Effect of PMMA Removal Methods on Opto-Mechanical Behaviors of Optical Fiber Resonant Sensor With Graphene Diaphragm

Regarding the dependence of the treatment of removing polymethyl methacrylate(PMMA)from graphene upon the prestress in the film,two typical PMMA removal methods including acetone-vaporing and high-temperature annealing were investigated based on the opto-mechanical behaviors of the developed optical fiber Fabry-Perot(F-P)resonant sensor with a 125-pm diameter and~10-layer-thickness graphene diaphragm.The measured resonant responses showed that the F-P sensor via annealing process exhibited the resonant frequency of 481kHz and quality factor of 1034 at~2Pa and room temperature,which are respectively 2.5 times and 33 times larger than the acetone-treated sensor.Moreover,the former achieved a high sensitivity of 110.4kHz/kPa in the tested range of 2Pa-2.5kPa,apparently superior to the sensitivity of 16.2kHz/kPa obtained in the latter.However,the time drift of resonant frequency also mostly tended to occur in the annealed sensor,thereby shedding light on the opto-mechanical characteristics of graphene-based F-P resonant sensors,along with an optimized optical excitation and detection scheme.

Hybrid opto-mechanical systems with nitrogen-vacancy centers

In this review, we briefly review recent works on hybrid （nano） and diamond nitrogen-vacancy （NV） centers. We also review opto-mechanical systems that contain both mechanical oscillators two different types of mechanical oscillators. The first one is a clamped mechanical oscillator, such as a cantilever, with a fixed frequency. The second one is an optically trapped nano-diamond with a built-in nitrogen-vacancy center. By coupling mechanical resonators with electron spins, we can use the spins to control the motion of mechanical oscillators. For the first setup, we discuss two different coupling mechanisms, which are magnetic coupling and strain induced coupling. We summarize their applications such as cooling the mechanical oscillator, generating entanglements between NV centers, squeezing spin ensembles etc. For the second setup, we discuss how to generate quantum superposition states with magnetic coupling, and realize matter wave interferometer. We will also review its applications as ultra-sensitive mass spectrometer. Finally, we discuss new coupling mechanisms and applications of the field.

Vibration induced transparency:Simulating an optomechanical system via the cavity QED setup with a movable atom

We simulate an optomechanical system via a cavity QED scenario with a movable atom and investigate its application in the tiny mass sensing.We find that the steady-state solution of the system exhibits a multiple stability behavior,which is similar to that in the optomechanical system.We explain this phenomenon by the opto-mechanical interaction term in the effective Hamiltonian.Due to the dressed states formed by the effective coupling between the vibration degree of the atom and the optical mode in the cavity,we observe a narrow transparent window in the output field.We utilize this vibration induced transparency phenomenon to perform the tiny mass sensing.We hope our study will broaden the application of the cavity QED system to quantum technologies.

Light-induced nonhomogeneity and gradient bending in photochromic liquid crystal elastomers

The recently reported opto-mechanical effect of some photochromic liquid crystal elastomers (LCEs) is studied. It is found that in such LCEs, material parameters such as the Young’s modulus and the stress-free strains will become nonhomogeneous under light irradiations. One may call them the light-induced functionally gradient materials. Analytical expressions for the dependence of the material parameters on the space varia- ble and possibly on the time variable are obtained. Exponential dependence can be derived under certain approximations. As an example, the light-induced bending of a beam is studied. Two neutral planes are found in the beam. Thus, along the thickness of the beam, there are extensions in the upper and lower parts and contractions in the middle.

Novel optoelectronic characteristics from manipulating general energy-bands by nanostructures

This paper summarizes our research work on optoelectronic devices with nanostructures. It was indi- cated that by manipulating so called ＂general energybands＂ of fundamental particles or quasi-particles, such as photon, phonon, and surface plasmon polariton （SPP）, novel optoelectronic characteristics can be obtained, which results in a series of new functional devices. A silicon based optical switch with an extremely broadband of 24 nm and an ultra-compact （8 μm -17.6μm） footprint was demonstrated with a photonic crystal slow light waveguides. By proposing a nanobeam based hereto optomechanical crystal, a high phonon frequency of 5.66 GHz was realized experimentally. Also, we observed and verified a novel effect of two-surface-plasmon-absorption （TSPA）, and realized diffraction-limit-overcoming photolithography with resolution of-1/11 of the exposure wavelength.

A novel MEMS-based focal plane array for infrared imaging

On the basis of opto-mechanical effect and micro electromechanical system(MEMS)technology,a novel substrate-free focal plane array(FPA)with the thermal isolated structure for uncooled infrared imaging is developed,even as alternate evaporated Au on SiN cantilever is used for thermal isolation.A human thermal image is obtained successfully by using the infrared imaging system composed of the FPA and optical detecting system.The experiment results show that the realization of thermal isolation structure in substrate-free FPA increases the temperature rise of the deflecting leg effectively,whereas the noise equivalent temperature difference(NETD)is about 200 mK.

The next detectors for gravitational wave astronomy

This paper focuses on the next detectors for gravitational wave astronomy which will be required after the current ground based detectors have completed their initial observations, and probably achieved the first direct detection of gravitational waves. The next detectors will need to have greater sensitivity, while also enabling the world array of detectors to have improved angular resolution to allow localisation of signal sources. Sect. 1 of this paper begins by reviewing proposals for the next ground based detectors,and presents an analysis of the sensitivity of an 8 km armlength detector, which is proposed as a safe and cost-effective means to attain a 4-fold improvement in sensitivity. The scientific benefits of creating a pair of such detectors in China and Australia is emphasised. Sect. 2 of this paper discusses the high performance suspension systems for test masses that will be an essential component for future detectors, while sect. 3 discusses solutions to the problem of Newtonian noise which arise from fluctuations in gravity gradient forces acting on test masses. Such gravitational perturbations cannot be shielded, and set limits to low frequency sensitivity unless measured and suppressed. Sects. 4 and 5 address critical operational technologies that will be ongoing issues in future detectors. Sect. 4 addresses the design of thermal compensation systems needed in all high optical power interferometers operating at room temperature. Parametric instability control is addressed in sect. 5. Only recently proven to occur in Advanced LIGO, parametric instability phenomenon brings both risks and opportunities for future detectors. The path to future enhancements of detectors will come from quantum measurement technologies. Sect. 6 focuses on the use of optomechanical devices for obtaining enhanced sensitivity, while sect. 7 reviews a range of quantum measurement options.

Optomechanical control of stacking patterns of h-BN bilayer

Few-layer two-dime nsion al(2D)materials usually have differe nt(meta)-stable stacking patterns,which have distinet electronic and optical properties.In spired by optical tweezers,we show that a laser with selected freque ncy can modify the gen eralized stacking-fault en ergy Iandscape of bilayer hexagonal boron nitride(BBN),by coupling to the slip-dependent dielectric response.Consequently,BBN can be reversibly and barrier-freely switched betwee n its stacking patter ns in a controllable way.We simulate the dyn amics of the stacki ng transition with a simplified equati on of motion and dem on strate that it happe ns at picosec ond timescale.When one layer of BBN has a nearly-free surface boundary condition,BBN can be locked in its metastable stacking modes for a long time.Such a fast,reversible and non-volatile transition makes BBN a potential media for data storage and optical phase mask.