Determination of oscillator strengths with the phase-matching condition

Kojiro Koyanagi, Teruhito Mishima, Ichiro Sakuraba

Abstract A new method is proposed for measurement of the index of refraction of gas and oscillator strength. In four‐wave sum‐mixing in such nonlinear media as metal vapor or rare gas using the third‐order nonlinear optical effect, the refractive index of a nonlinear medium at the sum frequency in the vacuum ultraviolet range is found from the angle phase‐matching condition for the maximum conversion efficiency, and the oscillator strength is determined from the measurement of refractive index by the phase matching in terms of the sum frequency. The present method in which the refractive index and the oscillator strength are determined from the incident angle of each wave satisfying the angle phase‐matching has the advantage of fewer measurement parameters compared to the conventional methods in which a phase‐matching is accomplished with a mixture of gases with ordinary and extraordinary dispersions. This is because no buffer gas is mixed. In addition, the measurement accuracy is found theoretically to improve in the region with a higher atomic density.

Lianjun Zheng

Thomas M. Bieniewski

A. V. Smith, W. J. Alford

We have developed new techniques based on four-wave mixing for the accurate determination of oscillator strengths and applied them to measure 61S - n1,3P and 71S - n1,3P (n = 6 - 13) matrix elements of atomic Hg. For transitions from the 61S ground state, index matching conditions were used to determine refractive indicies and thus f-values, while the frequency dependence of the nonlinear susceptibility was used to deduce matrix elements for transitions involving 71S. For all measurements, two-photon resonance with the 71S state was maintained.

Emil Rizvanov, Samuel Kern, P. Neilinger +1 more

High gain and large bandwidth of traveling-wave parametric amplifier exploiting the nonlinearity of Josephson Junctions can be achieved by fulfilling the so-called phase-matching condition. This condition is usually addressed by placing resonant structures along the waveguide or by periodic modulations of its parameters, creating gaps in the waveguide’s dispersion. Here, we propose to employ the Josephson junctions, which constitute the centerline of the amplifier, as resonant elements for phase matching. By numerical simulations in JoSIM (and WRspice) software, we show that Josephson plasma oscillations can be utilized to create wave vector mismatch sufficient for phase matching as well as to prevent the conversion of the pump energy to higher harmonics. The proposed traveling wave parametric amplifier design has a gain of 15 dB and a 3 GHz bandwidth, which is comparable to the state-of-the-art TWPAs.

William Arie van Wijngaarden, Keith Bonin, W. Happer