Pengfei Qi

In-situ visualization of multiple filament competition dynamic during nonlinear propagation of femtosecond laser

In this work, multiple filamentation competition of femtosecond pulse in methanol is studied both experimentally and numerically. The visualization of multiple filamentation competition has been realized in the experiment performing the three-photon fluorescence of Coumarin 440. The random changes of multiple filamentation stemmed from the jitter of the peak laser intensity ratio of initial hot spots are first observed directly and visually, which can be well explained by a simplified (2D+1)-dimensional model.

Image fiber-based miniature multi-functional suspended solid sensor

An image fiber-based miniature suspended solid sensor has been demonstrated. The diameter of the sensor is only a few millimeters. A superhydrophobic material is coated on the end of the image fiber to avoid the adsorption of suspended solids and bubbles. Multiple parameters, including mass concentration, morphology and particle sizes of suspended solids, can be visually measured in real time. Dynamic ranges of 0 ~ 100 kg/m3, full range accuracies of ±2‰ and a response time of 0.05 s were experimentally realized for the mass concentration measurements. Determinations of particle sizes of the suspended solids are also presented by means of digital image processing. This new technique will significantly advance ultralow-intrusion measurements in studies on the dynamics of suspended solids.

Image Fiber-Based Miniature Suspended Solid Sensor with High Accuracy and a Large Dynamic Range

An image fiber-based miniature suspended solid sensor has been demonstrated. The diameter of the sensor is only a few millimeters. A superhydrophobic material is coated on the end of the image fiber to avoid the adsorption of suspended solids and bubbles. Multiple parameters, including mass concentration, morphology and particle sizes of suspended solids, can be visually measured in real time. Dynamic ranges of 0 ~100u2009kg/m3, full range accuracies of ±2‰ and a response time of 0.05u2009s were experimentally realized for the mass concentration measurements. Determinations of particle sizes of the suspended solids are also presented by means of digital image processing. This new technique will significantly advance ultralow-intrusion measurements in studies on the dynamics of suspended solids.

Regulation of photorefractive surface apodized and chirped waveguide arrays

The tangent-like and sine-like characteristics in the head and tail regions of photorefractive surface waveguide arrays are elaborately demonstrated, and the regulation of such waveguide arrays on the written beam, background illumination, and external electric field is systematically studied for the first time. For the photorefractive surface apodized waveguide arrays, it is observed that guided mode bands of the fundamental mode gradually split and eventually reach saturation as a result of the influence of the power of photorefractive surface waves on the modulation depth of the refractive index; the period can be effectively adjusted by the wavelength and grazing angle of the written beam. However, there is an interesting chirp near surface for a large grazing angle. For the photorefractive surface nonlinearly chirped waveguide arrays, the amplitude, sign, and initial position of chirp can be conveniently regulated by an external electric field, background illumination, and incident beam, etc., and the modulation depth can also be flexibly adjusted by the influence of external electric fields on the refractive index of substrate.