Cadmium Selenide Polymer Microfiber Saturable Absorber for Q-Switched Fiber Laser Applications

We demonstrate the generation of a Q-switching pulse train in an erbium-doped fiber laser （EDFL） cavity using a newly developed cadmium selenide （CdSe） based saturable absorber （SA）. The SA is obtained by embedding CdSe nanomaterials into a polymethyl methacrylate （PMMA） microfiber. It is incorporated into an EDFL cavity to generate a Q-switched laser operating at 1533.6nm. The repetition rates of the produced pulse train are tunable within 37–64kHz as the pump power is varied from 34mW to 74mW. The corresponding pulse width reduces from 7.96μs to 4.84μs, and the maximum pulse energy of 1.16nJ is obtained at the pump power of 74mW.

In situ polymerization of aniline in electrospun microfibers

Conductive microfibers with an average diameter of ca. 1.0 μm were prepared by in situ polymerization of aniline, in which poly（vinylchloride-acrylonitrile） （PVC-AN） was used as the filament-material in electrospinning to form precursor microfibers and carry the aniline monomers. Fourier-transform infrared （FTIR） results demonstrated that PANi was successfully polymerized in the microfibers. The morphology of the PVC-AN-PANi microfibers was observed by scanning electron microscopy （SEM）. Results of differential scanning calorimetry indicated that the polymer composite of PVC-AN-PANi formed via molecular interactions. Although the conductivity of PVC-AN-PANi microfibers was still limited （2.2 × 10^-8 S/cm）, this method provided an effective and convenient approach for preparing highly uniform and soft microfibrous electrodes.

Long-period grating inscription on polymer functionalized optical microfibers and its applications in optical sensing

We demonstrated long-period grating(LPG) inscription on polymer functionalized optical microfibers and its applications in optical sensing. Optical microfibers were functionalized with ultraviolet-sensitive polymethyl methacrylate jackets and, thus, LPGs could be inscribed on optical microfibers via point-by-point ultraviolet laser exposure. For a 2 mm long microfiber LPG(MLPG) inscribed on optical microfibers with a diameter of 5.4 μm, a resonant dip of 15 d B at 1377 nm was observed. This MLPG showed a high sensitivity of strain and axial force, i.e.,-1.93 pm∕με and-1.15 pm∕μN, respectively. Although the intrinsic temperature sensitivity of the LPGs is relatively low, i.e.,-12.75 pm∕°C, it can be increased to be-385.11 pm∕°C by appropriate sealing. Benefiting from the small footprint and high sensitivity, MLPGs could have potential applications in optical sensing of strain,axial force, and temperature.

Printable microlaser arrays with programmable modes for information encryption

Lasing emissions with multiple and tunable modes are promising in coding field as a novel cryptographic primitive.With the advantages of simple fabrication,full-color and high-quality-factor whispering gallery mode lasing inside a circular cross-section,polymer microfibers are attractive for photonic devices.However,polymer lasing microfibers for information encryption have never been reported.Herein,we propose a design of printable lasing microfiber encryption chip by in-situ tuning the effective refractive index of the microresonator arrays via a facile approach.Through inkjet printing high-refractive-index nanoparticles on the designated position of lasing microfiber arrays,the effective refractive index of the microcavities is regulated,and the ratio of wavenumber spacing between transverse electric and transverse magnetic mode to the free spectral range can be modulated,particularly with neglectable influence by the size factor.Thus,the programmable region selective encoding process can be conducted simply by a printing program within several minutes.Besides,the encoded microfiber arrays are encapsulated into polydimethylsiloxane to reduce the scattering loss and environmental interference,and a printable encryption chip is realized.This work is expected to provide a platform for the printable encrypted devices.