It is very important to have high spatial resolution in all three dimensions for imaging complex 3D biological structures. In this paper, the three-dimensional (3D) fluorescent spot breaking the diffraction-limited resolution barrier is produced by radially polarized Laguerre-Gaussian(LG) beams from stimulated emission depletion(STED) principle. The pump beam is generated by 4π tight focusing of LG<sub>01</sub> with high numerical aperture(NA), the full width at half maximum(FWHM) of longitudinal intensity field is 0.42λ , the FWHM of transverse component field is 0.48 λ . The depletion 3D hollow dark spot beam is generated with a topological charge of 1 LG<sub>11</sub> through high NA tight focusing. The behavior of the two-beam produced fluorescent spot is examined and the fluorescent spot size is minimized obviously. The super resolutions of 0.034λ and 0.094λ for longitudinal and transverse directions can be achieved, respectively.
Structural Long period gratings (LPGs) in photonic crystal fiber (PCF) were successfully fabricated using the femtosecond laser micromachining system by introducing periodic side-holes. High temperature characterizations of the fabricated gratings have been performed. The structural gratings written with the femtosecond laser micromachining technique can suffer a low shift of the resonance wavelengths with sensitivity of 23pm/oC while the temperature is increased from 20°C to 1200°C. The LPGs have been found to have negligible temperature sensitivity whilst exhibiting useful strain (-1.86pm/με)and strong directional bend sensitivity with -4.40nm•m (180°) and -2.79nm•m (0°) at low temperature. The unique sensing characteristics enable many potential sensing applications in high temperature environments, such as space aircraft, nuclear power plants, and the chemical industry.