arXiv subjects

Arkadev Roy

Publications and source records attributed to Arkadev Roy.

21 records · Page 2Linked to original sources

arXiv2020

Non-Dissipative Non-Hermitian Dynamics and Exceptional Points in Coupled Optical Parametric Oscillators

Engineered non-Hermitian systems featuring exceptional points can lead to a host of extraordinary phenomena in diverse fields ranging from photonics, acoustics, opto-mechanics, electronics, to atomic physics. Here we introduce and present non-Hermitian dynamics of coupled optical parametric oscillators (OPOs) arising from phase-sensitive amplification and de-amplification, and show their distinct advantages over conventional non-Hermitian systems relying on laser gain and loss. OPO-based non-Hermitian systems can benefit from the instantaneous nature of the parametric gain, noiseless phase-sensitive amplification, and rich quantum and classical nonlinear dynamics. We show that two coupled OPOs can exhibit spectral anti-PT symmetry and an exceptional point between its degenerate and non-degenerate operation regimes. To demonstrate the distinct potentials of the coupled OPO system compared to conventional non-Hermitian systems, we present higher-order exceptional points with two OPOs, tunable Floquet exceptional points in a reconfigurable dynamic non-Hermitian system, and generation of squeezed vacuum around exceptional points, all of which are not easy to realize in other non-Hermitian platforms. Our results show that coupled OPOs are an outstanding non-Hermitian setting with unprecedented opportunities in realizing nonlinear dynamical systems for enhanced sensing and quantum information processing.

quant-ph↗

arXiv2020

Spectral Phase Transitions in Optical Parametric Oscillators

Spectral behaviors of photonic resonators have been the basis for a range of fundamental studies, with applications in classical and quantum technologies. Driven nonlinear resonators provide a fertile ground for phenomena related to phase transitions far from equilibrium, which can open opportunities unattainable in their linear counterparts. Here, we show that optical parametric oscillators (OPOs) can undergo second-order phase transitions in the spectral domain between degenerate and non-degenerate regimes. This abrupt change in the spectral response follows a square-root dependence around the critical point, exhibiting high sensitivity to parameter variation akin to systems around an exceptional point. We experimentally demonstrate such a phase transition in a quadratic OPO, map its dynamics to the universal Swift-Hohenberg equation, and extend it to Kerr OPOs. To emphasize the fundamental importance and consequences of this phase transition, we show that the divergent susceptibility of the critical point is accompanied by spontaneous symmetry breaking and distinct phase noise properties in the two regimes, indicating the importance of a beyond nonlinear bifurcation interpretation. We also predict the occurrence of first-order spectral phase transitions in coupled OPOs. Our results on non-equilibrium spectral behaviors can be utilized for enhanced sensing, advanced computing, and quantum information processing.

physics.optics↗

arXiv2018

Generalized Mathematical Formalism Governing Free-carrier Driven Kerr Frequency Comb in Optical Micro-cavities

Continuous-wave pumped optical microresonators have been vastly exploited to generate frequency comb (FC) utilizing the Kerr nonlinearity. Most of the nonlinear materials used to build photonic platforms exhibit nonlinear losses such as multi-photon absorption, free-carrier absorption (FCA), and free-carrier dispersion (FCD) which can strongly affect the nonlinear characteristics of the devices made out of these materials. In this work, we model the Kerr FC based on modified Lugiato-Lefever Equation (LLE) along with the rate equation and develop analytical formulations to make quick estimations of the steady-state, modulation instability (MI) gain, bandwidth and the dynamics of Kerr Frequency-Comb (FC) in presence of nonlinear losses. Our analytical model is valid over a broad wavelength range of interest as it includes the effects of all nonlinear losses. Higher order (>3) characteristic polynomial of intra-cavity power describing the steady-state homogeneous solution of the modified LLE are discussed in detail. We derive the generalized analytical expressions for the threshold of normalized pump detuning to initiate the optical bistability which is a necessary condition for the FC generation. Free-carrier dispersion-led nonlinear cavity detuning is observed through the reverse Kerr-tilt of the resonant-peaks. We further deduce the expressions for the threshold pump intensity and the range of possible cavity detuning for the initiation of the MI when all the nonlinear losses are present. To corroborate our analytical findings, LLE along with the rate equations are solved numerically through split-step Fourier method. Our theoretical study can explain several experimental results which are previously reported and thereby is able to provide a better understanding of the comb dynamics.

physics.optics↗