Jinhuan Li

Au/Ag nanoalloy shells as near-infrared SERS nanoprobe for the detection of protein

We provide a highly sensitive, uniform and reproducible surface-enhanced Raman scattering (SERS) performance obtained from the randomly aggregated Au/Ag nanoalloy shells substrate. Au/Ag nanoalloy shells consist of SiO2 core and Au/Ag alloy shells layer. The obtained Au/Ag nanoalloy shells with a monodisperse size distribution exhibit different morphology by the analysis of TEM. By changing the ratio of Au and Ag, the plasmonic extinction of Au/Ag nanoshells varied in near-infrared window region. In this experiment, Au/Ag nanoshells with controllable ratio can obtain larger SERS signals, which can be used for ultrasensitive detection of biomolecules. These SERS-active spheres show interesting properties as a novel Raman tag for immunoassays.

555 nm laser sources based on intracavity frequency doubling of Nd:YGG laser

We report for the first time a yellow-green laser at 555 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a 1110 nm Nd-doped yttrium gallium garnet (Nd:YGG) laser under in-band diode pumping at 808 nm. An LBO crystal, cut for critical type I phase matching is used for second harmonic generation of the laser. At an incident pump power of 18.5 W, as high as 2.31 W of CW output power at 555 nm is achieved. The optical-to-optical conversion efficiency is up to 12.4%, and the fluctuation of the yellow-green output power was better than 2.8% in the given 4 h.

Measurement of a cross-sectional profile of a thread gauge using a sinusoidally vibrating interference pattern

A sinusoidally vibrating interference pattern (SVIP) is used as an exact spatial scale in order to measure a cross-sectional profile of a thread gauge. The SVIP is projected on the thread gauge surface, and lights diffracted and reflected from the end points of the thread gauge surface are extracted by spatial frequency filtering in an imaging system to make an image of the end points whose positions are decided by the peak positions of amplitude distributions in the image. The coordinates of the end points or the cross-sectional profile of the thread gauge is obtained from the phases measured at the positions of the end points, phase distribution of the SVIP on a CCD image sensor, and the pixel positions of the CCD image sensor.

The effect of Au nanoshells with controllable aggregation on SERS enhancement

Au nanoshells consisting of a dielectric core with a metallic layer of nanometer thickness exhibit tunable local surface plasmon resonance property. The core size has a great effect on the aggregation state of formed Au nanoshells, which leads to the variation of the intensity of surface enhanced Raman scattering (SERS). This paper reports a controllable aggregation for the fabrication of Au nanoshells with different size of core. TEM results demonstrated that formed Au nanoshells showed obvious aggregation with decreasing the size of core. By SERS analysis, different aggregation state leads to different SERS signal intensity. By comparison, Au nanoshells with core size of 50–80 nm exhibit high SERS enhancement effect.

Sodium D2 resonance radiation based on intracavity sum-frequency-mixing laser operation in Nd:GdVO4–Nd:YLiF4 crystals

We present a laser architecture to obtain continuous-wave orange–yellow radiation at 589 nm. A 808 nm diode-pumped the Nd:GdVO4 crystal emitting at 1341 nm. A part of the pump power was then absorbed by the Nd:GdVO4 crystal. The remainder was used to pump the Nd:YLiF4 (Nd:YLF) crystal emitting at 1053 nm. Intracavity sum-frequency-mixing at 1341 and 1053 nm was then realized in a LiB3O5 (LBO) crystal to produce orange–yellow radiation. We obtained a continuous-wave output power of 352 mW at 589 nm with a pump laser diode emitting 18.4 W at 808 nm.

Diode-pumped Nd:YGG continuous-wave laser at 1.33 μm

We demonstrated a laser-diode pumped Nd-doped yttrium gallium garnet (Nd:YGG) crystal continuous wave (CW) laser at 1.33 μm for the first time to our knowledge. At an incident pump power of 18.5 W, as high as 3.09 W of CW output power at 1.33 μm is achieved. The slope efficiency with respect to the incident pump power was 21.3%, and the fluctuation of the output power was better than 2.8% in the given 4 h. The beam quality factor M2 is 1.14 and 1.16 for tangential direction and sagittal direction, respectively.

High efficiency 1341 nm Nd:GdVO4 bounce laser in-band pumped at 879 nm

A high-efficiency Nd:GdVO4 bounce laser in-band pumped at 879 nm is demonstrated for the first time. From a side-pumped Nd:GdVO4 crystal, 8.2 W output was obtained with 18.5 W absorbed pump power. Corresponding slope efficiency with respect to the absorbed pump power was 51.4%, and the beam quality factor M2 is 1.13 and 1.15 for tangential direction and sagittal direction, respectively. Effects of crystal’s doping concentration and temperature on laser power and conversion efficiency were also investigated.

Diode pumped Pr3+:LiYF4-BBO ultraviolet laser at 320 nm

A diode pumped Pr3+:LiYF4 laser at 639.5 nm has been demonstrated. With an incident pump power of 920 mW, the maximum red output power was 272 mW. Moreover, intracavity second-harmonic generation (SHG) has also been achieved with a maximum ultraviolet power of 23 mW by using a β-BaB2O4 (BBO) nonlinear crystal. To the best of our knowledge, this is the first report on continuous-wave ultraviolet generation by intracavity frequency doubling Pr3+:LiYF4 laser.