Electronics and Communications in Japan (Part II Electronics)
Nonlinear susceptibility of cesium and sodium atoms for frequency upconversion from 10‐μm atmospheric window to the visible
Teruhito Mishima, Kenji Hisadome, Ichiro Sakuraba, Members
Abstract
Abstract This paper presents a calculation of the third‐order nonlinear susceptibility for the frequency upconversion of 10‐μm atmospheric window to the visible band. The following cases are compared. Two‐photon resonance 1 at 6 d 2D3/2, and 2 at 6 d 2D5/2 of cesium to generate difference frequency. 3 Two‐photon resonance at 7 s 2S1/2 of cesium to generate sum frequency. 4 Two‐photon resonance at 3 d 2D5/2 of sodium to generate sum frequency. Density matrix is used in the calculation, and the spinorbit coupling and the Doppler effect are considered. The major results are the following. In 1, a large nonlinear susceptibility and large number density is obtained at relatively low temperature. The nonlinear susceptibility has the maximum at the wavelength of 12.1 μm. In 2, a large nonlinear susceptibility and large number density are obtained at relatively low temperature. The nonlinear susceptibility increases with the increase of infrared wavelength. In 3, a system free from polarization property can be constructed, but the temperature must be raised by more than 100°C, compared with the forementioned two cases. In 4 the largest nonlinear susceptibility is obtained for the wavelength of 9.1 μm. However, the temperature must be raised by several hundreds degree compared with the cases of 1 and 2.