Numerical analysis of on-chip acousto-optic modulators for visible wavelengths.

On-chip acousto-optic modulators that operate at an optical wavelength of 780 nm and a microwave frequency of 6.835 GHz are proposed. The modulators are based on a lithium-niobate-on-sapphire platform and efficiently excite surface acoustic waves and exhibit strong interactions with tightly confined optical modes in waveguides. In particular, a high-efficiency phase modulator and single-sideband mode converter are designed. We found that for both microwave and optical wavelengths below 1 µm, the interactions at the cross-sections of photonic waveguides are sensitive to the waveguide width and are significantly different from those in previous studies. Our designed devices have small footprints and high efficiencies, making them suitable for controlling rubidium atoms and realizing hybrid photonic-atomic chips. Furthermore, our devices have the potential to extend the acousto-optic modulators to other visible wavelengths for other atom transitions and for visible light applications, including imaging and sensing.

Magnetic-free polarization rotation in an atomic vapor cell.

Magnetic-free nonreciprocal optical devices have attracted great attention in recent years. Here, we investigated the magnetic-free polarization rotation of light in an atom vapor cell. Two mechanisms of magnetic-free nonreciprocity have been realized in ensembles of hot atoms, including electromagnetically induced transparency and optically-induced magnetization. For a linearly polarized input probe light, a rotation angle up to 86.4° has been realized with external control and pump laser powers of 10 mW and is mainly attributed to the optically-induced magnetization effect. Our demonstration offers a new approach to realize nonreciprocal devices, which can be applied to solid-state atom ensembles and may be useful in photonic integrated circuits.

Transition from electromagnetically-induced transparency to absorption in a single microresonator.

Electromagnetically induced transparency (EIT) and absorption (EIA) are two phenomena that can be observed in whispering-gallery-mode (WGM) optical microresonators. Transition from EIT to EIA has potential applications in optical switching, filtering and sensing. In this paper an observation of the transition from EIT to EIA in a single WGM microresonator is presented. A fiber taper is used to couple light into and out of a sausage-like microresonator (SLM) that contains two coupled optical modes with significantly different quality factors. By stretching the SLM axially the resonance frequencies of the two coupled modes are tuned to the same, a transition from EIT to EIA is then observed in the transmission spectra when the fiber taper is moved closer to the SLM. It is the special spatial distribution of the optical modes of the SLM that provide a theoretical basis for the observation.

Generation of robust optical entanglement in cavity optomagnonics.

We propose a scheme to realize robust optical entanglement in cavity optomagnonics, where two optical whispering gallery modes (WGMs) couple to a magnon mode in a yttrium iron garnet (YIG) sphere. The beam-splitter-like and two-mode squeezing magnon-photon interactions can be realized simultaneously when the two optical WGMs are driven by external fields. Entanglement between the two optical modes is then generated via their coupling with magnons. By exploiting the destructive quantum interference between the bright modes of the interface, the effects of initial thermal occupations of magnons can be eliminated. Moreover, the excitation of the Bogoliubov dark mode is capable of protecting the optical entanglement from thermal heating effects. Therefore, the generated optical entanglement is robust against thermal noise and the requirement of cooling the magnon mode is relaxed. Our scheme may find applications in the study of magnon-based quantum information processing.

Robust quantum state transfer by optimal invariant-based reverse engineering.

Shortening the operation time of implementing scheme and reducing the influence of harmful factors have always been the research objectives pursued by people. Based on invariant-based reverse engineering, we present a general scheme for implementing robust population transfer in a three-level system via optimal shortcut to adiabatic passage. The systematic error sensitivity is introduced to measure the robustness of the process. The smooth Rabi frequencies are expressed with some coefficients, which are also related to the systematic error sensitivity and the population of intermediate state. When the amplitude of control field is given, the transfer can be optimized within as small systematic error sensitivity as possible, i.e., the robustness against systematic errors is further improved by choosing suitable correlation coefficient. Additionally, we apply the technique to achieve robust excitation fluctuation transfer between two membranes in an optomechanical system. The relation between the fidelity of excitation fluctuation transfer and variation of effective optomechanical coupling strengths is analysed. Numerical result shows that the fidelity keeps over 0.95 even if the coupling strengths deviates from 20% of the theoretical value. Moreover, comparison with existing literature [Opt. Express29, 7998 (2021)10.1364/OE.417343], the proposed scheme possesses stronger robustness against variations of effective optomechanical coupling strengths and lower population of unwanted states. The idea may provide a promising approach for quantum information processing.

Dissipation-driven entanglement between two microwave fields in a four-mode hybrid cavity optomechanical system.

The generation and manipulation of highly pure and strongly entangled steady state in a quantum system are vital tasks in the standard continuous-variable teleportation protocol. Especially, the manipulation implemented in integrated devices is even more crucial in practical quantum information applications. Here we propose an effective approach for creating steady-state entanglement between two microwave fields in a four-mode hybrid cavity optomechanical system. The entanglement can be achieved by combining the processes of three beam-splitter interactions and two parametric-amplifier interactions. Due to the dissipation-driven and cavity cooling processes, the entanglement obtained can go far beyond the entanglement limit based on coherent parametric coupling. Moreover, our proposal allows the engineered bath to cool both Bogoliubov modes almost simultaneously. In this way, a highly pure and strongly entangled steady state of two microwave modes is obtained. Our finding may be significant for using the hybrid opto-electro-mechanical system fabricated on chips in various quantum tasks, where the strong and pure entanglement is an important resource.

Gas chromatographic-ion mobility spectrometry combined with a multivariate analysis model exploring the characteristic changes of odor components during the processing of black sesame.

Black sesame (Sesamum indicum L.) is a Chinese dietary herb that has been widely used in the medical and healthcare fields in China. According to the theory of Traditional Chinese medicine processing, reasonable processing (steaming and drying many times) can increase the tonic effect and reduce the adverse factors generated during long-term use. At present, the processing degree of black sesame is mainly judged based on subjective experience. However, due to the lack of objective and quantitative control indicators, quality fluctuations easily occur. Therefore, for better application, its processing technology needs scientific monitoring methods. Herein a gas chromatography-ion mobility spectrometry (GC-IMS) technique was applied as a monitoring method to differentiate the processed products of black sesame in different processing stages. The response data of volatile components obtained from the samples were processed by the built-in data processing software in the instrument to identify the different components for further principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). From fingerprint comparison, 70 differential signal peaks were screened, 32 of which were qualitatively identified, mainly monomers and dimers of 20 compounds. On this basis, the PCA model shows that there was a significant difference between the raw product (S1) and the processed products (H1-9); moreover, there was a certain correlation between the differential changes of samples in different processing stages (H1-9) and the processing times. The OPLS-DA model specifically shows the differential components in the processing with potential characteristics peaks of 41, 105, n-nonanal, 2 and ethanol can discriminate whether the BS has undergone the first processed. And the dynamic changes of the three characteristic peaks of 1-hexanol, acetic acid and 107 can determine the specific degree of processing of BS. The research proves that GC-IMS combined with a multivariate analysis model can provide scientific data for identifying the characteristic odor components of black sesame.

[Transformation and attribution of drug properties in Galla Chinesis fermented Baiyaojian based on cold and heat syndrome rats].

To reveal the transformation and attribution of drug properties in Galla Chinesis fermented Baiyaojian by studying the effect of Galla Chinesis and Baiyaojian on cold and heat syndrome rats. Euthyrox was used to induce the hyperthyrosis model,ice water stimulation was used to induce the cold syndrome model,and different concentrations of Galla Chinesis and Baiyaojian water decoction were administrated by gavage for 15 d continuously. Symptom indexes were evaluated,content of pyruvic acid( PA),ATPase activity in liver and contents of DA,T4,cAMP,5-HT,NE,17-OHCS,TRH and TSH in serum were assayed by enzyme linked immunosorbent assay and spectrophotometry. The rectal temperature,water consumption and body weight of heat syndrome rats in model group were increased,cAMP,NE,17-OHCS,TRH and PA were increased,TSH,Na-K ATPase and Ca-Mg ATPase were increased significantly( P<0. 01),while 5-HT was decreased,compared with those of the blank group( P< 0. 05),the contents of T4,DA,NE,TSH,TRH,cAMP and 17-OHCS were decreased significantly( P<0. 01),PA and Ca-Mg ATPase in WG and BG groups were decreased compared with those of the model group( P<0. 05),and the Galla Chinesis content of WG group was lower than that of BG group,while the contents of 5-HT in WG and BG groups were increased,and the Galla Chinesis content of WG group was higher than that of BG group,with no significant difference of viscera index between heat syndrome rats in blank group,model group and drug groups. The rectal temperature,water consumption and body weight of cold syndrome rats in model group were decreased,DA,T4,cAMP,NE,17-OHCS,TRH,TSH,PA,Na-K ATPase and Ca-Mg ATPase of rats in model group were decreased,whereas 5-HT was increased compared with those of the blank group( P<0. 05),the indexes of heart,lung and kidney were significantly higher than those in the blank group( P<0. 05). Both Galla Chinesis and Baiyaojian can significantly alleviate the symptoms of heat syndrome rats caused by levothyroxine sodium. Galla Chinesis has a better effect than Baiyaojian,but cannot alleviate the symptoms of cold syndrome caused by ice water stimulation,suggestting that the decoction of Galla Chinesis and Baiyaojian are both cold,but Galla Chinesis is colder than Baiyaojian. Cold property in Galla Chinesis fermented Baiyaojian can be relieved. In clinical application,the property of " slight cold" is more accurate than " neutral property" for Baiyaojian.

Enhancement of steady-state bosonic squeezing and entanglement in a dissipative optomechanical system.

We systematically study the influence of amplitude modulation on the steady-state bosonic squeezing and entanglement in a dissipative three-mode optomechanical system, where a vibrational mode of the membrane is coupled to the left and right cavity modes via the radiation pressure. Numerical simulation results show that the steady-state bosonic squeezing and entanglement can be significantly enhanced by periodically modulated external laser driving either or both ends of the cavity. Remarkably, the fact that as long as one periodically modulated external laser driving either end of the cavities is sufficient to enhance the squeezing and entanglement is convenient for actual experiment, whose cost is that required modulation period number for achieving system stability is more. In addition, we numerically confirm the analytical prediction for optimal modulation frequency and discuss the corresponding physical mechanism.

Author Correction: Ringing phenomenon based measurement of weak mode-coupling strength in an optical microresonator.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Ringing phenomenon based measurement of weak mode-coupling strength in an optical microresonator.

There is always a coupling between the degenerate clockwise (CW) and counter-clockwise (CCW) modes in a whisperinggallery- mode (WGM) optical microresonator, since the surface of the microresonator can not be perfectly smooth. It is important to measure this coupling strength in many applications. When the coupling strength is strong, the conventional method by observing mode splitting in the stationary spectrum can be used to measure its value. However, when the coupling strength is weak, the conventional method will not work. We experimentally demonstrate that the ringing phenomenon can be used to measure weak coupling strength between the CW and CCW modes in a WGM optical microresonator.

Dissipative generation of significant amount of mechanical entanglement in a coupled optomechanical system.

We propose an approach for generating steady-state mechanical entanglement in a coupled optomechanical system. By applying four-tone driving lasers with weighted amplitudes and specific frequencies, we obtain an effective Hamiltonian that couples the delocalized Bogoliubov modes of the two mechanical oscillators to the cavity modes via beam-splitter-like interactions. When the mechanical decay rate is small, the Bogoliubov modes can be effectively cooled by the dissipative dynamics of the cavity modes, generating steady-state entanglement of the mechanical modes. The mechanical entanglement obtained in the stationary regime is strongly dependent on the values of the ratio of the effective optomechanical coupling strengths. Numerical simulation with the full linearized Hamiltonian shows that significant amount of mechanical entanglement can indeed be obtained by balancing the opposing effects of varying the ratio and by carefully avoiding the system parameters that may lead to amplified oscillations of the mechanical mean values detrimental to the entanglement generation.

Energy transmission using recyclable quantum entanglement.

It is known that faster-than-light (FTL) transmission of energy could be achieved if the transmission were considered in the framework of non-relativistic classical mechanics. Here we show that FTL transmission of energy could also be achieved if the transmission were considered in the framework of non-relativistic quantum mechanics. In our transmission protocol a two-spin Heisenberg model is considered and the energy is transmitted by two successive local unitary operations on the initially entangled spins. Our protocol does not mean that FTL transmission can be achieved in reality when the theory of relativity is considered, but it shows that quantum entanglement can be used in a recyclable way in energy transmission.

Ringing phenomenon based whispering-gallery-mode sensing.

Highly sensitive sensing is one of the most important applications of whispering-gallery-mode (WGM) microresonators, which is usually accomplished through a tunable continuous-wave laser sweeping over a whispering-gallery mode with the help of a fiber taper in a relative slow speed. It is known that if a tunable continuous-wave laser sweeps over a high quality whispering-gallery mode in a fast speed, a ringing phenomenon will be observed. The ringing phenomenon in WGM microresonators is mainly used to measure the Q factors and mode-coupling strengths. Here we experimentally demonstrate that the WGM sensing can be achieved based on the ringing phenomenon. This kind of sensing is accomplished in a much shorter time and is immune to the noise caused by the laser wavelength drift.

Transmission spectra of sausage-like microresonators.

We experimentally develop a sausage-like microresonator (SLM) by making two microtapers on a single-mode fiber, and study whispering-gallery modes (WGMs) in SLMs with different lengths. The transmission spectra from 1530 nm to 1550 nm of several SLMs are presented and SLMs with different lengths are shown to have different transmission features. The maximal Q factor observed in the SLMs is 3.8 * 10(7). For comparison, the transmission spectrum of a fiber cylinder microresonator is given and the maximal Q factor achieved in the fiber microcylinder resonator is 1.7 * 10(7). The strain tuning of the SLM is also demonstrated.