Tunneling dynamics of correlated bosons in a double well potential

The quantum dynamics of a few bosons in a double well potential is studied using a Bose Hubbard model. We consider both signs for the on-site interparticle interaction and also investigated the situations where they are large and small. Interesting distinctive features are noted for the tunneling oscillations of these bosons corresponding to the above scenarios. Further, the sensitivity of the particle dynamics to the initial conditions has been studied. It is found that corresponding to an odd number of particles, such as three (or five), an initial condition of having unequal number of particles in the wells has interesting consequences, which is most discernible when the population difference between the wells is unity.Comment: To appear in Eur. Phys. J.

Bidirectional microwave-optical transduction based on integration of high-overtone bulk acoustic resonators and photonic circuits

Coherent interconversion between microwave and optical frequencies can serve as both classical and quantum interfaces for computing, communication, and sensing. Here, we present a compact microwave-optical transducer based on monolithic integration of piezoelectric actuators atop silicon nitride photonic circuits. Such an actuator directly couples microwave signals to a high-overtone bulk acoustic resonator defined by the suspended silica cladding of the optical waveguide core, which leads to enhanced electromechanical and optomechanical couplings. At room temperature, this triply resonant piezo-optomechanical transducer achieves an off-chip photon number conversion efficiency of -48 dB over a bandwidth of 25 MHz at an input pump power of 21 dBm. The approach is scalable in manufacturing and, unlike existing electro-optic transducers, does not rely on superconducting resonators. As the transduction process is bidirectional, we further demonstrate synthesis of microwave pulses from a purely optical input. Combined with the capability of leveraging multiple acoustic modes for transduction, the present platform offers prospects for building frequency-multiplexed qubit interconnects and for microwave photonics at large

A Nitride Ring Isolator

A silicon nitride optical ring isolator is realized by spatiotemporal modulation using bulk acoustic wave stress-optical transducers. By driving three actuators with fixed relative phases, over 17 dB isolation is achieved. (C) 2020 The Author(s

Coherent terahertz-to-microwave link using electro-optic-modulated Turing rolls

Arising from modulation instability, Turing rolls in optical Kerr microresonators have been used in the generation of optical frequency combs and the synthesis of microwave and terahertz frequencies. In this work, by applying electro-optic modulation on terahertz-frequency Turing rolls, we implement electro-optic frequency division with a microcomb to synthesize variable low-noise microwave signals. We also actively stabilize the terahertz oscillations to a microwave reference via intracavity power modulation, obtaining fractional frequency instabilities that are better than those of the free-running situation by up to six orders of magnitude. This study not only highlights the extraordinary spectral purity of Turing-roll oscillations but also opens the way for bidirectional terahertz-to-microwave links with hybrid optical-frequency-comb techniques

Single-Frequency Violet and Blue Laser Emission from AlGaInN Photonic Integrated Circuit Chips

Chip-based, single-frequency and low phase-noise integrated photonic laser diodes emitting in the violet (412 nm) and blue (461 nm) regime are demonstrated. The GaN-based edge-emitting laser diodes were coupled to high-Q on-chip micro-resonators for optical feedback and mode selection resulting in laser self-injection locking with narrow emission linewidth. Multiple group III-nitride (III-N) based photonic integrated circuit chips with different waveguide designs including single-crystalline AlN, AlGaN, and GaN were developed and characterized. Single-frequency laser operation was demonstrated for all studied waveguide core materials. The best side-mode suppression ratio was determined to be ∼36 dB at 412 nm with a single-frequency laser emission linewidth of only about 3.8 MHz at 461 nm. The performance metrics of this novel type of laser suggest potential implementation in next generation, portable quantum systems

A heterogeneously integrated lithium niobate-on-silicon nitride photonic platform

The availability of thin-film lithium niobate on insulator (LNOI) and advances in processing have led to the emergence of fully integrated LiNbO3 electro-optic devices. Yet to date, LiNbO3 photonic integrated circuits have mostly been fabricated using non-standard etching techniques and partially etched waveguides, that lack the reproducibility achieved in silicon photonics. Widespread application of thin-film LiNbO3 requires a reliable solution with precise lithographic control. Here we demonstrate a heterogeneously integrated LiNbO3 photonic platform employing wafer-scale bonding of thin-film LiNbO3 to silicon nitride (Si3N4) photonic integrated circuits. The platform maintains the low propagation loss (<0.1 dB/cm) and efficient fiber-to-chip coupling (<2.5 dB per facet) of the Si3N4 waveguides and provides a link between passive Si3N4 circuits and electro-optic components with adiabatic mode converters experiencing insertion losses below 0.1 dB. Using this approach we demonstrate several key applications, thus providing a scalable, foundry-ready solution to complex LiNbO3 integrated photonic circuits.ISSN:2041-172

Ultrafast tunable lasers using lithium niobate integrated photonics

Early works1 and recent advances in thin-film lithium niobate (LiNbO3) on insulator have enabled low-loss photonic integrated circuits2,3, modulators with improved half-wave voltage4,5, electro-optic frequency combs6 and on-chip electro-optic devices, with applications ranging from microwave photonics to microwave-to-optical quantum interfaces7. Although recent advances have demonstrated tunable integrated lasers based on LiNbO3 (refs. 8,9), the full potential of this platform to demonstrate frequency-agile, narrow-linewidth integrated lasers has not been achieved. Here we report such a laser with a fast tuning rate based on a hybrid silicon nitride (Si3N4)-LiNbO3 photonic platform and demonstrate its use for coherent laser ranging. Our platform is based on heterogeneous integration of ultralow-loss Si3N4 photonic integrated circuits with thin-film LiNbO3 through direct bonding at the wafer level, in contrast to previously demonstrated chiplet-level integration10, featuring low propagation loss of 8.5 decibels per metre, enabling narrow-linewidth lasing (intrinsic linewidth of 3 kilohertz) by self-injection locking to a laser diode. The hybrid mode of the resonator allows electro-optic laser frequency tuning at a speed of 12 × 1015 hertz per second with high linearity and low hysteresis while retaining the narrow linewidth. Using a hybrid integrated laser, we perform a proof-of-concept coherent optical ranging (FMCW LiDAR) experiment. Endowing Si3N4 photonic integrated circuits with LiNbO3 creates a platform that combines the individual advantages of thin-film LiNbO3 with those of Si3N4, which show precise lithographic control, mature manufacturing and ultralow loss11,12.ISSN:0028-0836ISSN:1476-468