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Ultrashort pulse lasers focused in air result in plasma filaments that generate ultra-broadband secondary radiation that ranges from the megahertz to terahertz. The plasma currents responsible for the broadband radiation are the ponderomotive for the terahertz regime and the plasma wake surface wave (PWSW) for the gigahertz regime. Through experimental studies, I explore the optimization of microwave regime (1 - 67 GHz) of the spectrum. The experiments consider the effects of background gas and pressure in the filamentation region, pulse length of the laser, and wavelength of the laser on the plasma currents that produce the broadband radiated pulse. The results of the first experiment suggest that reduction of the electron-neutral collisions permits the growth of the PWSW and improve microwave amplitude. The second experiment demonstrates a growth in resulting microwave signal as a result of collisional processes driven by longer pulse durations. The final experiment demonstrates and order of magnitude increase in the microwave field amplitudes when the wavelength of a picosecond scale, terawatt class laser pulse is increased from 1.035 microns to 9.2 microns.

The research presented here is focused on achieving an active compact RF/Photonic antenna module based on a broadband antenna design integrated with a quantum dot mode-locked laser (QDMLL). A two-section QDMLL is used to produce pulsed microwaves signals to feed the radiating antenna. To realize the microwave signal radiation generated by the QDMLL, several possible MLL-integrated-antennas are proposed. The prototype integrated antenna is fully described, including the design, fabrication, and characterization of the antenna performance. Additionally, this work deals with the improvement of the radiation efficiency and functionality of the integrated module. An impedance matching network is designed to match the QDMLL to a bowtie slot antenna. The RF/Photonic integrated prototype is tested and analyzed over a wide frequency range. Finally a QDMLL-integrated-phased antenna array is designed to achieve beam steering. By manipulating the applied voltage bias of each QDMLL, one can achieve beam steering without the use of external RF phase shifters yielding a more compact design of an RF/photonic antenna on a chip. The 2-element integrated prototype is presented and discussed. Beam-steering is fully demonstrated via both simulation and measurements.

Analysis of the limit-cycle, also known as period-one (P1), dynamics induced by strong optical injection to a semiconductor laser is carried out. Based on the well-established laser rate equations, an approximate solution of the P1 dynamics can be obtained by starting with a general limit-cycle solution. Our results are in good agreement with numerical and experimental results by taking the second harmonic of the P1 frequency into account. Our analysis shows that the strong coupling between the oscillating carrier density and the oscillating optical field is responsible for the high nonlinearity of these P1 dynamics.