Near-infrared supercontinuum source from an ultrafast erbium-doped fiber laser based on polyacrylonitrile absorber

Abstract Our study explores the application of Polyacrylonitrile (PAN), a soluble organic material valued for its thermal stability, UV resistance, high strength, and chemical inertness, in the field of supercontinuum generation (SCG). Specifically, we investigate its use as a saturable absorber (SA) in an erbium-doped fiber laser (EDFL) for ultrafast laser generation. The PAN SA is fabricated by embedding PAN compounds into a Polyvinyl Alcohol (PVA) host polymer. Integration of the PAN SA into the laser cavity enables stable mode-locking operation, generating a conventional soliton pulse train centred at 1567.0 nm wavelength. Mode-locking is maintained over a pump power range of 87.2 to 254.1 mW at a repetition rate of 1.78 MHz, producing pulses with a duration of 920 fs and a maximum peak power of 0.67 kW. Upon amplification with an Erbium-doped fiber amplifier, the average output power reaches 24 dBm, albeit with a slight increase in pulse duration to 1 ps. The amplified soliton pulse is then coupled into a 100 m long highly nonlinear photonic crystal fiber (HN-PCF) with zero dispersion at 1550 nm, resulting in the realization of near infrared SCG. The supercontinuum spans from 1375 nm to at least 2000 nm, achieving spectral power exceeding −35 dBm. To our knowledge, this work represents the first demonstration of SCG by utilizing PAN-based femtosecond pulses to pump a nonlinear fiber.