Real-time continuous-wave imaging with a 1.63THz OPTL and a pyroelectric camera

Real-time continuous-wave terahertz imaging is demonstrated with a 1.63 THz （184.31 lam） optically-pumped terahertz laser （OPTL） and a 124 × 124 element room-temperature pyroelectric camera. Transmission-mode THz imaging is presented for the samples hidden in various wrapping materials. These experimental results reveal the possibility to construct a simple real-time THz imaging system applied to nondestructive inspection.

A Switchable Multi-wavelength Erbium-Doped Photonic Crystal Fiber Laser with Linear Cavity Configuration

A switchable multi-wavelength erbium-doped photonic crystal fiber laser with a linear cavity configuration based on a Sagnac loop mirror is proposed and demonstrated experimentally.The laser is based on saturated spectral hole burning and the polarization hole burning effects can be switched among single-wavelength,dual-wavelength,triple-wavelength and quadruple-wavelength outputs at room temperature.The wavelength period of the output spectrum is easily varied by using polarization maintaining fibers of different lengths.The proposed fiber laser has a signal-to-noise ratio of higher than 30 dB and achieves a low threshold power of 37 mW.The power fluctuations of the lasing lines are less than 0.54 dB,1.7 dB and 2.9 dB when the laser operates at single-wavelength,dual-wavelength and triple-wavelength for one hour.

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.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 6.8μs to 2.72μs,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.

High-Stability Superfluorescent Fiber Source Based on an Er3+-Doped Photonic Crystal Fiber

A superfluorescent fiber source (SFS) based on an Er3+-doped photonic crystal fiber (EDPCF) is reported.Owing to the temperature insensitivity of the EDPCF,we show that it is possible to improve the mean wavelength stability of an SFS.Using single-backward configuration,the EDPCF SFS mean wavelength variation at temperatures from -40℃ to 60℃ is less than 100ppm,indicating that the thermal coefficient of the EDPCF is smaller than 1 ppm/℃ and 3-6 times smaller than those of two conventional Er3+-doped fibers under the same experimental conditions.The best performance of the EDPCF-based SFS is obtained between 0℃ and 60℃,at which the change in the mean wavelength is only 17.445 ppm.

Q-Switched Thulium-Doped Domestic Silica Fiber Laser

We report a cladding-pumped Tm^(3+)-doped domestic silica fiber laser operated at 2pm and actively Q-switched with an acousto-optic modulator.Pulse trains are obtained as pumped by a 785nm laser diode.The maximum average output power is 1.27W.Peak power up to 4.2kW and pulse energy up to 840μJ are obtained with the pulse duration of 200ns produced at a repetition rate of 1 kHz.The laser performance is studied under different repetition rates and pump powers.Lastly,we give some discussion.

H_(2)-Assistance One-Step Growth of Si Nanowires and Their Growth Mechanism

Large-scale nanowires are grown on Si wafers by the catalyst-free one-step thermal reaction method in Ar/H_(2) mixture atmosphere at 1000°C.The x−ray diffraction and energy dispersive x-ray spectroscopy results reveal that the final nanowires are of silicon nanostructures.The field emission scanning electron microscopy shows that these self-organized Si nanowires(SiNWs)possess curly crowns with diameters varying from 10 to 300 nm and lengths of up to several hundreds of micrometers.The transmission electron microscopy indicates that the nanowires are pure Si with amorphous structures.All the measurement results show that no silicon oxide is generated in our products.The growth mechanism is proposed tentatively.Silicon oxide is reduced into Si nanoparticles under the Ar/H_(2) mixture,which is the main reason for the formation of such SiNWs.Our experiments offer a method of preparing Si nanostructures by simply reducing silicon oxide at high temperature.