文摘
We show analytically as well as demonstrate experimentally an approach to generate microwave waveforms with wide chirp tuning range. The approach is based on the interference of two temporally-stretched pulses which are time-delayed with respect to each other and having different frequency chirp. This approach is realized by an unbalanced Mach Zehnder Interferometer (MZI) incorporating a linearly-chirped fiber-Bragg-grating (LCFBG) whose group-delay-dispersion (GDD) can be tuned across a wide range. In general, tuning the GDD of the LCFBG changes the chirp rate of the generated microwave waveform and tuning the relative time-delay between the interferometer arms changes the center frequency of the generated microwave waveform. Balanced photodetection is also implemented to obtain DC-free microwave waveforms. Based on this approach, we demonstrate the generation of microwave waveforms with different center frequencies and with the chirp rates ranging from¡«?126.7 GHz/ns to ¡«+120.8 GHz/ns, including the zero-chirp case.