Dye laser pumped, continuous-wave KTP optical parametric oscillators

4 (KTP) optical parametric oscillators (OPOs) with pump and idler resonant cavities. With a linear two-mirror cavity the pump power at threshold was 70 mW. The single-frequency signal and idler output wavelengths were tuned in the range of 1025 to 1040 nm and 1250 to 1380 nm by tuning the dye laser in the range of 565 to 588 nm. With a dual three-mirror cavity the threshold was 135 mW. Pumped by 500 mW of 578 nm radiation the 1040 nm single-frequency signal wave output power was 84 mW. Power and frequency stable operation with a spectral bandwidth of less than 9 MHz was obtained by piezo-electrically locking the length of the pump resonant cavity to the dye laser wavelength. Similar performance was achieved by placing the idler resonant OPO inside the resonator of the dye laser. With this system power stable and single-frequency operation was achieved with a spectral bandwidth of less than 11 MHz for the idler wave. Received: 3 February 1998/Revised version: 9 March 1998     

Autoinjection of Single-Pulse Priming Radiation in a Laser with a Bifurcated Anisotropic Resonator

The optical schemes of lasers with autoinjection of priming radiation in a bifurcated anisotropic resonator are described that make it possible to increase the efficiency of the formation of highly coherent giant pulses by raising the priming radiation intensity level. The parameters of radiation of that kind of ruby lasers have been experimentally studied with Q-switching of a low Q resonator by a bleaching filter and electrooptical switching of the generation channel into the resonator with a higher Q and/or the gain coefficient of an active element, and/or the active material space factor of the resonator.     

光纤环形谐振腔的频率锁定及其特性

基于可调分束比的光纤分束器,制作了光纤环形谐振腔并通过调节分束比实现了对光纤环形谐振腔的欠耦合、临界耦合和过耦合的状态控制.实验测量了腔最小反射率与腔损耗之间的关系,获得光纤环形谐振腔的腔内衰减率为κ_0=2π×(1.60±0.03) MHz ,品质因子为Q=(1.10±0.02)×10.8.在此基础上,结合了压电陶瓷拉伸光纤以控制腔长和Pound-Drever-Hall锁频两大技术优势,克服了之前温度反馈控制等方法的反馈带宽窄、噪声大和稳定性差等问题,实现了对光纤环形谐振腔共振频率的快速、灵敏的控制和锁定.结果表明,锁频过程中相位调制功率与相位调制引起腔反射光的强度调制之间的关系为线性关系,进而通过降低相位调制信号的功率以减小相位调制对腔反射光强度调制的影响.当调制功率设定最低为–9 dBm时,光纤环形谐振腔仍能被稳定锁定.该光纤环形谐振腔为其与原子、金刚石色心等发光粒子相互作用的腔量子电动力学实验研究奠定了坚实的基础.     

三镜级联结构Gires-Tournois谐振腔的色散特性分析

系统分析了三镜级联结构G-T谐振腔的色散特性,表明三镜级联结构G-T谐振腔具有不同于两镜级联结构G-T谐振腔的特有色散特性.利用该特性以三镜级联结构G-T谐振腔作为色散补偿元件可有效改善MGTI型interleaver的色散性能,并给出了以三镜级联结构G-T谐振腔为补偿元件的具体补偿实例.模拟结果表明：对50 GHz的MGTI型光交错复用器,可实现中心波长附近±0.08 nm、±0.09 nm和±0.1 nm范围内的色散绝对值分别小于1 ps/nm、2.4 ps/nm和6.6 ps/nm的良好的补偿结果.与文献报道的两镜级联结构G-T腔补偿结果相比,色散绝对值小于1 ps/nm的波长范围扩大了60%;在中心波长附近±0.09 nm范围内的色散绝对值降低了92%.     

Parametric generation of solitonlike spin-wave pulses in ring resonators based on ferromagnetic films

Parametric generation of intense solitonlike spin-wave pulses is experimentally observed in ring resonators based on ferromagnetic films under the effect of a periodic parallel pulsed magnetic pumping. Depending on the repetition rate of the pumping pulses and the position of their carrier frequency about the eigenfrequency spectrum of the ring resonator, different types of nonlinear pulse sequences are obtained. The theoretical explanation of this phenomenon is proposed.     

Travelling-wave 1.57-µm optical parametric oscillator driven by a pulsed multimode Nd3+:YAG laser

The generation properties of an optical parametric oscillator (OPO) with a three-mirror ring resonator have been investigated under conditions of a pulsed pump by multimode radiation from a Nd³⁺:YAG laser. KTP crystals were used as the OPO nonlinear medium. At pump energies up to 100 mJ, decreasing the diameter d of the Nd³⁺:YAG laser beam causes a decrease in OPO radiation divergence and an increase in the generation efficiency at λ = 1.571 μm despite a decrease in the differential efficiency. At d = 2.25 mm and a KTP crystal total length of 40 mm, the efficiency of the pump conversion to the signal-wave pulse reaches 36.5%. Based on the traveling-wave OPO, a compact, highly effective, eye-safe laser source radiating pulses of up to 35 mJ in energy, 11 nsec in duration, and 10 Hz in repetition rate at electrical pump energy of ≤ 8 J is developed. At the 86.5% level of the total pulse energy, the source-beam divergence does not exceed seven diffraction limits. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 516–523, July–August, 2008.     

On the influence of spatial hole-burning on mode selection and mode synchronization in a CW laser

The influence of spatial saturation modulation of both the amplifier and absorber in a laser with a Fabry-Perot resonator, and of the associated Bragg-reflection, on the frequency-dependent losses necessary for single-frequency operation, as well as on the frequency synchronization of three modes, has been examined. Conditions for mode selection and mode synchronization are given. To achieve single-frequency operation in a laser with a Fabry-Perot resonator the loss difference between the mode to be selected and modes to be quenched has to be proportional to the Bragg losses of the selected mode suffered by its self-induced grating. The proportionality factor depends on the length and position of the amplifier in the cavity. In the case of a short amplifier and a short absorber inside the resonator, the discussion of conditions for synchronization of three modes shows that the synchronization regime is also determined by the position of the absorber.     

A simple method for counting the number of trapped ions in an ion trap

A technique is proposed for injection-seeding control of tunable lasers. It is based on a combination of successive external injection and intracavity self-injection of radiation when the active medium is pumped by dual-step pulses. The technique is tested both experimentally (in the case of Nd:YAG-laser-pumped pulsed dye lasers) and numerically, using a model developed by us. Full conversion of the broadband spectrum into the injected line is achieved for an output energy greater by a factor of about 50 than that managed by means of the traditional injection-seeding technique under identical conditions.     

Nonlinear phenomena accompanying the development of oscillations excited in a layer of a linear dissipative medium by finite displacements of its boundary

A method of describing oscillations in resonators on the basis of evolution equations is proposed. The latter are obtained by simplifying the functional equations under the assumption that the distortions of travelling waves within the resonator length are small, that the Mach number for the moving boundary oscillations is small, and that the frequency is close to one of the natural frequencies of the resonator. The problems of nonstationary oscillations of a layer with a moving boundary are solved. The law that should govern the wall oscillations to provide the development of steady-state linear resonance oscillations is determined. The shape of the resonance curve formed in the presence of a boundary nonlinearity is calculated. The method of matching of asymptotics is applied to the singularly perturbed problem with small dissipation. It is shown that a boundary nonlinearity leads to a distortion of the temporal profile of the standing wave and to the generation of higher harmonics in the process of the development of steady-state oscillations. In contrast to the classical linear problems where the resonance occurs at the coincidence of the external force frequency with one of the natural frequencies, in the case under study the resonance behavior is observed in frequency bands, which are wider the higher the amplitude of the boundary oscillations is.     

Theorie der Erzeugung der Differenzfrequenz zwischen Signal- und Idlerwelle eines optisch-parametrischen Oszillators innerhalb eines Resonators für die Differenzfrequenz

Theory of Difference Frequency Generation between Signal and Idler Waves of an Optical Parametric Oscillator inside a Resonator for the Difference Frequency The generation of difference frequency between signal and idler waves in an optical parametric oscillator, inside a resonator for the difference frequency, is investigated theoretically. For the stationary state the efficiency of difference frequency generation is computed as function of the relative excitation and of the parameters of the resonators and crystals used if for the generation of the signal and the idler wave both a triply resonant and a doubly resonant oscillator is used. It is shown that the frequency transformation can be obtained with the same efficiency as in the set-up without a resonator for the difference frequency, but under experimentally more easily realizable conditions.     

Effect of resonator dimensions on nonlinear standing waves

An investigation of the effect of resonator dimensions on nonlinear standing waves in shaped resonators is conducted. Simple forms of the shear viscosity term in the momentum equations are developed for an axisymmetric (2D) resonator and a low aspect ratio rectangular (3D) resonator. The cross sections of the resonators are exponentially expanded and the one-dimensional wave equations are solved by using the Galerkin's method. The quality factors, pressure waveforms, compression ratios, and resonance frequencies are calculated for different dimensionless cross sections and lengths of the resonators. The results show that, apart from the resonator length, the ratio of the cross-section dimension to the length of the resonator is an important parameter. If the ratio is greater than 0.04, the characteristics of the shaped resonator are not affected significantly. However, when the ratio is less than 0.01, the resonance becomes weak, the compression ratio drops substantially, and the frequency response changes as well.     

Multifrequency Probe for Pulsed EPR and ENDOR Spectroscopy

The design, construction, and performance of a multifrequency pulsed EPR and ENDOR probe for use at cryogenic temperatures are described. Interchangeable resonators based on a folded strip line design allow variation of the resonance frequency over a range of 5-11 GHz. Variable coupling to the resonator is achieved capacitively via a simple mechanical adjustment which is thermally and mechanically stable. The entire assembly is robust and easily fabricated. Common methods of analyzing the resonator parameters such as the Q-factor and coupling coefficient are discussed quantitatively. Probe performance data and multifrequency pulsed ENDOR spectra are presented.     

A simple method for single-frequency operation and stabilization of a He−Ne laser

A simple method for single-frequency operation and stabilization of a low power He–Ne laser has been described and used. With a proper resonator length very weak sideband modes on each side of the strong mode produce a feedback signal to a piezoelectric pusher which controls the resonator length. The long-term frequency stability was estimated to be about ±10 MHz.     

An extension of the transfer matrix method to analyzing acoustic resonators with gradually varying cross-sectional area

The transfer matrix method was used to analyze the acoustical properties of stepped acoustic resonator in the previous paper. The present paper extends the application of the transfer matrix method to analyzing acoustic resonators with gradually varying cross-sectional area. The transfer matrices and the resonant conditions are derived for acoustic resonators with four different kinds of gradually varying geometric shape: tapered, trigonometric, exponential and hyperbolic. Based on the derived transfer matrices, the acoustic properties of these resonators are derived, including the resonant frequency, phase and radiation impedance. Compared with other analytical methods based on the wave equation and boundary conditions, the transfer matrix method is simple to implement and convenient for computation.     

The design and construction of a pulsed beam generation system based on high intensity cyclotron

In order to perform the studies on a pulsed beam generation system based on a high intensity cyclotron, a test beam line with a pulsed beam generation for a 10 MeV compact cyclotron (CYCIAE-10) has been designed and constructed at China Institute of Atomic Energy (CIAE). A 70 MHz continuous H-beam can be pulsed to the pulse length of less than 10 ns with a repetition rate of 4.4 MHz. The sine waveform with a frequency of 2.2 MHz is adopted for the chopper and a mesh structure with single drift and dual gaps is used for the 70 MHz buncher. A helical resonator is designed and constructed based on simulations and experiments on the RF matching for the chopper. A helical inductance loop that is exceptionally large of its kind and equipped with water cooling for the resonator has been successfully wound and a 500 W solid RF amplifier has been manufactured. A special measuring device has been designed, which can be used to measure both the DC beam and the pulsed beam. The required pulsed beam was obtained after pulsed beam tuning.     

新型准光学可调辐射源研究

 本文介绍一种新型毫米波准光学可调辐射源,它采用由面对称三反射镜准光学谐振腔和绕射光栅组成高频互作用系统,利用中等能量级的相对论带状电子注激励,产生频率可调的宽带毫米波、远红外波段的辐射。这种新方案的机理性实验在电子科技大学首次获得成功,其主要实验参数：电子注的能量为400~500kV,电压脉冲宽度70ns,同步脉冲磁场强度1.2T; 磁场脉冲宽度10ms,带状电子注尺寸10nm×1mm;通过热测实验,我们成功地检测到3mm波段的高频信号,其峰值功率达到数十千瓦量级。     

The possibility of detecting gravitational waves from a shift in the resonance frequency of an optical resonator

Under the action of the gravitational wave, the length of an optical resonator and, therefore, its resonance frequency change. In conventional resonators, this frequency shift is too small to be detected. We propose a method that provides a very high resonance frequency-versus-resonator length slope. As a result, a gravitational wave with an intensity of 10⁻²¹ can shift the resonance frequency by more than 10 kHz, which can easily be detected.     

Sound absorption by an active resonator array near an impedance surface

Absorption of sound waves incident on a plane surface with arbitrary impedance by a planar active resonator array consisting of monopole or dipole resonators and positioned near the surface is considered. Appropriate tuning of active resonators ensures complete absorption of sound waves incident at a fixed angle in a broad frequency band. The effect of tuning errors on the efficiency of sound absorption by the systems under study is investigated. It is shown that, for rigid surfaces, a monopole resonator array yields a higher absorption efficiency, whereas for soft surfaces, a dipole resonator array is the more efficient one.     

Intracavity two-photon polarization spectroscopy on the basis of light-induced peaks of radiation power

A calculation of the selective losses of a spectrometer based on a broad-band laser with an anisotropic three-mirror ring resonator containing a two-photon-absorbing atomic gas medium with a light-induced resonance anisotropy has been performed. The conditions under which laser radiation power resonances appear in the output radiation spectrum and the contribution of different factors to their formation have been revealed. Possible ways of obtaining information on the polarization effects induced by a powerful light wave in a medium at the frequencies of two-quantum transitions were investigated. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 48–53, January–February, 1999.     

High-frequency EPR applications of open nonradiative resonators

A new class of open single-mode cavities, the nonradiative (NR) resonators, has recently been proposed in order to overcome the limitations of standard cylindrical cavities and Fabry-Perot resonators at millimeter wavelengths. This paper presents the first applications of a NR resonator in W-band pulsed electron paramagnetic resonance spectroscopy. It consists of a cylindrical cavity having a lateral aperture that represents about 35% of its total height. Electron-spin-echo measurements performed on different samples show that the signal-to-noise ratio and the optimal pulse length obtained with the proposed device are comparable to those obtained with the closed cavity used in the commercial W-band spectrometer, at both cryogenic and room temperature. Similar results have been obtained for paramagnetic species optically activated by means of an optical fiber inserted in the aperture of the resonator. The insertion losses estimated for the probe employed with the NR resonator are higher than those of the commercial probe, hence, demonstrating that the proposed cavity holds the promise of improved resonator performance.