ABSTRACT
Monolithic two-section InGaAs/GaAs double quantum well (DQW) passively mode-locked lasers (MLLs) with asymmetric waveguide, consisting of the layers of p-doped AlGaAs waveguide and no-doped InGaAsP waveguide, emitting at ~ 1.06 µm, with a fundamental repetition rate at ~ 19.56 GHz have been demonstrated. Modal gain characteristics, such as a gain bandwidth and a gain peak wavelength of the MLL, as a function of the saturable absorber (SA) bias voltage (Va) as well as the injection current of gain section (Ig), were investigated by the Hakki-Paoli method. With the increase of Va, the lasing wavelength and net modal gain peak of the MLL both exhibited red-shifts to longer wavelength significantly, while the modal gain bandwidth was narrowed. Both the net modal gain bandwidth and gain peak of the MLL followed a polynomial distribution versus the reverse bias at the absorber section. In addition, for the first time, it was found that Va had an obvious effect on the modal gain characteristics of the MLL.
ABSTRACT
A planar flow cytometric microimaging system is mainly used for cell recognition and classification in urinary sediment and gynecological secretion analysis. The depth of field (DOF) of the microscope seriously restricts its imaging range in the direction of the optical axis, rendering it incapable of imaging all the cells in the whole laminar thickness of the planar flow cytometric microimaging system. In this paper, the DOF is extended by using dual sensors with a common light path, and imaging of high-speed moving cells at a large DOF is realized, thus solving the difficulty that the multifocus super-depth technique can only be used in a static observation sample. A fusion algorithm based on saliency detection and multiscale image decomposition is developed to fuse the dual-depth-of-field images. The multiscale image decomposition uses L0 smoothing for multiscale image decomposition. L0 smoothing is particularly effective in sharpening major edges by increasing the steepness of transition, while eliminating a manageable degree of low-amplitude structures. It can globally control the number of non-zero gradients that result in an approximately prominent structure in a sparsity-control approach; this does not depend on the local features, instead it locates important edges globally. Experimental results show that our approach can enlarge the DOF 1.89 times, and the dual-DOF fusion algorithm can fuse two images with different DOFs into one image with clear multiple targets.
Subject(s)
Flow Cytometry/methods , Imaging, Three-Dimensional , AlgorithmsABSTRACT
A novel approach to generating 40 GHz narrow linewidth frequency-switched microwave signals is proposed and demonstrated. In this scheme, a single-longitudinal-mode (SLM) double-Brillouin-frequency spaced Brillouin fiber laser with dual-ring configuration and unpumped erbium-doped fiber (EDF) is used to generate dual-wavelength lasers, and a fiber Bragg grating is used to select the laser for different Brillouin frequency spacings. Dual-ring configuration and unpumped EDF are designed to select the mode for the SLM laser. Dual-wavelength lasers are inserted into a photodetector, and microwave signals at 10.66, 21.39, 32.12, or 42.85 GHz can be obtained. The linewidth of the generated microwave signals is less than 69 kHz. The frequency drift at each frequency is less than 0.83 MHz. The frequency noise and linewidth of Stokes signals are measured, and the linewidth broadening effect of microwave signals is analyzed.
