Optical array antennas have diverse applications in optical communication, remote sensing, imaging, and astronomy, supporting a broad range of optical and photonics-based technologies. Traditional square phased array antennas require a half-wavelength emitter spacing to prevent secondary orders of emission (aliasing). However, achieving such small distances in optics is impractical. To break this limitation irregularly-placed arrays has been proposed. This study focuses on the alias-free spiral array, which allows for high level of sidelobe suppression. Using standard Huygens–Fresnel principle approach to calculate the emission pattern, we identify key parameters of the spiral and consider their influence on the result. We perform multi-parametric optimisation of the spiral array for maximum suppression of sidelobes, enhancing its performance by dB compared to previously suggested bio-inspired design. This research provides insights into overcoming aliasing challenges and improving the efficiency of optical array antennas.
Self-injection locking is a dynamic process that passively stabilizes the emission frequency of a laser through resonant optical feedback. In the conventional approach, the laser is self-injection locked to a high-Q microresonator via front facet coupling. However, the front facet power of such lasers is limited by nonlinear effects in the microresonator. In this study, we propose an alternative self-injection locking scheme using a back facet-coupled laser, where the power from the back facet is optimally tuned to avoid nonlinear effects in the microresonator. We develop a model for the proposed scheme and find the optimal states of the scheme.
The effect of the self-injection locking (SIL) is well-known for many years in the theory of oscillations, radiophysics and optics and is actively used for the stabilization and spectral purification of the corresponding generators. Last years it has attracted even more attention due to the possibility of using such stabilized lasers as pump sources for the realization of the nonlinear processes in the same microresonators, simultaneously used for laser linewidth reduction. However, existing linear theories of the self-injection locking unable to predict soliton generation because enough value of the pump frequency detuning can not be obtained in the linear regime. The development of full nonlinear theory becomes even more important, since recently generation of the solitonic pulses at normal group velocity dispersion has been demonstrated in the self-injection locking regime
We developed an original model describing the process of the frequency comb generation in the self-injection locking regime and performed numerical simulation of this process. Generation of the dissipative Kerr solitons in the self-injection locking regime at anomalous group velocity dispersion was studied numerically. Different regimes of the soliton excitation depending on the locking phase, backscattering parameter and pump power were identified. It was also proposed and confirmed numerically that self-injection locking may provide an easy way for the generation of the frequency combs at normal group velocity dispersion. Generation of platicons was demonstrated and studied in detail. Parameter range providing platicon excitation was found.
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