Design of Fluorotellurite Microstructured Fibers With Near-Zero-Flattened Dispersion Profiles for Optical-Frequency Comb Generation

We present the design of fluorotellurite microstructured fibers (FTMFs) with near-zero-flattened dispersion profiles in the wavelength range of 1500-1600 nm for optical frequency comb (OFC) generation. The FTMFs are based on TeO
₂
-BaF
₂
-Y
₂
O
₃
glass with a zero-dispersion wavelength of ~2160 nm. The fiber core is surrounded by the two layers of air holes. The addition of large size air holes in the outer layer is to shift the zero-dispersion wavelength of the fiber from ~2160 nm to the wavelength region of 1500-1600 nm. The addition of small size air holes in the inner layer is to make the dispersion profile of the fiber become flat in the wavelength range of 1500-1600 nm. By optimizing the parameters (the core diameter, the air hole size, the pitch of air holes, etc.) of FTMFs, the fiber with the chromatic dispersion value between -0.5 and 0.3 ps/nm/km in the wavelength range of 1500-1600 nm is achieved. Furthermore, numerical simulations are used to show the potential of the fiber for OFC generation via cascaded four-wave mixing. Flat top OFC extending from 1500 to 1600 nm with tunable mode spacing from 25 to 100 GHz can be generated in a 2-m-long fiber by using a 1550-nm laser with a pulse width of 0.85 ps and a peak power of 49 W as the pump source. The effects of stimulated Brillouin scattering on OFC generation are also investigated.