Ultraviolet-Extended Supercontinuum Generation in Zero-Dispersion Wavelength Decreasing Photonic Crystal Fibers

Wanjun Bi,Meisong Liao,Liang Chen,Lili Hu,Xia Li,Peiwen Kuan,Weiqing Gao,Tianxing Wang

doi:10.1109/jphot.2020.3034235

Abstract

Supercontinuum covering the ultraviolet-blue region is highly useful for fluorescence microscopy. Four zero-dispersion wavelength decreasing photonic crystal fibers with different fiber cross structures and taper profiles are fabricated to extend the short wavelength edge of supercontinuum. Both nanosecond and picosecond pump pulses at 1 μm are used to generate supercontinuum. With a 3 ns pump pulse, the short wavelength edge of supercontinuum is extended to below 400 nm in a fiber with high air-hole ratio (named T3). The underlying mechanism of supercontinuum generation is explored. The short and long wavelength edges of supercontinuum are highly related with the phase-matching condition which decided by the group velocity curve of fiber small core end. With a 10 ps pump pulse, the spectral intensity around ∼800 nm increases in all four fibers. However, the intensity in shorter wavelength band decreased in fibers with a high air-hole ratio (named T3, T4). The experimental results imply that a zero-dispersion wavelength decreasing photonic crystal fiber suitable for nanosecond pulse pumping is not necessarily suitable for picosecond pulse pumping, especially for fibers with high air-hole ratio.

Highlights

Supercontinuum (SC), which covers broad spectral band, offers an attractive optical source in diverse applications like metrology [1], [2], biomedical imaging [3]–[5], and astronomy [6]
Four photonic crystal fiber (PCF) with decreasing zero-dispersion wavelength (ZDW) were directly fabricated from fiber draw tower in our laboratory
These PCFs had different fiber cross structures and taper profiles. Both nanosecond and picosecond pump pulses at 1 μm were used for SC generation

Summary

Introduction

Supercontinuum (SC), which covers broad spectral band, offers an attractive optical source in diverse applications like metrology [1], [2], biomedical imaging [3]–[5], and astronomy [6]. The short wavelength edge of SC which determined by the group velocity profile can be shifted into blue by decreasing the core diameter or increasing the air-hole ratio of the uniform PCF. In this approach, the fiber zero-dispersion wavelength (ZDW) is away from the pump wavelength, and the intensity of the visible part of SC decreases. An ultra-broadband SC from 400 to 5140 nm was generated in a tapered ultra-high numerical aperture (NA) all-solid fluorotellurite fiber pumped by a 1560 nm mode-locked fiber laser [22] Both the taper profile and the fiber cross structure (e.g., fiber core diameter, and air-hole ratio) could be changed to regulate the dispersion and nonlinearity characteristics of the taper fiber, the SC generation process becomes more sophisticated, needs much more investigation. This systematical investigation could provide practical guidance to design PCF with decreasing ZDW

Theory

Supercontinuum Generation With Nanosecond Pump Pulse

Supercontinuum Generation With Picosecond Pump Pulse

Conclusion