirrors with an intracavity concave lens to expand the cavity mode size for generating a high-power Laguerre–Gaussian TEM_5,0 mode. We further confirm that the TEM_5,0 mode is noticeably superior to the TEM_0,0 mode in the processes of second and third harmonic generations.     

Calculations,in the three-dimensional approximation,for a half-symmetric unstable resonator with internal axicon (HSURIA) in the three-dimensional diffraction approximation with annular shape of the active medium

6. Conclusions 1. It was shown that, compared with other methods, realization of the analytic Prony method increases strongly the effective establishment of the radiation of the mode structure of the radiation field in an empty cavity having o complex configuration, such as the HSURIA resonator. 2. We investigated the dependence of the losses of various azimuthal and radial modes in an empty HSURIA resonator on the value of N_eq. We have shown that in the region N_eq=20−25 and at M=2 the losses of the highest-Q zeroth and first azimuthal modes amount to ≈0.65 and ≈0.70 respectively, which ensures lasing in the single-mode regime in the case of a sufficiently homogeneous active medium. 3. We found the field distributions of various azimuthal and radial modes in the HSURIA resonator in the absence of a medium. 4. We have shown that in the case of lasing on one highest-Q mode the radiation intensity on the tip of a W-axicon is not more than 2–3 times larger than the average over the central region of the W-axicon. Translated from Preprint No. 31 of the Lebedev Physics Institute, Russian Academy of Sciences, Moscow, 1991.     

Active frequency stabilization of an ultra-high Q whispering-gallery-mode microresonator

We report on active frequency stabilization of a whispering-gallery-mode microresonator with an ultra-high quality factor exceeding 2×10⁸ to an atomic transition using the Pound–Drever–Hall technique. The critically coupled resonator is stabilized to 5.4% of its linewidth, or 206 kHz. Thermal bistability and mode-splitting are also observed and have a significant effect on the error signal.     

Stable diode lasers for hydrogen precision spectroscopy

We report on an external cavity diode laser at 972 nmstabilized to a mid-plane mounted Fabry-Perot (FP) resonator with afinesse of 400000. The 0.5 Hz optical beat note line width betweentwo similar lasers (Allan deviation 2 × 10^-15) is limitedby thermal noise properties of two independent FP resonators. Thelong term drift of the FP resonator and mirror substrates made fromUltra-Low-Expansion glass (ULE) is small and can be well predictedon time intervals up to many hours if the resonator is stabilized atthe zero thermal expansion temperature T_c. Using a Peltierelement in a vacuum chamber for temperature stabilization allowsstabilization of the FP cavity to T_c which is usually below theroom temperature. Beat note measurements with a femtosecond opticalfrequency comb referenced to a H-maser during 15 hours have shown awell defined linear drift of the FP resonance frequency of about 60 mHz/s with residual frequency excursions of less than ±20 Hz.     

Microwave and MM-wave magnetoelectric interactions in ferrite-ferroelectric bilayers

Measurements of the strength of magnetoelectric (ME) interactions at microwave and millimeter-wave frequencies have been carried out on layered ferrite-piezoelectric oxides. An electric field E applied to the composite produces a mechanical deformation, resulting in a field shift δH_E or a frequency shift δf_E in the resonance. A stripline structure or a cavity resonator was used. The strength of ME coupling is obtained from data on δH_E or δf_E vs. E. Studies were performed at 1–110 GHz on bilayers of single crystal nickel zinc ferrite or hexagonal ferrites and single crystal lead magnesium niobate-lead titanate, lead zinc niobate-lead titanate or polycrystalline lead zirconium titanate. The coupling strength has been found to be dependent on the nature of piezoelectric phase, magnetic field orientation and volume for both phases. The ME coupling strength is on the order of 1–2 Oe cm/kV (or 3–6 MHz cm/kV) and is an order of magnitude stronger than in polycrystalline ferrite-piezoelectric bilayers. The high frequency ME effect is of importance for dual electric and magnetic field tunable ferrite-piezoelectric devices.     

Two-dimensional array of room-temperature nanophotonic logic gates using InAs quantum dots in mesa structures

We present a detailed study of the dynamics of light in passive nonlinear resonators with shallow and deep intracavity periodic modulation of the refractive index in both longitudinal and transverse directions of the resonator. We investigate solutions localized in the transverse direction (so-called Bloch cavity solitons) by means of envelope equations for underlying linear Bloch modes and solving Maxwell’s equations directly. Using a round-trip model for forward and backward propagating waves we review different types of Bloch cavity solitons supported by both focusing (at normal diffraction) and defocussing (at anomalous diffraction) nonlinearities in a cavity with a weak-contrast modulation of the refractive index. Moreover, we identify Bloch cavity solitons in a Kerr-nonlinear all-photonic crystal resonator solving Maxwell’s equations directly. In order to analyze the properties of Bloch cavity solitons and to obtain analytical access we develop a modified mean-field model and prove its validity. In particular, we demonstrate a substantial narrowing of Bloch cavity solitons near the zero-diffraction regime. Adjusting the quality factor and resonance frequencies of the resonator optimal Bloch cavity solitons in terms of width and pump energy are identified.     

微波谐振器系统的调谐实验研究

圆台谐振腔和微波产生及传输装置可以形成一套和外界独立的微波谐振器系统.由于壁面上电磁压强差的作用,圆台谐振腔可能产生净电磁力,这需要从实验上给予证明.为此首先应对独立的微波谐振器系统进行调谐实验研究,使系统时刻处于谐振状态,这是实验证明净电磁力存在的重要保证.为此,本文对圆台谐振腔进行低信号调谐实验,同时配合调谐元件,准确地调试2.45 GHz频率下的谐振状态,分析温度对谐振状态的影响.实验结果表明该微波谐振器谐振频率2.44895 GHz、品质因数117495.0823,而且当腔体壁温升高时谐振频率减小、品质因数出现周期性振荡.     

Compact cavity resonators using high impedance surfaces

This paper presents a miniaturization concept for cavity resonators. The idea is to create a λ/4 long cavity resonator by using a combination of Perfect Electric Conductor (PEC) and Perfect Magnetic Conductor (PMC) boundary conditions. Reducing by half the length and width of a metallic cavity resonator and placing PMC boundary conditions on two adjacent side walls allows the resonance of a λ/4 mode inside the hybrid cavity resonator, at the same frequency as the λ/2 long metallic one. The practical implementation of the PMC boundary condition is realized by using High Impedance Surfaces (HIS). The design of the surfaces is realized at the element level and is implemented on standard microwave substrate. Measurements demonstrate a cavity resonator operating at 4 GHz with half the length and width of a metallic cavity resonator, meanwhile its volume is divided by four.     

Influence of the modal composition of the radiation on the oscillation dynamics of a CO2-laser with a saturable absorber

The influence of the modal composition (transverse modes of a single longitudinal mode) of the laser radiation on the oscillation dynamics of a CO₂-laser with a saturable absorber in the cavity is investigated. Passive Q-switching in initiation of the fundamental mode TEM₀₀ and the modes of the first family TEM₀₁ and TEM₁₀ is considered. It is established that in the case of multimode oscillations sequences of single pulses with an irregular change in their amplitude can be observed. The multimode oscillations obtained are compared with similar single-mode oscillations, and their special features and differences are discussed. Reported at the Second International Scientific and Technical Conference on Quantum Electronics, Minsk, November 23–25, 1998. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 681–687, September–October, 1999.     

Effect of a dielectric film on the characteristics of an open Fabry-Perot resonator cavity

It is demonstrated that placing a thin dielectric film inside the cavity of an open Fabry-Perot resonator, at an angle to its axis, will remove the polarizational degeneracy of the principal TEM_q00 oscillation modes. Upon excitation of such a resonator cavity by a plane wave, the reflected electromagnetic field is in general elliptically polarized. The shape of the resonance curve depends on the thickness of that film, on its orientation inside the cavity, on the conditions under which the cavity has been excited, and on the conditions under which the reflected signal appears in the receiver. Changing the polarization plane of the incident plane wave does not result in a smooth variation of the resonator Q factor.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 21, No. 11, pp. 1648–1652, November, 1978.     

Quasi-monolithic ring resonator for efficient frequency doubling of an external cavity diode laser

A quasi-monolithic second-harmonic-generation ring resonator assembled with miniaturized components is presented. The ring contains a 10-mm-long bulk periodically poled lithium niobate crystal for second-harmonic generation, four plane mirrors and two gradient-index lenses. All parts are mounted on a glass substrate with an overall size of 19.5 mm×8.5 mm×4 mm. As pump source a broad-area laser diode operated in an external resonator with Littrow arrangement is utilized. This external cavity diode laser provides near diffraction limited, narrow-bandwidth emission with an optical output power of 450 mW at a wavelength of 976 nm. Locking of the diode laser emission to the resonance frequency of the ring cavity was achieved by an optical self-injection locking technique. With this setup more than 126 mW of diffraction-limited blue light at 488 nm could be generated. The opto–optical conversion efficiency was 28% and a wall plug efficiency better than 5.5% could be achieved.     

Multiwatt, tunable, diode-pumped CW Yb:GdCOB laser

We demonstrate that Yb-doped Ca₄GdO(BO₃)₃ (GdCOB) crystals are suitable for the development of high-power diode-pumped lasers emitting at around 1.04 μm. A 15%-doped Yb:GdCOB crystal was longitudinally pumped with a cw fiber-coupled diode emitting 10 W at 976 nm. While 5.2 W of diode power was absorbed, we obtained 3.2 W of 1043-μm laser light, with a beam quality factor M² equal to 3, and 2.5 W in a diffraction-limited beam. Furthermore, the laser is continuously tunable between 1018 and 1086 nm. Thermal effects have been investigated with a Shack–Hartmann wavefront analyser: although thermal lensing is not negligible, it does not affect the performance of the laser with the resonator design we used. Received: 1 August 2000 / Revised version: 18 September 2000 / Published online: 21 February 2001     

Quantum nondemolition measurement by optomechanical coupling

 We show that a single-port optical cavity with a movable mirror can provide a quantum non-demolition measurement of the intensity of a light beam. Due to radiation pressure, the cavity length is sensitive to the light intensity and can be measured with a secondary light beam. Signal-meter correlations can be made very large even at non-zero temperature. We study these correlations when the moving mirror is a plane–convex crystal resonator and we show the importance of spatial matching between light and acoustic modes. Received: 12 June 1996/Revised version: 3 September 1996     

衰荡腔测量中的腔参数选择

 基于谐振腔失调灵敏度参量随腔长的变化关系,提出了一种衰荡腔,它是由共焦腔将腔长缩短为原来的0.73得到的稳定腔。根据光束传输规律和失调腔矩阵方法,以及光腔衰荡法测量原理和曲线拟合方法,建立了腔长、腔镜角度失调下光腔衰荡法的反射率测量模型。通过数值模拟,研究了这种稳定衰荡腔中,腔微小失调对反射率测量结果的影响,并与相同失调情况下共焦衰荡腔的测量结果进行了对比分析。结果表明,这种稳定腔用作衰荡腔,测量结果受腔镜角度失调影响较大,而受腔长失调影响小;其长度较短,便于工程应用;衍射损耗较小,测量精度高。     

Active Bragg Compressor of 3-cm Wavelength Microwave Pulses

We present the results of studies of the active compressor of 3-cm wavelength microwave pulses, which uses a high-Q storage Bragg resonator excited at the H₀₁ mode and new types of plasma switches. Phase variation during a compressed pulse and phase correlation of the input and compressed microwave pulses are studied both experimentally and theoretically. Using a single-channel compressor excited at the megawatt power level by the magnicon radiation with frequency 11.4 GHz, a power amplification factor equal to 9 was reached for an output-pulse duration of 40–50 ns and a peak power of up to 25 MW. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 7, pp. 597–616, July 2008.     

EPR Uniform Field Signal Enhancement by Dielectric Tubes in Cavities

The dielectric tube resonator (DTR) for electron paramagnetic resonance spectroscopy is introduced. It is defined as a metallic cylindrical TE₀₁₁ microwave cavity that contains a dielectric tube centered on the axis of the cylinder. Contour plots of dimensions of the metallic cylinder to achieve resonance at 9.5 GHz are shown for quartz, sapphire, and rutile tubes as a function of wall thickness and average radius. These contour plots were developed using analytical equations and confirmed by finite-element modeling. They can be used in two ways: design of the metallic cylinder for use at 9.5 GHz that incorporates a readily available tube such as a sapphire tube intended for NMR and design of a custom procured tube for optimized performance for specific sample-size constraints. The charts extend to the limiting condition where the dielectric fills the tube. However, the structure at this limit is not a dielectric resonator due to the metal wall and does not radiate. In addition, the uniform field (UF) DTR is introduced. Development of the UF resonator starting with a DTR is shown. The diameter of the tube remains constant along the cavity axis, and the diameter of the cylindrical metallic enclosure increases at the ends of the cavity to satisfy the uniform field condition. This structure has advantages over the previously developed UF TE₀₁₁ resonators: higher resonator efficiency parameter Λ, convenient overall size when using sapphire tubes, and higher quality data for small samples. The DTR and UF DTR structures fill the gap between free space and dielectric resonator limits in a continuous manner.     

Ka波段分布作用速调管多间隙谐振腔研究

谐振腔作为速调管的高频互作用电路,其特性对速调管的功率、效率、增益和带宽等性能具有决定性影响。主要介绍了某Ka波段分布作用速调管谐振腔的设计过程:基于多间隙谐振腔理论,利用电磁仿真软件CST详细分析了谐振腔不同结构尺寸对特性参数,如品质因子、特性阻抗、耦合系数、有效特性阻抗的影响,优化得到谐振频率为35 GHz的五间隙谐振腔的物理结构模型,并给出互作用仿真结果,为Ka波段分布作用速调管设计及其高频注波互作用的计算提供重要的参考和依据。