Papers by Author: Tong Gang Zhao

Abstract: A new measurement of surface reflection index distribution is introduced. Using walk-off induced by return laser pulse power variation, which usually should be eliminated in LADAR system, relative reflection index distribution of material surface could be deduced from the 3D point-cloud data. Detection of actual pulse waveform is the first step, and then the mapping of time walk-off and amplitude is obtained. According to this relationship, amplitude distribution could be deduced from the angle/angle/time data of LADAR. After detaching the influence of detect direction based on the ladar detection range function, the reflection index distribution is acquired finally. The experimental result of this method is shown in the last of paper.

Abstract: We experimentally demonstrate a tunable fiber ring laser with narrow linewidth and fine tuning resolution based on Er³⁺-doped fiber(EDF) laser material. A tunable fiber Bragg grating(FBG) filter is used in the system as the frequency selecting element, and a stepping motor together with a single chip acts as the precise tuning mechanism. The fiber ring laser has a narrow linewidth of ~0.07nm, a tuning resolution of ~1.5pm/pulse, an output power of ~25 mW, and a slope efficiency of ~17.9%.

Abstract: As development of laser technology, the characteristic of laser atmospheric propagation is always hot spot in laser domain. Using theoretical models of laser atmospheric propagation, a simulation system is researched by implementing a scientific method of software development. This simulation system can simulate the radiate property of laser propagation in atmosphere, and demonstrate the course of laser propagation. This theoretical model of atmospheric propagation is based on Lambert-Beer law, combined with other classic theoretical model such as Rayleigh scattering and Mie scattering. Multiple scattering theories are used when simulating the laser propagation in smoke or fog. In calculation, the atmosphere is divided into layer. An appropriate model will be selected for calculation in each layer in order to enhance the stimulation precision. Lastly, the figure of light spot is drawn along with transmission space. Laser atmospheric propagation is demonstrated.

Abstract: An aperiodic fiber grating with asymmetric reflection spectrum structure is studied, and its spectrum characteristics are described by an introduced parameter, the spectrum profile slope, which can measure the spectrum asymmetric property. Based on the fiber gratings with asymmetric reflection spectra, a new sort of tunable narrow band-pass fiber grating filter is designed as its application, whose characteristics, namely working wavelength, band width, and tunable range, are analyzed as well.

Abstract: Analyze the fiber amplified theory and obtain the transmission formula of pump and signal for the use of rate equation. In the experiment, take the Yb-doped double cladding fiber based on phosphor silicate as gain medium, high power single emitter in 915nm as pump source. According to gain fiber length obtained by the theory analyses, the output power achieves 20W above. Apply the cladding power stripper at the output end for stripping the remained pump power.