Broadband mid-infrared supercontinuum generation in 1-meter-long As_2S_3-based fiber with ultra-large core diameter

Abstract

In this study, the supercontinuum (SC) generation in a 1-m-long As₂S₃ fiber with a 200 μm core diameter was demonstrated experimentally. The high-purity As₂S₃ fiber we used exhibited very low optical loss with a background loss of approximately 0.1 dB/m at a wavelength of 2-5 μm. SC generation was studied by pumping the fiber at different wavelengths and different peak powers. A strong spectral broadening with a 30 dB spectral flatness spanning from 1.4 to 7.0 µm was obtained when the fiber was pumped with 150 fs short pulses at 5.0 µm. The SC generation in bent fiber was also studied. The result showed that the bending radius of the fiber will significantly affect the SC spectra bandwidth and the output power. The SC spectra in the used fiber could still be maintained when it was bent to a radius of 5 cm.

Ultra‐large mode area mid‐infrared fiber based on chalcogenide glasses extrusion

“…For mid‐infrared SC generation, the pump pulses (a duration of ~150 fs, a repetition rate of 1 kHz) from a tunable optical parametric amplifier (OPA) system was launched into a 17‐cm‐long fiber. Similar SC generation experimental setup has been reported in our previous work 19 . The high NA and large core may be more beneficial to transmit multimode light of long wavelength in the fiber.…”

“…Similar SC generation experimental setup has been reported in our previous work. 19 The high NA and large core may be more beneficial to transmit multimode light of long wavelength in the fiber. Ideally, the broadest SC spectrum could be generated only in one polarization under a single-mode condition possibly, 31,39 but its energy was limited by its little core.…”

“…The initial SC spectral broadening are firstly dominated by the self-phase modulation (SPM), four-wave mixing (FWM), and Raman effects in the multi-mode fiber with large core. 19 In the normal dispersion region, SC generation exhibits significant broadening mainly due to the SPM and pump wavelength closer to the ZDW of the fiber for high efficiency. 22 High NA of 1.44 in the fiber contributes much to confine the fundamental mode light in the ultra-large core at all wavelengths, therefore, SC generation could proceed unhindered.…”

“…Ideally, the broadest SC spectrum could be generated only in one polarization under a single‐mode condition possibly, 31,39 but its energy was limited by its little core. Large core fiber can withstand high‐energy pluses, and SC generation has the possibility of achieving high‐power output due to the HOMs being excited, 19 although SC generation in this multimode fiber was more complex than the case of single mode fiber. The pulse of ~150 fs allowed the light in HOMs to build up and increase with the larger amount of longer pulse durations.…”

“…To the development of LMA chalcogenide fiber, most researches are focused on sulfur, 18,19 selenium, 20,21 and tellurium‐based 22,23 glasses according to their different transmission window. Wang et al 13 reported a kind of seven‐core Ge‐As‐Se‐Te fiber with each core diameter of 60 μm and NA of ~0.8, for high‐power CO 2 laser transmission, but it is difficult to couple the seven‐cores effectively and suppress its super‐mode.…”