We study mode competition in a multimode "phonon laser" comprised of an optical cavity employing a highly reflective membrane as the output coupler. Mechanical gain is provided by the intracavity radiation pressure, to which many mechanical modes are coupled. We calculate the gain and find that strong oscillation in one mode suppresses the gain in other modes. For sufficiently strong oscillation, the gain of the other modes actually switches sign and becomes damping, a process we call "anomalous cooling." We demonstrate that mode competition leads to single-mode operation and find excellent agreement with our theory, including anomalous cooling.

"Cavity-optomechanics" aims to study the quantum properties of mechanical systems. A common strategy implemented in order to achieve this goal couples a high finesse photonic cavity to a high quality factor mechanical resonator. Then, using feedback forces such as radiation pressure, one can cool the mechanical mode of interest into the quantum ground state and create non-classical states of mechanical motion. On the path towards achieving these goals, many near-term applications of this field have emerged. After briefly introducing optomechanical systems and describing the current state-of-the-art experimental results, this article summarizes some of the more exciting practical applications such as ultra-sensitive, high bandwidth accelerometers and force sensors, low phase noise x-band integrated microwave oscillators and optical signal processing such as optical delay-lines, wavelength converters, and tunable optical filters. In this rapidly evolving field, new applications are emerging at a fast pace, but this article concentrates on the aforementioned lab-based applications as these are the most promising avenues for near-term real-world applications. New basic science applications are also becoming apparent such as the generation of squeezed light, testing gravitational theories and for providing a link between disparate quantum systems. (C) 2014 AIP Publishing LLC.

Resonant elastic scattering from InAs quantum dots (QDs) is studied by heterodyne spectroscopy. We show theoretically that heterodyne spectroscopy of a two-level quantum emitter is not sensitive to the inelastic fluorescence component. In practice, we easily measure the elastic emission even when the fluorescence is dominated by inelastic scattering. We are able to distinguish the resonant elastic fluorescence from a large background of scattered pump light by modulating the QD transition frequency with a surface acoustic wave. The signal linewidth is 250 Hz, limited by vibration-induced phase noise in the optical fibers used for resonant optical drive and fluorescence collection.

We design, fabricate and study a novel platform for cavity optomechanics: a silicon nitride membrane patterned as a sub-wavelength diffraction grating. Using the grating as one mirror of a Fabry-Perot cavity, we realize an optical finesse of F = 2830 +/- 60, corresponding to a grating reflectivity of R = 0.998. The finesse we achieve appears to be within a factor of two of the limit set by material absorption. We study the finesse as a function of wavelength and optical spot size in order to elucidate various optical loss mechanisms. We find that the cavity exhibits birefringence, and establish that it, too, is a source of optical loss. We then characterize the mechanical motion. We observe hundreds of normal modes, and find the fluctuating amplitude of one of them to be very well described by a Boltzmann distribution. By injecting a red-detuned cooling laser, we optically cool all of the modes that we observe. The lowest effective temperature we achieve is T-eff approximate to 1 K.

We demonstrate micromechanical reflectors with a reflectivity as large as 99.4% and a mechanical quality factor Q as large as 7.8 × 105 for optomechanical applications. The reflectors are silicon nitride membranes patterned with sub-wavelength grating structures, obviating the need for the many dielectric layers used in conventional mirrors. We have employed the reflectors in the construction of a Fabry-Perot cavity with a finesse as high as F = 1200, and used the optical response to probe the mechanical properties of the membrane.

We demonstrate radiation pressure cooling of silicon nitride membranes, patterned as subwavelength gratings, from room temperature to sub-kelvin temperatures. We discuss the current limitations and future prospects of grating membranes in optomechanics.

We have developed micromechanical membranes with high reflectivity and low mass for optical cooling. By patterning silicon nitride membranes with grating structures we have achieved reflectivity of R = 99% and a quality factor of Q = 1.6 × 104.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text U. Kemiktarak, M. Metcalfe, M. Durand, and J. Lawall, "Cavity Optomechanics with Silicon Nitride Membrane Gratings," in Frontiers in Optics 2011/Laser Science XXVII, OSA Technical Digest (Optica Publishing Group, 2011), paper FTuN4. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Single InAs semiconductor quantum dots were coupled to a microcavity consisting of a semiconductor Bragg reflector below the quantum dot layer, and an external micromirror fabricated at the tip of a single mode fiber.

The processing of the single-quantum-level signals produced by current nanoscale solid-state devices such as qubits and nanomechanical resonators would require the development of very sensitive active circuits, such as amplifiers or frequency up- and down-converters that could attain the ultimate performances limited by the laws of quantum mechanics, while remaining of practical use. Bergeal et al. now demonstrate a phase-preserving, superconducting parametric amplifier with ultra-low noise properties, following theoretical principles recently presented in Nature Physics ( http://go.nature.com/F7lwR2 ). Based on a Josephson ring modulator, the new device can operate within a factor of three of the quantum limit. Possible applications include quantum analog signal processing such as the production of entangled microwave signal pairs. Recent progress in solid-state quantum information processing has stimulated the search for amplifiers and frequency converters with quantum-limited performance in the microwave range. Here, a phase-preserving, superconducting parametric amplifier with ultra-low-noise properties has been experimentally realized. Recent progress in solid-state quantum information processing1 has stimulated the search for amplifiers and frequency converters with quantum-limited performance in the microwave range. Depending on the gain applied to the quadratures of a single spatial and temporal mode of the electromagnetic field, linear amplifiers can be classified into two categories (phase sensitive and phase preserving) with fundamentally different noise properties2. Phase-sensitive amplifiers use squeezing to reduce the quantum noise, but are useful only in cases in which a reference phase is attached to the signal, such as in homodyne detection. A phase-preserving amplifier would be preferable in many applications, but such devices have not been available until now. Here we experimentally realize a proposal3 for an intrinsically phase-preserving, superconducting parametric amplifier of non-degenerate type. It is based on a Josephson ring modulator, which consists of four Josephson junctions in a Wheatstone bridge configuration. The device symmetry greatly enhances the purity of the amplification process and simplifies both its operation and its analysis. The measured characteristics of the amplifier in terms of gain and bandwidth are in good agreement with analytical predictions. Using a newly developed noise source, we show that the upper bound on the total system noise of our device under real operating conditions is three times the quantum limit. We foresee applications in the area of quantum analog signal processing, such as quantum non-demolition single-shot readout of qubits4, quantum feedback5 and the production of entangled microwave signal pairs6.

The dynamic response of InAs/GaAs self-assembled quantum dots (QDs) to strain is studied experimentally by periodically modulating the QDs with a surface acoustic wave and measuring the QD fluorescence with photoluminescence and resonant spectroscopy. When the acoustic frequency is larger than the QD linewidth, we resolve phonon sidebands in the QD fluorescence spectrum. Using a resonant pump laser, we have demonstrated optical frequency conversion via the dynamically modulated QD, which is the physical mechanism underlying laser sideband cooling a nanomechanical resonator by means of an embedded QD.

InAs quantum dots (QD) are modulated with a surface acoustic wave inducing phonon sidebands of the fluorescence. This constitutes an important step towards sideband cooling of a nanomechanical resonator via coupling to an embedded QD [1].

We present a detailed study of the use of Fabry-Perot (FP) cavities for the spectroscopy of single InAs quantum dots (QDs). We derive optimal cavity characteristics and resolution limits and measure photoluminescence linewidths as low as 0.9 GHz. By embedding the QDs in a planar cavity, we obtain a sufficiently large signal to actively feed back on the length of the FP to lock to the emission of a single QD with a stability below 2% of the QD linewidth. An integration time of approximately two seconds is found to yield an optimum compromise between shot noise and cavity length fluctuations.

We report the coupling of individual InAs quantum dots (QDs) to an external-mirror microcavity. The external mirror is bonded to a fiber and positioned above a semiconductor sample consisting of a QD-containing GaAs layer on top of a distributed Bragg reflector (DBR). This open cavity can be rapidly tuned with a piezoelectric actuator without negatively affecting the QD linewidth. A mirror radius of curvature of 42 microns and a cavity length of 10 microns enable good mode-matching and thus high collection efficiency directly into the fiber. With an improved finesse this system may enter the strong coupling regime.

Submitted for the MAR08 Meeting of The American Physical Society Microwave characterization of Josephson junction arrays in superconducting regime for Coulomb blockade and quantum metrology VLADIMIR MANUCHARYAN, Yale Applied Physics, MICHAEL METCALFE, JENS KOCH, Yale Applied Physics, LUIGI FRUNZIO, MARKUS BRINK, NICOLAS BERGEAL, LEONID GLAZMAN, MICHEL DEVORET, Yale Applied Physics — Although the phenomenon of Bloch Oscillations could in principle lead to a primary standard of electrical current, it requires in practice the embedding of a Josephson junction in an electrodynamic environment with microwave impedance much greater than resistance quantum for Cooper pairs. A promising candidate for such environment is an array of Josephson tunnel junctions in the superconducting (non-insulating) regime. We have developed a new technique to dispersively probe the electromagnetic properties of such arrays. We access the RF impedance of the array by placing it as a “mirror” in a high-Q planar superconducting microwave resonator, whose phase and magnitude response are measured. The advantage of this configuration is that, while measuring the RF property of the array, we can pass DC current through it. This serves three purposes: i) emulating the situation of a current standard experiment with arrays, ii) providing a knob for control experiments on the RF dissipation in arrays, iii) exploring a novel out-of-equilibrium non-linear collective system. Our experiment also contributes to the physics of superconducting qubits and nano-wires. Vladimir Manucharyan Date submitted: 13 Dec 2007 Electronic form version 1.4

A Josephson tunnel junction which is rf driven near a dynamical bifurcation point can amplify quantum signals. However, the bifurcation point will exist robustly only if the electrodynamic environment of the junction meets certain criteria. We develop a general formalism for dealing with the nonlinear dynamics of a Josephson junction embedded in an arbitrary microwave circuit. We find sufficient conditions for the existence of the bifurcation regime: (a) the embedding impedance of the junction needs to present a resonance at a particular frequency ${\ensuremath{\omega}}_{R}$, with the quality factor $Q$ of the resonance and the participation ratio $p$ of the junction satisfying $Qp⪢1$, and (b) the drive frequency should be low frequency detuned away from ${\ensuremath{\omega}}_{R}$ by more than $\sqrt{3}{\ensuremath{\omega}}_{R}∕(2Q)$.