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.

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.

Supercontinuum covering the ultraviolet-blue region is highly useful for fluorescence microscopy. Four zero-dispersion wavelength decreasing photonic crystal fibers with different fiber cross structures and taper profiles are fabricated to extend the short wavelength edge of supercontinuum. Both nanosecond and picosecond pump pulses at 1 μm are used to generate supercontinuum. With a 3 ns pump pulse, the short wavelength edge of supercontinuum is extended to below 400 nm in a fiber with high air-hole ratio (named T3). The underlying mechanism of supercontinuum generation is explored. The short and long wavelength edges of supercontinuum are highly related with the phase-matching condition which decided by the group velocity curve of fiber small core end. With a 10 ps pump pulse, the spectral intensity around ∼800 nm increases in all four fibers. However, the intensity in shorter wavelength band decreased in fibers with a high air-hole ratio (named T3, T4). The experimental results imply that a zero-dispersion wavelength decreasing photonic crystal fiber suitable for nanosecond pulse pumping is not necessarily suitable for picosecond pulse pumping, especially for fibers with high air-hole ratio.

The step-index heavily germanium-doped silica fibers with all normal dispersion (ANDi) are promising candidates for highly coherent supercontinuum (SC). These ANDi step-index silica fibers are easier to fabricate, splice and handle than silica photonic crystal fibers (PCFs). 40 % GeO2 doped step-index silica fiber of 3 μm core diameter has flat and near-zero dispersion which is between -5.5 and 0 ps/nm/km from 1.4 to 2.4 μm. Highly coherent SC spanning from 1050 nm to 2100 nm generated from the ANDi step-index heavily germanium-doped silica fiber pumped at 1560 nm. All-fiber coherent SC source from 1200 nm to 2200 nm is achieved by splicing the ANDi silica fiber with a 1560 nm femtosecond fiber laser of 90 % couple efficiency. Moreover, the step-index ANDi germania-core silica fiber of 2.2 μm core diameter is proposed to generate coherent mid-infrared SC from 1.7 to 3 μm. The ANDi step-index silica fibers not only can generate highly coherent broadband SC at near infrared or mid-infrared region but also can easily achieve all-fiber structure coherent SC source. And the experiment of supercontinuum generation in UNNA4 and UHNA7 fibers with different pump wavelengths indicates that the pump of 1064 nm is not suitable for coherent supercontinuum generation in the fiber of UNNA4 and UHNA7.

Supercontinuum generation (SCG) in an all-normal dispersion fiber possesses a high degree of coherence, which has several applications. Traditional air-hole photonic crystal fibers have some limitations for achieving such light emission. In this paper, hybrid fibers with a silica glass cladding and a yttria-alumino-silicate glass core, designed for flat coherent SCG, were fabricated. The core material features a high nonlinearity and a large refractive index difference with silica for dispersion engineering. We achieved a flat normal dispersion in this hybrid fiber. Flat supercontinuums (SCs) were generated under different pump conditions. Numerical studies coincided well with the experimental results. The simulated results indicate that the spectrum can extend to more than one octave with high input power. The generated SC spectrum has good coherence.

We proposed a method for flat supercontinuum (SC) in specified band based on non-degenerate Raman four-wave mixing (NRFWM) modulation. The dispersion of the photonic crystal fiber (PCF) and peak power of the pump light, are controlled such that the gain of the NRFWM falls in our desired band. This provides a new method for realizing SC with broadband hyperspectral intensities in the short-wavelength direction. By this method we developed a near-infrared flat SC. Its spectral intensity of 3 dB corresponds to a bandwidth of 420 nm at a central wavelength of 800 nm. In addition, the relative intensity of the anti-Stokes light is 75.2%, and 49.6 % of the total spectral energy is concentrated in the 610–1030 nm band, which provides a more effective light source for optical coherence tomography (OCT). Using this SC as the light source of OCT can improve the axial resolution to 0.8μm.