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An optoelectronic oscillation method with reconfigurable multiple formats for simultaneous generation of coherent dual-band signals is proposed and experimentally demonstrated. By introducing a compatible filtering mechanism based on stimulated Brillouin scattering (SBS) effect into a typical Phase-shifted grating Bragg fiber (PS-FBG) notch filtering cavity, dual mode-selection mechanisms which have independent frequency and time tuning mechanism can be constructed. By regulating three controllers, the proposed scheme can work in different states, named mode 1, mode 2 and mode 3. At mode 1 state, a dual single-frequency hopping signals is achieved with 50 ns hopping speed and flexible central frequency and pulse duration ratio. The mode 2 state is realized by applying the Fourier domain mode-locked (FDML) technology into the proposed optoelectrical oscillator, in which dual coherent pulsed single-frequency signal and broadband signal is generated simultaneously. The adjustability of the time duration of the single-frequency signal and the bandwidth of the broadband signal are shown and discussed. The mode 3 state is a dual broadband signal generator which is realized by injecting a triangular wave into the signal laser. The detection performance of the generated broadband signals has also been evaluated by the pulse compression and the phase noise figure. The proposed method may provide a multifunctional radar system signal generator based on the simply external controllers, which can realize low-phase-noise or multifunctional detection with high resolution imaging ability, especially in a complex interference environment., Comment: 12 pages, 8 figures

Photoelectric conversion efficiency of organic-inorganic perovskite solar cells has been rapidly raised and attracted great attention in recent years. The quality of perovskite films is vital for the performance of devices. We used the anti-solvent method to prepare CH$_3$NH$_3$PbI$_3$ thin films by spin coating and dried them at various temperature to transform adduct MAI.PbI$_2$.DMSO into CH$_3$NH$_3$PbI$_3$. We researched in detail on the relationship between surface morphology of MAPbI$_3$ thin films fabricated by the anti-solvent method and various drying temperature. We found that surface roughness and grain size of CH$_3$NH$_3$PbI$_3$ films together increased with increasing drying temperature. The larger grain size could efficiently reduce crystal boundaries which is advantageous for the suppression of photo-induced charge carrier recombination resulting in increase of FF. However, increase of surface roughness resulted in larger contact area at interface which might produce more tarp states and poorer wettability of HTM solution leading in decrease of Jsc. Surface morphology of MAPbI3 layer on the performance of solar cell devices is also an important research issue. By optimizing the drying temperature to 60 oC, the highest efficiency of 14.4% was achieved for the CH3NH3PbI3-based solar cell devices., Comment: 17 pages, 7 figures