Advanced refractive index sensing through ultra-short pulse compression in hollow core photonic crystal fiber

This manuscript investigates the propagation of ultra-short pulses through hollow-core photonic crystal fibers (HC-PCF) and explores their application as high-sensitivity refractive index sensors. The unique guiding properties of HC-PCFs, combined with the ability to confine light within the hollow core, enable enhanced light-matter interactions. When exposed to intense light, these interactions can demonstrate nonlinear optical phenomena, such as pulse compression, which has been utilized here as a tool for detecting changes in refractive index. The HC-PCF has been designed to allow testing materials with refractive indices ranging from 1.4 to 1.45 to be placed in the core, where ultra-short pulses centered at 1550 nm with a duration of 1 picosecond and an input power of 1 KW, are sent from one end to leverage the nonlinear optical properties. By leveraging these nonlinear phenomena, it has been demonstrated that HC-PCFs exhibit unique attributes when the testing materials inside the core have varying refractive indices. Employing this novel technique, unique compression sensitivity and significant power upsurges have been achieved for the materials under test (MUT) with different refractive indices. Unlike the refractive index sensing methods in practice, this novel technique works based on lesser detection parameters and offers improved sensitivity and selectivity. The proposed method has achieved a minimum sensitivity of 11.6 %, which means the pulse is compressed by a factor of nine, and the maximum power surge recorded is 2313.918 W. This innovative approach opens new avenues for developing advanced sensing systems using HC-PCFs in fields such as environmental monitoring, bio-sensing, and chemical detection.