A multi-GHz chaotic optoelectronic oscillator based on an external cavity semiconductor laser (ECL) is demonstrated. Unlike standard optoelectronic oscillators for microwave applications, we do not employ the dynamic light output incident on a photodiode to generate the microwave signal, but instead generate the microwave signal directly by measuring the terminal voltage V (t) of the laser diode of the ECL under constant-current operation, thus obviating the photodiode entirely.
Laser diodes with optical feedback can exhibit periodic intensity oscillations at or near the relaxation-oscillation frequency. We demonstrate optoelectronic oscillators based on external-cavity semiconductor lasers in a periodic dynamical regime tunable over the entire X-band. Moreover, unlike standard optoelectronic oscillators, we need not employ the time-dependent optical intensity incident on a photodiode to generate the microwave signal, but rather have the option of generating the electrical microwave signal directly as a voltage V (t) at the laser-diode injection terminals under constant current operation; no photodiode need be involved, thus circumventing optical-toelectrical conversion. We achieve a timing jitter of 10 ps and a quality factor of 2 × 10 5 across the entire X-band, that ranges from 6.79 GHz to 11.48 GHz. Tuning is achieved by varying the injection current J. * cychang@gatech.edu † Present address: Almae Technologies, Route de Nozay,
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