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Now showing items 1 - 16 of 447

  • Phonon Coupling between a Nanomechanical Resonator and a Quantum Fluid

    Fong, King Yan   Jin, Dafei   Poot, Menno   Bruch, Alexander   Tang, Hong X.  

    Owing to their extraordinary sensitivity to external forces, nanomechanical systems have become an important tool for studying mesoscopic physics and realizing hybrid quantum systems. While nanomechanics has been widely applied in solid-state systems, its use in liquid receives less attention. There it finds unique applications such as biosensing, rheological sensing, and studying both classical and quantum fluid dynamics in unexplored regimes. In this work, we demonstrate efficient coupling of a nanooptomechanical resonator to a bosonic quantum fluid, superfluid He-4, through ultrahigh-frequency phonons (i.e., sound waves) approaching gigahertz frequencies. A high phonon exchange efficiency >92% and minimum excitation rate of 0.25 phonons per oscillations period, or equivalently k(B)T/hf(m)Q(m) =3D 0.044 << 1, are achieved. Based on our experimental results, we further predict that strong coupling between a nanomechanical resonator and superfluid cavity phonons with cooperativity up to 880 can be achieved. Our study opens new opportunities in controlling and manipulating superfluid at the nanoscale and lowexcitation level.
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  • Phononic integrated circuitry and spin-orbit interaction of phonons

    Fu, Wei   Shen, Zhen   Xu, Yuntao   Zou, Chang-Ling   Cheng, Risheng   Han, Xu   Tang, Hong X.  

    High-index-contrast optical waveguides are crucial for the development of photonic integrated circuits with complex functionalities. Despite many similarities between optical and acoustic waves, high-acoustic-index-contrast phononic waveguides remain elusive, preventing intricate manipulation of phonons on par with its photonic counterpart. Here, we present the realization of such phononic waveguides and the formation of phononic integrated circuits through exploiting a gallium-nitride-on-sapphire platform, which provides strong confinement and control of phonons. By demonstrating key building blocks analogous to photonic circuit components, we establish the functionality and scalability of the phononic circuits. Moreover, the unidirectional excitation of propagating phononic modes allows the exploration of unconventional spin-orbit interaction of phonons in this circuit platform, which opens up the possibility of novel applications such as acoustic gyroscopic and non-reciprocal devices. Such phononic integrated circuits could provide an invaluable resource for both classical and quantum information processing.
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  • Broadband on-chip single-photon spectrometer

    Cheng, Risheng   Zou, Chang-Ling   Guo, Xiang   Wang, Sihao   Han, Xu   Tang, Hong X.  

    Single-photon counters are single-pixel binary devices that click upon the absorption of a photon but obscure its spectral information, whereas resolving the color of detected photons has been in critical demand for frontier astronomical observation, spectroscopic imaging and wavelength division multiplexed quantum communications. Current implementations of single-photon spectrometers either consist of bulky wavelength-scanning components or have limited detection channels, preventing parallel detection of broadband single photons with high spectral resolutions. Here, we present the first broadband chip-scale single-photon spectrometer covering both visible and infrared wavebands spanning from 600 nm to 2000 nm. The spectrometer integrates an on-chip dispersive echelle grating with a single-element propagating superconducting nanowire detector of ultraslow-velocity for mapping the dispersed photons with high spatial resolutions. The demonstrated on-chip single-photon spectrometer features small device footprint, high robustness with no moving parts and meanwhile offers more than 200 equivalent wavelength detection channels with further scalability.
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  • Strong Pockels materials

    Li, Mo   Tang, Hong X.  

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  • High quality factor surface Fabry-Perot cavity of acoustic waves

    Xu, Yuntao   Fu, Wei   Zou, Chang-ling   Shen, Zhen   Tang, Hong X.  

    Surface acoustic wave (SAW) resonators are critical components in wireless communications and many sensing applications. They have also recently emerged as a subject of study in quantum acoustics at the single phonon level. Acoustic loss reduction and mode confinement are key performance factors in SAW resonators. Here, we report the design and experimental realization of high quality factor Fabry-Perot SAW resonators formed in between the tapered phononic crystal mirrors patterned on a GaN-on-sapphire material platform. The fabricated SAW resonators are characterized by both an electrical network analyzer and an optical heterodyne vibrometer. We observed standing Rayleigh waves inside the cavity, with an intrinsic quality factor exceeding 1.3 x 10(4) at ambient conditions. Published by AIP Publishing.
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  • Spectrotemporal shaping of itinerant photons via distributed nanomechanics

    Fan, Linran   Zou, Chang-Ling   Zhu, Na   Tang, Hong X.  

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  • Spectrotemporal shaping of itinerant photons via distributed nanomechanics

    Fan, Linran   Zou, Chang-Ling   Zhu, Na   Tang, Hong X.  

    Efficient phase manipulation of light is the cornerstone of many advanced photonic applications(1-4). However, the pursuit of compact, broadband and deep phase control of light has been hindered by the finite nonlinearity of the optical materials available for integrated photonics(5,6). Here, we propose a dynamically driven photonic structure for deep phase manipulation and coherent spectrotemporal control of light based on distributed nanomechanics. We experimentally demonstrate the quasi-phase-matched interaction between stationary mechanical vibration and itinerant optical fields, which is used to generate an on-chip modulated frequency comb over 1.15 THz (160 lines), corresponding to a phase modulation depth of over 21.6 pi. In addition, an optical time-lens effect induced by mechanical vibration is realized, leading to optical pulse compression of over 70-fold to obtain a minimum pulse duration of 1.02 ps. The high efficiency and versatility make such mechanically driven dynamic photonic structures ideal for realizing complex optical control schemes, such as lossless non-reciprocity7, frequency division optical communication-1 and optical frequency comb division(8).
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  • 70 dB long-pass filter on a nanophotonic chip

    Guo, Xiang   Zou, Chang-Ling   Tang, Hong X.  

    Integrated quantum photonic chips are promising for scalable, photonic based quantum information processing. Although on-chip quantum photon sources and single photon detectors have been demostrated separately, the full integration of these components on single chip is hindered by the background photons from the strong classical pump light. Here we design and fabricate an on-chip long-pass filter which can provide 70 dB attenuation for visible light near 775 nm with less than 3 dB insertion loss for light in the telecom C-band near 1550 nm. The adiabatic design makes this device broadband and robust against fabrication errors as well as working conditions. Combined with the previously demonstrated non-classical on-chip source based on spontaneous parametric down conversion on the same material system, this platform could enable 100 dB suppression of pump light and holds promise in realizing fully integrated quantum photonic chips where the sources, filters and detectors are monolithically integrated. (C) 2016 Optical Society of America
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  • Nano-Optomechanical Resonators in Microfluidics

    Fong, King Yan   Poot, Menno   Tang, Hong X.  

    Operation of nanomechanical devices in liquid has been challenging due to the strong viscous damping that greatly impedes the mechanical motion. Here we demonstrate an optomechanical microwheel resonator integrated in microfluidic system that supports low-loss optical resonances at near-visible wavelength with quality factor up to 1.5 million, which allows the observation of the thermal Brownian motion of the mechanical mode in both air and water environment with high signal-to-background ratio. A numerical model is developed to calculate the hydrodynamic effect on the device due to the surrounding water, which agrees well with the experimental results. With its very high resonance frequency (170 MHz) and small loaded mass (75 pg), the present device has an estimated mass sensitivity at the attogram level in water.
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  • A 10-GHz film-thickness-mode cavity optomechanical resonator

    Han, Xu   Fong, King Y.   Tang, Hong X.  

    We report on the advance of chip-scale cavity optomechanical resonators to beyond 10 GHz by exploiting the fundamental acoustic thickness mode of an aluminum nitride micro-disk. By engineering the mechanical anchor to minimize the acoustic loss, a quality factor of 1830 and hence a frequency-quality factor product of 1.9 x 10(13) Hz are achieved in ambient air at room temperature. Actuated by strong piezo-electric force, the micro-disk resonator shows an excellent electro-optomechanical transduction efficiency. Our detailed analysis of the electro-optomechanical coupling allows identification and full quantification of various acoustic modes spanning from super-high to X-band microwave frequencies measured in the thin film resonator. (C) 2015 AIP Publishing LLC.
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  • Magnonic crystal as a delay line for low-noise auto-oscillators

    Bankowski, Elena   Meitzler, Thomas   Khymyn, Roman S.   Tiberkevich, Vasil S.   Slavin, Andrei N.   Tang, Hong X.  

    It is demonstrated that a delay line based on a one-dimensional magnonic crystal used in a feedback loop of a microwave auto-oscillator can substantially reduce the phase noise figure and improve other vital performance characteristics of the auto-oscillator. The advantage is achieved due to the increase of the effective delay time in the magnonic crystal, compared to the case of an unpatterned yttrium iron garnet (YIG) film, and improvement of the power-handling characteristics due to the now possible increase of the YIG film thickness. The internal modes of a magnonic crystal caused by the periodic energy exchange between the incident and reflected spin waves play the dominant role in the described effect. (C) 2015 AIP Publishing LLC.
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  • Self-aligned multi-channel superconducting nanowire single-photon detectors

    Cheng, Risheng   Guo, Xiang   Ma, Xiaosong   Fan, Linran   Fong, King Y.   Poot, Menno   Tang, Hong X.  

    We describe a micromachining process to allow back-side coupling of an array of single-mode telecommunication fibers to individual superconducting nanowire single photon detectors (SNSPDs). This approach enables a back-illuminated detector structure which separates the optical access and electrical readout on two sides of the chip and thus allows for compact integration of multi-channel detectors. As proof of principle, we show the integration of four detectors on the same silicon chip with two different designs and their performances are compared. In the optimized design, the device shows saturated system detection efficiency of 16% while the dark count rate is less than 20 Hz, all achieved without the use of metal reflectors or distributed Bragg reflectors (DBRs). This back-illumination approach also eliminates the cross-talk between different detection channels. (C) 2016 Optical Society of America
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  • Triply resonant cavity electro-optomechanics at X-band

    Han, Xu   Xiong, Chi   Fong, King Y.   Zhang, Xufeng   Tang, Hong X.  

    Optomechanical microcavities with high-frequency mechanical resonances facilitate experimental access to mechanical states with low phonon occupation and also hold promise for practical device applications including compact microwave sources. However, the weak radiation pressure force poses practical limits on achievable amplitudes at super-high frequencies. Here, we demonstrate a piezoelectric force-enhanced microcavity system that simultaneously supports microwave, optical and mechanical resonant modes. The combination of the highly sensitive optical readout and resonantly enhanced strong piezoelectric actuation enables us to build a microwave oscillator with excellent phase noise performance, which pushes the micromechanical signal source into the microwave X-band.
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  • Low-loss aluminium nitride thin film for mid-infrared microphotonics

    Lin, Pao Tai   Jung, Hojoong   Kimerling, Lionel C.   Agarwal, Anu   Tang, Hong X.  

    Mid-infrared (mid-IR) microphotonic devices including (i) straight/bent waveguides and (ii) Y-junction beam splitters are developed on thin films of CMOS-compatible sputter deposited aluminum nitride (AlN)-on-silicon. An optical loss of 0.83 dB/cm at = 2.5 mu m is achieved. In addition, an efficient mid-IR 50:50 beam splitter is demonstrated over 200nm spectral bandwidth along with a <2% power difference between adjacent channels. With the inherent advantage of an ultra-wide transparent window (ultraviolent to mid-IR), our AlN mid-IR platform can enable broadband optical networks on a chip.
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  • Active Silicon Integrated Nanophotonics: Ferroelectric BaTiO3 Devices

    Xiong, Chi   Pernice, Wolfram H. P.   Ngai, Joseph H.   Reiner, James W.   Kumah, Divine   Walker, Frederick J.   Ahn, Charles H.   Tang, Hong X.  

    The integration of complex oxides on silicon presents opportunities to extend and enhance silicon technology with novel electronic, magnetic, and photonic properties. Among these materials, barium titanate (BaTiO3) is a particularly strong ferroelectric perovskite oxide with attractive dielectric and electro-optic properties. Here we demonstrate nanophotonic circuits incorporating ferroelectric BaTiO3 thin films on the ubiquitous silicon-on-insulator (Sal) platform. We grow epitaxial, single-crystalline BaTiO3 directly on SOI and engineer integrated waveguide structures that simultaneously confine light and an RF electric field in the BaTiO3 layer. Using on-chip photonic interferometers, we extract a large effective Pockels coefficient of 213 +/- 49 pm/V, a value more than six times larger than found in commercial optical modulators based on lithium niobate. The monolithically integrated BaTiO3 optical modulators show modulation bandwidth in the gigahertz regime, which is promising for broadband applications.
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  • Incorporation of erbium ions into thin-film lithium niobate integrated photonics

    Wang, Sihao   Yang, Likai   Cheng, Risheng   Xu, Yuntao   Shen, Mohan   Cone, Rufus L.   Thiel, Charles W.   Tang, Hong X.  

    As an active material with favorable linear and nonlinear optical properties, thin-film lithium niobate has demonstrated its potential in integrated photonics. Integration with rare-earth ions, which are promising candidates for quantum memories and transducers, will enrich the system with new applications in quantum information processing. Here, we investigate the optical properties at 1.5 mu m wavelengths of rare-earth ions ( Er 3 +) implanted in thin-film lithium niobate waveguides and micro-ring resonators. Optical quality factors near a million after post-annealing show that ion implantation damage can be repaired. The transition linewidth and fluorescence lifetime of erbium ions are characterized. The ion-cavity coupling is observed through a Purcell enhanced fluorescence from which a Purcell factor of 3.8 +/- 0.5, compared with waveguide lifetime, is extracted. This platform is compatible with top-down lithography processes and leads to a scalable path for controlling spin-photon interfaces in photonic circuits.
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