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1.
Phys Rev Lett ; 129(10): 103401, 2022 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-36112456

RESUMO

A mobility edge, a critical energy separating localized and extended excitations, is a key concept for understanding quantum localization. The Aubry-André (AA) model, a paradigm for exploring quantum localization, does not naturally allow mobility edges due to self-duality. Using the momentum-state lattice of quantum gas of Cs atoms to synthesize a nonlinear AA model, we provide experimental evidence for a mobility edge induced by interactions. By identifying the extended-to-localized transition of different energy eigenstates, we construct a mobility-edge phase diagram. The location of a mobility edge in the low- or high-energy region is tunable via repulsive or attractive interactions. Our observation is in good agreement with the theory and supports an interpretation of such interaction-induced mobility edge via a generalized AA model. Our Letter also offers new possibilities to engineer quantum transport and phase transitions in disordered systems.

2.
Photoacoustics ; 27: 100388, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-36068802

RESUMO

A breath sensor for real-time measurement of human exhaled carbon monoxide is reported. This breath sensor is based on a novel photoacoustic heterodyne gas sensing technique, which combines the conventional photoacoustic spectroscopy with the beat-frequency detection algorithm, thus offering a fast response time and a convenient optical alignment, as well as eliminating the needs for frequency calibration and wavelength locking. The principle of photoacoustic heterodyne gas sensing was explained in detail. The performance of the photoacoustic heterodyne breath sensor was evaluated in terms of minimum detection limit, response time, and linearity. The exhaled carbon monoxide levels of eight volunteers were measured and the results demonstrate the reliability and feasibility of this breath sensor.

3.
ACS Appl Mater Interfaces ; 14(28): 32387-32394, 2022 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-35818991

RESUMO

The development of microstrain sensors offers significant prospects in diverse applications, such as microrobots, intelligent human-computer interaction, health monitoring, and medical rehabilitation. Among strain sensor materials, vertical graphene (VG) has demonstrated considerable potential as a resistive material; however, VG-based strain sensors with high resolution are yet to be developed. In addition, the detection mechanism of VG has not been extensively investigated. Herein, we developed a VG canal mesh (VGCM) to fabricate a flexible strain sensor for ultralow strain sensing, achieving an accurate response to strains as low as 0.1‰ within a total strain range of 0%-4%. The detection of such low strains is due to the rigorous structural design and strain concentration effect of the three-dimensional micronano structure of the VGCM. Through experimental results and theoretical simulation, the evolution of microcracks in VG and the sensing mechanism of VG and VGCM are elaborated, and the unique advantages of VGCM are revealed. Finally, the VGCM-based strain sensors are proposed as portable breathing test equipment for rapid breathing detection.

4.
Nanomaterials (Basel) ; 12(12)2022 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-35745326

RESUMO

A non-enzymatic electrochemical sensor, based on the electrode of a chitosan-derived carbon foam, has been successfully developed for the detection of glutamate. Attributed to the chelation of Cu ions and glutamate molecules, the glutamate could be detected in an amperometric way by means of the redox reactions of chelation compounds, which outperform the traditional enzymatic sensors. Moreover, due to the large electroactive surface area and effective electron transportation of the porous carbon foam, a remarkable electrochemical sensitivity up to 1.9 × 104 µA/mM∙cm2 and a broad-spectrum detection range from nM to mM scale have been achieved, which is two-orders of magnitude higher and one magnitude broader than the best reported values thus far. Furthermore, our reported glutamate detection system also demonstrates a desirable anti-interference ability as well as a durable stability. The experimental revelations show that the Cu ions chelation-assisted electrochemical sensor with carbon foam electrode has significant potential for an easy fabricating, enzyme-free, broad-spectrum, sensitive, anti-interfering, and stable glutamate-sensing platform.

5.
Phys Chem Chem Phys ; 24(24): 15135-15139, 2022 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-35699449

RESUMO

We report the high-resolution photoassociation (PA) spectroscopy of 23Na excited from the spin-1 Bose-Einstein Condensate (BEC) to the molecular state of 0g-(P3/2)v = 4 and 1g(P3/2)v = 91. By comparing the PA spectra of different spin configurations, we experimentally studied the effect of spin on the PA spectra. The experimental spectra comply well with the theoretical consideration. The results will play an important role in the study of the spin interaction and control of the antiferromagnetism in Na.

6.
Opt Express ; 30(8): 13522-13529, 2022 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-35472962

RESUMO

We demonstrate an atom-based amplitude-modulation (AM) receiver for digital communication with a weak continuous frequency carrier using a Rydberg AC Stark effect in a vapor cell and achieve the operating carrier frequency continuously from 0.1 GHz to 5 GHz at a single Rydberg state. A strong local oscillator (LO) field ELO acts as a gain to shift the Rydberg level to a high sensitivity region, and a weak carrier field ECarr keeps the same frequency with the LO field. The digital baseband signals are encoded onto the ECarr using the amplitude modulation technique with the different modulation frequency. The response of Rydberg atom to the baseband signal is probed via a Rydberg electromagnetically induced transparency (EIT). The measured instantaneous bandwidth of the system is about 230 kHz. To demonstrate the performance of our system for an actual communication, we consider a color image as an example, the received image displays that the bit error rate (BER) is less than 5% when the maximum data transfer rate is about 238 kbps. Meanwhile, our system shows the weak carrier field of ECarr ≥ 13.52 µV/cm can be used for the practical communication with BER less than 5%. Our works break the limitation that EIT-AT based atomic receivers only operate at the near resonant frequencies of the Rydberg transitions, making this emerging of quantum technology close to the practical application with high sensitivity and broad bandwidth.

7.
Opt Express ; 30(5): 7291-7298, 2022 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-35299493

RESUMO

Characterizing the nonlinear optical properties of numerous materials plays a prerequisite role in nonlinear imaging and quantum sensing. Here, we present the evaluation of the nonlinear optical properties of Rb vapor by the Gaussian-Bessel beam assisted z-scan method. Owed to the concentrated energy in the central waist spot and the constant intensity of the beam distribution, the Gaussian-Bessel beam enables enhanced sensitivity for nonlinear refractive index measurement. The nonlinear self-focusing and self-defocusing effects of the Rb vapor are illustrated in the case of blue and red frequency detunings from 5S1/2 - 5P3/2 transition, respectively. The complete images of the evolution of nonlinear optical properties with laser power and frequency detuning are acquired. Furthermore, the nonlinear refractive index n2 with a large scale of 10-6 cm2/W is determined from the measured transmittance peak-to-valley difference of z-scan curves, which is enhanced by a factor of ∼ 1.73 compared to the result of a equivalent Gaussian beam. Our research provides an effective method for measuring nonlinear refractive index, which will considerably enrich the application range of nonlinear material.

8.
Opt Express ; 30(4): 6332-6340, 2022 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-35209573

RESUMO

A novel technique for performing fiber pigtailed DFB laser and linear Fabry-Pérot cavity based optical feedback cavity enhanced absorption spectroscopy (OF-CEAS) is proposed. A fiber-coupled electro-optic modulator (f-EOM) with x-cut y-propagation LiNbO3 waveguide is employed, instead of PZT used in traditional OF-CEAS, to correct the feedback phase, which improves the compactness and applicability of OF-CEAS. Through the efficient and real-time control of the feedback phase by actively changing the input voltage of the f-EOM, a good long-term stability of the signal has been achieved. Consequently, a detection sensitivity down to 7.8×10-10 cm-1, better than the previous by PZT based OF-CEAS, has been achieved over the integration time of 200 s, even by use of a cavity with moderate finesse of 2850.

9.
Light Sci Appl ; 11(1): 13, 2022 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-34996893

RESUMO

Synthetic gauge fields in synthetic dimensions are now of great interest. This concept provides a convenient manner for exploring topological phases of matter. Here, we report on the first experimental realization of an atom-optically synthetic gauge field based on the synthetic momentum-state lattice of a Bose gas of 133Cs atoms, where magnetically controlled Feshbach resonance is used to tune the interacting lattice into noninteracting regime. Specifically, we engineer a noninteracting one-dimensional lattice into a two-leg ladder with tunable synthetic gauge fields. We observe the flux-dependent populations of atoms and measure the gauge field-induced chiral currents in the two legs. We also show that an inhomogeneous gauge field could control the atomic transport in the ladder. Our results lay the groundwork for using a clean noninteracting synthetic momentum-state lattice to study the gauge field-induced topological physics.

10.
Opt Express ; 29(21): 32892-32899, 2021 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-34809111

RESUMO

Herein, we report on the experimental observations and a quantitative determination of the laser-induced frequency shift (LIFS) in the photoassociation (PA) spectra of spinor Bose-Einstein condensate of sodium. Our investigations revealed a nonlinear dependence of the LIFS on the intensity of PA laser. By developing a model within the quadratic Stark effect, we simulate the experimental results via a theoretical model that confirms the former. The experimental observations and the theoretical analysis can further improve the accuracy of investigations on important molecular properties and on preparation of specific molecular states, with possible applications in various key fields.

11.
Opt Express ; 29(15): 22855-22867, 2021 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-34614564

RESUMO

Au nanoparticles are attractive contrast agents for noninvasive living tissue imaging with deep penetration because of their strong two-photon photoluminescence (TPPL) intensity and excellent biocompatibility. However, the inevitable phototoxicity and huge auto-fluorescence are consistently associated with laser excitation. Therefore, enhancement of TPPL intensity and suppression of backgrounds are always highly desired under the demand of reducing excitation powers. In this work, we develop a double-pulse TPPL (DP-TPPL) scheme with controlled phase differences (Δφ) between the double pulses to significantly improve the signal-to-noise ratio (SNR) of TPPL imaging. Under the modulated phase (Δφ periodically varying between 0-2π), our results show that SNR can be improved from 4.3 to 1715, with an enhancement of up to 400 folds at the integration of 50 ms. More importantly, this enhancement can be unlimitedly lifted by increasing the number of photons or integration times in principle. Further boosting has been achieved by reducing the magnitude of background noises; subsequently, SNR is improved by more than 104 times. Our schemes offer great potential for reducing phototoxicity and extracting extremely weak signals from huge backgrounds and open up a new possibility for a rapid, flexible, and reliable medical diagnosis by TPPL imaging with diminished laser powers.


Assuntos
Ouro/química , Nanopartículas Metálicas/química , Microscopia de Fluorescência por Excitação Multifotônica/métodos , Sondas Moleculares/química , Imagem Individual de Molécula/métodos , Fluorescência , Lasers
12.
Opt Express ; 29(16): 25439-25448, 2021 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-34614875

RESUMO

Beam splitting of high-order Gaussian (HOG) beams increases the channel capacity and improves the processing speed of the incoming information. Here a novel all-optical tunable multi-port HOG beam splitter under a periodic dielectric atomic structure is proposed and demonstrated. The original HOG beam is replicated in the output beams. A distinguishable five-port output beam is observed in the experiment, which is beneficial for high-speed optical communications. By tuning the optical properties of this periodic dielectric structure, the spatial position and intensity distribution of each output port are precisely controllable. The splitting ratio δ can be finely adjusted in the range 0 - 4.8. This work provides a new approach for multi-port HOG beam splitters and the basis for all-optical communication.

13.
Opt Express ; 29(17): 26831-26840, 2021 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-34615110

RESUMO

A simple and universal technique for performing optical feedback cavity enhanced absorption spectroscopy with a linear Fabry-Pérot cavity is presented. We demonstrate through both theoretical analysis and experiment that a diode laser can be sequentially stabilized to a series of cavity modes without any influence from the direct reflection if the feedback phase is appropriately controlled. With robust handling of the feedback phase and help from balanced detection, a detection limit of 1.3 × 10-9 cm-1 was achieved in an integration time of 30 s. The spectrometer performance enabled precision monitoring of atmospheric methane (CH4) concentrations over a time period of 72 h.

14.
Opt Lett ; 46(17): 4184-4187, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34469970

RESUMO

Optical vortex arrays (OVAs) containing multiple vortices have been in demand for multi-channel optical communications and multiple-particle trapping. In this Letter, an OVA with tunable intensity and spatial distribution was implemented all-optically in a two-dimensional (2D) electromagnetically induced atomic lattice (EIL). Such a square lattice is constructed by two orthogonal standing-wave fields in 85Rb vapor, resulting in the periodically modulated susceptibility of the probe beam based on electromagnetically induced transparency (EIT). An OVA with dark-hollow intensity distribution based on 2D EIL was observed in the experiment first. This work thus studied the nonlinear 2D EIL process both theoretically and experimentally, presenting, to the best of our knowledge, a novel method of dynamically obtaining and controlling an OVA and further promoting the construction of all-optical networks with atomic ensembles.

15.
Opt Lett ; 46(17): 4284-4287, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34469995

RESUMO

The characterization of the layer properties of multilayered structures has attracted research interest owing to advanced applications in fields of atom-based sensors, ultra-narrow optical filters, and composite films. Here, a robust non-destructive multipath interferometry method is proposed to characterize the features of a thin cell with a borosilicate glass-rubidium-borosilicate glass sandwiched structure using a femtosecond optical frequency comb. The multipath interference method serves as a powerful tool for identification of the layer number and physical thickness of a three-layered structure. Moreover, the global distribution map is obtained by scanning the entire region. Furthermore, the amplitude of sub-Doppler reflection spectra of the rubidium D2 line is confirmed at different target points to validate this method. This result promotes the development of thin-cell-based atomic devices with strong light-matter interaction at atomic scales.

16.
Opt Lett ; 46(16): 3965-3968, 2021 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-34388786

RESUMO

An equal-intensity beam splitter (EIBS) for passive laser speckle reduction is reported. The EIBS consists of a segmented half-wave plate (SHWP) with the designed orientation of the fast axis of each segment, a polarization beam splitter, and a mirror. The SHWP is fabricated using patterned photoalignment material and liquid crystal polymer. Ten laser sub-beams are generated by the twenty-one-pixelated EIBS, where the largest intensity ratio among them is 7.6. Laser temporal and spatial coherences are destroyed because of the optical path delays among the laser sub-beams. The EIBS is used to reduce laser speckle passively, and objective speckle contrast is reduced from 0.82 to 0.33 when all 10 laser sub-beams are used.

17.
Light Sci Appl ; 10(1): 173, 2021 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-34462419

RESUMO

Higher-order topological insulators, as newly found non-trivial materials and structures, possess topological phases beyond the conventional bulk-boundary correspondence. In previous studies, in-gap boundary states such as the corner states were regarded as conclusive evidence for the emergence of higher-order topological insulators. Here, we present an experimental observation of a photonic higher-order topological insulator with corner states embedded into the bulk spectrum, denoted as the higher-order topological bound states in the continuum. Especially, we propose and experimentally demonstrate a new way to identify topological corner states by exciting them separately from the bulk states with photonic quantum superposition states. Our results extend the topological bound states in the continuum into higher-order cases, providing an unprecedented mechanism to achieve robust and localized states in a bulk spectrum. More importantly, our experiments exhibit the advantage of using the time evolution of quantum superposition states to identify topological corner modes, which may shed light on future exploration between quantum dynamics and higher-order topological photonics.

18.
Phys Rev Lett ; 127(7): 073902, 2021 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-34459625

RESUMO

The interaction between light and metal nanoparticles enables investigations of microscopic phenomena on nanometer length and ultrashort timescales, benefiting from strong confinement and enhancement of the optical field. However, the ultrafast dynamics of these nanoparticles are primarily investigated by multiphoton photoluminescence on picoseconds or photoemission on femtoseconds independently. Here, we presented two-photon photoluminescence (TPPL) measurements on individual Au nanobipyramids (AuNP) to reveal their ultrafast dynamics by double-pulse excitation on a global timescale ranging from subfemtosecond to tens of picoseconds. Two orders of magnitude photoluminescence enhancement, namely, coherent interference fringes, has been demonstrated. Power-dependent measurements uncovered the transform of the nonlinearity from 1 to 2 when the interpulse delay varied from tens of femtoseconds to tens of picoseconds. We proved that the real intermediate state plays a critical role in the observed phenomena, supported by numerical simulations with a three-state model. Our results provide insight into the role of intermediate states in the ultrafast dynamics of noble metal nanoparticles. The presence of the intermediate states in AuNP and the coherent control of state populations offer interesting perspectives for imaging, sensing, nanophotonics, and in particular, for preparing macroscopic superposition states at room temperature and low-power superresolution stimulated emission depletion microscopy.

19.
ACS Nano ; 2021 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-34314151

RESUMO

van der Waals (vdW) heterostructures of transition metal dichalcogenides (TMDCs) provide an excellent paradigm for next-generation electronic and optoelectronic applications. However, the reproducible fabrications of vdW heterostructure devices and the boosting of practical applications are severely hindered by their unstable performance, due to the lack of criteria to assess the interlayer coupling in heterostructures. Here we propose a physical model involving ultrafast electron transfer in the heterostructures and provide two criteria, η (the ratio of the transferred electrons to the total excited electrons) and ζ (the relative photoluminescence variation), to evaluate the interlayer coupling by considering the electron transfer in TMDC heterostructures and numerically simulating the corresponding rate equations. We have proved the effectiveness and robustness of two criteria by measuring the pump-probe photoluminescence intensity of monolayer WS2 in the WS2/WSe2 heterostructures. During thermal annealing of WS2/WSe2, ζ varies from negative to positive values and η changes between 0 and 4.5 × 10-3 as the coupling strength enhanced; both of them can well characterize the tuning of interlayer coupling. We also design a scheme to image the interlayer coupling by performing PL imaging at two time delays. Our scheme offers powerful criteria to assess the interlayer coupling in TMDC heterostructures, offering opportunities for the implementation of vdW heterostructures for broadband and high-performance electronic and optoelectronic applications.

20.
Opt Express ; 29(8): 11406-11415, 2021 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-33984920

RESUMO

Electromagnetically induced transparency (EIT) and Autler-Townes splitting (ATS) are two similar quantum coherent phenomena but have different mechanisms and applications. Akaike information criteria (AIC), an objective method to discriminate EIT and ATS from an experimental viewpoint, has been employed in a variety of systems. Here we use AIC method to quantitively discriminate a series of spectra of cold atoms in a Rydberg-involved upper-driving ladder-type. The derived weights of EIT and ATS reflect that our spectra change from EIT-ATS intermediate region to ATS-dominated region along Rabi frequency of coupling field increases. We find that there are two factors affecting EIT-ATS weights in a Rydberg-involved three-level system: dephasing rate, induced by the interactions among Rydberg atoms, makes the EIT-ATS crossover move to the direction of low Rabi frequency of coupling field and the experimental noise makes the difference between EIT and ATS weights reduce at elsewhere. Our investigation could provide a meaningful reference for the observations and applications of Rydberg-involved quantum coherent spectroscopy.

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