Feng Xu

Bio: Feng Xu is an academic researcher from Beijing University of Posts and Telecommunications. The author has contributed to research in topics: Photonic-crystal fiber & Supercontinuum. The author has an hindex of 3, co-authored 8 publications receiving 38 citations.

Highly coherent supercontinuum generation in a polarization-maintaining CS2-core photonic crystal fiber.

Abstract: In this paper, we design a polarization-maintaining CS2-core photonic crystal fiber (PM-CCPCF). The two air holes in the x direction are infiltrated with C2H5OH in order to introduce birefringence. By optimizing the structure parameters of the PM-CCPCF, it is demonstrated that the x-polarization fundamental mode has an all-normal dispersion profile and the corresponding y-polarization fundamental mode has an anomalous dispersion profile for a pump wavelength of 1.76 μm. Then, we investigate the supercontinuum (SC) generations when different fiber lengths, pump peak powers, and pump pulse widths are chosen, respectively. Simulation results show that for the x-polarization and y-polarization fundamental modes, highly coherent SCs can be generated by appropriately choosing the fiber length and pump pulse parameters. Finally, nonlinear propagation dynamics are analysed when the optimized fiber length and pump pulse parameters are used. The bandwidth of the SCs generated for the x-polarization and y-polarization fundamental modes can be up to 0.82 and 1.26 octave, respectively.

Slow-Nonlinearity Assisted Supercontinuum Generation in a CS2-Core Photonic Crystal Fiber

Abstract: In this paper, we theoretically investigate the supercontinuum generations (SCGs) in a carbon disulfide (CS 2 )-core photonic crystal fiber (PCF). We show that the intrinsic slow nonlinearity of CS 2 plays a significant role to control the soliton fission process. The initiation of the soliton fission process can be distinctly delayed. More importantly, the transition between the smooth soliton fission and the sub-solitons' chaotic-like interference is sufficiently extended so that the optical spectrum can keep broadening continuously while still maintaining a smooth spectral profile. When pumping a designed CS 2 -core PCF at wavelength 1.55 μm in the anomalous dispersion region, we obtain temperature-controllable and highly coherent SCs spanning over one octave at the -30-dB spectral intensity. The unique feature of large slow nonlinearity and the controllable dispersion and nonlinearity of CS 2 -core PCF confirm that as a versatile platform for highly coherent and octave-spanning SCGs.

Mid-Infrared Self-Similar Pulse Compression in a Tapered Tellurite Photonic Crystal Fiber and Its Application in Supercontinuum Generation

Abstract: In this paper, we design a tapered tellurite photonic crystal fiber (TTPCF) with nonlinear coefficient increasing along the propagation direction, and demonstrate the mid-infrared self-similar pulse compression of the fundamental soliton in such a TTPCF. When the variation of group-velocity dispersion, higher-order dispersion, higher-order nonlinearity, and linear loss are considered, a 1 ps pulse at wavelength 2.5 μm can be compressed to 62.16 fs after a 1.63-m long propagation, along with the negligible pedestal, compression factor F c of 16.09, and quality factor Q c of 83.16%. Then the compressed pulse is launched into another uniform tellurite PCF, where highly coherent and octave-spanning supercontinuum (SC) is generated. Compared to the initial picosecond pulse, the compressed pulse has much larger tolerance of noise level for the SC generation. Our research results provide a promising solution to realize the fiber-based mid-infrared femtosecond pulse source for nonlinear photonics and spectroscopy.

Supercontinuum Generation in an All-Normal Dispersion Tellurite Photonic Crystal Fiber

Abstract: We design a tellurite photonic crystal fiber with all-normal dispersion profile for generating supercontinuum (SC). The octave-spanning SC can be generated when the pump pulses with different widths, peak powers, and center wavelengths are used.

Cascaded-tapered silica photonic crystal fiber for supercontinuum generation

Abstract: We propose the two-stage cascaded-tapered silica photonic crystal fiber (PCF) for the supercontinuum (SC) generation. The cascaded-tapered silica PCF is designed to have a spatial periodic structure. The physical scenarios of the spectral broadening due to the interaction between the structure-induced periodic dispersion and Kerr nonlinearity under different pulse widths and peak powers are investigated. It is found that when the pump pulses with width of <100 fs and peak power of not more than 10 kW are propagated in the cascaded-tapered silica PCF, the SC with good coherence can be generated. It is believed that the research results have potential applications in the nonlinear photonics and spectroscopy.

Supercontinuum generation, photonic crystal fiber

Abstract: A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Highly coherent supercontinuum generation in a polarization-maintaining CS2-core photonic crystal fiber.

Abstract: In this paper, we design a polarization-maintaining CS2-core photonic crystal fiber (PM-CCPCF). The two air holes in the x direction are infiltrated with C2H5OH in order to introduce birefringence. By optimizing the structure parameters of the PM-CCPCF, it is demonstrated that the x-polarization fundamental mode has an all-normal dispersion profile and the corresponding y-polarization fundamental mode has an anomalous dispersion profile for a pump wavelength of 1.76 μm. Then, we investigate the supercontinuum (SC) generations when different fiber lengths, pump peak powers, and pump pulse widths are chosen, respectively. Simulation results show that for the x-polarization and y-polarization fundamental modes, highly coherent SCs can be generated by appropriately choosing the fiber length and pump pulse parameters. Finally, nonlinear propagation dynamics are analysed when the optimized fiber length and pump pulse parameters are used. The bandwidth of the SCs generated for the x-polarization and y-polarization fundamental modes can be up to 0.82 and 1.26 octave, respectively.

Tailoring modulation instabilities and four-wave mixing in dispersion-managed composite liquid-core fibers.

Abstract: We show that the ultrafast nonlinear dynamics in supercontinuum generation can be tailored via mixture-based liquid core fibers. Samples containing mixtures of inorganic solvents allow changing dispersion from anomalous to normal, i.e., shifting zero dispersion across pump laser wavelength. A significant control over modulation instability and four-wave mixing has been demonstrated experimentally in record-long (up to 60 cm) samples in agreement with simulations when using sub-psec pulses at 1.555 µm. The smallest concentration ratio yields indications of soliton-fission based supercontinuum generation at soliton numbers that are beyond the coherence limit. The presented dispersion tuning scheme allows creating unprecedented dispersion landscapes for accessing unexplored nonlinear phenomena and selected laser sources.