Wireless injection locking and phase noise reduction in a semiconductor laser driven by a resonant tunnelling diode nonlinear oscillator

The development of optoelectronic integrated circuits (OEIC) that combine optical and electronic functionalities on a single chip have been driven by numerous telecommunications applications including microwave-optical interfaces for radio-over-fiber picocellular networks for the next-generation wireless communication systems, also know as fourth-generation (4G) systems. The integration of a resonant tunnelling diode (RTD) with laser diode (LD) gives rise to a novel nonlinear optoelectronic oscillator, the RTD- LD oscillator, with innovative functionalities capable of various electro-photonic operation modes including optoelectronic voltage controlled oscillator and synchronization to low power RF signals. The circuit nonlinear behaviour is a consequence of the RTD nonlinear current-voltage characteristic that shows negative differential resistance region. This paper investigates by experimental evidence the potential application of the RTD-LD oscillator as a wireless-to- optical (WO) converter. The RTD-LD WO converter includes a patch antenna for directional reception of broadcasted signals at microwave frequencies. In the presence of radio-broadcasted signals with frequencies within the RTD-LD oscillator locking ranges the radio sub-carrier of the laser optical output follows the phase of the broadcasted signals with significant noise reduction around the locking frequencies. The circuit locking ranges around the oscillator´s natural frequency and its sub-harmonics/harmonics frequencies are controlled by the oscillator quiescent bias voltage.