High-Q double-disk microcavities for cavity optomechanics

We design a double-disk microcavity consisting of a pair of silica microdisks separated by a nanoscale gap region on a silicon chip for cavity optomechanics. We show that this type of photonic structure can provide a per-photon gradient force with a magnitude much larger than for scattering-force-based structures. Moreover, this device provides for nearly independent optimization of optical and mechanical properties. We present the processing details of fabricated devices

Parity-time symmetry in optical microcavity systems

Canonical quantum mechanics postulates Hermitian Hamiltonians to ensure real eigenvalues. Counterintuitively, a non-Hermitian Hamiltonian, satisfying combined parity-time (PT) symmetry, could display entirely real spectra above some phase-transition threshold. This stems from the existence of a parameter in the Hamiltonian governing characteristics features of eigenvalues and eigenfunctions. Varying this parameter causes real eigenvalues to coalesce and become complex conjugate pairs, signaling the occurrence of a nontrivial phase transition and the breakdown of PT symmetry. Such an appealing discovery has aroused extensive theoretical interest in extending canonical quantum theory by including non-Hermitian but PT-symmetric operators in the last two decades. Despite much fundamental theoretical success in the development of PT-symmetric quantum mechanics, an experimental observation of pseudo-Hermiticity remains elusive as these systems with complex potential seem absent in Nature. But nevertheless, the notion of PT symmetry has survived in many other branches of physics including optics, photonics, AMO physics, acoustics, electronic circuits, and material science over the past ten years, where a judicious balance of gain and loss constitutes ingeniously a PT-symmetric system. Here, although we concentrate upon reviewing recent progress on PT symmetry in optical microcavity systems, we also wish to present some new results that may help to accelerate the research in the area. These compound photonic structures with gain and loss provide a powerful platform for testing various theoretical proposals on PT symmetry, and initiate new possibilities for shaping optical beams and pulses beyond conservative structures. Throughout this article there is an effort to clearly present the physical aspects of PT-symmetry in optical microcavity systems, but mathematical formulations are reduced to the indispensable ones. Readers who prefer strict mathematical treatments should resort to the extensive list of references. Despite the rapid progress on the subject, new ideas and applications of PT symmetry using optical microcavities are still expected in the future

Mechanical oscillation and cooling actuated by the optical gradient force

In this work we combine the large per-photon optical gradient force with the sensitive feedback of a high quality factor whispering-gallery microcavity. The cavity geometry, consisting of a pair of silica disks separated by a nanoscale gap, shows extremely strong dynamical backaction, powerful enough to excite giant coherent oscillations even under heavily damped conditions (mechanical Q=4). In vacuum, the threshold for regenerative mechanical oscillation is lowered to an optical input power of only 270-nanoWatts, or roughly 1000 stored cavity photons, and efficient cooling of the mechanical motion is obtained with a temperature compression factor of 13-dB for 4-microWatts of dropped optical input power.Comment: 29 pages, 8 figure

A conceptual framework for after-sales service risk reduction of Chinese agricultural machinery in South Africa

After-sales service (ASS) plays a significant role following the agricultural machinery being sold. With the development of trade and economic exchange between South Africa and China. Chinese agricultural machinery has increasingly sold to South African and Africa. After- sales service becomes crucial important to maintenance the machinery. Results found that the people whose age was between 30 and 49 that much involved in the research findings. Comparison between South African and China found to be more males participate (79.2%) in China, and more females (29.2%) in South Africa. It found that South African female engaged more than Chinese females. The staff and directors made up the majority of participants, where staff and directors accounted for 54.2% in South Africa and 70.9% from China’s side. The percentage on the degree of high school level of Chinese interviewees showed the highest among these five items, which were 50% compared to the highest degree of South African participants at the college level (37.5%). There was no interviewer who earned a major in engineering in South African involved in this study and there was an endeavor to employ more engineers in South Africa. The highest point was the value of spare parts factor from the perspective of South African participants, followed by the factors repairing, maintenance, technician and training. The focus group was concerned with the other factors that impacted on the ASS of AM. The focus-group in China showed that except for the factors that influenced the ASS of AM, Sanbao; three Guarantees: repair, replacement and return, and customer’s satisfaction played a significant role in the process of ASS of AM. With this, the factors included the revisiting, maintenance, technology assistance, tracking service and customer’s satisfaction. The focus-group in South Africa found that after-sales service was faced a crucial effect to ASS of AM.http://www.ijat-aatsea.comhj2023Graduate School of Technology Management (GSTM

Stacked integrated double-disks for cavity optomechanics

The coupling of mechanical oscillators and optical cavity modes through scattering forces has received considerable attention in recent years [1]. This interaction provides a way, through the principle of dynamic back action [2], to amplify [2,3] and cool mechanical motion [4–6]. It could also soon provide a practical means to entangle macroscopic mechanical motion with a variety of other quantum systems, including light [7,8]. To date, experimental work has relied upon the optical scattering force to create conditions necessary for observation of dynamical back action effects. However, alongside the scattering force there are also dipole optical forces that can furnish optomechanical coupling. These forces, also referred to as dispersive or gradient forces, have been used to control coupling of a waveguide to a resonator [9] and to couple pairs of waveguides [10,11]. In the present work, a stacked, double-disk whispering gallery system is demonstrated as a new means to cavity optomechanical phenomena. Dipole-force coupling between the disks creates optomechnical coupling, causing displacement of the disks and tuning of the underlying whispering gallery resonances. In comparison to scattering-force-based systems, this double-disk configuration has the significant advantage of providing a larger optomechanical coupling constant, independent of the cavity round trip length