Abstract
The effect of optical feedback on the stability and linewidth of a photonic microwave generated in an optically injected single-mode vertical-cavity surface-emitting laser has been investigated in both cases of single feedback and double feedback. The stability of the photonic microwave is quantified by measuring the microwave frequency range using the long sweep time of the radio frequency spectrum analyzer. The effect of the feedback phase on the side peaks in the single feedback has also been studied. The experimental results show that both single feedback and double feedback can reduce the linewidth of the photonic microwave and improve its stabilization. A narrow linewidth photonic microwave spectrum with suppressed side peaks has been achieved in a single feedback configuration at the optimal feedback phase condition. The simulated results using the spin-flip model confirm that side peaks suppression in the single optical feedback configuration is sensitive to the feedback phase. For nonoptimal feedback phase conditions, single optical feedback can generate many side peaks which are related to external cavity. These side peaks can be suppressed by introducing the second feedback.
Highlights
M ICROWAVE photonics technology has attracted significantly research interest due to its wide variety of applications [1,2,3,4,5,6]
We have studied the effect of optical feedback on the linewidth and stability of photonic microwave generated based on P1
The results show that both single feedback and double feedback can reduce the linewidth
Summary
M ICROWAVE photonics technology has attracted significantly research interest due to its wide variety of applications [1,2,3,4,5,6]. Many techniques have been proposed and demonstrated in generating photonic microwave, which includes direct modulation, optical heterodyne technique, external modulation, mode-locked semiconductor lasers, optoelectronic oscillator (OEO) and period one (P1) oscillation [4, 8] Among these techniques, photonic microwave generation based on P1 oscillation dynamics has many advantages, such as a nearly single sideband (SSB) spectrum, which minimizes the power penalty, low cost due to all-optical components configuration and widely tunable oscillation frequency far from its original relaxation resonance frequency [9,10,11]. To the best of our knowledge, no study has been reported the effect of the optical feedback on the stabilization of the broadly tunable photonic microwave in single-transverse mode VCSELs or the linewidth reduction via the control of the optical feedback phase in long external cavity. We study the effect of both single optical feedback and double optical feedback on the linewidth of the generated photonic microwave based P1 oscillation in a single-mode VCSEL. The frequency resolution of the RF spectrum analyzer’s was set at 10 kHz and the sweep time was 50 milliseconds unless stated otherwise
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