• Infrared and Laser Engineering
  • Vol. 52, Issue 5, 20220745 (2023)
Hang Ren1, Tianshu Wang1, Lei Du1, Xin Li1, Lin Xiao1, and Jianhong Zhou2、*
Author Affiliations
  • 1Institute of Space Optoelectronic Technology, School of Optoelectronic Engineering, Changchun University of Science and Technology, Changchun 130022, China
  • 2Department of Optical Engineering, School of Optoelectronic Engineering, Changchun University of Science and Technology, Changchun 130022, China
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    DOI: 10.3788/IRLA20220745 Cite this Article
    Hang Ren, Tianshu Wang, Lei Du, Xin Li, Lin Xiao, Jianhong Zhou. Flat supercontinuum generation via wave-free breaking pulse in the optical fiber[J]. Infrared and Laser Engineering, 2023, 52(5): 20220745 Copy Citation Text show less

    Abstract

    ObjectiveSupercontinuum light source has the advantages of wide spectral range and good spatial coherence. Thus, it is widely applied in optical communication, optical frequency comb, optical fiber sensing, spectrum detection, and other fields. With the development of new technology such as optical coherence tomography and fluorescence lifetime imaging, supercontinuum light source has become an interesting research field. Although the combination of 1.55 μm mode-locked pulse and highly nonlinear fiber can realize all-fiber near-infrared supercontinuum light source. However, due to the low output energy of the mode-locked pulse, the energy of the supercontinuum light source is mainly concentrated in the spectral region of the pump wavelength. How to enhance the coverage and flatness of the near-infrared supercontinuum is a problem need to be solved. For this purpose, we designed a high-energy erbium-doped fiber laser.MethodsThe generation of flat supercontinuum via wave-free breaking pulse is proposed. Nonlinear polarization rotation (NPR) is employed as a mode-locking way to switch the output of dissipative soliton pulse and wave-free breaking pulse (Fig.1). Dissipative soliton pulse is obtained at 0.3 W pump power (Fig.3). The pulse width is 5.8 ps, and the pulse interval is 54 ns corresponding to the cavity length of 11.05 m. The signal-to-noise ratio is 55 dB, and the compressed pulse width is 0.61 ps (Fig.4). The pulse peak power can be increased to 1.18 kW. By properly adjusting the cavity polarization state and increasing the pump power, the dissipative soliton pulse can evolve into wave-free breaking pulse (Fig.5). With the increase of pump power, the pulse width increases almost twice from 11.7 ps to 20.2 ps. After calculation, the time bandwidth product increases from 23.9 to 53.43. The larger chirp can resist the influence of nonlinear phase shift, avoiding pulse splitting. The pulse energy of wave-free breaking pulse can be increased to 3.89 nJ, which is five times of the pulse energy of dissipative soliton (Fig.6).Results and Discussionswe use dissipative soliton pulse and wave-free breaking pulse as seed sources to obtain supercontinuum in tapered highly nonlinear fiber. After the taper is pulled, the core diameter will change from 9 μm to 6 μm. Since the peak power of the wave-free breaking pulse has been maintained at about 197 W, which can effectively avoid the pulse splitting caused by higher-order dispersion and nonlinear disturbance of the tapered high nonlinear fiber, and the spectrum can be effectively broadened by self-phase modulation. In the experiment, the total length of the tapered highly nonlinear fiber is 4 m, the waist area is 3 m, and the taper region is 1 m (Fig.2). The results show that the supercontinuum range and flatness produced by wave-free breaking pulse is better than dissipative soliton pulse in tapered highly nonlinear fiber (Fig.7). The supercontinuum range based on dissipative soliton pulse and wave-free breaking pulse is 1 400-2 000 nm covered communication region of S-band, C-band, and L-band. And the 20 dB bandwidth is 310.3 nm and 426.4 nm respectively.ConclusionA passively mode-locked structure of nonlinear polarization rotation is used to realize ultra-fast pulse output. And the conversion of dissipative soliton pulse and wave-free breaking pulse is realized through dispersion management. Under the mode-locked state of dissipative soliton pulse, the maximum output pulse energy is 0.82 nJ, and the peak power is 124.4 W. By adjusting the cavity parameters and increasing the pump power, the mode-locked state of wave-free breaking pulse can be realized. The pulse energy of wave-free breaking pulse can be increased to 3.89 nJ, which is 5 times of the energy of dissipative soliton pulse. In tapered HNLF, the flatness of supercontinuum generated by employing wave-free splitting pulse as seed source is better than dissipative soliton pulse. At the same time, the supercontinuum range covers three main communication bands (S-band, C-band and L-band). This flat supercontinuum is not only of great significance for the research of multi-channel wavelength division multiplexing light source applications, but also can be applied in biomedical imaging and other fields. This work will contribute to the development of high-energy pulse fiber lasers and improve their potential applications in supercontinuum generation and optical communication.
    Hang Ren, Tianshu Wang, Lei Du, Xin Li, Lin Xiao, Jianhong Zhou. Flat supercontinuum generation via wave-free breaking pulse in the optical fiber[J]. Infrared and Laser Engineering, 2023, 52(5): 20220745
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