Development of coherent mid-infrared source using chalcogenide photonic crystal fibers

Many molecule bonds have vibration frequencies in the mid-infrared band. Thus, this band is of great interest to molecular spectroscopy, material processing and medical applications. However, many optical materials typically used for laser sources experience high losses due to the presence of such vibration bonds making the design of mid-infrared coherent sources challenging. Such task is even more difficult when considering designing all-fiber sources which offer additional compactness and robustness. The goal of this project is to address such challenge by designing all-fiber mid-infrared sources based on chalcogenide fibers and nonlinear effects. Using degenerated parametric conversion of a 2 um pump and a telecom band signal laser, one can generate an idler in the mid-infrared band.

As a first step, the linear and nonlinear performances of several chalcogenide fibers were compared. The results prove the chalcogenide photonic crystal fiber design to be the ideal platform for this project as it offers high nonlinearity and low loss. Numerical simulations provide further improvement of photonic crystal geometry. Our improved designs allow for an extreme shaping of the dispersion to optimize the four-wave-mixing process within the thulium /holmium fiber laser band.

In the meantime, several cavity configurations were tested to boost the thulium/holmium laser performance, that are required for pumping of our chalcogenide fibers. Polarizer-free cavity designs result more compact laser footprint, which moreover enables a higher slope efficiency. Such lasers enable precise measurements of sample fiber optical parameters.

The combined efforts on fiber and laser optimization leads to efficient continuous-wave parametric conversion. Thanks to the excellent mid-infrared transmittance of chalcogenide glass, this high efficiency can be extended to longer pumps in mid-infrared. However, fiber fuse, a result of heat dissipative solitons, is the main constrain for reaching better conversion efficiency.

For ultrafast applications, a sub-cm length chalcogenide photonic crystal fiber generates flat-top, linearly chirped supercontinuum in the normal dispersion region. This pulse length could be compressed to two optical cycles by linear compression. Once again, the experimental results match perfectly with the simulations.

Overall, we show in this thesis that chalcogenide PCFs are promising for highly efficient and low threshold nonlinear optics in the middle infrared, offering new options for light generation in this critical wavelength band.

Mid-infrared continuous-wave parametric amplification in chalcogenide microstructured fibers

Camille Sophie Brès, Davide Grassani, Svyatoslav Kharitonov, Sida Xing

The persistent growth of interest in the middle infrared (MIR) is stimulating the development of sources and components. Novel waveguides and fibers for the efficient use of nonlinear effects in the MIR are being intensively studied. Highly nonlinear silica fibers have enabled record performances of highly versatile parametric processes in the telecommunication band. However, no waveguiding platforms (to our knowledge) have yet solved the trade-off among high nonlinearity, low propagation losses and dispersion in the MIR. As single waveguide designs have not yet hit this particular optimal point, only pulsed–pumped demonstrations have been carried out, hindering any application requiring narrow linewidth, continuous-wave (c.w.) operation, or signal modulation. Here, we show MIR c.w. parametric amplification in a Ge10As22Se68 tapered fiber. Leveraging state-of-the-art fabrication techniques, we use a photonic crystal fiber (PCF) geometry combining high nonlinearity and low dispersion, while maintaining single mode and low losses in the short-wave IR and MIR. We experimentally demonstrate 5 dB signal amplification and 3 dB idler conversion efficiency using only 125 mW of pump in the 2 μm wavelength range. Our result is not only the first c.w. parametric amplification measured at 2 μm in any waveguide, but it also establishes GeAsSe PCF tapers as the most promising all-fibered, high-efficiency parametric converter for advanced applications in the MIR. © 2017 Optical Society of America

2017

Characterization and modeling of microstructured chalcogenide fibers for efficient mid-infrared wavelength conversion

Adrien Billat, Camille Sophie Brès, Davide Grassani, Svyatoslav Kharitonov, Sida Xing

We experimentally demonstrate wavelength conversion in the 2 μm region by four-wave mixing in an AsSe and a GeAsSe chalcogenide photonic crystal fibers. A maximum conversion efficiency of −25.4 dB is measured for 112 mW of coupled continuous wave pump in a 27 cm long fiber. We estimate the dispersion parameters and the nonlinear refractive indexes of the chalcogenide PCFs, establishing a good agreement with the values expected from simulations. The different fiber geometries and glass compositions are compared in terms of performance, showing that GeAsSe is a more suited candidate for nonlinear optics at 2 μm. Building from the fitted parameters we then propose a new tapered GeAsSe PCF geometry to tailor the waveguide dispersion and lower the zero dispersion wavelength (ZDW) closer to the 2 μm pump wavelength. Numerical simulations shows that the new design allows both an increased conversion efficiency and bandwidth, and the generation of idler waves further in the mid-IR regions, by tuning the pump wavelength in the vicinity of the fiber ZDW.

Optical Society of America2016

Small core Chalcogenide photonic crystal fiber for midinfrared wavelength conversion: experiment and design

Adrien Billat, Camille Sophie Brès, Davide Grassani, Svyatoslav Kharitonov, Sida Xing

Kerr index and dispersion parameter of a small core chalcogenide photonic crystal fiber are estimated via four-wave mixing near 2μm. From these values, new fiber design is proposed to efficiently generate idlers in mid-infrared.

Ieee2016