arXiv subjects

Jonathan Musgrave

Publications and source records attributed to Jonathan Musgrave.

4 recordsLinked to original sources

arXiv2026

Dissipative quadratic soliton mode-locked optical parametric oscillator

Femtosecond mode-locked lasers are foundational to ultrafast science, yet their spectral reach remains constrained by the finite emission bandwidth of available gain media. Optical parametric oscillators (OPOs) overcome this constraint but typically require complex synchronous pumping by external femtosecond lasers. Here we demonstrate a fundamentally different approach: passive mode-locking of a continuous-wave-driven, doubly resonant degenerate OPO via the spontaneous formation of femtosecond dissipative quadratic solitons (DQS). We show that phase-matched intracavity cascaded quadratic nonlinearity (PICQN), enabled by negligible pump-signal walk-off in a doubly resonant cavity, generates a non-local effective Kerr nonlinearity (EKN) that governs the cavity dynamics and drives soliton formation. The engineered EKN exceeds the intrinsic material Kerr nonlinearity by more than three orders of magnitude and is continuously tunable in magnitude and sign via pump phase detuning, enabling a paradigm shift from dispersion to nonlinearity engineering for dissipative soliton formation. Comprehensive stability analysis reveals distinct dynamical regimes governed by pumping and cavity conditions, providing a versatile framework for exploring previously understudied quadratic soliton physics. Experimentally, we observe bichromatic femtosecond DQSs at 1572 nm and 786 nm with pulse durations of 336 fs and 447 fs, respectively, peak powers up to 150 W, and a conversion efficiency of 5% under 600 mW continuous-wave pumping. Our work establishes a simple, flexible, and scalable architecture for femtosecond OPOs that bypasses the need for synchronized mode-locked pump lasers. By shifting from traditional dispersion engineering to in-situ nonlinearity engineering, this platform extends the reach of soliton-based technologies and enables dissipative solitons across diverse platforms and spectral regimes.

physics.optics↗

arXiv2025

Dissipative quadratic soliton mode-locking of nonlinear frequency conversion

Nonlinear frequency conversion underpins numerous classical and quantum photonics applications but conventionally relies on synchronized femtosecond mode-locked lasers and dispersion-engineered enhancement cavities - an approach that imposes substantial system complexity. Here, we report a fundamentally different paradigm: dissipative quadratic soliton (DQS) mode-locking in a continuous-wave (CW)-pumped, doubly resonant second-harmonic generation cavity. By leveraging a cascaded quadratic nonlinear process, we realize an effective Kerr nonlinearity (EKN) that exceeds the intrinsic material Kerr response by over three orders of magnitude and is tunable in both magnitude and sign via pump detuning. This engineered nonlinearity enables femtosecond DQS formation in a free-space lithium niobate cavity with normal dispersion, without dispersion engineering or synchronization electronics. Numerical simulations predict distinct dynamical regimes depending on phase detuning, and experiments confirm the spontaneous emergence of bichromatic femtosecond solitons spanning visible and near-infrared wavelengths. The observed DQSs exhibit spectral 3 dB bandwidths and transform-limited pulse durations of 1.15 THz and 274 fs for the pump and 1.13 THz and 279 fs for the second harmonic. Our results establish a versatile platform for efficient and broadband nonlinear frequency conversion and frequency comb generation based on quadratic nonlinearities, with significant implications for scalable ultrafast and nonlinear photonics applications.

physics.optics↗

arXiv2024

Fourier Domain Physics Informed Neural Network

Ultrafast optics is driven by a myriad of complex nonlinear dynamics. The ubiquitous presence of governing equations in the form of partial integro-differential equations (PIDE) necessitates the need for advanced computational tools to understand the underlying physical mechanisms. From the experimental perspective, signal-to-noise ratio and availability of measurable data, accounts for a bottle neck in numerical and data-driven modeling methods. In this paper we extend the application of the physics informed neural network (PINN) architecture to include prior knowledge in both the physical and Fourier domain. We demonstrate our Fourier Domain PINN (FD-PINN) in two distinct forms. The Continuous time FD-PINN is used to predict accurate solutions to the Generalized Pulse Propagation Equation, which includes the complete delayed nonlinear response, in the data-starved and noisy regime. We extend the architecture to the Discrete time FD-PINN to recover the delayed-response physics from spatially separated measurement points. We conducted the first systematic study of the effect of SNR on the spatiotemporal field prediction as well as physics discovery. Our architecture ensures high fidelity predictive modeling and hidden physics recovery for applications such as image reconstruction, pulse characterization and shaping, as well as hidden parameter discovery. The benefits of the FD-PINN for ultrafast nonlinear optics make it immediately experimentally deployable. FD-PINN represents the next generation of tools to study optical phenomena both through modeling and measurements for both forward and inverse problems.

physics.optics↗

arXiv2024

Cross-polarized stimulated Brillouin scattering empowered photonics

This paper explores the integration of cross-polarized stimulated Brillouin scattering (XP-SBS) with Kerr and quadratic nonlinearities in lithium niobate (LN) to enhance photonic device performance. Three novel applications are demonstrated: (i) a reconfigurable stimulated Brillouin laser (SBL) with 0.7-Hz narrow linewidth and 40-nm tunability, enabled by XP-SBS's thermo-optic phase matching; (ii) an efficient coherent mode converter achieving 55% conversion efficiency via intracavity Brillouin-enhanced four-wave mixing; (iii) a Brillouin-quadratic laser and frequency comb operational in near-infrared and visible bands, benefiting from the interaction between XP-SBS and quadratic nonlinearity. These advancements promise significant improvements in photonic technologies, including narrow-linewidth laser, microcomb generation, and optical signal processing, paving the way for more robust and versatile applications.

physics.optics↗