High-speed direct single-frequency modulation with large tuning rate and frequency excursion in cleaved-coupled-cavity semiconductor lasers

Abstract

We report a new mechanism of direct frequency modulation, the cavity-mode enhanced frequency modulation (CME-FM), using the newly developed cleaved-coupled-cavity (C3) semiconductor laser. In this operation, one of the diode of the C3 laser was operated as a laser, while the other diode was operated as a frequency modulator. It was shown that a very large frequency excursion of 150 Å and frequency tuning rate of 10 Å/mA have been obtained with a C3 GaInAsP crescent laser operating at 1.3 μm. Time-resolved spectral and spectral-resolved pulse response measurements also showed that such C3 lasers operated in highly stable single-longitudinal mode at all times even under high-speed direct frequency modulation. In addition to the important application as the optical source in FM optical communication systems, the present CME-FM C3 laser can also be used as the optical source in wavelength-division multiplexing systems. Further, it opens the possibility of ultrahigh capacity multilevel optical FM information transmission systems.