Tonglei Cheng

Mid-infrared supercontinuum generation in a suspended-core As2S3 chalcogenide microstructured optical fiber.

We demonstrate the supercontinuum (SC) generation in a suspended-core As(2)S(3) chalcogenide microstructured optical fiber (MOF). The variation of SC is investigated by changing the fiber length, pump peak power and pump wavelength. In the case of long fibers (20 and 40 cm), the SC ranges are discontinuous and stop at the wavelengths shorter than 3500 nm, due to the absorption of fiber. In the case of short fibers (1.3 and 2.4 cm), the SC ranges are continuous and can extend to the wavelengths longer than 4 μm. The SC broadening is observed when the pump peak power increases from 0.24 to 1.32 kW at 2500 nm. The SC range increases with the pump wavelength changing from 2200 to 2600 nm, corresponding to the dispersion of As(2)S(3) MOF from the normal to anomalous region. The SC generation is simulated by the generalized nonlinear Schrödinger equation. The simulation includes the SC difference between 1.3 and 2.4 cm long fiber by 2500 nm pumping, the variation of SC with pump peak power in 2.4 cm long fiber, and the variation of SC with pump wavelength in 1.3 cm long fiber. The simulation agrees well with the experiment.

Mid-infrared supercontinuum generation spanning 2.0 to 15.1 μm in a chalcogenide step-index fiber.

We experimentally demonstrate mid-infrared (MIR) supercontinuum (SC) generation spanning ∼2.0 to 15.1 μm in a 3 cm-long chalcogenide step-index fiber. The pump source is generated by the difference frequency generation with a pulse width of ∼170  fs, a repetition rate of ∼1000  Hz, and a wavelength range tunable from 2.4 to 11 μm. To the best of our knowledge, this is the broadest MIR SC generation observed so far in optical fibers. It facilitates fiber-based applications in sensing, medical, and biological imaging areas.

Coherent mid-infrared supercontinuum generation in all-solid chalcogenide microstructured fibers with all-normal dispersion

We report the coherent mid-infrared supercontinuum generation in an all-solid chalcogenide microstructured fiber with all-normal dispersion. The chalcogenide microstructured fiber is a four-hole structure with core material of AsSe2 and air holes that are replaced by As2S5 glass rods. Coherent mid-infrared supercontinuum light extended to 3.3 μm is generated in a 2 cm long chalcogenide microstructured fiber pumped by a 2.7 μm laser.

Fabrication and characterization of a hybrid four-hole AsSe 2 -As 2 S 5 microstructured optical fiber with a large refractive index difference

A hybrid four-hole AsSe2-As2S5 microstructured optical fiber (MOF) with a large refractive index difference is fabricated by the rod-in-tube drawing technique. The core and the cladding are made from the AsSe2 glass and As2S5 glass, respectively. The propagation loss is ~1.8 dB/m and the nonlinear coefficient is ~2.03 × 10(4) km(-1)W(-1) at 2000 nm. Raman scattering is observed in the normal dispersion regime when the fiber is pumped by a 2 μm mode-locked picosecond fiber laser. Additionally, soliton is generated in the anomalous dispersion regime when the fiber is pumped by an optical parametric oscillator (OPO) at the pump wavelength of ~3000 nm.

Broadband cascaded four-wave mixing and supercontinuum generation in a tellurite microstructured optical fiber pumped at 2 μm

We demonstrate the broadband cascaded four-wave mixing (FWM) and supercontinuum (SC) generation in a tellurite MOF which is made from 76.5TeO(2)-6ZnO-11.5Li(2)O-6Bi(2)O(3) (TZLB, mol%) glass. By using a 2-μm picosecond laser with the center wavelength of ~1958 nm as the pump source, the broadband FWM with the frequency separation of ~1.1 THz is obtained. The bandwidth of the frequency comb spans a range of ~630 nm from ~1620 to 2250 nm at the average pump power of ~125 mW. With the average pump power increasing to ~800 mW, the broadband mid-infrared SC generation with the spectrum from ~900 to 3900 nm is observed. Changing the pump source to a femtosecond laser (optical parametric oscillator, OPO) with the center wavelength of ~2000 nm, solitons and dispersive waves (DWs) are obtained.

Mid-infrared supercontinuum generation in a novel AsSe 2 -As 2 S 5 hybrid microstructured optical fiber

A four-hole AsSe₂-As₂S₅ hybrid microstructured optical fiber (HMOF) with a large refractive index difference is fabricated by the rod-in-tube drawing technique. The core and the cladding are made from the AsSe₂ glass and As₂S₅ glass, respectively. The propagation loss is ~1.2 dB/m and the nonlinear coefficient is ~4.937×10⁴ km^-1W^-1 at ~3000 nm. Zero dispersion wavelength (ZDW) of the HMOF is ~3380 nm. Supercontinuum (SC) generation in the HMOF is investigated by pumping a 2 cm-long AsSe₂-As₂S₅ HMOF with the wavelengths of ~3062, 3241 and 3389 nm from a tunable optical parametric oscillator (OPO) system. Broadband mid-infrared SC generation with the spectrum from ~1256 to 6385 nm is obtained with the peak power of ~1337 kW at the wavelength of ~3389 nm.

Ultrabroad supercontinuum generation through filamentation in tellurite glass

Although soft glass such as tellurite or chalcogenide glass is transparent in the range of 3–6 μm, fiber made of it is difficult to generate as a supercontinuum (SC) to that range because of the high loss, the wavelength limit of the pump source, and the challenges in light-coupling. To circumvent these problems, we developed an SC light source by using tellurite bulk glass through filamentation. For this scheme, the optical path length in the glass is very short due to the adopted high pump power, so the negative influence of material loss is reduced greatly. The light-coupling is straightforward, and the coupling efficiency is high. The bulk glass for SC generation is cheap, and can be fabricated easily. We have shown that under suitable pump conditions, the SC generation by filamentation can cover from visible to 6 μm. It is the broadest SC generation by tellurite (including glass and fiber). For suitable pump conditions, the glass was free of optical breakdown. If the interface reflections were deducted, the SC conversion efficiency was 87%; the SC conversion efficiency was stable. To the best of our knowledge, this is the first report on filamentation in tellurite glass which has a comparatively small bandgap.

Soliton self-frequency shift and third-harmonic generation in a four-hole As 2 S 5 microstructured optical fiber

Soliton self-frequency shift (SSFS) and third-harmonic generation (THG) are observed in a four-hole As2S5 chalcogenide microstructured optical fiber (MOF). The As2S5 MOF is tapered to offer an ideal environment for SSFS. After tapering, the zero-dispersion wavelength (ZDW) shifts from 2.02 to 1.61 μm, and the rate of SSFS can be enhanced by increasing the energy density of the pulse. By varying the average input power from 220 to 340 mW, SSFS of a soliton central wavelength from 2.206 to 2.600 μm in the mid-infrared is observed in the tapered segment, and THG at 632 nm is observed in the untapered segment.

Soliton self-frequency shift and dispersive wave in a hybrid four-hole AsSe2-As2S5 microstructured optical fiber

A hybrid four-hole AsSe2-As2S5 microstructured optical fiber (MOF) is fabricated by the rod-in-tube drawing technique. The core is made of AsSe2 glass and the cladding is made of As2S5 glass. The material refractive indices of the core and the cladding are ∼2.832 and ∼2.219 at the wavelength of ∼2.8 μm, respectively. The calculated zero-dispersion wavelength of the AsSe2-As2S5 MOF is 2.759 μm. Soliton self-frequency shift with a soliton central wavelength from 2.986 to 3.419 μm is observed when the AsSe2-As2S5 MOF is pumped by an optical parametric oscillator at the pump wavelength of ∼2.8 μm. At the same time a blue-shift dispersive wave is emitted by the soliton.

A simple all-solid tellurite microstructured optical fiber

A simple all-solid tellurite microstructured optical fiber which has only one layer of high-index rods in the cladding is proposed and fabricated in the paper. The core and the cladding with the low index are made from the TeO(2)-ZnO-Na(2)O-La(2)O(3) glass, and the high-index rods are made from the TeO(2)-Li(2)O-WO(3)-MoO(3)-Nb(2)O(5) glass. The guiding regime in this fiber can be explained by ARROW model. The fiber can support the near- and mid-infrared light transmitting in the core within the transmission bands while the all-solid silica microstructured optical fiber cannot. When the pump light is outside the transmission bands, the light will transmit in six TLWMN rods.