Stimulated Raman Scattering in Hydrogen-Filled Hollow-Core Photonic Crystal Fiber

Abstract

We report on stimulated Raman scattering in an approximately 1-meter-long hollow-core photonic crystal fiber filled with hydrogen gas under pressure. Light was guided and confined in the 15-micrometer-diameter hollow core by a two-dimensional photonic bandgap. Using a pulsed laser source (pulse duration, 6 nanoseconds; wavelength, 532 nanometers), the threshold for Stokes (longer wavelength) generation was observed at pulse energies as low as 800 +/- 200 nanojoules, followed by a coherent anti-Stokes (shorter wavelength) generation threshold at 3.4 +/- 0.7 microjoules. The pump-to-Stokes conversion efficiency was 30 +/- 3% at a pulse energy of only 4.5 microjoules. These energies are almost two orders of magnitude lower than any other reported energy, moving gas-based nonlinear optics to previously inaccessible parameter regimes of high intensity and long interaction length.

Revolver Hollow Core Optical Fibers

“…HCFs paved the way to a new class of lasers-the gas fiber lasers (GFL) [51]. Such lasers combine the advantages of both fiber lasers (compactness, reliability and excellent beam quality) and gas lasers (wide range of lasing wavelengths, high output power and narrow linewidth).…”

“…For example, 2.9-4.4 µm Raman lasers that are based on gas-filled revolver silica fibers have been recently demonstrated [43,44,52]. Such lasers in the NIR range have been implemented with fewer difficulties, since RF and HCF of other types have significantly lower optical losses in this region [51,53].…”

“…In most studies, gas fiber lasers are constructed in a cavity-free, single-pass scheme [5,51,[53][54][55]. Due to strong localization of light in their core (MFD~5 ÷ 50 µm) along the entire length of the fiber (~1 ÷ 10 m) active gas-filled HCFs provide a single-pass gain that is sufficient for laser radiation build-up from quantum noise.…”

“…Due to strong localization of light in their core (MFD~5 ÷ 50 µm) along the entire length of the fiber (~1 ÷ 10 m) active gas-filled HCFs provide a single-pass gain that is sufficient for laser radiation build-up from quantum noise. Thus, a single-pass scheme allows for one to realize efficient GFLs that are based on both SRS [51][52][53][54] and population inversion [55]. Designing a cavity for GFLs remains a challenging problem because there are neither fiber couplers nor analogues of fiber Bragg gratings for hollow-core fibers.…”

Low loss hollow-core waveguide on a silicon substrate

“…In the past decade, the opposite schemeguiding light through a low-index core surrounded by high-index cladding layers has emerged as a new tool for applications. In particular, hollow-core optical waveguides/fi bers are desirable for gas sensors and gas-based non-linear optics because of the increased lengths for light-matter interaction [1,2] , and for laser surgery to guide light in mid-to far-infrared wavelength regimes that lack low-absorption materials [3,4] . Chip-scale hollow-core waveguides (HCWs) are desirable because they enable cost-effective manufacturing of on-chip systems with the potential to monolithically integrate light sources, detectors and electronics.…”