Xie Jian-Ping

Optical Transition Probability of Nd3+ Ions Doped in Ferroelectric Plzt for Active Electro-Optical Applications

The optical transition probability of Nd3+ (0.5 mol%) doped lanthanum-modified lead zirconate titanate (PLZT) is investigated. The absolute intensities of its forced electric dipole transitions between 400 nm and 1000 nm were measured, from which we obtain three phenomenological parameters, Ω2 = 0.787×10−20 cm2, Ω4 = 1.182×10−20 cm2, and Ω6 = 1.042×10−20 cm2, according to the Judd–Ofelt theory. The radiation lifetime (346.9 μs) of the 4F3/2 metastable state, the stimulated emission cross-section σij (2.49×10−21 cm2, 6.51×10−21 cm2, 2.17×10−21 cm2) and the fluorescence branch ratios are calculated. We also measured the fluorescence lifetime (155.84 μs) and calculated the quantum efficiency (46.1%). The analysis reveals that Nd3+-doped PLZT, based on its large electro-optical effect, has potential applications in active optical devices.

Binary pure-phase filter optimized the optical distribution of solid immersion lens ☆

Abstract A binary (π/2−0) two-zone phase filter is proposed to optimize the optical distribution of solid immersion lens (SIL). The analysis using angular spectrum method shows that the phase filter can not only decrease the full-width at half maximum (FWHM) of the optical distribution but also increase the depth of focus of the SIL system. Furthermore, the lateral distribution profile is also optimized.

Design of Polarization Beam Splitter in Two-Dimensional Triangular Photonic Crystals

A design of a polarization beam splitter (PBS) in two-dimensional triangular photonic crystals is proposed and numerically demonstrated, for the first time to our knowledge. The principle of the model is based on the polarization dependence of the photonic band gaps in photonic crystals; the polarization extinction ratios for transverse-magnetic and transverse-electric modes are 11.5 dB and 46.7 dB at the centre of its operating frequency range, respectively. When the central wavelength is tuned at 1550 nm, the possible operation wavelength range of this structure can be as large as 28.5 nm, which almost covers the whole C band in modern optical communication systems. Furthermore, due to its small size and only one kind of material being involved, the PBS structure may have practical applications in the integrated optics field.

Analysis of Photosensitivity of Copolymer Optical Fibre Preform

The photosensitivity of copolymer optical fibre preform is analysed in comparison with the doped one. The effects of write conditions such as pump power and pump time have been studied. Then, the preform is drawn into single mode polymer optical fibre with core refractive index of 1.499, and core-cladding refractive-index difference of 0.008. Long-period birefringence gratings with period of 120 um are fabricated in the fibre. The duty cycle is 50%, and the refractive index change in the exposed area is about 1×10−3.

Analysis of Near-Field Diffraction Pattern of a Metallic Probe Tip with the Boundary Diffraction Wave Method

The boundary diffraction wave theory is introduced to analyse a near-field diffraction (NFD) pattern of a metallic probe tip of apertureless scanning near-field microscopy. This method is simple and can give a clear physical picture. The polarization effect of the incident light and the different shapes of the metallic probe tip are simulated. The results show that the NFD pattern of the metallic probe tip is directly related to those factors.

Microstructure and Magnetic Domains of Iron Films on Liquid Surfaces

Iron (Fe) films with a thickness ranging from 1.0 nm to 80.0 nm are deposited on silicone oil surfaces by a vapor phase deposition method. The films with a thickness of d < 2.0 nm do not exhibit planar morphology but ramified aggregates instead. Magnetic force microscopy studies for the Fe films (10.0 nm ≤ d ≤ 80.0 nm) show that the domain wall structure is widespread and irregularly shaped and the oscillation phase shift Δθ, which records as the magnetic force image, changes from 0.29° to 0.81°. Correspondingly, the magnetic force gradient varies from 1.4 × 10−3 to 4.0 × 10−3 N/m, respectively. In our measurement, the characteristic domain walls, such as Bloch walls, Neel walls and cross-tie walls, are not observed in the film system clearly.

Flattening Spectrum of a Broadband and Wavelength Stable Erbium Doped Superfluorescent Fiber Source

A technique is used to design the spectra in erbium doped superfluorescent fiber source experimentally and theoretically. In an erbium doped fiber with a 10 m length and 300 ppm concentration, a line width of about 42 nm and high mean wavelength stability (<0.1ppm/K, <0.2ppm/mW) were obtained by means of a suitable population distribution, and adjusting the ratio of backward to forward pump power. Also, its thermal characteristic is studied. These results will improve the performance of fiber optical gyroscope and fiber sensors, and will be applied in erbium doped fiber amplifier with flattening gain.

High accuracy laser range sensor system based on the self-mixing effect in a single mode VCSEL

A miniaturized laser range sensor system based on the self-mixing effect in a single mode VCSEL is proposed. The system accuracy is better than 2mm and distance is from 100mm to 1000mm with 0.1s sampling time.

Birefringence Grating and Surface Grating in Azobenzene Polymer Liquid Crystal Films Investigated by Near-Field Optical Method

The birefringence grating and the surface grating in azobenzene polymer liquid-crystal (Azo-PLC) films are studied by a near-field scanning optical microscope. With laser irradiation, the refractive index change caused by birefringence and the sinusoidal surface profile are observed at the near-field transmittance image and the surface topography of the grating. The grating period and the peak-to-peak value of the sinusoidal surface profile are 0.8 µm and 40 nm, respectively. The maximum diffractive efficiency of the grating is 2%. The dynamic process of the grating formation is probed and analysed. The mass diffusion responsible for the formation of the surface grating due to the temperature rise is analysed.

Fractal clusters in Eu doped polymer fiber studied by near-field scanning optical microscopy

Using near-field scanning optical microscopy (NSOM), we explore the chromatic dispersion and absorption characteristics of fractal clusters in Eu doped polymer fiber. We present the near-field transmitted light intensity of fiber slice. The near-field light intensity of dots with clusters and without clusters is analyzed and compared and the agreement is obtained between experiment and theory which is based on the effective-medium approximation (EMA) and the differential effective-medium approximation (DEMA) of fractal clusters, respectively.