Abstract

Fermann et al.¹ induced a (2) in an optical fiber by simultaneous blue-light excitation and dc-electric-field poling and subsequently demonstrated second-harmonic generation into a phase-matched higher-order mode from a 1208 nm pump wavelength. Unfortunately, it is not possible to design a fiber for the most desirable phase-matched interaction into the lowest order HE211 frequency-doubled mode, so only a less efficient interaction can be achieved by the poling scheme used by Fermann et al. However, by applying a spatially periodic electric field across a fiber, the fundamental wavelength mode can be phase-matched to any of the propagating second-harmonic modes.²,³ In this paper we report the first results on periodic poling and seeding of an optical fiber using spatially periodic static fields. We show that applying a spatially periodic electric field can quasi-phase match the 1064 nm wavelength mode to the lowest order 532 nm wavelength mode. The presence of the 532 nm mode and the periodic electric field permanently poles the fiber periodically and can also seed the fiber. There appears to be competition between seeded and poling-induced SHG. The significant and important uses of periodic poling are in extending the frequency-doubling capability of optical fibers into the infrared wavelengths and removing the need for designing a fiber for phase-matched interaction.

© 1990 Optical Society of America