Offset-enhanced slow light in femtosecond laser-fabricated Bragg gratings.

We report a strength-enhanced waveguide second-order line-Bragg grating (WLBG) directly written with femtosecond laser in bulk glass by using "offset" to exploit the slow-light effect. This design eschews the use of multiple waveguides and/or waveguide bundles for light guiding. Instead, it only employs a single-laser-pass waveguide (SLPWG) with a refractive index change of 1.

Generation of THz radiation through molecular modulation in hydrogen-filled hybrid anti-resonant fibers.

We study the generation of narrowband terahertz (THz) pulses by stimulated Raman scattering and molecular modulation in hydrogen-filled hybrid hollow-core fibers. Using a judicious combination of materials and transverse structures, this waveguide design enables simultaneous confinement of optical and THz signals with reasonably low attenuation, as well as high nonlinear overlap. The THz pulses are then generated as the second Stokes band of a ns-long near-infrared pump pulse, aided by Raman coherence waves excited in the gaseous core by the beat-note created by the pump and its first Stokes band.

Profilometry of an optical microfiber based on modal evolution.

The waist diameter of a tapered optical fiber (TOF) has been determined using the modal evolution during the tapering process of a single-mode optical fiber (SMF28) through the short-time Fourier transform (STFT) analysis. The STFT was utilized to calculate the cutoff moment of the different modes. By the knowledge of the cutoff diameter, the final diameter of the waist with accuracy better than 5 nm was measured.