Tunable X-band optoelectronic oscillators based on external-cavity semiconductor lasers

TL;DR

This paper presents a tunable X-band optoelectronic oscillator using external-cavity semiconductor lasers that can generate microwave signals directly as voltage without a photodiode, achieving low jitter and high quality factor.

Contribution

It introduces a novel method for generating microwave signals directly from laser diodes with optical feedback, eliminating the need for optical-to-electrical conversion.

Findings

Achieved tunable microwave frequencies from 6.79 GHz to 11.48 GHz.

Demonstrated low timing jitter of less than 10 ps.

Attained a high quality factor exceeding 2×10^5.

Abstract

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-to-electrical conversion. We achieve a timing jitter of $\lesssim 10$ ps and a quality factor of $\gtrsim 2\times 10^5$ across the entire X-band, that ranges from 6.79 GHz to 11.48 GHz. Tuning is achieved by varying the injection current $J$.