Yu Yongqin

Graphene-Oxide-Based Q-Switched Fiber Laser with Stable Five-Wavelength Operation

We demonstrate an erbium-doped ring-cavity fiber laser Q-switched by a graphene oxide-based saturable absorber (GOSA). The GOSA was fabricated by vertically evaporating GO-polyvinylalcohol (GO/PVA) composite dispersion, and has a good performance under room temperature. Utilizing a specially fabricated fiber Bragg grating (FBG), stable five-wavelength lasing is realized and stabilized at different pump powers under any polarization state. When the pump power increases from 78.4 mW to 379.3 mW, the output power ranging from 1.9 mW to 16.6 mW could be obtained, with pulse duration from 6.8 μs to 2.72 μs, single pulse energy from 123.73 nJ to 229.74 nJ, and pulse repetition rate from 15.36 kHz to 72.25 kHz. To the best of our knowledge, it is the first simultaneous realization of five-wavelength operation and pulse output in a GO Q-switched all fiber laser system.

Multi-wavelength graphene-based Q-switched erbium-doped fiber laser

We investigate on a multi-wavelength operation erbium-doped fiber laser Q-switched by a graphene-based saturable absorber. Stable pulses were generated with the widths from 6.9 to 1.5 μs, energies from 40.4 to 130.2 nJ and repetition rates from 68.32 to 132.9 kHz, when the pump power increased from 142.32 to 441.86 mW. A fiber Bragg grating with five reflective peaks was inserted into the fiber ring through an optical circulator, resulting in a stable output of five- lasing-wavelength output. The laser can perform as a low-cost and easy-built all fiber light source, and has potential applications in the fields where pulses at multi-wavelength operation are needed, i.e., temperature or strain fiber sensors.

Analysis on Temperature Sensing Properties of Photonic Crystal Fiber Based on Liquid Filling

提出了一种基于在折射率引导型光子晶体光纤(PCF)中填充高折射率温度系数液体的新型折射率型光纤温度传感器.通过建立理论模型,设定入射波长和材料参数及完美匹配层边界条件,采用全矢量有限元法对六角形结构排列的折射率引导型光子晶体光纤的温度特性进行了分析.研究表明,在空气孔中填充液体乙醇,PCF模场分布随着温度变化明显,其有效折射率和限制损耗都随着温度升高而减小.相同的孔间距,占空比越大,输入波长越长,有效折射率和限制损耗受温度影响越大.当波长为1500 nm,占空比为0.7,温度从-20℃升至70℃时,限制损耗从3.5×102dB/m减小到22 dB/m.

Microbending optical fiber sensors and their applications

Microbending optical fiber sensors based on bend-induced loss in optical fiber have proved themselves useful for detecting environmental changes. Many different mechanical elements have been developed to perform the sensing, each with attributes suitable for a particular application. The key structures and principles of microbending optical fiber sensors for special applications are introduced in this paper. It mainly includes strain sensor, liquid lever and pressure sensor, differential force and displacement sensor, and temperature sensor specially.

High Power Photonic Crystal Fibre Raman Laser

A cw Raman laser based on a 100-m photonic crystal fibre is demonstrated with up to 3.8 W output power at the incident pump power of 12 W, corresponding to an optical-to-optical efficiency of about 31.6%. The second order Stokes light, which is firstly reported in a cw photonic crystal fibre Raman laser, is obtained at 1183 nm with an output power of 1.6 W and a slope efficiency of about 45.7%.

Spectral Broadening in a Polarization-Maintaining Photonic Crystal Fibre by Femtosecond Pulses from an Optical Parametric Amplifier

The spectral broadening with the bandwidth of 83 nm (1.2486–1.3318 μm) in the 1.3 μm region is achieved in a 0.2-m-long, polarization-maintaining photonic crystal fibre (PCF) with an average core radius of 1.8 μm, pumped by optical pulses at the wavelength 1.269 μm, with the duration 250 fs and the repetition rate 250 kHz from an optical parametric amplifier. The polarization characteristics of the output spectra are also investigated.

A Low-Pump-Threshold Photonic Crystal Fibre Raman Laser

We investigate a photonic crystal fibre Raman laser using fibre Bragg grating pairs as cavity mirrors. The threshold pump power is up to 0.65 W by decreasing the cavity loss and using a photonic crystal fibre with high Raman gain coefficient. A maximum continuous-wave output power of 2.7 W is obtained at the maximum incident pump power of 5.6 W. The corresponding optical conversion efficiency and the slope efficiency are about 48% and 56%, respectively.