A Wide-Band High-Linearity Down-Conversion Mixer for Cable Receptions

We analyze a wide-band,high-linearity down-conversion mixer for cable receptions that is implemented in 0. 35μm SiGe BiCMOS technology. The bandwidth of the RF （radio frequency） input covers the range from 1 to 1.8GHz. The measured input power at the - 1dB compression point of the mixer reaches ＋ 14.23dBm. The highest voltage conversion gain is 8. 31dB, while the lowest noise figure is 19.4dB. The power consumed is 54mW with a 5V supply. The test result of the down-conversion mixer is outlined.

Low-power system model for quantum entangled photon-pair source

The quantum entangled photon-pair source,as an essential component of optical quantum systems,holds great potential for applications such as quantum teleportation,quan-tum computing,and quantum imaging.The current workhorse technique for preparing photon pairs involves performing spon-taneous parametric down conversion(SPDC)in bulk nonlinear crystals.However,the current power consumption and cost of preparing entangled photon-pair sources are relatively high,pos-ing challenges to their integration and scalability.In this paper,we propose a low-power system model for the quantum entan-gled photon-pair source based on SPDC theory and phase matching technology.This model allows us to analyze the per-formance of each module and the influence of component cha-racteristics on the overall system.In our experimental setup,we utilize a 5 mW laser diode and a typical type-II barium metabo-rate(BBO)crystal to prepare an entangled photon-pair source.The experimental results are in excellent agreement with the model,indicating a significant step towards achieving the goal of low-power and low-cost entangled photon-pair sources.This achievement not only contributes to the practical application of quantum entanglement lighting,but also paves the way for the widespread adoption of optical quantum systems in the future.

Experimentally testing Hardy's theorem on nonlocality with entangled mixed states

Hardy＇s theorem on nonlocality has been verified by a series of experiments with two-qubit entangled pure states.However,in this paper we demonstrate the experimental test of the theorem by using the two-photon entangled mixed states.We first investigate the generic logic in Hardy＇s proof of nonlocality,which can be applied for arbitrary two-qubit mixed polarization entangled states and can be reduced naturally to the well-known logic tested successfully by the previous pure state experiments.Then,the optimized violations of locality for various experimental parameters are delivered by the numerical method.Finally,the logic argued above for testing Hardy＇s theorem on nonlocality is demonstrated experimentally by using the mixed entangled-photon pairs generated via pumping two type-I BBO crystals.Our experimental results shows that Hardy＇s proof of nonlocality can also be verified with two-qubit polarization entangled mixed states,with a violation of about 3.4 standard deviations.

Continuous variable entanglement generation in coupled cavities

We investigate continuous variable entanglement produced in two distant coupled cavities, in which two four-level atoms are driven by classical fields respectively. Under the large detuning condition, an effective Hamiltonian containing the square of the creation （annihilation） operator of the cavity field is derived. Due to the nonlinearity, entanglement formally created by the beam splitter type interaction is transformed into the nondegenerate parametric down conversion type. Employing the operator algebraic method, we study the time evolution of the entanglement condition, and show that the system provides us an advantage in achieving a larger photon number with better entanglement. We also discuss the dissipation of the cavities affecting the entanglement.

Quantum analysis on the four-photon interference

We present a theory for quantum interference of four photons generated by spontaneous parametric downconversion. Detailed investigation of the dependence of fourfold coincidence count rate on time delay between the incident and the reflective pump laser pulses is carried out. Gaussian type dependence is found, and good agreement between our theoretical results and experimental data reported in the literature is achieved.

Recent advances and emerging trends of rare-earth-ion doped spectral conversion nanomaterials in perovskite solar cells

Organic-inorganic lead halide based perovskite solar cells(PSCs)have attracted unprecedented research interest over last decade.The high performance,combined with merits of low fabrication costs and ease of synthesis make PSCs promising alternate to state of the art silicon(Si)based solar cells.Howeve r,some inherent shortcomings of PSCs are hindering their market dominance over conventional photovoltaic technologies such as transmission loss of sub-bandgap photons,poor stability and hysteresis effects.Recently,use of rare earth(RE)ions doped nanomaterials in PSCs,has been identified as an effective means to address the aforementioned issues by expanding the range of absorption spectra minimizing the non-absorption loss of solar photons,enhancing light scattering and improving operational stability.This article reviews the recent progress in doping rare-earth(RE)ions in the building blocks of PSCs such as semiconductor electrodes and photoactive perovskite layers,and its use as a separate spectral conversion layer in PSCs.The effect of size,shape,constitution and concentration of RE-nanoparticles on the overall performance and device stability will be analyzed in detail.Moreover,we provide an outlook on the opportunities this newly developed field offers and the critical challenges faced in rationally and effectively using RE-ion-doped nanomaterials in PSCs for better operational stability and enhanced performance.

Influence of local phonon energy on quantum efficiency of Tb^(3+)-Yb^(3+) co-doped glass ceramics containing fluoride nanocrystals

The Tb3＋single-doped and Tb3＋-Yb3＋co-doped glass ceramics with the precipitation of CaF2, CaF2-SrF2 solid state solu-tion and SrF2 nanocrystals were designed and prepared by taking different amounts of CaF2 and SrF2 as the starting fluorides to inves-tigate the influence of the crystalline phase on the total quantum efficiency. The formation of the fluoride nanocrystals and the incor-poration of the doped rare earth ions into the fluoride nanocrystals were proved by the XRD measurement. The energy transfer from Tb3＋to Yb3＋was studied by the steady and time resolved spectra. The total internal quantum efficiencies were calculated based on the measured Tb3＋lifetime, which was about 10.5%improved in the SrF2 nanocrystals precipitated glass ceramics compared with that in the CaF2 nanocrystals precipitated glass ceramics mainly due to the lower phonon energy environment. Meanwhile, the total external quantum efficiencies were evaluated with the integrating sphere measurement system, which were 18.6%, 19.3%and 24.4%, respec-tively, for the CaF2, CaF2-SrF2 and SrF2 nanocrystals precipitated glass ceramics. Additionally, obvious difference between the calcu-lated total internal quantum efficiency and the measured total external quantum efficiency was also discussed.

Realization of the first sub-shot-noise wide field microscope

Recently,several proof of principle experiments have demonstrated the advantages of quantum technologies over classical schemes.The present challenge is to surpass the limits of proof of principle demonstrations to approach real applications.This letter presents such an achievement in the field of quantum enhanced imaging.In particular,we describe the realization of a sub-shot-noise wide field microscope based on spatially multi-mode non-classical photon number correlations in twin beams.The microscope produces realtime images of 8000 pixels at full resolution,for a 500μm2 field of view,with noise reduced to 80%of the shot noise level(for each pixel),which is suitable for absorption imaging of complex structures.By fast post-elaboration,specifically applying a quantum enhanced median filter,the noise can be further reduced(to o30%of the shot noise level)by setting a trade-off with the resolution,thus achieving the best sensitivity per incident photon reported in absorption microscopy.

Orbital angular momentum photonic quantum interface

Light-carrying orbital angular momentum(OAM)has great potential in enhancing the information channel capacity in both classical and quantum optical communications.Long distance optical communication requires the wavelengths of light are situated in the low-loss communication windows,but most quantum memories currently being developed for use in a quantum repeater work at different wavelengths,so a quantum interface to bridge the wavelength gap is necessary.So far,such an interface for OAM-carried light has not been realized yet.Here,we report the first experimental realization of a quantum interface for a heralded single photon carrying OAM using a nonlinear crystal in an optical cavity.The spatial structures of input and output photons exhibit strong similarity.More importantly,single-photon coherence is preserved during up-conversion as demonstrated.

Energy transfer in co-and tri-doped Y3Al5O12 phosphors

Single-doped（Ce3＋,Tb3＋）, co-doped（Ce3＋-Tb3＋, Ce3＋-Yb3＋, Tb3＋-Yb3＋） and tri-doped（Ce3＋-Tb3＋-Yb3＋） Y3Al5O12 phosphors were synthesized by a solid-state reaction method. The XRD, excitation and emission spectra and the fluorescence lifetime of the samples were measured. The energy transfer mechanism was also investigated. The results showed that the energy transfer efficiency from Tb3＋ to Ce3＋ was 51% and the energy transfer efficiency from Ce3＋ to Yb3＋ was 63.1%. Concomitantly, both were more efficient than that from Ce3＋ to Tb3＋（7%） and from Tb3＋ to Yb3＋（10.2%）. Also, the Yb3＋ ions received energy mainly from Ce3＋ ions in Ce3＋-Tb3＋-Yb3＋ tri-doped Y3Al5O12 phosphors. Among these materials, Ce3＋-Yb3＋ co-doped YAG phosphors are a better choice than others as a down-conversion material due to their higher energy transfer efficiency.

Luminescence anti-counterfeiting:From elementary to advanced

Luminescence anti-counterfeiting derives from the easily changeable luminescence behaviors of luminescence materials under the regulation of various external stimuli(such as excitation light,chemical reagent,heat,and mechanical force,etc.)and luminescence lifetime,which plays an important role in preventing forgery of currency,artworks,and product brands.According to the numbers of changes of anti-counterfeiting labels under various regulation conditions,luminescence anti-counterfeiting can be classified into three levels from elementary to advanced:single-level anti-counterfeiting,double-level anti-counterfeiting,and multilevel anti-counterfeiting.In this review,the recent achievements in luminescence anti-counterfeiting are summarized,and the regulation of various factors to anti-counterfeiting labels is discussed.Finally,existing problems,future challenges,and possible development directions are proposed in order to realize facile,quick,low-cost,environmentally friendly,and difficult-to-replicate advanced luminescence anti-counterfeiting.

Structural parameters improvement of an integrated HBT in a cascode configuration opto-electronic mixer

We analyze an integrated electrically pumped opto-electronic mixer, which consists of two InP/GalnAs hetero junction bipolar transistors （HBT）, in a cascode configuration. A new HBT with modified physical structure is proposed and simulated to improve the frequency characteristics of a cascode mixer. For the verification and calibrating software simulator, we compare the simulation results of a typical HBT, before modifying it and com paring it with empirical reported experiments. Then we examine the simulator on our modified proposed HBT to prove its wider frequency characteristics with better flatness and acceptable down conversion gain. Although the idea is examined in several GHz modulation, it may easily be extended to state of the art HBT cascode mixers in much higher frequency range.

Classical and quantum photonic sources based upon a nonlinear GaP/Si-superlattice micro-ring resonator

We present a theoretical investigation,based on the tight-binding Hamiltonian,of efficient second-and third-order nonlinear optical processes in the lattice-matched undoped(GaP)N/(Si 2)M short-period superlattice that is waveguide-integrated in a microring resonator on an opto-electronic chip.The nonlinear superlattice structures are sit-uated on the optically pumped input area of a heterogeneous“XOI”chip based on silicon.The spectra ofχ(2)zzz(2ω,ω,ω),χ(2)xzx(2ω,ω,ω),χ(3)xxxx(3ω,ω,ω,ω)and the Kerr refractive index(n 2),have been simu-lated as a function of the number of the atomic monolayers for“non-relaxed”heterointerfaces;These nonlinearities are induced by transi-tions between valence and conduction bands.The large obtained val-ues make the(GaP)N/(Si 2)M short-period superlattice a good can-didate for future high-performance XOI photonic integrated chips that may include Si 3 N 4 or SiC or AlGaAs or Si.Near or at the 810-nm and 1550-nm wavelengths,we have made detailed calculations of the efficiency of second-and third-harmonic generation as well as the performances of entangled photon-pair quantum sources that are based upon spontaneous parametric down conversion and sponta-neous four-wave mixing.The results indicate that the(GaP)N/(Si 2)M short-period superlattice is competitive with present technologies and is practical for classical and quantum applications.