Optics (physics.optics)

Abstract: Raman lasers is an actively developing field of nonlinear optics aiming to create efficient frequency converters and various optical sensors. Due to the growing importance of ultracompact chip-scale technologies, there is a constant demand for optical devices miniaturization, however, the development of a nanoscale Raman laser remains a challenging endeavor. In this work, we propose a fully subwavelength Raman laser operating in visible range based on a gallium phosphide nanocylinder resonator supporting a quasi bound state in the continuum (quasi-BIC). We perform precise spectral matching of nanoparticle's high-$Q$ modes with the pump and detuned Raman emission wavelengths. As a result of our simulations, we demonstrate a design of Raman nanolaser, ready for experimental realization, with the lasing threshold expected to be as low as $P_{\mathrm{th}} \approx 21~\mathrm{mW}$. The suggested configuration, to the best of our knowledge, represents the very first prototype of a low-threshold Raman nanolaser with all the dimensions smaller than the operational wavelength.

Abstract: We consider theoretically a network of directly coupled optical microcavities to implement a space-multiplexed optical neural network in an integrated nanophotonic circuit. Nonlinear photonic network integrations based on direct coupling ensures a highly dense integration, reducing the chip footprint by several orders of magnitude compared to other implementations. Different nonlinear effects inherent to such microcavities are studied when used for realizing an all-optical autonomous computing substrate, here based on the reservoir computing concept. We provide an in-depth analysis of the impact of basic microcavity parameters on computational metrics of the system, namely, the dimensionality and the consistency. Importantly, we find that differences between frequencies and bandwidths of supermodes formed by the direct coupling is the determining factor of the reservoir's dimensionality and its scalability. The network's dimensionality can be improved with frequency-shifting nonlinear effects such as the Kerr effect, while two-photon absorption has an opposite effect. Finally, we demonstrate in simulation that the proposed reservoir is capable of solving the Mackey-Glass prediction and the optical signal recovery tasks at GHz timescale.

Abstract: An integrated photonic circuit architecture to perform a modified-convolution operation based on the Discrete Fractional Fourier Transform (DFrFT) is introduced. This is accomplished by utilizing two nonuniformly-coupled waveguide lattices with equally-spaced eigenmode spectra and with different lengths that perform DFrDT operations of complementary orders sandwiching a modulator array. Numerical simulations show that smoothing and edge detection tasks are indeed performed even for noisy input signals.