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Mark Earnshaw

Publications and source records attributed to Mark Earnshaw.

10 recordsLinked to original sources
arXiv2026

Unveiling charge dynamics on the generation of high extinction wide pulse generation on thin-film lithium tantalate

We experimentally demonstrate high-extinction optical pulse generation in thin-film lithium tantalate (TFLT), achieving a wide range of pulse widths with sharp rise and fall edges, without measurable distortion or long temporal tails. We further provide a direct one-to-one comparison with thin-film lithium niobate (TFLN) modulators under identical measurement conditions. Our results reveal that the distorted pulse response observed in TFLN originates from charge activation and transport, whereas the distortion-free response in TFLT is enabled by the substantially larger activation energy of defect-related charge carriers. This larger activation barrier suppresses leakage-current-induced charging dynamics, thereby enabling stable and distortion-free pulse generation. The successful generation of high-extinction, distortion-free optical pulses in TFLT can play a significant role in integrated quantum photonic technologies, particularly for qubit preparation, measurement, and fast feedback circuits.

physics.optics↗
arXiv2026

Stable thin-film lithium tantalate modulators operating at high temperature for uncooled operation

We demonstrate stable operation of a thin-film lithium tantalate (TFLT) modulator at very high operating temperatures. We show that the electro-optic modulation and bandwidth of the TFLT modulators are not affected by high-temperature operation, and both waveguide and resonant modulators are DC-bias stable even at 120{\deg}C. At higher temperatures, we even observe 10% reduction of the V{\pi} of the modulator. Our results position TFLT modulators as a strong candidate for uncooled operation in co-packaged optics.

physics.optics↗
arXiv2026

High-power handling and bias stability of thin-film Lithium Tantalate microring and coupling resonators

In this paper, we demonstrate the ultra-high-power handling capability and DC bias stability of optical microring and electro-optic (EO) coupling resonators on the thin-film lithium tantalate (TFLT) platform. We show that, with annealing, oxide-cladded TFLT resonators can handle several watts (4W) of circulating power with minimal frequency shift and no observable photo-refractive effect. Furthermore, we demonstrate a compact 2mm coupling modulator achieving a low Vpi of 3V with stable bias and phase control in the telecom C-band.

physics.optics↗
arXiv2025

A tunable FP Perot coupling interferometer on thin-film lithium niobate

We experimentally show an electro-optic tunable Fabry-Perot cavity on thin-film lithium niobate (TFLN). Instead of tuning the cavity phase and thus resonant frequency, we demonstrate modulation of the FP cavity by tuning the cavity mirrors via the electro-optic effect in the couplers. We enable full tuning of a low-Q FP cavity with only 3.5 V Vpi and a very short 3.5 mm long Mach-Zehnder interferometer (MZI) mirror.

physics.optics↗
arXiv2025

Periodically poled thin-film lithium niobate ring Mach Zehnder coupling interferometer for efficient quantum frequency conversion

Quantum frequency conversion is unavoidable for a true quantum communication network as most quantum memories work in the visible spectrum. Here, we propose a unique design of a quantum frequency converter based on a ring-Mach Zehnder interferometer coupled with a periodically poled thin-film lithium niobate waveguide. The proposed device can be-directionally convert quantum signals i.e. single photons from quantum memory such as SiV-center in diamond to the telecom wavelength offering conversion efficiency as high as 90% at mW pump power with noise photon rate below 0.1Hz.

quant-ph↗
arXiv2024

Periodically poled thin-film lithium niobate ring Mach Zehnder coupling interferometer as an efficient quantum source of light

Single photons and squeezed light are the two primary workhorses for quantum computation and quantum communication. Generating high-efficiency single photons with high purity and heralding efficiency is the prerequisite for photonic quantum computers. At the same time, generating high-efficiency scalable squeezed light is the prerequisite for continuous variable quantum computing along with sensing applications. Here, we propose a symmetric ring-Mach-Zehnder interferometer (RMZI), which includes a periodically poled lithium niobate (PPLN) waveguide as an efficient source of squeezed light and a single-photon source. We numerically show that our proposed design can generate tunable squeezed light with a squeezing level higher than -12dB with sub-milli-watt (mW) pump power. The proposed device can also generate single photons with purity as high as 99(95)% with heralding efficiency 94(99)% using only 20ps long pulses. Our proposed design is fully compatible with current fabrication technology.

physics.optics↗
arXiv2023

Unveiling the origins of quasi-phase matching spectral imperfections in thin-film lithium niobate frequency doublers

Thin-film lithium niobate (TFLN) based frequency doublers have been widely recognized as essential components for both classical and quantum optical communications. Nonetheless, the efficiency of these devices is hindered by imperfections present in the quasi-phase matching (QPM) spectrum. In this study, we present a thorough analysis of the spectral imperfections in TFLN frequency doublers with varying lengths, ranging from 5 mm to 15 mm. Employing a non-destructive diagnostic method based on scattered light imaging, we identify the sources and waveguide sections that contribute to the imperfections in the QPM spectrum. Furthermore, by mapping the TFLN film thickness across the entire waveguiding regions, we successfully reproduce the QPM spectra numerically, thus confirming the prominent influence of film thickness variations on the observed spectral imperfections. This comprehensive investigation provides valuable insights into the identification and mitigation of spectral imperfections in TFLN-based frequency doublers, paving the way toward the realization of nonlinear optical devices with enhanced efficiency and improved spectral fidelity.

physics.optics↗
arXiv2023

A surface-normal photodetector as nonlinear activation function in diffractive optical neural networks

Optical neural networks (ONNs) enable high speed parallel and energy efficient processing compared to conventional digital electronic counterparts. However, realizing large scale systems is an open problem. Among various integrated and non-integrated ONNs, free-space diffractive ONNs benefit from a large number of pixels of spatial light modulators to realize millions of neurons. However, a significant fraction of computation time and energy is consumed by the nonlinear activation function that is typically implemented using a camera sensor. Here, we propose a novel surface-normal photodetector (SNPD) with a nonlinear response to replace the camera sensor that enables about three orders of magnitude faster (5.7 us response time) and more energy efficient (less than 10 nW/pixel) response. Direct efficient vertical optical coupling, polarization insensitivity, inherent nonlinearity with no control electronics, low optical power requirements, and the possibility of implementing large scale arrays make the SNPD a promising nonlinear activation function for diffractive ONNs. To show the applicability, successful classification simulation of MNIST and Fashion MNIST datasets using the measured response of SNPD with accuracy comparable to that of an ideal ReLU function are demonstrated.

physics.optics↗