An All Fiber 1.94µm Nanosecond Pulse Laser Amplified by Highly Tm^(3+)-Doped Silicon Fibers

We present an all-fiber 1.94μm nanosecond pulse laser in master oscillation-power amplifier configuration.A dual-FBGs gain-switched Tm^(3+)-doped fiber laser is built and is used as the seed laser.The output characteristics of the amplifier are studied at different pulse repetition rates,and the maximum output energy of 500μJ is achieved under incident pump power of 39 W.The emitting spectra are checked at 5 and 10 kHz,and no obvious nonlinear effects are observed in the spectrum of the amplified laser.The beam quality factor is M^(2)=2.1±0.03 measured by the traveling knife-edge method,and the laser beam spot is also monitored by an infrared vidicon camera.

All-Fiber Gain-Switched Thulium-Doped Fiber Laser Pumped by 1.558 μm Laser

We present an all-fiber gain-switched thulium (Tm) doped fiber laser operating in the eye-safe region at 1940nm.The fibre Bragg gratings (FBGs) inscribed by phase mask technology are used as cavity mirrors,and the transmission spectra of FBGs are also measured.The output cbaracteristics are studied at pulse repetition frequene cies of 10,20 and 30kHz,and the maximum output powers of 28.9,67.0 and 71.0mW are achieved under incident pump powers of 122,247and 250mW.The narrowest pulse width of29ns and shortest pulse built-time of 140 ns are obtained at 10 kHz.The relation between pulse built-time and cavity length are discussed.

Acousto-Optic Q-Switched Operation Ho:YAP Laser Pumped by a Tm-Doped Fiber Laser

We report on the acousto-optic Q-switched operation of a Ho:YAP laser double-passed pumped by an all-fiber Tm-doped fiber laser.The output characteristics of the Ho:YAP laser are studied at pulse repetition frequencies of 1,2,5 and 10 kHz.The shortest pulse width,the maximum pulse energy and the highest peak power are measured to be 17 ns,1.71 mJ and 71.25 kW,respectively.The output wavelength is centered at 2115.96 nm with a bandwidth of about 1.5 nm.The beam quality factor M^(2)=2.41±0.03 at the output power of 3.54 W was measured by using the traveling knife-edge method.

Neural Mechanism in Emotion Regulation by Simultaneous Recording of EEG and fMRI

The combination of electroencephalogram (EEG) and functional magnetic resonance imaging(fMRI) is a very attractive aim in neuroscience in order to achieve both high temporal and spatial resolution for the non-invasive study of cognitive brain function. In this paper, we record simultaneous EEG-fMRI of the same subject in emotional processing experiment in order to explore the characteristics of different emotional picture processing, and try to find the difference of the subjects' brain hemisphere while viewing different valence emotional pictures. The late positive potential(LPP) is a reliable electrophysiological index of emotional perception in humans. According to the analysis results, the slow-wave LPP and visual cortical blood oxygen level-dependent (BOLD) signals are both modulated by the rated intensity of picture arousal. The amplitude of the LPP correlate significantly with BOLD intensity in visual cortex, amygdala, temporal area, prefrontal and central areas across picture contents.