The elliptic-triangle-like CeO2 nanosheets with many fissures have been purposefully fabricated via controlling the morphology of CeCO3OH precursors by an efficient hydrothermal route. The X-ray diffraction results indicate that the calcined samples have a cubic fluorite structure of CeO2 with no crystalline impurity phase. The scanning electron microscope images display that the morphology of the as-synthesized nanostructures gradually changes from diamond-like to tabular, then to elliptic-triangle-like nanosheet, and finally to fireworks-like/circular nanosheets mixed structure with the decrease of reaction temperature. X-ray photoelectron spectroscopy and Raman analyses demonstrate that there are Ce3+ ions and oxygen vacancies in the surface of samples. It is also found that there is a red-shifting in the band gap of the obtained material compared to bulk one, which is mainly attributed to the influences of the Ce3+ ions, oxygen vacancies and the morphology. All the samples exhibit the similar emission peaks of room temperature photoluminescence and the emission intensity increases with the increase of concentration of oxygen vacancies.

•The differentiating interferometer is composed of ASE source and hybrid configuration.•This interferometer adopts triple detection passive demodulation scheme.•It can realize the real-time measurement of absolute phase amplitude.•The signal absolute measurement range is from 6×10−5 rad to up to 90 rad.•Low frequency environmental disturbance is avoided naturally.This paper presents a triple detection fiber differential interferometer and its passive demodulation scheme. The interferometer is based on an all fiber Mach–Zehnder and Sagnac hybrid configuration, which is composed of a fiber ASE source, a section of delay fiber, a 3×3 fiber coupler and several other fiber components. In the interferometer, the signal beam and reference beam travel along the same path but in opposite directions. The received signal is demodulated by a triple detection passive demodulation scheme. The interferometer can measure the absolute amplitudes and frequencies of phase sensitive signals with large dynamic range, and the low frequency environmental disturbance is removed simultaneously due to the phase compression mechanism. The experimental results demonstrate that the phase demodulation resolution is 6×10−5 rad and the maximum measuring amplitude is up to 90 rad. This method can be used to measure many kinds of parameters such as vibration and refractive index.

We demonstrate a multiplexed fiber interferometer measurement system for eliminating the external disturbance using the digital phase generated carrier (PGC) demodulation technique. By applying two fiber Bragg gratings (FBG) and two fiber interferometers that share the reference arm and part of the sensing arm in this measurement system, we find that the system can be used for detecting the useful signal and the external disturbances is reduced by 26 dB. Thus, our work may provide some new possibilities for technological applications in vibration measurement.

We investigate the optical bistability and multistability behaviors in a four-level Λ-typeΛ-type system using a microwave field driving a hyperfine transition between two lower states inside a unidirectional ring cavity. By controlling the microwave field and the frequency detunings of the three fields, we find that the appearance and disappearance of OB (or OM) can easily be controlled by adjusting the positions of the dual-EIT windows. Our scheme may be used for building more efficient all-optical switches and logic-gate devices for optical computing and quantum information processing.Highlights► Optical bistability and multistability via dual-EIT windows are investigated. ► The scheme shows some intrinsic characteristics that other schemes do not have. ► The appearance and disappearance of OB/OM can easily be controlled by adjusting the positions of dual-EIT windows.

A simple flat-top all-fiber comb filter based on two high birefringence fiber (HBF) Sagnac loop filters is presented. The proposed flat-top comb filter consists of two HBF Sagnac loop filters with two polarization controllers (PCs) and a fiber circulator. According to the theoretical analysis, with proper settings of the polarization state of the PCs, the comb filter can realize flat-top passband and the channel spacing also can be switched when the comb filter is convex spectrum. The 0.3 dB bandwidth of the flat-top passband is 0.49 nm with a free spectral range of 1.4 nm. The maximum extinction ratio is nearly 20 dB. The comb filter with switchable channel spacing can be obtained from 0.7 nm to 1.4 nm.

We propose and demonstrate a strictly all-fiber, erbium doped passively mode-locked figure-eight fiber laser (EDFL). In the laser structure, we use the nonlinear optical loop mirror combination with a variable ratio coupler (VRC-NOLM) to achieve mode-locking. Due to the nonlinear effect in the nonlinear fiber, stable self-starting pulse is obtained. In order to reduce the repetition of pulse, a segment of nonlinear fiber (NLF) has been incorporated into the VRC-NOLM. The laser generates stable rectangular pulses with a low repetition rate (kilohertz magnitude) by extending the length of the cavity. Furthermore, the output pulse width of the fiber laser can be varied by changing the coupler ratio of the variable ratio coupler.

We propose and demonstrate a novel switchable quadruple-wavelength erbium-doped fiber ring laser (EDFL) based on two-segment Lyot–Sagnac filter which is used as the wavelength-selective filter. Due to the deeply saturated spectral hole-burning (SHB) effect in an ordinary erbium-doped fiber, the laser realizes stable single-wavelength, dual-wavelength, triple-wavelength, and quadruple-wavelength output by controlling two polarization controllers (PCs) appropriately. The optical signal-to-noise ratio (OSNR) is over 30 dB. The peak fluctuation is less than ~2 dB over 1.5 h at room temperature.

A novel configuration of fiber laser with frequency modulation is presented. Frequency modulation, stable polarization state and narrow linewidth are realized by using the waveguide phase modulator, polarization maintaining devices and saturable absorber. It is shown that the laser output reaches 23 mW, linewidth is less than 1 kHz, polarization extinction ratio is higher than 20 dB and maximum value of frequency deviation can reach 7.5 MHz.