Mid-infrared frequency conversion via normal dispersion modulation instability in chalcogenide fibers has been numerically investigated by calculating the phase matching conditions and solving the generalized nonlinear Schrödinger equation. The core material of the chalcogenide fibers is As2Se3 and the cladding material is As2S5. Usually, the larger converted wavelength spacing between the pump and the far-detuned converted signal, the smaller gain. Therefore, the dispersion of the chalcogenide fibers are optimized to balance the gain and the converted signal wavelength spacing. The results show that the converted far-detuned mid-infrared signal can be tuned to 10 μm. The results also show that for a pumping source with the fixed wavelength, the far-detuned frequency conversion can be optimized by controlling the core size of step-index chalcogenide fibers. By using the simple step-index structure and controlling the core size of the chalcogenide fibers, the far-detuned mid-infrared frequency conversion can be achieved.
We experimentally demonstrate mid-infrared supercontinuum (SC) generation in chalcogenide multi-step index fibers (MSIF) pumped by a femtosecond laser. The fabricated chalcogenide MSIF is composed of a high refractive index core (C1) in the center, which is enclosed by a lower refractive index core layer (C2) and an outer cladding. This fiber structure is advantageous to tailor the chromatic dispersion with higher freedom and to keep the effective mode area small at long wavelengths. The high refractive index core, low refractive index core, and the outer cladding materials are As2Se3, AsSe2 and As2S5, respectively. When the diameter of C1 and C2 are 7.8 and 30 μm, respectively, the zerodispersion wavelength (ZDW) of the fiber is 12.5 μm. The chromatic dispersion profile is near-zero and flattened within the range of ±20 ps/km/nm in the wavelength range from 4 to 17 μm and a broad normal dispersion region is obtained in the wavelength range shorter than the ZDW. In practice, a 2.8 cm long fiber is pumped at 10 μm by using a femtosecond laser whose pulse width is ~200 fs. The SC generation extending from 2 to 14 μm is obtained. Most of its spectrum is in the normal dispersion region of the fiber. These results are promising for the highly coherent mid-infrared SC generation.
The supercontinuum generation and rogue wave generation in a step-index chalcogenide fiber are numerically investigated by solving the generalized nonlinear Schrödinger equation. Two noise models have been used to model the noise of the pump laser pulses to investigate the consistency of the noise modeling in rogue wave generation. First noise model is 0.1% amplitude noise which has been used in the report of rogue wave generation. Second noise model is the widely used one-photon-per-mode-noise and phase diffusion-noise. The results show that these two commonly used noise models have a good consistency in the simulations of rogue wave generation. The results also show that if the pump laser pulses carry more noise, the chance of a rogue wave with a high peak power becomes higher. This is harmful to the SC generation by using picosecond lasers in the chalcogenide fibers.
The novel property of the mid-infrared (MIR) higher-order soliton fission in a tapered tellurite microstructured optical fiber (TMOF) is experimentally investigated. The TMOF is tapered to offer an ideal environment for the formation of optical solitons. From ∼30 to 80 mW, the redshift of the first fundamental soliton (SSFS) is obvious. From ∼80 to 120 mW, two fundamental solitons are obtained by the fission of the higher-order solitons. The redshift of the first fundamental soliton almost stops because the increased pump power is preferentially distributed to the second fundamental soliton. From ∼120 to 180 mW, obvious redshift of the first fundamental soliton is observed again, and a third fundamental soliton is obtained at ∼180 mW. With the average pump power increasing to ∼220 mW, five fundamental solitons are observed.
We report the coherent mid-infrared supercontinuum generation in an all-solid chalcogenide microstructured fiber with all-normal dispersion. The chalcogenide microstructured fiber is four-hole structure with core material of AsSe2 and air holes are replaced by As2S5 glass rods. Coherent mid-infrared supercontinuum light is generated in a 2-cm-long chalcogenide microstructured fiber pumped by a 2.7 μm laser. The simulated and experimental results have a good match and the coherence property of supercontinuum light in the chalcogenide microstructured fiber has been studied by using the complex degree of coherence theory. Coherent mid-infrared supercontinuum generation is extended to 3.3 μm in this work.
Nonlinear optical polymers show promising potential applications in photonics, for example, electro-optical devices. Poly (methyl methacrylate) (PMMA) is widely used in optical waveguides, integrated optics and optical fibers. However, PMMA has not been used for nonlinear optical waveguides since it has a low nonlinear refractive index. We successfully prepared chalcogenide amorphous nanoparticles doped PMMA that had a high nonlinearity. The As3S7 bulk glass was dissolved in propylamine to form a cluster solution. Then the As3S7/propylamine solution was added into methyl methacrylate (MMA) containing photoinitiator Irgacure 184 about 0.5 wt%. After well mixing the As3S7 nanoparticle doped MMA was transparent. Under the irradiation by a 365 nm UV lamp, As3S7 nanoparticles doped PMMA was obtained with yellow color. The third-order nonlinear optical susceptibility of As3S7 nanoparticles doped PMMA was investigated. An optical waveguide array based on the As3S7 nanoparticles doped PMMA composite of high nonlinearity was fabricated.
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