Stark-induced three-wave mixing in molecular gases--Part I: Theory

Application of dc electric field to a gaseous system destroys the basic inversion symmetry and allows three-wave mixing processes to occur. A theoretical derivation of this effect under conditions of resonantly enhanced nonlinearities is given for a three-level system. Calculations are presented for mixing of a CO2laser with 4-GHz microwaves in the molecule NH2D, producing single lower sideband radiation.     

Optimal design and applications for quasi-phase-matching three-wave mixing

Solutions of quasi-phase-matching three-wave mixing (TWM) for a nonuniform grating structure with phase-shifted segments are derived by use of a matrix operator, for the first time to the authors' knowledge, under the small-signal approximation. Compared with iterative methods of coupled-mode equations, using these expressions can significantly shorten the calculation time, and they can be effectively applied to all-optical signal processing in TWM. The signal and pump bandwidths of wavelength conversion in difference-frequency mixing, as well as the all-optical gating bandwidth in sum-frequency mixing, are optimized with the matrix solutions. By comparison with loss-free waveguide, the propagation loss a of the waveguide decreases the conversion efficiency /spl eta/, but has little influence on the bandwidth. Numerical results show that /spl alpha/ can be ignored for nonlinear lengths L<20 mm, and the optimal bandwidth /spl Delta//spl lambda/ is sensitive to /spl eta/ and the variation in the grating period, but not to /spl alpha/.     

特殊三波混频导致的介质折射率的感应变化

本文从非线性耦合波理论出发,证明了在特殊的三波混频条件下光频普克尔斯效应的存在,并导出了所必须满足的物理条件。     

Comparison of two-wave and three-wave forward mixing in bismuthsilicon oxide-theory and experiment

A comparison is made between the traditional two-wave amplification mechanism and a new mechanism that is due to forward three-wave mixing. It is found experimentally that considerably higher amplification is available using forward three-wave mixing. Experimental results are in good qualitative agreement with theory concerning dependence on frequency detuning and interbeam angle, but there is a discrepancy between experiment and theory relating to the magnitude of the gain obtainable by two-wave and three-wave mixing, respectively. It is suggested that an additional physical gain mechanism arising from large modulation effects should be included in the theory to account fully for the discrepancy between two-wave and three-wave results     

约瑟夫森混合器等效电路参数对三波混频强度的影响研究

约瑟夫森混合器是一种能够生成纠缠量子微波信号的电路。建立了约瑟夫森混合器的等效电路模型,对三波混频哈密顿量进行量子化,研究了约瑟夫森结的临界电流、分路线性电感、谐振器传输线等效电感以及外加穿过环路磁通对三波混频强度的影响。仿真结果表明,约瑟夫森结的临界电流决定了选择的线性电感最大值,而对三波混频强度影响不大;线性电感的大小决定了外加穿过环路磁通的最优值以及三波混频强度的最大值;谐振器传输线等效电感在允许范围内越小越好。研究对于有效选择电路元器件参数,提高纠缠量子微波生成能力有重要价值。     

Efficient large-frequency-shifted three-wave mixing in low dispersion wavelength region in single-mode optical fibre

In a low-loss single-mode fibre pumped with a 1.3 ?m Q-switched Nd:y.a.g. laser, an injected weak (~ 1 mW) signal has been strongly amplified and mixed efficiently with the pump (~ 70 W) to generate new waves (?1 W) at multiple wavelengths with total spectral range extended as wide as 660 cm?1.     

Diagrammatical analysis of phase conjugation using four- and three-wave mixing processes in Kerr-like nonsaturated media

Double-sided Feynman diagrams, which trace the evolution of the density operator in time during a nonlinear optical interaction, are used to analyze the processes of four- and three-wave mixing which lead to the production of phase conjugate waves.     

10-GHz clock recovery using an optoelectronic phase-locked loop based on three-wave mixing in periodically poled lithium niobate

Clock recovery is a critical function of any digital communications system. To replace the classical electronic phase-locked loops (PLLs) at higher bit rates, several all-optical or optoelectronic clock recovery methods are being studied. This letter presents an optoelectronic PLL where three-wave mixing in a periodically poled lithium niobate (PPLN) device provides the phase comparator. Since PPLN is passive, it generates no amplified spontaneous emission noise; also, the error signal is in the visible (763 nm), therefore easily separated from infrared input signals. Clock recovery is performed on a 10-GHz sinusoidal optical signal. Being based on ultrafast nonlinear effects, this scheme should be able to reach still higher bit rates, on the order of several hundred gigahertz. Also, subclock extraction (e.g., 40-to-10 GHz) should be possible without modifications.     

Millimeter-wave orotron oscillation--Part II: Experiment

Experimental observation of orotron oscillation is reported in the frequency band from 53 to 73 GHz. The output power in a quasi-CW mode and beyond an output window is approximately 100 mW at a beam current of 90-100 mA. Oscillation has been observed on several modes of the open resonator of the orotron, with starting currents ranging from 35 to 82 mA. The electronic tuning transconductance within a single mode was measured by mixing the orotron signal with another signal from a klystron, yieldingdf/dV = 0.25MHz/V. The spectrum of the orotron output signal was also measured by this method, and the linewidth was determined to be less than 0.4 MHz at 70 GHz.     

Microstrip Propagation on Magnetic Substrates---Part II: Experiment

Experimental data taken on microstrip built on ferrite and garnet substrates are presented and compared with theoretical values calculated from formulas derived in a previous paper which were extended to gyromagnetic media. Good agreement has been obtained between experiment and theory. In particular the observed increase in wave attenuation at frequencies near /spl omega//sub m/ is fully explained when the frequency dependence of the characteristic impedance is taken into account.     

Photo-thermal probing of Si-SiO2 surface centers—II: Experiment

The results of photo-thermal probing measurements are presented and interpreted to characterize the Si-SiO₂ surface center photoresponse and to provide information relevant to the evaluation of existing surface state models. Data is first presented to indisputably confirm the facts that surface center photoemission had indeed been observed and that the photoresponse could be isolated from competing relaxation mechanisms. The subsequent presentation is devoted primarily to an examination and analysis of photovoltage vs time data characterizing the surface center response. From the analysis it is concluded that two distinct types of surface centers are quasi-continuously distributed in energy over the central portion of the Si band gap, with both types of states acting as if they were positioned right at the Si-SiO₂ interface. The feature distinguishing the two types of states, referred to as A-states and B-states, is a widely different photocapture cross section at any given band gap energy, measured photocapture cross sections being on the order of 10^?19 cm² and 10^?20 cm² for A- and B-states, respectively. B-states, which exhibit the longer photorelaxation time constant, dominate the response in the upper portion of the band gap, while A-states dominate the response below approximately E_v + 0.3 eV. Finally, the photocapture cross section of each type of state was found to increase systematically toward the band edges due to a Lucovsky-type energy dependence.     

Millimeter-wave integrated-horn antenna. II. Experiment

For pt.I see ibid., vol.39, no.11, p.1575-81 (1991). The impedance and radiation patterns of a dipole-fed horn antenna in a ground plane are experimentally investigated at microwave and millimeter-wave frequencies. The agreement with the full-wave analysis technique presented in part I is good. The results indicate that for a 70° flare-angle horn, horn apertures from 1.0 λ-square to 1.5 λ-square with dipole positions between 0.36 and 0.55 λ yield good radiation patterns with a gain of 10-13 dB a cross-polarization level lower than -20 dB, and resonant dipole impedances between 40 Ω and 120 Ω. It is also found that the impedance measurements can be safely used for 2-D horn arrays, but the radiation patterns differ because of the Floquet modes associated with the array environment. The integrated horn antenna is a high-efficiency antenna suitable for applications in millimeter-wave imaging systems, remote-sensing, and radioastronomy     

The design of a slot array in nonradiating dielectric waveguide, part II: Experiment

Measurement procedures for obtaining the self-impedance of an isolated inclined radiating slot in the metal wall of a nonradiating dielectric (NRD) waveguide are discussed. The design procedure for an antenna array fed by NRD-waveguide and making use of this information is described. As an example, the design, construction and evaluation of a ten-element input-matched broadside linear array is described.     

The design of microstrip dipole arrays including mutual coupling, part II: Experiment

Experiments are described from which determination can be made of the self and mutual impedance for microstrip dipoles and of the backscattering relation involving the radiating current. Functional representations of these sources of input data then permits the design of planar microstrip dipole arrays, including the effects of mutual coupling. The design, construction, and performance of a typical array are described. Agreement between theory and experiment is good.     

Numerical calculation of the effective second-order nonlinearcoefficient along collinear phase-matching directions inside nonlinearcrystals in three-wave interaction

In this work, we present the first numerically calculated values of the second-order nonlinear coefficient D_eff along collinear phase-matching directions inside the biaxial crystal. We have demonstrated our results using KTP in optical parametric generation. Our results are in agreement with recent experimental data. The theoretical approach presented here is a simple and generalized method which encompasses H. Ito's and B. Wyncke's works     

Location of 1/f noise sources in BJT's—II. Experiment

The exact location and magnitude of 1/f noise sources in silicon transistors was determined by a simple technique described in a previous publication [1]. This method, implementing the natural feedback action of actively biased devices, can generally be utilized to locate low-frequency noise generators in bipolar transistors. This paper presents measurements done on two silicon p⁺-n-p transistors. In the first device, the dominant noise source is due to generation-recombination, whereas the other less noisy device exhibits mainly diffusion noise.     

Linear array of coaxially fed monopole elements in a parallel-platewaveguide. II. Experiment

For pt.I see ibid., vol.36, no.4, 1988. A 30-element linear array of coaxially fed equispaced monopoles in a parallel-plate waveguide, and a one-element and two half-element waveguide simulators were constructed. The experimental effort is described. Measured data is presented for the active impedance, coupling coefficients, and element patterns for the arrays of coaxially fed monopoles radiating into the semi-infinite parallel-plate region. Measurements of active impedance, coupling (scattering) coefficients, and element patterns show an excellent agreement with the theoretically predicted results     

Four-wave mixing in indium antimonide

We report a range of experiments in both the degenerate and nondegenerate regimes of four-wave mixing in indium antimonide using CW CO laser sources. For the degenerate case, we specify all the polarization source terms and the signals which they radiate. We identify the dominant term for the phase-conjugate signal experimentally, and confirm that this involves a large-period grating formed by the forward pump and probe. The third-order susceptibility was measured asX^{(3)} sim 1.1esu. This was shown to be highly resonant with the InSb bandgap. By varying the pump-probe input angle, the period of the grating was changed, and thus a carrier diffusion length ofl_{D} = 60 mum was determined. By probing the grating with a second laser, the dispersion of the grating was measured over a wide range of frequencies, and was found to be much less resonant with the band edge thanX^{(3)}. Saturation ofX^{(3)}was observed and possible sources are identified and discussed. The results of near-resonant nondegenerate mixing experiments are presented and the measured value ofX^{(3)} = 5 times 10^{-7}esu under these conditions is discussed in relation to the much larger degenerate, resonantX^{(3)}.