Shuangchen Ruan

Terahertz surface wave propagation and focusing on conical metal wires

A theory for treating terahertz (THz) surface wave propagation and focusing on conical metal wire waveguides is presented. According to the theory, the surface wave propagation and focusing on the conical copper wire waveguide is investigated by the numerical calculation, and the results show the theory agrees with experimental measurement result obtained by Ji et al. The theory presented provides a basis for describing surface wave propagation and focusing on conical metal wire waveguides and, importantly, the theory suggests that a simple conical metal wire can be used for subwavelength energy concentration and superfocusing.

6-W diode-end-pumped Nd:GdVO4/LBO quasi-continuous-wave red laser at 671 nm.

We report a high-power diode-end-pumped Q-switched Nd:GdVO4 red laser through intracavity frequency-doubling with a type-I critical phase-matched LBO crystal. The maximum average output power at 671 nm was obtained to be 6 W at the repetition frequency of 47 kHz, with the corresponding optical conversion efficiency of 12.8% and the pulse width of about 97 ns. At the average output power around 5 W, the power stability was better than 5.8% for one hour.

10.2-W Q-switched intracavity frequency-doubled Nd:YVO 4 /LBO red laser double-end-pumped by laser-diode-arrays

We report a high-power diode-double-end-pumped Q-switched Nd:YVO4 red laser through intracavity frequency-doubling with a type-I critical phase-matched LBO crystal. At a repetition frequency of 21.72 kHz, a maximum average output power of 10.2 W at 671 nm was measured to while the incident pump power was 78.4 W, the corresponding optical conversion efficiency was 13.0%, with a pulse width of about 94 ns and a pulse energy of 469.6 muJ, the peak power was 5.0 kW. At an average output power around 9.6 W a power stability better than 2.3% was maintained for half an hour.

Realization of optical perfect shuffle with microoptical array element

A new method to realize the optical perfect shuffle (PS) with a microoptical array element is presented in this paper. The whole process is simulated by computer, and parameters of the structure to fabricate the experimental component are given. The microoptical array element has been fabricated by introducing very large scale integration (VLSI), stepping photolithography and reactive iron etching (RIE), which can realize 8-channel PS transformation. Experiments, tests and analysis have been done using the array element. The experimental results show that the method proposed in this paper agrees well with theoretical expectation. This success of the experiment lays a good foundation for us to do further research on realization of optical switching and communication through cascade multilevel PS interconnection.

High-power intracavity second-harmonic generation of 1.34 μm in BiB 3 O 6 crystal

The phase-matching curve and effective nonlinear optical coefficient distribution for the second-harmonic generation of 1342 nm in BiB3O6 crystal were calculated. High-power intracavity second-harmonic generation of 1.34 microm in BiB3O6 crystals, at a type-I phase-matching direction of (theta, ø)=(9.07 degrees , 0 degrees ), was performed with a LD-end-pumped Nd:YVO4 laser. The maximum continuous-wave (CW) and quasi-CW output powers at 671 nm were obtained to be 1.22 W and 4.38 W, with the corresponding optical conversion efficiency of 4.9% and 9.5%, respectively.

Laser-diode-array end-pumped 8.2-W CW Nd : GdVO/sub 4/ laser at 1.34 /spl mu/m

A laser-diode-array end-pumped 0.3-at.% Nd-doped GdVO/sub 4/ high-power continuous-wave (CW) laser operating at 1.34 /spl mu/m has been demonstrated. The maximum CW output power of 8.23 W was obtained at the incident pump power of 27.9 W, giving the corresponding optical conversion efficiency of 29.5% and the average slope efficiency of 30.2%. Two Nd : GdVO/sub 4/ crystals with Nd/sup 3+/ concentration of 0.5 and 1.14 at.% were also investigated for the comparison to show the advantage of lowly Nd-doped crystals applied to high-power lasers.

LD-pumped passive Q-switched Nd:LuVO4 laser

The absorption spectrum from 300 to 1000 nm and emission spectrum from 960 to 1450 nm of Nd:LuVO4 crystal were measured. A LD-end-pumped passive Q-switched Nd:LuVO4 laser was reported. With a Cr4+:YAG crystal as the saturable absorber, the maximum average output power was measured to be 4.58 W, and the corresponding optical conversion efficiency was 24.0 %, with the pulse energy, peak power, and pulse width being 36.6 μJ, 436.2 W, and 84 ns, respectively.

In-Fiber Grating Fabricated by Femtosecond Laser Direct Writing for Strain Sensing

In this letter, we reported long period fiber gratings (LPFGs) fabricated by femtosecond laser pulses direct writing in grapefruit microstructured fiber. The mode field distribution and dispersion property of this fiber was analyzed by finite-element method. Two LPFGs were fabricated with different periods of 230 and 250 μm, the resonant dips appeared at the wavelengths of 1325.8 and 1449.4 nm, respectively. In addition, sensing characteristics of the LPFG with the period of 250 μm were investigated in theory and experiment. The experimental results show that the strain and temperature sensitivities are 1.88 pm/με and 0.267 pm/°C, respectively. It indicates that the temperature cross sensitivity is as low as 0.142 με/°C.

Far-Field Radiation Patterns of Terahertz Wire Waveguides

A formula for describing far-field radiation properties of metal wire waveguides is derived based on the Fresnel-Huygens diffraction theory. According to the formula, we find that the far-field patterns are the same for waveguides with different metal materials, and the amplitude of the electric field is in inverse proportion to the radiation distance. Furthermore, the far-field radiation properties versus the terahertz (THz) wave frequency and versus the metal wire diameter are investigated. Finally, we demonstrate that direction angles and shapes of the radiation lobes can be changed by using diaphragms with different aperture sizes.

Double-end-pumped acoustic-optically Q-switched intracavity-frequency-doubling red laser

We report a high-power diode-double-end-pumped Q-switched Nd:YVO4 red laser through intracavity frequency-doubling with a type-I critical phase-matched LBO crystal. At the repetition frequency of 26 kHz, the maximum quasi-continuous-wave (QCW) output power at 671 nm was measured to be 9.2 W at the incident pump power of 62.4 W with the corresponding optical conversion efficiency of 14.7%; the pulse width of about 106 ns; the pulse energy of 353.8μJ; the peak power of 3.34 kW, respectively. The perfect performance indicated that the double-end-pumped technique could effectively diminish the thermal lens effect, extend the range of the stable resonator region and achieve a high optical conversion efficiency to obtain a high output power.