Analysis of higher-order soliton compression for formation of ultra-short pulses

Abstract

In this study, propagation of ultrashort fundamental and higher-order soliton pulse has been studied in details for both communication and medical applications. Although so many researchers already have studied the propagation of ultrashort pulse, the effect of self-steepening and Raman scattering are not so far taken into consideration in same study yet. But in addition to group-velocity dispersion and self-phase modulation, third order dispersion as higher-order dispersive effect, self-steepening and intrapulse Raman scattering as higher-order nonlinear effects are of great concern for ultrashort pulses. Considering all the effects mentioned above, soliton pulse propagation operating at a speed of 400 Gb/s and 1 Tb/s in different types of optical fiber like standard single mode fiber, nonzero dispersion shifted fiber, large effective area fiber, multiclad dispersion flattening fiber and multiclad dispersion shifted fiber has been investigated. Multiclad dispersion shifted fiber has been proposed to be a flexible and effective means for ultrashort soliton propagation for high speed communication applications. At the same time compressed ultrashort soliton has become prominent in removal of tissue as well as cancer cell treatment. The compressed ultrashort soliton has spatial dimension (nm-pm range) lower than that of cancer cell size, hence it causes no side effect other then removing the specific affected tissue. To get ultrashort soliton of specific spatial range a good compressor is needed. Dispersion decreasing fiber has been proposed to be a good compressor (calculated pulse width after compression is 90fs and spatial dispersion is 722.6pm) of ultrashort soliton instead of dispersion compensating fiber and fiber Bragg grating for medical applications. For radiotherapy of cancer treatment the laser beam spot size is in mm2. Recently in 2014 the beam spot size has been used as 70-100nm2 for nanosurgical tools and removal of tissue as well as ablation of cancer cell. But for precision ablation like Corneal sculpting, neuron disruption (brain: seizure control), Stapedectomy (ear: hearing restoration), bone resection near nerve, Transmyocardial revascularization (heart: improved output, pain) we need to go for more small beam spot. Here in this study we have proposed fiber based soliton pulse of beam spot size as 2nm2 - 722pm2 range that can be used for both precision ablation and soliton therapy in cancer treatment.