Wuqi Wen

Surface Plasmon Resonance Sensor Based on Polymer Photonic Crystal Fibers with Metal Nanolayers

A large-mode-area polymer photonic crystal fiber made of polymethyl methacrylate with the cladding having only one layer of air holes near the edge of the fiber is designed and proposed to be used in surface plasmon resonance sensors. In such sensor, a nanoscale metal film and analyte can be deposited on the outer side of the fiber instead of coating or filling in the holes of the conventional PCF, which make the real time detection with high sensitivity easily to realize. Moreover, it is relatively stable to changes of the amount and the diameter of air holes, which is very beneficial for sensor fabrication and sensing applications. Numerical simulation results show that under the conditions of the similar spectral and intensity sensitivity of 8.3 × 10−5–9.4 × 10−5 RIU, the confinement loss can be increased dramatically.

Continuous-wave operation at 1386 nm in a diode-end-pumped Nd:YVO4 laser.

We report a diode-end-pumped continuous wave (cw) Nd:YVO4 laser operation at 1386 nm. A maximum output power of 305 mW is achieved at an incident pump power of 4.24 W, achieving a slope efficiency of 13.9%. To the best of our knowledge, this is the first time that cw operation at this transition of Nd:YVO4 crystal is reported. By using the experimentally measured threshold data, the stimulated-emission cross-section of this gain medium at 1386 nm transition is determined to be 3x10- 19cm2. In addition, simultaneous cw operation at 1342 nm and 1386 nm is also observed.

8.3 W diode-end-pumped continuous-wave Nd:YAG laser operating at 946-nm

This paper reports a diode-end-pumped continuous-wave (CW) Nd:YAG laser operating at 946-nm by utilizing the 4F3/2-4I9/2 transition. We demonstrated that at an incident pump power of 27.7 W, an output power of 8.3-W could be achieved with a slope efficiency of 33.5%. To the best of our knowledge, this is the highest CW output power at 946 nm generated by LD end-pumped Nd:YAG lasers. By using intracavity frequency doubling with an LBO crystal, we further obtained a 473-nm blue laser with an output power of 1.2 W, achieving an optical-to-optical conversion efficiency of 7.1% at a pump power of 16.9 W. The short-term power instability of the blue laser was less than 1 %.

Grapefruit fiber filled with silver nanowires surface plasmon resonance sensor in aqueous environments.

A kind of surface plasmon resonance sensor based on grapefruit photonic crystal fiber (PCF) filled with different numbers of silver nanowires has been studied in this paper. The surface plasmon resonance modes and the sensing properties are investigated comprehensively using the finite element method (FEM). The simulation results show that the intensity sensitivity is related to nanowire numbers and the distance between two nanowires. The optimum value obtained is 2,400 nm/RIU, corresponding to a resolution of 4.51 × 10−5 RIU with a maximum distance of 2 μm. To a certain extent, the PCF filled with more nanowires is better than with just one. Furthermore, the air holes of grapefruit PCF are large enough to operate in practice. Moreover, the irregularity of the filled nanowires has no effect on sensitivity, which will be very convenient for the implementation of experiments.

High-efficiency direct-pumped Nd:YVO 4 laser operating at 1.34 μm

We report a high-efficiency Nd:YVO4 laser operating at 1342 nm pumped by an all-solid-state Q-switched Ti:Sapphire laser at 879 nm. A plano-concave cavity was optimized to obtain high efficiency and good beam quality. Output power for two Nd:YVO4 crystals with 1.0- and 3.0-at.% Nd3+ doping under 879-nm pumping was measured respectively. Comparative results obtained by traditional pumping at 808 nm into the highly absorbing 4F5/2 level were presented, showing that the slope efficiency of the 1.0-at.% Nd:YVO4 laser under 879-nm pumping was 10.5% higher than that of 808-nm pumping. In a 4-mm-thick, 1.0-at.% Nd:YVO4 crystal, a high slope efficiency of 64% was achieved under 879- nm pumping, with an optical-to-optical conversion efficiency of 41.3%.

Continuous-wave mid-infrared intra-cavity singly resonant PPLN-OPO under 880 nm in-band pumping

We report herein a continuous-wave mid-infrared intra-cavity singly resonant optical parametric oscillator (ICSRO) which is the first example of ICSRO that utilize in-band pumped Nd-doped vanadate laser as pump source. A 1064 nm Nd:YVO₄ laser in-band pumped by 880 nm LD and a periodically poled lithium niobate (PPLN) crystal are employed as the parent pump laser and the nonlinear medium, respectively. The idler output wavelength tuning range is 3.66-4.22 µm. A maximum output power of 1.54 W at 3.66 µm is obtained at absorbed pump power of 21.9 W, with corresponding optical efficiency being 7.0%. The control experiment of ICSRO under 808 nm traditional pumping is also carried out. The results show that in-band pumped ICSRO has better performance in terms of threshold, power scaling, efficiency and power stability than ICSRO traditionally pumped at 808 nm.

Multi-wavelength generation based on cascaded Raman scattering and self-frequency-doubling in KTA

A multi-wavelength laser is developed based on cascaded stimulated Raman scattering (SRS) and self-frequency-doubling in an x-cut KTA crystal pumped by an A-O Q-switched Nd:YAG laser. The generation of 1178 nm from cascaded SRS of 234 and 671 cm−1 Raman modes is observed. The six wavelengths, including the fundamental 1064 nm, four Stokes waves at 1091, 1120, 1146, 1178 nm, and the second harmonic generation (SHG) of 1146 nm, are tens to hundreds of millwatts for each at 10 kHz, corresponding to a total conversion efficiency of 8.72%.

Generation of 3.5W high efficiency blue-violet laser by intracavity frequency-doubling of an all-solid-state tunable Ti:sapphire laser

In this paper, we report a high power, high efficiency blue-violet laser obtained by intracavity frequency-doubling of an all-solid-state Q-switched tunable Ti:sapphire laser, which was pumped by a 532 nm intracavity frequency-doubled Nd:YAG laser. A beta-BaB2O4 (BBO) crystal was used for frequency-doubling of the Ti:sapphire laser and a V-shape folded three-mirror cavity was optimized to obtain high power high efficiency second harmonic generation (SHG). At an incident pump power of 22 W, the tunable output from 355 nm to 475 nm was achieved, involving the maximum average output of 3.5 W at 400 nm with an optical conversion efficiency of 16% from the 532 nm pump laser to the blue-violet output. The beam quality factor M(2) was measured to be Mx(2)=2.15, My(2)=2.38 for characterizing the tunable blue laser.

Continuous-wave intra-cavity singly resonant optical parametric oscillator with resonant wave output coupling

We report herein the enhancement in both power and efficiency performance of a continuous-wave intra-cavity singly resonant optical parametric oscillator (ICSRO) by introducing finite resonant wave output coupling. While coupling out the resonant wave to useful output, the output coupling increases the SRO threshold properly thus suppresses the back-conversion under high pump power. Therefore, the down-conversion efficiency is maintained under high pump without having to raise the threshold by defocusing. With a T = 9.6% signal wave output coupler used, the SRO threshold is 2.46 W and the down-conversion efficiency is 72.9% under the maximum pump power of 21.4 W. 1.43 W idler power at 3.66 μm and 5.03 W signal power at 1.5 μm are obtained, corresponding to a total extraction efficiency of 30.2%. The resonant wave out coupling significantly levels up the upper limit for the power range where the ICSRO exhibits high efficiency, without impeding its advantage of low threshold.

Efficient Nd:YVO4 self-Raman laser in-band pumped by wavelength-locked laser diode at 878.7 nm

A frequency-doubled Nd:YVO4 self-Raman laser in-band pumped by an 878.7 nm wavelength-locked laser diode (LD) is demonstrated, with the purpose of improving the pump absorption of in-band pumping and thus enhancing optical efficiency. 2.64 W average output power at 588 nm is obtained under incident LD power of 9.7 W, corresponding to an optical efficiency of 27.2%. The results of control experiments show that in-band pumping leads to higher conversion efficiency of a self-Raman laser than does traditional pumping. Moreover, the application of a wavelength-locked LD further improves optical efficiency significantly.