ABSTRACT
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(2) nonlinearity of a thin-film lithium niobate (TFLN) resonator device to efficiently generate squeezed states of light. Our system integrates all essential components-except for the laser and two detectors-on a single chip with an area of one square centimeter, reducing the size, operational complexity, and power consumption associated with conventional setups. Using the balanced homodyne measurement subsystem that we implemented on the same chip, we measure a squeezing of 0.55 decibels and an anti-squeezing of 1.55 decibels. We use 20 milliwatts of input power to generate the parametric oscillator pump field by using second harmonic generation on the same chip. Our work represents a step toward compact and efficient quantum optical systems posed to leverage the rapid advances in integrated nonlinear and quantum photonics.
ABSTRACT
In situ tunable photonic filters and memories are important for emerging quantum and classical optics technologies. However, most photonic devices have fixed resonances and bandwidths determined at the time of fabrication. Here we present an in situ tunable optical resonator on thin-film lithium niobate. By leveraging the linear electro-optic effect, we demonstrate widely tunable control over resonator frequency and bandwidth on two different devices. We observe up to â¼50 × tuning in the bandwidth over â¼50 V with linear frequency control of â¼230 MHz/V. We also develop a closed-form model predicting the tuning behavior of the device. This paves the way for rapid phase and amplitude control over light transmitted through our device.
ABSTRACT
Optical frequency combs have revolutionized precision measurement, time-keeping and molecular spectroscopy1-7. A substantial effort has developed around 'microcombs': integrating comb-generating technologies into compact photonic platforms5,7-9. Current approaches for generating these microcombs involve either the electro-optic10 or Kerr mechanisms11. Despite rapid progress, maintaining high efficiency and wide bandwidth remains challenging. Here we introduce a previously unknown class of microcomb-an integrated device that combines electro-optics and parametric amplification to yield a frequency-modulated optical parametric oscillator (FM-OPO). In contrast to the other solutions, it does not form pulses but maintains operational simplicity and highly efficient pump power use with an output resembling a frequency-modulated laser12. We outline the working principles of our device and demonstrate it by fabricating the complete optical system in thin-film lithium niobate. We measure pump-to-comb internal conversion efficiency exceeding 93% (34% out-coupled) over a nearly flat-top spectral distribution spanning about 200 modes (over 1 THz). Compared with an electro-optic comb, the cavity dispersion rather than loss determines the FM-OPO bandwidth, enabling broadband combs with a smaller radio-frequency modulation power. The FM-OPO microcomb offers robust operational dynamics, high efficiency and broad bandwidth, promising compact precision tools for metrology, spectroscopy, telecommunications, sensing and computing.
ABSTRACT
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. Here we present a photonic integrated circuit in thin-film lithium niobate that meets these requirements. We use the second-order nonlinearity to produce a squeezed state at the same frequency as the pump light and realize circuit control and sensing with electro-optics. Using 26.2 milliwatts of optical power, we measure (2.7 ± 0.2)% squeezing and apply it to increase the signal-to-noise ratio of phase measurement. We anticipate that photonic systems like this, which operate with low power and integrate all of the needed functionality on a single die, will open new opportunities for quantum optical sensing.
Subject(s)
Oxides , Photons , Records , Signal-To-Noise RatioABSTRACT
BACKGROUND: Recently, surface EMG of parasternal intercostal muscle has been incorporated in the "ERS Statement of Respiratory Muscle Testing" as a clinical technique to monitor the neural respiratory drive (NRD). However, the anatomy of the parasternal muscle risks confounding EMG "crosstalk" activity from neighboring muscles. OBJECTIVES: To determine if surface "parasternal" EMG: 1) reliably estimates parasternal intercostal EMG activity, 2) is a valid surrogate expressing neural respiratory drive (NRD). METHODS: Fine wire electrodes were implanted into parasternal intercostal muscle in 20 severe COPD patients along with a pair of surface EMG electrodes at the same intercostal level. We recorded both direct fine wire parasternal EMG (EMGPARA) and surface estimated "parasternal" EMG (SurfEMGpara) simultaneously during resting breathing, volitional inspiratory maneuvers, apnoea with extraneous movement of upper extremity, and hypercapnic ventilation. RESULTS: Surface estimated "parasternal" EMG showed spurious "pseudobreathing" activity without any airflow while real parasternal EMG was silent, during apnoea with body extremity movement. Surface estimated "parasternal" EMG did not faithfully represent real measured parasternal EMG. Surface estimated "parasternal" EMG was significantly less active than directly measured parasternal EMG during all conditions including baseline, inspiratory capacity and hypercapnic ventilation. Bland-Altman analysis showed consistent bias between direct parasternal EMG recording and surface estimated EMG during stimulated breathing. CONCLUSION: Surface "parasternal" EMG does not consistently or reliably express EMG activity of parasternal intercostal as recorded directly by implanted fine wires. A chest wall surface estimate of parasternal intercostal EMG may not faithfully express NRD and is of limited utility as a biomarker in clinical applications.