High flatness, wide bandwidth, and high-coherence properties of supercontinuum (SC) generation in fibers are crucial in many applications. It is challenging to achieve SC spectra in a combination of the properties, since special dispersion profiles are required, especially when pump pulses with duration over 100 fs are employed. We propose an all-solid microstructured fiber composed only of hexagonal glass elements. The optimized fiber possesses an ultraflat all-normal dispersion profile, covering a wide wavelength interval of approximately 1.55 μm. An SC spectrum spanning from approximately 1030 to 2030 nm (corresponding to nearly one octave) with flatness <3 dB is numerically generated in the fiber with 200 fs pump pulses at 1.55 μm. The results indicate that the broadband ultraflat SC sources can be all-fiber and miniaturized due to commercially achievable 200-fs fiber lasers. Moreover, the SC pulses feature high coherence and a single pulse in the time domain, which can be compressed to 13.9-fs pulses with high quality even for simple linear chirp compensation. The Fourier-limited pulse duration of the spectrum is 3.19 fs, corresponding to only 0.62 optical cycles.

Optical neural networks (ONNs) are particularly advantageous owing to their inherent parallelism and low energy consumption. However, one of the obstacles to the implementation of ONNs is the lack of optical nonlinearity. In this study, optical nonlinear activators for ONNs are prepared by combining Ti3C2Tx MXene with microfibers and their principles are verified. Activation functions obtained from experimental measurements are used to simulate multiclassification and super‐resolution reconstruction tasks with performance comparable to that of activation functions commonly used in computers. Four necessary criteria are proposed and validated for evaluating the performance of the nonlinear activator: recovery time, deviation from linearity, the activation function close to identity mapping, and reconfigurability of the configuration. Theoretically, the nonlinear activator can compute 100 times faster than commonly used electronic computers and can be used as a nonlinear activation unit for ONNs to help the integration of ONNs with artificial intelligence.

Wavelength conversion to the wavelength range that is not covered by commercially available lasers could be accomplished through the soliton self-frequency shift (SSFS) effect. In this study, the phenomenon of SSFS pumped by a picosecond-order pulse in a tellurite microstructured fiber is investigated both theoretically and experimentally. The balance between the dispersion and the nonlinearity achieved by a 1958 nm pump laser induces a distinct SSFS effect. Attributed to the large spectral distance between the pump pulse and the fiber zero-dispersion wavelength, the SSFS is not cancelled due to energy shedding from the soliton to the dispersive wave. Details about the physical mechanisms behind this phenomenon and the variations of the wavelength shift, the conversion efficiency are revealed based on numerical simulations. Owing to the large soliton number N, the pulse width of the first split fundamental soliton is approximately 40 fs, producing a pulse compression factor of ∼38, much higher than that pumped by a femtosecond pulse. Experiments were also conducted to confirm the validity of the simulation results. By varying the pump power, a continuous soliton shift from 1990 nm to 2264 nm was generated. The generation of SSFS in tellurite microstructured fibers with picosecond pump pulse can provide a new approach for wavelength conversion in the mid-infrared range and could be useful in medical and some other areas.

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A broadband supercontinuum (SC) covering 400–2800 nm in a 20 dB dynamic range is reported in a piece of highly nonlinear, low-dispersion bulk lanthanum glass without employing any lens to focus the pump pulse. The spectrum width obtained in this study is broader than the maximum spectrum width obtained in silica photonic crystal fibers. The filaments and bright conical visible emission patterns of the SC are analyzed. Under optimum pump conditions, an SC conversion efficiency of 75% is obtained. The SC conversion efficiency is confirmed to be stable. Additionally, the relationship between the input peak intensity and the output beam radius is elucidated by simulating the propagation of a Gaussian beam in the bulk lanthanum glass. A 0.20 mm stable laser beam radius at the end of the propagation domain is demonstrated in a certain input peak intensity range. This small value of the beam radius indicates that most of the output power is localized over a small region because of the Kerr focusing effect despite the existence of conical emission in the SC generation by filamentation. The findings of this study are of significance for the development of ultra-broadband SC sources based on bulk glasses and high peak power lasers.

We selected two thermally matched silicate glasses with fair refractive index contrast and developed an asterisk-shaped all-solid microstructured optical fiber. The fiber presents a low, ultra-flat, and all-normal dispersion in a wide wavelength range, allowing for the generation of an octave-spanning coherent supercontinuum (SC) in a 20 dB dynamic range with 0.5 ps pump pulses at 1.55 μm. This result improves pump pulse duration that is only ∼100  fs, related to the broadband and highly coherent SC generation in fibers with all-normal dispersion. This enables broadband SC sources with all-fiber, high-power, and highly coherent properties.

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