Optimized design of high power mid-infrared Er3+, Pr3+ -codoped ZBLAN fiber laser

Based on the rate equations describing the operation of the Er3+, Pr3+ -codoped ZBLAN fiber lasers with different pump configurations, theoretical calculations that relate to the population characteristics and optimization of CW operation of high power Er3+, Pr3+ :ZBLAN double-clad fiber lasers are presented. Using the measured ET (energy-transfer), ETU (energy-transfer-upconversion) and CR (cross-relaxation) parameters relevant to Er3+, Pr3+ -codoped ZBLAN, a good agreement between the theoretical results from the model and recently reported experimental measurements is obtained. The effects on the slope efficiency of a number of laser parameters including fiber length, reflectance of the output mirror and pumping configuration are quantitatively analyzed and used for the design and optimization of high power Er3+, Pr3+ -codoped ZBLAN fiber lasers.

Optimized design of high power mid-infrared Er3+, Pr3+ -codoped ZBLAN fiber laser

Based on the rate equations describing the operation of the Er3+, Pr3+ -codoped ZBLAN fiber lasers with different pump configurations, theoretical calculations that relate to the population characteristics and optimization of CW operation of high power Er3+, Pr3+ :ZBLAN double-clad fiber lasers are presented. Using the measured ET (energy-transfer), ETU (energy-transfer-upconversion) and CR (cross-relaxation) parameters relevant to Er3+, Pr3+ -codoped ZBLAN, a good agreement between the theoretical results from the model and recently reported experimental measurements is obtained. The effects on the slope efficiency of a number of laser parameters including fiber length, reflectance of the output mirror and pumping configuration are quantitatively analyzed and used for the design and optimization of high power Er3+, Pr3+ -codoped ZBLAN fiber lasers.

High-temperature sensitivity of long-period gratings in B-Ge codoped fiber

We report an investigation of thermal properties of long-period fiber gratings (LPFGs) of various periods fabricated in the conventional B-Ge codoped fiber. It has been found that the temperature sensitivity of the LPFGs produced in the B-Ge fiber can be significantly enhanced as compared with the standard telecom fiber. A total of 27.5-nm spectral shift was achieved from only 10 °C change in temperature for an LPFG with 240-μm period, demonstrating a first ever reported high sensitivity of 2.75 nm/°C. Such an LPFG may lead to high-efficiency and low-cost thermal/electrical tunable loss filters or sensors with extremely high-temperature resolution. The nonlinear thermal response of the supersensitive LPG was also reported and first explained.

Synthesis of Cr and La-codoped SrTiO3 nanoparticles for enhanced photocatalytic performance under sunlight irradiation

In this study, we report a facile polymeric citrate strategy for the synthesis of Cr,La-codoped SrTiO3 nanoparticles. The synthesized samples were well characterized by various analytical techniques. The UV-vis DRS studies reveal that the absorption edge shifts towards the visible light region after doping with Cr, which is highly beneficial for absorbing the visible light in the solar spectrum. More attractively, codoping with La exhibits greatly enhanced photocatalytic activity for the degradation of Rhodamine B under sunlight irradiation. The optimum photocatalytic activity at 1 atom% of Cr,La-codoped SrTiO3 nanoparticles is almost 6 times higher than that of pure SrTiO3 nanoparticles and 3 times higher than that of Cr-doped SrTiO3 nanoparticles. The high photocatalytic performance in the present photocatalytic system is due to codoping with La, which acts as a most effective donor for stabilizing Cr3+ in Cr,La-codoped SrTiO3 nanoparticles. More importantly, the synthesized photocatalysts possess high reusability. A proposed mechanism for the enhanced photocatalytic activity of Cr,La-codoped SrTiO3 nanoparticles was also investigated by trapping experiments. Therefore, our results not only demonstrate the highly efficient visible light photocatalytic activity of the Cr,La-codoped SrTiO3 photocatalyst, but also enlighten the codoping strategy in the design and development of advanced photocatalytic materials for energy and environmental applications.

Sensing characteristics of a novel two-section long-period grating

The behavior of a temperature self-compensating, fiber, long-period grating (LPG) device is studied. This device consists of a single 325-µm-period LPG recorded across two sections of a single-mode B-Ge-codoped fiber—one section bare and the other coated with a 1-µm thickness of Ag. This structure generates two attenuation bands associated with the eighth and ninth cladding modes, which are spectrally close together (~60 nm). The attenuation band associated with the Ag-coated section is unaffected by changes in the refractive index of the surrounding medium and can be used to compensate for the temperature of the bare-fiber section. The sensor has a resolution of ±1.0 × 10-3 for the refractive index and ±0.3 °C for the temperature. The effect of bending on the spectral characteristics of the two attenuation bands was found to be nonlinear, with the Ag-coated LPG having the greater sensitivity.

Optically tunable fiber grating transmission filters

We propose and demonstrate single- and multiple-passband fiber grating transmission filters that are remotely tunable by exploitation of the optical pump-induced thermal effects in Er Yb-codoped fiber sections. A repeatable, wavelength-independent induced phase shift of 0.1p mW is obtained without hysteresis and anisotropic effects. A transmission extinction ratio of .23 dB with a 3-mW change in pump power is achieved.

Effectively simultaneous temperature and strain measurement utilising a dual-grating sensor formed by type IA and type IIA FBGs

In this paper, we report a systematic investigation of the dependence of both temperature and strain sensitivities on the jiber Bragg grating (FBG) type, including the wellknown Type I, Type IIA, and a new type which we have designated Type 1.4, using both hydrogen-Ji-ee and hydrogenated B/Ge codoped jibers. We have identijed distinct sensitivity characteristics for each grating type, and we have utilised them to implement a novel dual-grating, duul-parameter sensor device. Three dual-grating sensing schemes with different combinations of gruting types have been constructed and compared. The Type IA-Type IIA combination exhibits the best pe$ormance and is superior to that of previously reported gruting-based structures. The characteristics of the measurement errors in such dualgrating sensor systems is also presented in detail.

Optically controlled tunable dispersion compensators based on pumped fiber gratings

We demonstrate optically tunable dispersion compensators based on pumping fiber Bragg gratings made in Er/Yb codoped fiber. The tunable dispersion for a chirped grating and also a uniform-period grating was successfully demonstrated in the experiment. The dispersion of the chirped grating was tuned from 900 to 1990 ps/nm and also from -600 to -950 ps/nm in the experiment.

Efficient 2.87 μm fiber laser passively switched using a semiconductor saturable absorber mirror

A passively switched Ho3+, Pr3+ codoped fluoride fiber laser using a semiconductor saturable absorber mirror (SESAM) is demonstrated. Q-switching and partial mode-locking were observed with the output power produced at a slope efficiency of 24% with respect to the absorbed pump power. The partially mode-locked 2.87 µm pulses operated at a repetition rate of 27.1 MHz with an average power of 132 mW, pulse energy of 4.9 nJ, and pulse width of 24 ps.

Effectively simultaneous temperature and strain measurement utilising a dual-grating sensor formed by type IA and type IIA FBGs

In this paper, we report a systematic investigation of the dependence of both temperature and strain sensitivities on the jiber Bragg grating (FBG) type, including the wellknown Type I, Type IIA, and a new type which we have designated Type 1.4, using both hydrogen-Ji-ee and hydrogenated B/Ge codoped jibers. We have identijed distinct sensitivity characteristics for each grating type, and we have utilised them to implement a novel dual-grating, duul-parameter sensor device. Three dual-grating sensing schemes with different combinations of gruting types have been constructed and compared. The Type IA-Type IIA combination exhibits the best pe$ormance and is superior to that of previously reported gruting-based structures. The characteristics of the measurement errors in such dualgrating sensor systems is also presented in detail.

Optically controlled tunable dispersion compensators based on pumped fiber gratings

We demonstrate optically tunable dispersion compensators based on pumping fiber Bragg gratings made in Er/Yb codoped fiber. The tunable dispersion for a chirped grating and also a uniform-period grating was successfully demonstrated in the experiment. The dispersion of the chirped grating was tuned from 900 to 1990 ps/nm and also from -600 to -950 ps/nm in the experiment.

Fiber grating type dependence of temperature and strain coefficients and application to simultaneous temperature and strain measurement

Although fiber Bragg gratings (FBGs) have been widely used as advanced optical sensors, the cross-sensitivity between temperature and strain has complicated independent measurement procedures for these two measurands. We report here, for the first time to our knowledge, the results of a systematic investigation of the dependence of both temperature and strain sensitivities on the grating type, including the well-known Type I, Type IIA, and a new type which we have designated Type IA, using both hydrogen-free and hydrogenated B/Ge codoped fibers. We have identified distinct sensitivity characteristics for each grating type, and we have utilised them to implement a novel dual-grating, dual-parameter sensor device with performance superior to that of previously reported grating-based structures.

Room-temperature operation of widely tunable loss filter

A widely tunable and room-temperature operationable loss filter based on a long-period fibre grating (LPFG) fabricated in a B/Ge codoped fibre is reported. The filter exhibits extremely high temperature sensitivity. A maximum spectral shift of -48.1 nm from 10 to 40°C is achieved, corresponding to a thermal tuning efficiency of 1.6nm/°C. This value is increased by more than one order of magnitude compared with the LPFGs fabricated in standard telecom fibre, and even twice that of a LPFG with sensitivity enhanced by a special polymer.

Use of dual-grating sensors formed by different types of fiber Bragg gratings for simultaneous temperature and strain measurements

We report on a systematic investigation of the dependence of both temperature and strain sensitivities on the fiber Bragg grating type, including the well-known Type I, Type IIA, and a new type that we have designated Type IA, using both hydrogen-free and hydrogenated B/Ge codoped fibres. We have identified distinct sensitivity characteristics for each grating type, and we have used them to implement a novel dual-grating, dual-parameter sensor device. Three dual-grating sensing schemes with different combinations of grating type have been constructed and compared, and that of a Type IA-Type IIA combination exhibits the best performance, which is also superior to that of previously reported grating-based structures. The characteristics of the measurement errors in such dual-grating sensor systems is also presented in detail. © 2004 Optical Society of America.

Optically tunable fiber grating transmission filters

We propose and demonstrate single- and multiple-passband fiber grating transmission filters that are remotely tunable by exploitation of the optical pump-induced thermal effects in Er Yb-codoped fiber sections. A repeatable, wavelength-independent induced phase shift of 0.1p mW is obtained without hysteresis and anisotropic effects. A transmission extinction ratio of .23 dB with a 3-mW change in pump power is achieved.