CLEO 2018 Pacific Rim Ranmaru Ishida

Tu2E.2 Low loss bandwidth seven-cell hollow core photonic bandgap fiber at 1 μm spectral range(Beijing University of Technology)

Since there was a presentation on PBG fibers at the monthly meeting in July, I listened to two oral presentations including the one mentioned above for my own study on PBG fibers. I had thought that PBG fibers only have circular air holes in them, but recently, various structures are used for air holes in fibers, not only circular ones. In the above presentation, the loss was 26.7 dB/km at 1090 nm and the bandwidth was as high as 255 nm by fabricating HCPBG fiber with an appropriate structure. The content of the presentation was easy to understand, and the optimization at 1.55 μm is also in progress.

Compared with the loss of conventional optical fibers of 0.2 dB/km @ 1550 nm, PBG fibers have a large loss and a narrow wavelength bandwidth that can be used, and I had the impression that research on lowering the loss and broadening the bandwidth has been conducted since about 15 years ago. When I asked if it is possible to combine PBG fiber with rare-earth doping, he replied that there is a researcher who is working on "All-Solid PBG fiber" in which Yb and other elements are doped in place of air holes, and that it is also possible to have gain. It is also possible to have gain.

W4A.5 1GHz harmonic mode-locked fiber laser by using carbon nanotubes film saturable absorber(Shanghai University)

By incorporating a PVA film of SWCNTs as a saturable absorber into a fiber ring resonator, a harmonic passive mode-locked (HML) pulsed laser with a 34th order repetition rate of 916 MHz has been achieved. In the future, they intend to achieve higher repetition rates by optimizing the cavity dispersion and nonlinear effects. I heard about four presentations on passive mode-locking, and I had the impression that different researchers focused on different aspects such as peak intensity, threshold, efficiency (equivalent to the slope between input and output intensity), repetition frequency, polarization, and so on.

In this study, 98.2 cm Er110-4/125 was used as the gain fiber, and 311.2 cm SMF and 303 cm HI 1060 were used with a resonator length of 7.83 m. Pulse generation occurred at a pump light intensity of 87 mW at 980 nm, achieving 34th order HML at 327 m. The HML was achieved at 327 m. The order was increased by increasing the pump intensity. Although the order increases as the pump intensity is increased, it is still not easy to maintain a stable HML.

Erbium can be pumped at 1480 nm and 980 nm, with the former having higher energy efficiency and the latter having lower noise.

... and upwards