Optomechanical controlling of intermolecular interaction and the application in molecular self-assembly.

In this paper, we combined cavity optomechanics and quantum mechanical mechanism of van der Waals force to study the dynamic behavior of interacting bimolecules in the plasmonic localized field, and extend it to the interacting multi-molecular system. We explored how plasmonic optomechanical coupling affects the strength of intermolecular interactions. Based on our results, we propose to use optical field to modulate the intermolecular interaction potential in plasmonic cavity, which can be utilized in the enhancement of the efficiency of the molecular self-assembly process and controlling the yield of the reaction in an optical environment. This research extends molecular optomechanics from intramolecular interactions to intermolecular interactions and may has high application potential in some nanostructure synthesis.

Optomechanical atomic force microscope.

In the scanning probe microscope system, the weak signal detection of cantilever vibration is one of the important factors affecting the sensor sensitivity. In our current work, we present a novel design concept for an atomic force microscope (AFM) combined with optomechanics with an ultra-high quality factor and a low thermal noise. The detection system consists of a fixed mirror placed on the cantilever of the AFM and pump-probe beams that is equivalent to a Fabry-Perot cavity. We realize that the AFM combined with an optical cavity can achieve ultra-sensitive detection of force gradients of 10-12 N m-1 in the case of high-vacuum and low effective temperature of 1 mK, which may open up new avenues for super-high resolution imaging and super-high precision force spectroscopy.

Optomechanical probe of an axial-vector mediated interaction in the quantum regime.

We present an atomic, molecular, and optical physics based method to search for axial-vector mediated dipole-dipole interaction between electrons. In our optomechanical scheme, applying a static magnetic field and a pump beam and a probe beam to a hybrid mechanical system composed of a nitrogen-vacancy center and a cantilever resonator, we could obtain a probe absorption spectrum. Based on the study of the relationship between this spectrum and the exotic dipole-dipole interaction, we put forward our detection principle and then provide a prospective constraint most stringent at a rough interaction range from 4 × 10-8 to 2 × 10-7m. Our results indicate that this scheme could be put into consideration in relevant experimental searches.

Fano Effect and Quantum Entanglement in Hybrid Semiconductor Quantum Dot-Metal Nanoparticle System.

In this paper, we review the investigation for the light-matter interaction between surface plasmon field in metal nanoparticle (MNP) and the excitons in semiconductor quantum dots (SQDs) in hybrid SQD-MNP system under the full quantum description. The exciton-plasmon interaction gives rise to the modified decay rate and the exciton energy shift which are related to the exciton energy by using a quantum transformation method. We illustrate the responses of the hybrid SQD-MNP system to external field, and reveal Fano effect shown in the absorption spectrum. We demonstrate quantum entanglement between two SQD mediated by surface plasmon field. In the absence of a laser field, concurrence of quantum entanglement will disappear after a few ns. If the laser field is present, the steady states appear, so that quantum entanglement produced will reach a steady-state entanglement. Because one of all optical pathways to induce Fano effect refers to the generation of quantum entangled states, It is shown that the concurrence of quantum entanglement can be obtained by observation for Fano effect. In a hybrid system including two MNP and a SQD, because the two Fano quantum interference processes share a segment of all optical pathways, there is correlation between the Fano effects of the two MNP. The investigations for the light-matter interaction in hybrid SQD-MNP system can pave the way for the development of the optical processing devices and quantum information based on the exciton-plasmon interaction.

Determination of nonlinear nanomechanical resonator-qubit coupling coefficient in a hybrid quantum system.

We have theoretically investigated a hybrid system that is composed of a traditional optomechanical component and an additional charge qubit (Cooper pair box) that induces a new nonlinear interaction. It is shown that the peak in optomechanically induced transparency has been split by the new nonlinear interaction, and the width of the splitting is proportional to the coupling coefficient of this nonlinear interaction. This may give a way to measure the nanomechanical oscillator-qubit coupling coefficient in hybrid quantum systems.

Sensitive detection of Majorana fermions based on a hybrid spin-microcantilever via enhanced spin resonance spectrum.

Motivated by recent experimental progress towards the detection and manipulation of Majorana fermions in ferromagnetic atomic chains on a superconductor, we present a novel proposal based on a single-crystal diamond (SCD) microcantilever with a single nitrogen-vacancy (NV) center spin embedded in ultrapure diamond substrate to probe Majorana fermions in an all-optical domain. With this scheme, a possible distinct Majorana signature is investigated via the electron spin resonance spectrum. In the proposal, the SCD microcantilever behaves as a phonon cavity and is robust for detecting of Majorana fermions, while the NV center spin can be considered as a sensitive probe. Further, the vibration of the microcantilever will enhance the coupling effect, which makes the Majorana fermions more sensitive to detection and the well-established optical NV spin readout technology will certainly promote the detection. This proposed method may provide a potential supplement for the detection of Majorana fermions.

Hybrid spin-microcantilever sensor for environmental, chemical, and biological detection.

Nowadays hybrid spin-micro/nanomechanical systems are being actively explored for potential quantum sensing applications. In combination with the pump-probe technique or the spin resonance spectrum, we theoretically propose a realistic, feasible, and an exact way to measure the cantilever frequency in a hybrid spin-micromechanical cantilever system which has a strong coherent coupling of a single nitrogen vacancy center in the single-crystal diamond cantilever with the microcantilever. The probe absorption spectrum which exhibits new features such as mechanically induced three-photon resonance and ac Stark effect is obtained. Simultaneously, we further develop this hybrid spin-micromechanical system to be an ultrasensitive mass sensor, which can be operated at 300 K with a mass responsivity 0.137 Hz ag(-1), for accurate sensing of gaseous or aqueous environments, chemical vapors, and biomolecules. And the best performance on the minimum detectable mass can be [Formula: see text] in vacuum. Finally, we illustrate an in situ measurement to detect Angiopoietin-1, a marker of tumor angiogenesis, accurately with this hybrid microcantilever at room temperature.

Nonlinear optical response of cavity optomechanical system with second-order coupling.

We theoretically investigate the optical response of a cavity optomechanical system via the nonlinear coupling between optical and mechanical resonators, which is expected to be strong. Our results show that the nonlinear coupling will significantly influence the optical bistability. We compare the transmission spectrum of linear coupling with that of nonlinear coupling up to the second order and observe a shift between the transmission peak, which indicates the energy-level modification induced by the nonlinear coupling. Based on this nonlinear optomechanical phenomenon, we propose a theoretical method to determine the mechanical frequency and the second-order coupling constant. This means will eliminate the influence caused by the first-order coupling, which enables much easier detection of second-order coupling constant.

Proposition of a Silica Nanoparticle-Enhanced Hybrid Spin-Microcantilever Sensor Using Nonlinear Optics for Detection of DNA in Liquid.

We theoretically propose a method based on the combination of a nonlinear optical mass sensor using a hybrid spin-microcantilever and the nanoparticle-enhanced technique, to detect and monitor DNA mutations. The technique theoretically allows the mass of external particles (ssDNA) landing on the surface of a hybrid spin-microcantilever to be detected directly and accurately at 300 K with a mass responsivity 0.137 Hz/ag in situ in liquid. Moreover, combined with the nanoparticle-enhanced technique, even only one base pair mutation in the target DNA sequence can be identified in real time accurately, and the DNA hybridization reactions can be monitored quantitatively. Furthermore, in situ detection in liquid and measurement of the proposed nonlinear optical spin resonance spectra will minimize the experimental errors.

Ultrasensitive nanomechanical mass sensor using hybrid opto-electromechanical systems.

Nanomechanical resonators provide an unparalleled mass sensitivity sufficient to detect single biomolecules, viruses and nanoparticles. In this work we propose a scheme for mass sensing based on the hybrid opto-electromechanical system, where a mechanical resonator is coupled to an optical cavity and a microwave cavity simultaneously. When the two cavities are driven by two pump fields with proper frequencies and powers, a weak probe field is used to scan across the optical cavity resonance frequency. The mass of a single baculovirus landing onto the surface of the mechanical resonator can be measured by tracking the resonance frequency shift in the probe transmission spectrum before and after the deposition. We also propose a nonlinear mass sensor based on the measurement of the four-wave mixing (FWM) spectrum, which can be used to weigh a single 20-nm-diameter gold nanoparticle with sub-femtogram resolution.

Graphene-based nanoresonator with applications in optical transistor and mass sensing.

Graphene has received significant attention due to its excellent properties currently. In this work, a nano-optomechanical system based on a doubly-clamped Z-shaped graphene nanoribbon (GNR) with an optical pump-probe scheme is proposed. We theoretically demonstrate the phenomenon of phonon-induced transparency and show an optical transistor in the system. In addition, the significantly enhanced nonlinear effect of the probe laser is also investigated, and we further put forward a nonlinear optical mass sensing that may be immune to detection noises. Molecules, such as NH3 and NO2, can be identified via using the nonlinear optical spectroscopy, which may be applied to environmental pollutant monitoring and trace chemical detection.

Nucleonic-resolution optical mass sensor based on a graphene nanoribbon quantum dot.

The high frequency and ultrasmall mass of graphene make it an ideal material for ultrasensitive mass sensing. In this article, based on the all-optical technique, we propose a scheme of an optical mass sensor to weigh the mass of a single atom or molecule via a doubly clamped Z-shaped graphene nanoribbon (GNR). We use the detection of shifts in the resonance frequency of the Z-shaped GNR to determine the mass of an external particle landing on the GNR. The highly sensitive mass sensor proposed here can weigh particles down to the yoctogram and may eventually be enable to realize the mass measurement of nucleons.

Tunable slow and fast light device based on a carbon nanotube resonator.

We report a tunable slow and fast light device based on a carbon nanotube resonator, in the presence of a strong pump laser and a weak signal laser. Detailed analysis shows that the signal laser displays the superluminal and ultraslow light characteristics via passing through a suspended carbon nanotube resonator, while the incident pump laser is on- and off-resonant with the exciton frequency, respectively. In particular, the fast and slow light correspond to the negative and positive dispersion, respectively, associating with the vanished absorption. The bandwidth of the signal spectrum is determined by the vibration decay rate of carbon nanotube.

Optical determination of vacuum Rabi splitting in a semiconductor quantum dot induced by a metal nanoparticle.

We propose a theoretical scheme to determine the vacuum Rabi splitting in a single semiconductor quantum dot (SQD) induced by a metal nanoparticle (MNP). Based on cavity quantum electrodynamics, the exciton-plasmon interaction between the SQD and the MNP is considered while a strong pump laser and a weak probe laser are simultaneously presented. By decreasing the distance between them, we can increase the coupling strength. At resonance, thanks to the strong coupling, a vacuum Rabi splitting can be observed clearly in the probe absorption spectrum. The coupling strength can be obtained by measuring the vacuum Rabi splitting. This strong coupling is significant for the investigation of surface-plasmon-based quantum information processing.

Weighing a single atom using a coupled plasmon-carbon nanotube system.

We propose an optical weighing technique with a sensitivity down to a single atom, using a surface plasmon and a doubly clamped carbon nanotube resonator. The mass of a single atom is determined via the vibrational frequency shift of the carbon nanotube while the atom attaches to the nanotube surface. Owing to the ultralight mass and high quality factor of the carbon nanotube, and the spectral enhancement by the use of surface plasmon, this method results in a narrow linewidth (kHz) and high sensitivity (2.3×10-28 Hz· g-1), which is five orders of magnitude more sensitive than traditional electrical mass detection techniques.

A quantum optical transistor with a single quantum dot in a photonic crystal nanocavity.

Laser and strong coupling can coexist in a single quantum dot (QD) coupled to a photonic crystal nanocavity. This provides an important clue towards the realization of a quantum optical transistor. Using experimentally realistic parameters, in this work, theoretical analysis shows that such a quantum optical transistor can be switched on or off by turning on or off the pump laser, which corresponds to attenuation or amplification of the probe laser, respectively. Furthermore, based on this quantum optical transistor, an all-optical measurement of the vacuum Rabi splitting is also presented. The idea of associating a quantum optical transistor with this coupled QD-nanocavity system may achieve images of light controlling light in all-optical logic circuits and quantum computers.

Coherent optical spectroscopy of a hybrid nanocrystal complex embedded in a nanomechanical resonator.

We have theoretically investigated a hybrid nanocrystal complex consisted of a metal nanoparticle (MNP) and a semiconductor quantum dot (SQD) embedded in a nanomechanical resonator in the simultaneous presence of a strong control field and a weak probe field. It is shown that the resonance amplification peak of the probe spectrum will enhance dramatically due to the coupling of the plasmon, exciton and nanomechanical resonator. The enhancement increases significantly with decreasing the distance between the metal nanoparticle and a quantum dot, which implies the strong plasmon enhancement effect in this coupled system. The results obtained here may have the potential applications such as tunable Raman lasers and bio-sensors.

Coupling-rate determination based on radiation-pressure-induced normal mode splitting in cavity optomechanical systems.

We theoretically propose a precise way to measure the coupling rate in an optomechanical system based on radiation-pressure-induced normal mode splitting. This all-optical method is effective in both weak and strong coupling regions. Simultaneously the vibrational frequency of the mechanical mode can also be detected easily in the reflected probe spectrum. The results are much useful for the extensive applications in optomechanical systems.

A tunable optical Kerr switch based on a nanomechanical resonator coupled to a quantum dot.

We have theoretically demonstrated the large enhancement of the optical Kerr effect in a scheme of a nanomechanical resonator coupled to a quantum dot and shown that this phenomenon can be used to realize a fast optical Kerr switch by turning the control field on or off. Due to the vibration of the nanoresonator, as we pump on the strong control beam, the optical spectrum shows that the magnitude of this optical Kerr effect is proportional to the intensity of the control field. In this case, a fast and tunable optical Kerr switch can be implemented easily by an intensity-adjustable laser. Based on this tunable optical Kerr switch, we also provide a detection method to measure the frequency of the nanomechanical resonator in this coupled system.

An efficient optical knob from slow light to fast light in a coupled nanomechanical resonator-quantum dot system.

We theoretically present a highly efficient optical method to obtain slow and fast light in a coupled system consisting of a nanomechanical resonator and quantum dots in terms of mechanically induced coherent population oscillation (MICPO). Turning on or turning off the specific detuning of pump field from exciton resonance, this coupling system can provide us a direct optical way to obtain the slow or fast group velocity without absorption. Our coupling scheme proposed here works as a fast and slow-light knob and may have potential applications in various domains such as optical communication and biology sensor.