Unprecedented Raman cascading and four-wave mixing from second-harmonic generation in optical fiber

Abstract

We experimentally demonstrate strong second-harmonic-generation from a self-induced all-optical poling in germanium-doped fiber with a subnanosecond laser pump at 1064 nm. The large second-harmonic conversion efficiency allows nonlinear spectral broadening at visible wavelengths so that up to nine distinct Raman sidebands have been obtained. In this work we emphasize how the Raman scattering, induced from the pump in the IR region, can drastically affect the optical poling effect, limiting in turn second-harmonic generation.

Second and third order susceptibilities mixing for supercontinuum generation and shaping

“…It was also demonstrated that the dual pumping process writes a permanent grating in the germanium-doped fiber, so that efficient broadband SHG can be obtained directly from the poled fiber when using the IR pump only [38]. Recent experiments have investigated the limitations due to the Raman effect in the self-poling process occurring in a germanium-doped standard single-mode fiber [39].…”

Glass Fiber Poling by an Extended Cavity Microchip Laser

“…Optical poling can turn a glass optical fiber in a versatile waveguide exhibiting both quadratic and cubic nonlinearities. The complex photoinduced processes leading to the growth of the quadratic coefficient  (2) require sufficiently high peak power pump pulses, and a few hours of writing time [1][2][3]. The poling mechanism introduces a periodic  (2) which guarantees the quasi-phase matching condition, thus enabling the poled fiber to be used to efficiently generate the second harmonic (SH) of a laser emitting at the same wavelength of the laser used to pole the fiber.…”

Observation of sum-frequency-generation-induced cascaded four-wave mixing using two crossing femtosecond laser pulses in a 01 mm beta-barium-borate crystal

“…Over the past decade, broadband and wavelengthtunable femtosecond (fs) laser pulses from ultraviolet (UV) to mid-IR range have been developed using cascaded four-wave mixing processes (CFWM) in transparent bulk media (e.g., BK7 glass, fused silica and sapphire plate) [1][2][3], nonlinear crystals [e.g., beta-barium borate (BBO), LiNbO 3 , KNbO 3 , and PbWO 4 ] [4][5][6][7], and optical fibers [8][9][10]. By using two sufficiently intense fs laser pulses with a finite crossing angle in the medium, several frequency up-and down-converted pulses can be generated with good spatial separation [1,[3][4][5][6][7].…”