arXiv subjects

Liam McRae

Publications and source records attributed to Liam McRae.

5 recordsLinked to original sources

arXiv2026

Ion-Implanted Silicon Nanoregions Enable Ultra-Low-Loss Trimming of Cladded Photonic Integrated Circuits

Photonic integrated circuits (PICs) have emerged as a key platform for information processing, including optical communication and computing. As PIC complexity increases, fabrication-induced response deviations accumulate, making post-fabrication trimming critical for unlocking their full potential. Here, we demonstrate that silicon ion implantation enables scalable, ultra-low-loss trimming of cladded PICs by locally forming a high-index silicon-rich region. Structural characterization confirms that the silicon-implanted nanoregion is confined to the cladding without observable damage to the underlying waveguide. The implantation-induced excess loss is below 0.001 dB per {\pi} phase shift, while the optical response remains stable over a four-month observation period. Automated trimming is demonstrated on a photonic crossbar array, reducing the average channel output variation from 78.5% to 5.9%. These results establish a practical route towards automated, ultra-low-loss post-fabrication trimming for large-scale cladded PICs.

physics.optics↗

arXiv2026

Octave bandwidth 3D-Printed Couplers for Low-Loss Thin-Film Lithium Tantalate Circuits

Low-loss, broadband photonic integrated circuits (PICs) are critical enablers for optical communications, photonic computing, and quantum applications. Lithium tantalate on insulator (LTOI) is an emerging photonic platform offering a wide transparency window and strong Pockels effect, and thereby enabling efficient electro-optic modulation and high data rates. Here, we present the first implementation of efficient out-of-plane polymer coupling interfaces fabricated via 3D direct laser writing for both fully etched strip and partially etched rib LTOI waveguides, achieving ultra-low coupling losses of 0.9 dB (strip) and 1.25 dB (rib) per interface. Both coupler types exhibit a 3 dB optical bandwidth spanning more than an octave from 850 nm to 1740 nm and maintain stable operation under 1 W optical input power. Combined with on-chip waveguides exhibiting propagation losses below 0.1 dB/cm, these characteristics represent a key step toward unlocking the full potential of LTOI for high-speed optical signal processing with an unprecedented degree of parallelism. In addition, the octave-spanning bandwidth enables efficient interfacing of both the fundamental and second-harmonic signals, making the platform highly attractive for second harmonic generation based quantum squeezing applications.

physics.optics↗

arXiv2026

Integrated squeezed light sources for two-mode entanglement in thin-film lithium niobate

Scalable generation of nonclassical light sources on an integrated platform is a key requirement for photonic quantum information processing. In particular, realizing multiple indistinguishable squeezed light sources on a single chip is an essential step toward continuous-variable quantum computing. Here, we demonstrate the fabrication of two indistinguishable and independently controllable optical parametric oscillators on a thin-film lithium niobate (TFLN) platform. The device design focuses on reproducibility, independent tunability, and compatibility with larger telecom-wavelength continuous-variable photonic circuits. We observe up to 0.5 dB of directly measured squeezing below the shot-noise level from each source. By interfering the two modes on a beam splitter, we generate an EPR-type two-mode squeezed state and verify continuous-variable entanglement through violation of the Duan-Simon inseparability criterion. This is the first demonstration of two independently tunable squeezed-light sources on a single TFLN chip and their use for generating continuous-variable entanglement.

quant-ph↗

arXiv2026

Voltage-Programmable Photon Statistics Using a High-Extinction Thin-film Lithium Niobate Modulator

Controlling the statistical properties of light, namely the fluctuations in photon arrival, entropy and number, is essential for both classical and quantum photonics. While integrated systems provide tunable control over amplitude, phase, and wavelength, real-time modulation of photon statistics has remained a long-standing challenge. Herein, we introduce the concept and experimental realization of a photon statistics transducer: a high-extinction, broadband electro-optic device capable of deterministically shaping photon-number distributions at nanosecond timescales. Our approach employs a cascaded thin-film lithium niobate (TFLN) Mach-Zehnder amplitude modulator delivering more than 50 dB extinction, enabling precise suppression and release of coherent seed light from an integrated InP laser. By exploiting the interplay between seed suppression and erbium-doped fiber amplifier dynamics, we demonstrate smooth, voltage-controlled switching between Poissonian and super-Poissonian photon statistics, with second-order coherence g2(0) tunable from 1.0 to 1.7. Complementary measurements with superconducting nanowire single-photon detectors further show photon-flux control down to sub-photon levels, highlighting the potential for future operation with non-classical sources. The photon statistics transducer thus establishes statistical modulation as a new functional primitive in integrated photonics. Applications range from entropy generation and secure communication to neuromorphic and hybrid quantum-classical processing, where controlled randomness and entropy are essential resources. By enabling programmable transitions between statistical regimes using only electronic drive signals, our work lays the foundation for adaptive, entropy-aware photonic systems that bridge classical and quantum domains.

physics.optics↗

arXiv2024

Fast thermo-optic switching on silicon nitride platform through parity-time symmetry breaking

This work demonstrates a fast thermo-optic switching mechanism on silicon nitride on insulator platform leveraging parity-time symmetry breaking. The cladding-free design enables low-loss optical propagation in a partially metal-covered waveguide, with the same metal layer serving as an integrated heater for rapid phase tuning. The fabricated device exhibits an 8.5 μs rise time for a π phase shift, despite the weak thermo-optic coefficient in silicon nitride. Additionally, the impact of thermal cross-talk is investigated and an insertion loss as low as 0.39 dB for a 100-μm-long heater-waveguide section is demonstrated.

physics.optics↗