A tunable dual-wavelength passively mode-locked thulium-doped fiber laser (TDFL) based on single-wall carbon nanotube is demonstrated. By properly tuning the pump power and the polarization controller, both single- and dual-wavelength mode-locked operation can be achieved. The repetition rates of the single- and dual-wavelength mode-locked operation are both 17.64 MHz. The duration of the ultrashort soliton pulse is about 3.7 ps. By appropriately adjusting the polarization state of the laser, the dual wavelength can be tuned from 1879.8 and 1894.5 nm to 1903.3 and 1914.1 nm.
A simple optical fiber relative humidity (RH) sensor was proposed and demonstrated. The humidity sensor was
fabricated by coating moisture-sensitive film on the end face of a multi-mode optical fiber. The film was
synthesized by doping CoCl<sub>2</sub> into a PVA/SiO<sub>2</sub> composite solution. Based on an optical absorption technique, the
sensor head was characterized. From the optical absorption, a relative humidity range of 25%~65% was detected.
Furthermore, the sensor has good repetitive response, and the response time was less than 2 min.
A fiber-optic temperature sensor was fabricated and studied by using a tapered optical fiber which is coated with a
quantum dots (QDs) doped sol-gel thin films. The CdSe/ZnS core-shell nanocrystals were trapped into sol-gel and coated
on a tapered optical fiber. The dependence of photoluminescence (PL) spectrum on temperature change was studied. The
sensor response is linear and repeatable to the temperature change.
An organic material, 4,5-bis(benzoylthio)-1,3-dithiole-2-thione (BBDT), was synthesized. The thin film of BBDT doped
into poly(methyl methacrylate) (PMMA) was prepared using spin-coating method. Its linear optical properties were
characterized with prism coupler (SPA-4000, Korea). The third-order nonlinear optical (NLO) properties were
investigated using Z-scan technique with pulses of picoseconds at 532 nm. The Z-scan spectra reveal a strong nonlinear
absorption (reverse saturable absorption) and a positive nonlinear refraction. The nonlinear absorption coefficient is
calculated to be 1.302×10<sup>-9</sup>m/W. The nonlinear refractive index is 2.243×10<sup>-9</sup>esu. The results show that the film exhibits
a great nonlinear optical response.
A dmit<sup>2-</sup> salt: [(C<sub>4</sub>H<sub>9</sub>)<sub>4</sub>N]Au(dmit)<sub>2</sub> was synthesized. Its third-order nonlinear optical properties of its acetone solution
were investigated by Z-scan technique using a pulsed laser with 28 ps duration and 10 Hz repetition at 532 nm. The
third-order nonlinear refractive index n<sub>2</sub> and nonlinear absorption coefficient β of the sample solution were obtained to
be about 4.997×10<sup>-12</sup> esu and 1.818 cm/GW at the concentration of 2×10-3 M. The second-order hyperpolarizability for
its molecular was estimated to be as large as 2.74×10<sup>-31</sup> esu, suggesting [(C<sub>4</sub>H<sub>9</sub>)<sub>4</sub>N]Au(dmit)<sub>2</sub> is a promising material for
Bismuth titanate, Bi4Ti3O12 (BTO), is a typical ferroelectric material with useful properties for optical memory,
piezoelectric and electro-optic devices. Its nano-crystals were compounded by the chemical solution decomposition
(CSD) technique. The structure and size of BTO were analyzed by X-ray diffraction (XRD) and transmissive electron
microscopy (TEM). Three sorts of composite films BTO/PEK-c with different BTO concentration were prepared by
spin-coating method at certain conditions. In this article, the scattering losses in thin films were obtained using the
photographic technique. The losses in the films with different BTO weight ratios were compared and analyzed.
A continue-wave (CW) laser-diode (LD) pumped passively Q-switched intracavity frequency-doubling green laser is reported in this paper. We used 3%at. Nd doped YVO4 with size of 3 X 3 X 1mm as gain medium, Cr4+:YAG as a saturable absorber with small-signal transmission T0=94% for passively Q-switch and periodically poled LiNbO3 (PPLN) with the grating period ? =6. 1 µm as a frequency doubler. The laser cavity was consisted of one face of the Nd:YVO4, coated high-reflectance (HR) coating at 1.06 µm and high transmittance (HT) at 0.808 µ m, and a 50mm radius of curvature output mirror with HR coating at 1.06 1 µm and HT coating at 0.53 µm.. A CW 1W LD and a grading-refractive-index lens were used for the end-pumping. The output energy of the green laser is 0.96 µ J with the pulse-width of 19ns. No green-noise problem exists in the green laser, because both the polarizations of fundamental wave and second harmonic wave are the same. Some theoretical results on the passively Q-switching and intracavity frequency-doubling are also reported.
To counter the best season for exploration of metal mineral under forests using imaging spectrometer, the authors made ground tests at the Zhaoyuan gold mine area of China from the end of April to the middle of November 1991. The characteristic wavelength parameters of the red-edge of the average curves for each time was extracted and analyzed. The results indicate that the three characteristic wavelengths for gold mine area show all annually blue shifts in varying degrees against background area, and the blue shifts in Autumn for the first year leaves, and in Spring for the second-year leaves, especially latter, are the biggest; so Spring and Autumn is the best season for the exploration of metal mineral under Korean Pine Forests.