High-mechanical-frequency characteristics of optomechanical crystal cavity with coupling waveguide

A Temperature Prediction Model for Flexible Electronic Devices Based on GA-BP Neural Network and Experimental Verification

The problem that the thermal safety of flexible electronic devices is difficult to evaluate in real time is addressed in this study by establishing a BP neural network (GA-BPNN) temperature prediction model based on genetic algorithm optimisation. The model uses a BP neural network to fit the functional relationship between the input condition and the steady-state temperature of the equipment and uses a genetic algorithm to optimise the parameter initialisation problem of the BP neural network. To overcome the challenge of the high cost of obtaining experimental data, finite element analysis software is used to simulate the temperature results of the equipment under different working conditions. The prediction variance of the GA-BPNN model does not exceed 0.57 °C and has good robustness, as the model is trained according to the simulation data. The study conducted thermal validation experiments on the temperature prediction model for this flexible electronic device. The device reached steady state after 1200 s of operation at rated power. The error between the predicted and experimental results was less than 0.9 °C, verifying the validity of the model's predictions. Compared with traditional thermal simulation and experimental methods, this model can quickly predict the temperature with a certain accuracy and has outstanding advantages in computational efficiency and integrated application of hardware and software.

Hetero-Optomechanical Crystal Zipper Cavity for Multimode Optomechanics

Multimode optomechanics exhibiting several intriguing phenomena, such as coherent wavelength conversion, optomechanical synchronization, and mechanical entanglements, has garnered considerable research interest for realizing a new generation of information processing devices and exploring macroscopic quantum effect. In this study, we proposed and designed a hetero-optomechanical crystal (OMC) zipper cavity comprising double OMC nanobeams as a versatile platform for multimode optomechanics. Herein, the heterostructure and breathing modes with high mechanical frequency ensured the operation of the zipper cavity at the deep-sideband-resolved regime and the mechanical coherence. Consequently, the mechanical breathing mode at 5.741 GHz and optical odd mode with an intrinsic optical Q factor of 3.93 × 105 were experimentally demonstrated with an optomechanical coupling rate g0 = 0.73 MHz between them, which is comparable to state-of-the-art properties of the reported OMC. In addition, the hetero-zipper cavity structure exhibited adequate degrees of freedom for designing multiple mechanical and optical modes. Thus, the proposed cavity will provide a playground for studying multimode optomechanics in both the classical and quantum regimes.

Optical gradient forces in PT-symmetric coupled-waveguide structures

Optical gradient force in a parity-time (PT)-symmetric coupled-waveguide system is theoretically studied. We find that when the system evolves from PT-symmetric region to broken-PT-symmetric region, the normalized optical forces of the two eigenmodes decrease first and become the same when the exceptional point is reached. Besides, the optical force induced PT phase transition is demonstrated. It is worth noting that, when the system is in the broken-PT-symmetric region and the length of the waveguide is much longer than the propagation length of the lossy eigenmode, the total optical gradient force acting on the two waveguides will decrease with the decreasing of the gap. This work gives us a new understanding of integrated optomechanics by combining with PT symmetry.

Hybrid Interference Induced Flat Band Localization in Bipartite Optomechanical Lattices

The flat band localization, as an important phenomenon in solid state physics, is fundamentally interesting in the exploration of exotic ground property of many-body system. Here we demonstrate the appearance of a flat band in a general bipartite optomechanical lattice, which could have one or two dimensional framework. Physically, it is induced by the hybrid interference between the photon and phonon modes in optomechanical lattice, which is quite different from the destructive interference resulted from the special geometry structure in the normal lattice (e.g., Lieb lattice). Moreover, this novel flat band is controllable and features a special local density of states (LDOS) pattern, which makes it is detectable in experiments. This work offers an alternative approach to control the flat band localization with optomechanical interaction, which may substantially advance the fields of cavity optomechanics and solid state physics.

A low-frequency chip-scale optomechanical oscillator with 58 kHz mechanical stiffening and more than 100th-order stable harmonics

For the sensitive high-resolution force- and field-sensing applications, the large-mass microelectromechanical system (MEMS) and optomechanical cavity have been proposed to realize the sub-aN/Hz^1/2 resolution levels. In view of the optomechanical cavity-based force- and field-sensors, the optomechanical coupling is the key parameter for achieving high sensitivity and resolution. Here we demonstrate a chip-scale optomechanical cavity with large mass which operates at ≈77.7 kHz fundamental mode and intrinsically exhibiting large optomechanical coupling of 44 GHz/nm or more, for both optical resonance modes. The mechanical stiffening range of ≈58 kHz and a more than 100^th-order harmonics are obtained, with which the free-running frequency instability is lower than 10⁻⁶ at 100 ms integration time. Such results can be applied to further improve the sensing performance of the optomechanical inspired chip-scale sensors.