Browsing by Author "Lin, Shih-Shian"

Now showing 1 - 4 of 4

Deep brain light stimulation effects on glutamate and dopamine concentration
(2015-01-01)
Kuo, Jinn-Rung
;
Lin, Shih-Shian
;
Liu, Janelle
;
Chen, Shih-How
;
Chio, Chung-Chin
Compared to deep brain electrical stimulation, which has been applied to treating pathological brain diseases, little work has been done on the effect of deep brain light stimulation. A fiber-coupled laser stimulator at 840 nm wavelength and 130 Hz pulse repetition rate is developed in this work for deep brain light stimulation in a rat model. Concentration changes in glutamate and dopamine in the striatum are observed using a microdialysis probe when the subthalamic nucleus (STN) is stimulated at various optical power levels. Experimental results show that light stimulation causes the concentration of glutamate to decrease while that of dopamine is increased. This suggests that deep brain light stimulation of the STN is a promising therapeutic strategy for dopamine-related diseases such as Parkinson's disease. The stimulator developed for this work is useful for deep brain light stimulation in biomedical research. (C) 2014 Optical Society of America
Generation of an octave-spanning supercontinuum in highly nonlinear fibers pumped by noise-like pulses
(2014-01-01)
Lin, Shih-Shian
;
Hwang, Sheng-Kwang
;
Liu, Jia-Ming
;
光電系統研究所
;
Institute of Photonic System
A supercontinuum generation system is developed, which consists of an erbium-doped fiber ring laser, an erbium-doped fiber amplifier, and a 100-m highly nonlinear fiber. Through nonlinear polarization rotation, the fiber ring laser generates a train of noise-like pulses in the form of repetitive picosecond pulse packets consisting of femtosecond noise-like fine temporal structures. The noise-like pulses are amplified before being sent into the highly nonlinear fiber. As a result, an octave-spanning supercontinuum from 1177 nm to 2449 nm is obtained, which has a 20-dB spectral width of 980 nm. Because of the nonlinearity of the fiber amplifier, the duration of the noise-like pulses is shortened while their average power is enhanced. However, the enhanced pulse energy makes the key contribution to the spectral broadening of the resulting spuercontinuum in this study since the highly nonlinear fiber is so long that the effect of the pulse compression on supercontinuum generation is weak.
High-power noise-like pulse generation using a 1.56-mu m all-fiber laser system
(2015-07-13)
Lin, Shih-Shian
;
Hwang, Sheng-Kwang
;
Liu, Jia-Ming
;
光電系統研究所
;
Institute of Photonic System
We demonstrated an all-fiber, high-power noise-like pulse laser system at the 1.56-mu m wavelength. A low-power noise-like pulse train generated by a ring oscillator was amplified using a two-stage amplifier, where the performance of the second-stage amplifier determined the final output power level. The optical intensity in the second-stage amplifier was managed well to avoid not only the excessive spectral broadening induced by nonlinearities but also any damage to the device. On the other hand, the power conversion efficiency of the amplifier was optimized through proper control of its pump wavelength. The pump wavelength determines the pump absorption and therefore the power conversion efficiency of the gain fiber. Through this approach, the average power of the noise-like pulse train was amplified considerably to an output of 13.1 W, resulting in a power conversion efficiency of 36.1% and a pulse energy of 0.85 mu J. To the best of our knowledge, these amplified pulses have the highest average power and pulse energy for noise-like pulses in the 1.56-mu m wavelength region. As a result, the net gain in the cascaded amplifier reached 30 dB. With peak and pedestal widths of 168 fs and 61.3 ps, respectively, for the amplified pulses, the pedestal-to-peak intensity ratio of the autocorrelation trace remains at the value of 0.5 required for truly noise-like pulses. (C) 2015 Optical Society of America
Supercontinuum generation in highly nonlinear fibers using amplified noise-like optical pulses
(2014-02-24)
Lin, Shih-Shian
;
Hwang, Sheng-Kwang
;
Liu, Jia-Ming
;
光電系統研究所
;
Institute of Photonic System
Supercontinuum generation in a highly nonlinear fiber pumped by noise-like pulses from an erbium-doped fiber ring laser is investigated. To generate ultrabroad spectra, a fiber amplifier is used to boost the power launched into the highly nonlinear fiber. After amplification, not only the average power of the noise-like pulses is enhanced but the spectrum of the pulses is also broadened due to nonlinear effects in the fiber amplifier. This leads to a reduction of the peak duration in their autocorrelation trace, suggesting a similar extent of pulse compression; by contrast, the pedestal duration increases only slightly, suggesting that the noise-like characteristic is maintained. By controlling the pump power of the fiber amplifier, the compression ratio of the noise-like pulse duration can be adjusted. Due to the pulse compression, supercontinuum generation with a broader spectrum is therefore feasible at a given average power level of the noise-like pulses launched into the highly nonlinear fiber. As a result, supercontinuum generation with an optical spectrum spanning from 1208 to 2111 nm is achieved using a 1-m nonlinear fiber pumped by amplified noise-like pulses of 15.5 MHz repetition rate at an average power of 202 mW. (C) 2014 Optical Society of America