Second-harmonic generation using gratings optically written by mode interference in poled optical fibers

Abstract

Second-order nonlinear susceptibility gratings are induced in optical fibers by mode interference of high-intensity blue light in the presence of an external dc electric poling field. As a result, efficient second-harmonic generation can be obtained for any infrared design wavelength.

Photoinduced self-organization in optical fiber: some answered and unanswered questions

“…It turns out that the period of this grating is exactly that needed for quasi-phase matching of the SHG interaction. The fact that the x'2 is periodic has been verified by other experiments [64,65,66,67], and is now well established, although the picture of defect alignment with the d.c. field does not seem to withstand the test of numbers: the d.c. field is actually too weak (only a few volts/cm) to overcome even the therma' fluctuations. It does appear however that a third order interaction (or higher: fifth or seven...) is needed to get the right period.…”

“…Still, however, light was needed, in particular from an argon laser again, to induce the permanent x2• Also, this scheme had the disadvantage that the interaction was not phase matched, since the x2 was not periodic. However, phase matching has been achieved by looking at wavelengths where the mode effective indices at the fundamental and harmonic are equal [72] , but also by poling the fiber in a periodic way, for example by launching the exciting light in two modes of the fiber that beat with the right period [66], or poling with periodic electrodes [73].…”

Optimizing Second-Harmonic Generation in a Circular Cylindrical Waveguide with Embedded Periodically Arranged Tubelets of Nonlinear Susceptibility

“…Second-harmonic generation in poled optical fibers using gratings optically written by mode interference was studied experimentally by Fermann et al [5]. Analogous experiments in thermally poled twin-hole glass fibers were performed by Mizunami et al [6], [7].…”

Second-order nonlinearity and phase matching in thermally poled twin-hole fiber

“…4 Then, it was found using D-shape fiber that the second-harmonic generation was enhanced by an external poling electric filed at room temperature. 5,6 On the other hand, the SHG by bulk silica glass by thermal poling was found, 7 and also the electron-beam 8 and the ultraviolet (UV) light poling 9 were developed for bulk glasses. Several mechanisms for the second-order nonlinearity were proposed for bulk glass such as depletion of impurity ions, 10,11 screening by ions from the air, 12 or accumulation of ions.…”