Roles of temperature, materials, and domain inversion in high-performance, low-bias-drift thin film lithium niobate blue light modulators.

We demonstrate a thin film lithium niobate electro-optic modulator operating at 456 nm with an RF voltage-length product of 0.38 V-cm and a bandwidth of 6.9 GHz.

Temperature Dependence of the Mechanical Dissipation of Gallium Bonds for Use in Gravitational Wave Detectors.

The mirror suspensions in gravitational wave detectors demand low mechanical loss jointing to ensure good enough detector performance and to enable the detection of gravitational waves. Hydroxide catalysis bonds have been used in the fused silica suspensions of the GEO600, Advanced LIGO, and Advanced Virgo detectors. Future detectors may use cryogenic cooling of the mirror suspensions and this leads to a potential change of mirror material and suspension design.

Picojoule-level supercontinuum generation in thin-film lithium niobate on sapphire.

We demonstrate ultraviolet-to-mid-infrared supercontinuum generation (SCG) inside thin-film lithium niobate (TFLN) on sapphire nanowaveguides. This platform combines wavelength-scale confinement and quasi-phasematched nonlinear interactions with a broad transparency window extending from 350 to 4500 nm. Our approach relies on group-velocity-matched second-harmonic generation, which uses an interplay between saturation and a small phase-mismatch to generate a spectrally broadened fundamental and second harmonic using only a few picojoules of in-coupled fundamental pulse energies.

Single-mode squeezed-light generation and tomography with an integrated optical parametric oscillator.

Quantum optical technologies promise advances in sensing, computing, and communication. A key resource is squeezed light, where quantum noise is redistributed between optical quadratures. We introduce a monolithic, chip-scale platform that exploits the χ nonlinearity of a thin-film lithium niobate (TFLN) resonator device to efficiently generate squeezed states of light.

Integrated frequency-modulated optical parametric oscillator.

Optical frequency combs have revolutionized precision measurement, time-keeping and molecular spectroscopy. A substantial effort has developed around 'microcombs': integrating comb-generating technologies into compact photonic platforms. Current approaches for generating these microcombs involve either the electro-optic or Kerr mechanisms.

Integrated quantum optical phase sensor in thin film lithium niobate.

The quantum noise of light, attributed to the random arrival time of photons from a coherent light source, fundamentally limits optical phase sensors. An engineered source of squeezed states suppresses this noise and allows phase detection sensitivity beyond the quantum noise limit (QNL). We need ways to use quantum light within deployable quantum sensors.

Ultra-low-power second-order nonlinear optics on a chip.

Second-order nonlinear optical processes convert light from one wavelength to another and generate quantum entanglement. Creating chip-scale devices to efficiently control these interactions greatly increases the reach of photonics. Existing silicon-based photonic circuits utilize the third-order optical nonlinearity, but an analogous integrated platform for second-order nonlinear optics remains an outstanding challenge.

Enhanced medium-range order in vapor-deposited germania glasses at elevated temperatures.

Glasses are nonequilibrium solids with properties highly dependent on their method of preparation. In vapor-deposited molecular glasses, structural organization could be readily tuned with deposition rate and substrate temperature. Here, we show that the atomic arrangement of strong network-forming GeO glass is modified at medium range (<2 nm) through vapor deposition at elevated temperatures.

Low Mechanical Loss TiO_{2}:GeO_{2} Coatings for Reduced Thermal Noise in Gravitational Wave Interferometers.

The sensitivity of current and planned gravitational wave interferometric detectors is limited, in the most critical frequency region around 100 Hz, by a combination of quantum noise and thermal noise. The latter is dominated by Brownian noise: thermal motion originating from the elastic energy dissipation in the dielectric coatings used in the interferometer mirrors. The energy dissipation is a material property characterized by the mechanical loss angle.

Analysis of two-level systems and mechanical loss in amorphous ZrO-doped TaO by non-cage-breaking and cage-breaking transitions.

The energy landscape of ZrO-doped amorphous TaO is explored in this work. With models corresponding to experimental concentrations of 50% Zr and 50% Ta cations, we search for, gather, and analyze two-level systems (TLSs) from molecular dynamic simulations. The mechanical loss function is calculated for each TLS individually.

Performance scaling of a 10-GHz solid-state laser enabling self-referenced CEO frequency detection without amplification.

A simple and compact straight-cavity laser oscillator incorporating a cascaded quadratic nonlinear crystal and a semiconductor saturable absorber mirror (SESAM) can deliver stable femtosecond modelocking at high pulse repetition rates >10 GHz. In this paper, we experimentally investigate the influence of intracavity dispersion, pump brightness, and cavity design on modelocking with high repetition rates, and use the resulting insights to demonstrate a 10.4-GHz straight-cavity SESAM-modelocked Yb:CALGO laser delivering 108-fs pulses with 812 mW of average output power.

Growth and characterization of ScO doped TaO thin films.

We present the optical and structural characterization of films of , , and doped with a cation ratio around 0.1 grown by reactive sputtering. The addition of as a dopant induces the formation of tantalum suboxide due to the "oxygen getter" property of scandium.

Experimental investigation of performance differences between coherent Ising machines and a quantum annealer.

Physical annealing systems provide heuristic approaches to solving combinatorial optimization problems. Here, we benchmark two types of annealing machines-a quantum annealer built by D-Wave Systems and measurement-feedback coherent Ising machines (CIMs) based on optical parametric oscillators-on two problem classes, the Sherrington-Kirkpatrick (SK) model and MAX-CUT. The D-Wave quantum annealer outperforms the CIMs on MAX-CUT on cubic graphs.

Pump-linewidth-tolerant wavelength multicasting using soliton Kerr frequency combs.

We experimentally demonstrate pump-linewidth-tolerant wavelength multicasting using microresonator-based soliton Kerr frequency combs. When Kerr comb lines serve as coherent pumps in a periodically poled lithium niobate waveguide, the linewidth of the multicast signal almost remains that of the original signal at different linewidths of Kerr combs, ranging from 100 kHz to 1 MHz. However, in conventional multicasting where free-running (FR) pumps are used, the linewidth of the converted signal significantly increases.

Pilot-tone-based self-homodyne detection using optical nonlinear wave mixing.

An all-optical pilot-tone-based self-homodyne detection scheme using nonlinear wave mixing is experimentally demonstrated. Two scenarios are investigated using (1) multiple wavelength-division-multiplexed channels with sufficient power of the pilot tones and (2) a single channel with a low-power pilot tone. The eye diagram and bit error rate of the system are studied by tuning various parameters such as pump power, relative phase, and pilot-to-signal ratio.

Simultaneous all-optical phase noise mitigation and automatically locked homodyne reception of an incoming QPSK data signal.

Simultaneous phase noise mitigation and automatic phase/frequency-locked homodyne reception is demonstrated for a 20-32 Gbaud QPSK signal. A phase quantization function is realized to squeeze the phase noise of the signal by optical wave mixing of the signal, its third-order harmonic, and their corresponding delayed variant conjugates, converting the noisy input into a noise-mitigated signal. In a simultaneous nonlinear process, the noise-mitigated signal is automatically phase- and frequency-locked with a "local" pump laser, avoiding the need for feedback or phase/frequency tracking for homodyne detection.

Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films.

Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance.

Nonlinear diffusion model for annealed proton-exchanged waveguides in zirconium-doped lithium niobate.

Photorefractive-damage- (PRD) resistant zirconium-oxide-doped lithium niobate is investigated as a substrate for the realization of annealed proton-exchanged (APE) waveguides. Its advantages are a favorable distribution coefficient, PRD resistance comparable to magnesium-oxide-doped lithium niobate, and a proton-diffusion behavior resembling congruent lithium niobate. A 1D model for APE waveguides was developed based on a previous model for congruently melting lithium niobate.

Demonstration of optical multicasting using Kerr frequency comb lines.

We experimentally demonstrate optical multicasting using Kerr frequency combs generated from a SiN microresonator. We obtain Kerr combs in two states with different noise properties by varying the pump wavelength in the resonator and investigate the effect of Kerr combs on multicasting. Seven-fold multicasting of 20 Gbaud quadrature phase-shift-keyed signals and four-fold multicasting of 16-quadrature amplitude modulation signals have been achieved when low-phase-noise combs are input into a periodically poled lithium niobate waveguide.

Experimental demonstration of tunable homodyne detection of WDM and dual-polarization PSK channels by automatically locking the channels to a local pump laser using nonlinear mixing.

This Letter proposes a method for tunable automatically locked homodyne detection of wavelength-division multiplexing (WDM) dual-polarization (DP) phase-shift keyed (PSK) channels using nonlinear mixing. Two stages of periodically poled lithium niobate (PPLN) waveguides and an LCoS filter enable automatic phase locking of the channels to a local laser.

Two-photon interference at telecom wavelengths for time-bin-encoded single photons from quantum-dot spin qubits.

Practical quantum communication between remote quantum memories rely on single photons at telecom wavelengths. Although spin-photon entanglement has been demonstrated in atomic and solid-state qubit systems, the produced single photons at short wavelengths and with polarization encoding are not suitable for long-distance communication, because they suffer from high propagation loss and depolarization in optical fibres. Establishing entanglement between remote quantum nodes would further require the photons generated from separate nodes to be indistinguishable.

Optical channel de-aggregation of quadrature-phase-shift-keying and eight-phase-shift-keying data using mapping onto constellation axes.

An eight-phase-shift-keying signal is experimentally de-aggregated onto two four-pulse amplitude modulation signals using nonlinear processes in optical elements. Quadrature-phase-shift-keying signals are similarly de-multiplexed into two binary phase shift keying signals by mapping the data points onto the constellation axes. De-multiplexing performance is evaluated as a function of the optical signal-to-noise ratio of the incoming signals.

Tunable delay control of entangled photons based on dispersion cancellation.

We propose and demonstrate a novel approach for controlling the temporal position of the biphoton correlation function using pump frequency tuning and dispersion cancellation; precise waveguide engineering enables biphoton generation at different pump frequencies while the idea of nonlocal dispersion cancellation is used to create the relative signal-idler delay and simultaneously prevents broadening of their correlation. Experimental results for delay shifts up to ±15 times the correlation width are shown along with discussions of the performance metrics of this approach.

Phase noise mitigation of QPSK signal utilizing phase-locked multiplexing of signal harmonics and amplitude saturation.

We demonstrate an all-optical phase noise mitigation scheme based on the generation, delay, and coherent summation of higher order signal harmonics. The signal, its third-order harmonic, and their corresponding delayed variant conjugates create a staircase phase-transfer function that quantizes the phase of quadrature-phase-shift-keying (QPSK) signal to mitigate phase noise. The signal and the harmonics are automatically phase-locked multiplexed, avoiding the need for phase-based feedback loop and injection locking to maintain coherency.

Tunable radio frequency photonics filter using a comb-based optical tapped delay line with an optical nonlinear multiplexer.

A radio frequency (RF) photonic filter is experimentally demonstrated using an optical tapped delay line (TDL) based on an optical frequency comb and a periodically poled lithium niobate (PPLN) waveguide as multiplexer. The approach is used to implement RF filters with variable bandwidth, shape, and center-frequency.