Laser-pumped drilling carbon nanotube vortex shock waves in optical fibers
Authors
Ricardo E. da Silva
Marcos A. R. Franco
Abstract
We experimentally demonstrate laser-induced vortex shock waves formed by carbon nanotubes drilling optical fibers for the first time. Three samples of standard single-mode optical fibers (SMF) are sequentially inserted in a syringe loaded with a 1 mL solution of single-walled carbon nanotubes (CNT) and methanol, and a high-power laser is injected into the fibers for 5 (SMF 1), 10 (SMF 2), and 20 (SMF 3) minutes. The CNT solution thermally expands and generates vortex acoustic flows, which are confined in the syringe cavity, significantly increasing the velocity and impact of nanotubes at the fiber tip. The resulting shock waves achieve estimated hypersonic velocities (5742 m/s) and high pressures (6.7 GPa), overcoming the silica tensile strength and ablating structured vortices in the fibers. The material, geometry, and depth profile of the vortices are characterized, providing details of mixing carbon and silica layers, increasing radially from the fiber core center and in thickness to the cladding for longer laser periods (850 nm to 10 micron thickness). The cross-sections of the measured vortices are compared to analytical simulations, revealing unprecedented Fibonacci helices drilling holes in the fiber core with a 5 micron maximum depth, while depositing nanoscale CNT-silica layers following Fibonacci spirals. These achievements point out a new route for laser-controlled deposition of nanoparticles and fabrication of vortex devices on fiber tips, which is promising for all-fiber vortex spatial phase modulators in optical communications, fiber sensors, high-power pulsed fiber lasers, and biomedical ultrasonic neurotransmitters.
