The temperature and stress characteristics of double-clad fiber Bragg grating are investigated, respectively. The thermal decay characteristics according to the different anneal thermal, 100°C, 150°C, 200°C and 250°C are got. These results are very significant to estimate the properties of grating, such as thermal, wavelength and anneal time. Birefringence effect of the grating is also detected in rectangular inner cladding DCF gratings. By applying stress on the grating, strain is induced. One reflection peak of double-clad fiber Bragg grating becomes two peaks. The relation between the stress and the peak shift is obtained. The two reflection peaks can be tuned from 0 to 0.8nm. These results are more significant for estimate the sensor properties of the DCF Bragg gratings.
The photosensitivity and thermal decay of DCF Bragg grating written in Yb3+-doped and Er3+/Yb3+-co-doped DCF are experimentally investigated, respectively. Variation of amplitude of reflective-index modulation and effective reflective index with the UV exposure time are observed. Depend on the photosensitivity relations of hydrogen-loaded rare-earth-doped DCF, we fabricate diversiform reflectivity of DCF Bragg gratings with phase mask method, and the best reflectivity of the grating is 99.9%. The thermal decay characteristics according to the different anneal thermal, 100°C, 150°C, 200°C and 250°C are got. These results are very significant to estimate the properties of grating, such as thermal, wavelength and anneal time.
A novel Moire grating in Yb3+-doped double-clad fiber is reported. It consists of two intracore Bragg reflection gratings separated by an optical phase shift; the grating was formed through double exposure phase-mask method. An Yb3+-doped double-clad fiber laser based on this grating is presented. The laser wavelengths are 1055nm and 1057nm, respectively, with less than 0.1nm line-width, over 40dB signal-to-noise ratio.
A high-power and broadband super-fluorescent source (SFS) based on an Yb-doped double-cladding fiber is described. The source is pumped at 976 nm from a laser diode by end-pumping system. The SFS generated a maximum 100 mW of broadband emission centered at 1066nm, with an about 40nm FWHM spectrum. The basic characteristics of the superfluorescent source, such as the output power and output linewidth, have been analyzed and studied.
We present a tunable multi-wavelength Yb3+-doped double-clad fiber laser based on a Fabry-Perot filter (FPF). By adjusting the FPF, the number of lasing wavelength and their spaces are controlled which is in agreement well with the numerical analysis. The laser can oscillate at different number of wavelengths from one to ten while the oscillation is quite stable. In ten-wavelength laser, the system allows us to extract more than 1.5 W with a slope efficiency of 67%.
Properties of the photonic bandgaps effect and guided modes in triangular photonic crystal fibers have been studied by means of a full-vectorial plane-wave expansion method. Photonic crystal fibers under consideration consist of a triangular array of microscopic holes forming a two-dimensional photonic crystal cladding and a defect as their core. The photonic band-structure for photonic crystal cladding structures and the field intensity distribution of defect mode with various air-filling fractions and defect size are calculated. Guidance mechanisms in photonic crystal fibers with different configuration are also investigated.