arXiv subjects

Nathan A. Harper

Publications and source records attributed to Nathan A. Harper.

4 recordsLinked to original sources

arXiv2026

Entangled photon triplets using lithium niobate nanophotonics

Multiphoton states are needed for quantum communication and computation. Multiphoton states are significantly more difficult to generate than one- and two-photon states because two individual down-conversion processes must be cascaded. Only efficiencies of $<100$ Hz/mW have been reported to date. We integrate two down-converters on the same thin-film lithium niobate waveguide, significantly enhancing the cascaded process efficiency to $237 \pm 36$ kHz/mW. The measured $4.4 \times 10^{-5}$ probability of the second down-converter, which sets the limit on detectable triplet rates, exceeds those of previous triplet sources by an order of magnitude and demonstrates a path towards MHz rates of triplets for quantum applications.

quant-ph↗

arXiv2025

Temperature-Tunable Entangled Photon Source for Multiplexed Time-Resolved Fluorescence on a Nanophotonic Platform

Compact, scalable, and multiplexed fluorescence lifetime sensors are of great interest for point-of-care diagnostics. However, current solutions either lack broad-range wavelength-tuning capabilities or involve complex optical setups that hinder miniaturization. On-chip entangled photon sources offer a promising alternative for time-resolved spectroscopy with their strong temporal correlations, tunable spectral characteristics, and small footprints. Here, we develop a temperature-tunable, visible quantum light source on thin-film lithium niobate (TFLN) with a continuous tuning range greater than one octave, spanning 564.5~nm to 1.494~$μ$m using only one waveguide. The tunability is enabled by utilizing type-I phase matching. We measured an on-chip efficiency of $(3.88\pm0.20)\times10^{9}$ pairs/s/mW, comparable to the most efficient type-0 bulk lithium niobate sources. These results show that the TFLN platform is ideal for on-chip integrated photonic and multiplexed lifetime imaging and sensing.

physics.optics↗

arXiv2024

Investigation of nanophotonic lithium niobate waveguides for on-chip evanescent wave sensing

Thin-film lithium niobate is a promising photonic platform for on-chip optical sensing because both nonlinear and linear components can be fabricated within one integrated device. To date, waveguided sample interactions for thin-film lithium niobate are not well explored. Compared to other integrated platforms, lithium niobate's high refractive index, birefringence, and angled sidewalls present unique design challenges for evanescent wave sensing. Here, we compare the performance of the quasi-transverse-electric (TE) and the quasi-transverse-magnetic (TM) mode for sensing on a thin-film lithium niobate rib waveguide with a 5 mM dye-doped polymer cladding pumped at 406 nm. We determine that both modes have propagation losses dominated by scatter, and that the absorption due to the sample only accounts for 3% of the measured losses for both modes. The TM mode has better overlap with the sample than the TE mode, but the TM mode also has a stronger propagation loss due to sidewall and sample induced scattering (32.5 $\pm$ 0.3 dB/cm) compared to the TE mode (23.0 $\pm$ 0.2 dB/cm). The TE mode is, therefore, more appropriate for sensing. Our findings have important implications for on-chip lithium niobate-based sensor designs.

physics.optics↗

arXiv2023

Highly efficient visible and near-IR photon pair generation with thin-film lithium niobate

Efficient on-chip entangled photon pair generation at telecom wavelengths is an integral aspect of emerging quantum optical technologies, particularly for quantum communication and computing. However, moving to shorter wavelengths enables the use of more accessible silicon detector technology and opens up applications in imaging and spectroscopy. Here, we present high brightness ($(1.6 \pm 0.3) \times 10^{9}$ pairs/mW/nm) visible-near-IR photon pair generation in a periodically poled lithium niobate nanophotonic waveguide. The degenerate spectrum of the photon pairs is centered at 811 nm with a bandwidth of 117 nm. The measured on-chip source efficiency of $(2.3\pm 0.5) \times 10^{11}$ pairs/mW is on par with source efficiencies at telecom wavelengths and is also orders of magnitude higher than the efficiencies of other visible sources implemented in bulk crystal or diffused waveguide-based technologies. These results represent the shortest wavelength of photon pairs generated in a nanophotonic waveguide reported to date by nearly an octave.

physics.optics↗