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1.
Nature ; 609(7927): 496-501, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-36104554

RESUMO

Lithium niobate (LiNbO3) is viewed as a promising material for optical communications and quantum photonic chips1,2. Recent breakthroughs in LiNbO3 nanophotonics have considerably boosted the development of high-speed electro-optic modulators3-5, frequency combs6,7 and broadband spectrometers8. However, the traditional method of electrical poling for ferroelectric domain engineering in optic9-13, acoustic14-17 and electronic applications18,19 is limited to two-dimensional space and micrometre-scale resolution. Here we demonstrate a non-reciprocal near-infrared laser-writing technique for reconfigurable three-dimensional ferroelectric domain engineering in LiNbO3 with nanoscale resolution. The proposed method is based on a laser-induced electric field that can either write or erase domain structures in the crystal, depending on the laser-writing direction. This approach offers a pathway for controllable nanoscale domain engineering in LiNbO3 and other transparent ferroelectric crystals, which has potential applications in high-efficiency frequency mixing20,21, high-frequency acoustic resonators14-17 and high-capacity non-volatile ferroelectric memory19,22.

2.
Nature ; 581(7809): 401-405, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32461649

RESUMO

Plasmonics enables the manipulation of light beyond the optical diffraction limit1-4 and may therefore confer advantages in applications such as photonic devices5-7, optical cloaking8,9, biochemical sensing10,11 and super-resolution imaging12,13. However, the essential field-confinement capability of plasmonic devices is always accompanied by a parasitic Ohmic loss, which severely reduces their performance. Therefore, plasmonic materials (those with collective oscillations of electrons) with a lower loss than noble metals have long been sought14-16. Here we present stable sodium-based plasmonic devices with state-of-the-art performance at near-infrared wavelengths. We fabricated high-quality sodium films with electron relaxation times as long as 0.42 picoseconds using a thermo-assisted spin-coating process. A direct-waveguide experiment shows that the propagation length of surface plasmon polaritons supported at the sodium-quartz interface can reach 200 micrometres at near-infrared wavelengths. We further demonstrate a room-temperature sodium-based plasmonic nanolaser with a lasing threshold of 140 kilowatts per square centimetre, lower than values previously reported for plasmonic nanolasers at near-infrared wavelengths. These sodium-based plasmonic devices show stable performance under ambient conditions over a period of several months after packaging with epoxy. These results indicate that the performance of plasmonic devices can be greatly improved beyond that of devices using noble metals, with implications for applications in plasmonics, nanophotonics and metamaterials.

3.
Nano Lett ; 24(4): 1303-1308, 2024 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-38232135

RESUMO

A nonlinear holographic technique is capable of processing optical information in the newly generated optical frequencies, enabling fascinating functions in laser display, security storage, and image recognition. One popular nonlinear hologram is based on a periodically poled lithium niobate (LN) crystal. However, due to the limitations of traditional fabrication techniques, the pixel size of the LN hologram is typically several micrometers, resulting in a limited field-of-voew (FOV) of several degrees. Here, we experimentally demonstrate an ultra-high-resolution LN hologram by using the laser poling technique. The minimal pixel size reaches 200 nm, and the FOV is extended above 120° in our experiments. The image distortions at large view angles are effectively suppressed through the Fourier transform. The FOV is further improved by combining multiple diffraction orders of SH fields. The ultimate FOV under our configuration is decided by a Fresnel transmission. Our results pave the way for expanding the applications of nonlinear holography to wide-view imaging and display.

4.
Opt Express ; 32(12): 21497-21505, 2024 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-38859502

RESUMO

Tamm plasmon polaritons (TPPs), localized near the boundary of a dielectric Bragg reflector (DBR) and a thin metal film, have attracted much attention for the lower ohm loss and flexible excitation. However, the radiation loss resulting from the direct coupling to the surroundings hinders their applications. Here, we propose and experimentally demonstrate a new type of hybrid plasmonic quasi-bound state in the continuum (BIC) in a Tamm-surface plasmon polariton system to suppress the radiation loss. Leveraging the scattering of the periodic metal array, the TPP interacts with the surface plasmon polariton (SPP) mode and form a Friedrich-Wintgen type quasi-BIC state that originated from the interference of two surface waves with different natures. Through angle resolved reflectance spectrum measurement, the hybrid plasmonic quasi-BIC was observed in the experiment. Our work proposes a new method to design a high Q mode in plasmonic systems, and thus holds promise for applications in the field of light matter interactions.

5.
Opt Express ; 32(9): 14904-14913, 2024 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-38859154

RESUMO

Nonlocality is the defining feature of quantum entanglement. Entangled states with multiple particles are of crucial importance in fundamental tests of quantum physics as well as in many quantum information tasks. One of the archetypal multipartite quantum states, Greenberger-Horne-Zeilinger (GHZ) state, allows one to observe the striking conflict of quantum physics to local realism in the so-called all-versus-nothing way. This is profoundly different from Bell's theorem for two particles, which relies on statistical predictions. Here, we demonstrate an integrated photonic chip capable of generating and manipulating the four-photon GHZ state. We perform a complete characterization of the four-photon GHZ state using quantum state tomography and obtain a state fidelity of 0.729±0.006. We further use the all-versus-nothing test and the Mermin inequalities to witness the quantum nonlocality of GHZ entanglement. Our work paves the way to perform fundamental tests of quantum physics with complex integrated quantum devices.

6.
Opt Express ; 32(8): 14801-14807, 2024 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-38859416

RESUMO

Nanodomain engineering in lithium niobate on insulator (LNOI) is critical to realize advanced photonic circuits. Here, we investigate the tip-induced nanodomain formation in x-cut LNOI. The effective electric field exhibits a mirror symmetry, which can be divided into preceding and sequential halves according to the tip movement. Under our configuration, the preceding electric field plays a decisive role rather than the sequential one as in previous reports. The mechanism is attributed to the screening field formed by the preceding field counteracting the effect of the subsequent one. In experiment, we successfully fabricate nanodomain dots, lines, and periodic arrays. Our work offers a useful approach for nanoscale domain engineering in x-cut LNOI, which has potential applications in integrated optoelectronic devices.

7.
Opt Express ; 32(7): 11509-11521, 2024 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-38570996

RESUMO

Stable Q-switched and femtosecond mode-locked erbium-doped fiber laser (EDFL) have been achieved using CuSe nanosheets as novel saturable absorber (SA), where the CuSe nanosheets were prepared by a hydrothermal method. The nonlinear optical properties of CuSe nanosheets were measured using an Z-scan setup, revealing nonlinear absorption coefficients of -3.67 ± 0.22 cm GW-1 at 1560 nm. The prepared CuSe nanosheets were mixed with polyvinyl alcohol (PVA) to obtain a CuSe-PVA SA with a modulation depth of 3.8 ± 0.13%, and it was utilized to realize a Q-switched EDFL, obtaining the narrowest pulse duration of 1.29 µs and the maximum output power of 5.96 mW, which corresponds to a pulse energy of up to 103.7 nJ. In addition, CuSe nanosheets were deposited on a D-shaped fiber (DSF) to fabricate a CuSe-DSF SA with a modulation depth of 5.6 ± 0.17%, and it was utilized to realize a mode-locked EDFL. The mode-locked EDFL demonstrated a low threshold of only 42 mW, a pulse duration of 740 fs, and a maximum output power of 9.7 mW. Meanwhile, it exhibited a high signal-to-noise ratio of 72 dB. To the best of our knowledge, this is the first time of CuSe nanosheets as SA in EDFL. The results demonstrate that CuSe nanosheets are a highly promising nonlinear optical material with great potential for applications in ultrafast photonics.

8.
Opt Express ; 32(3): 4334-4345, 2024 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-38297637

RESUMO

Integrated on-chip femtosecond (fs) laser optoelectronic system, with photodetector as a critical component for light-electrical signal conversion, is a long-sought-after goal for a wide range of frontier applications. However, the high laser peak intensity and complicated nanophotonic waveguide structure of on-chip fs laser are beyond the detectability and integrability of conventional photodetectors. Therefore, flexible photodetector with the response on intense fs laser is in urgent needs. Herein, we demonstrate the first (to our knowledge) two-photon absorption (TPA) flexible photodetector based on the strong TPA nonlinearity of layered hybrid perovskite (IA)2(MA)2Pb3Br10, exhibiting efficient sub-bandgap response on the infrared fs laser at 700-1000 nm. High saturation intensity up to ∼3.8 MW/cm2 is achieved. The device also shows superior current stability even after bending for 1000 cycles. This work may pave the new way for the application of flexible optoelectronics specialized in integrated fs-laser detection.

9.
Opt Lett ; 49(4): 931-934, 2024 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-38359219

RESUMO

A continuous-wave, tandem optical parametric oscillator (TOPO) based on a MgO-doped periodically poled LiNbO3 (MgO:PPLN) is demonstrated. Because the MgO:PPLN is tandemly pumped by the OPO's signal beam, it outputs simultaneously two groups of signal and idler with a single pump source. The entire range spans from 1398 to 1490 nm, 1914 to 2107 nm, 3720 to 4444 nm, and 4849 to 5190 nm, which is limited by periods of the MgO:PPLN and cavity mirror coatings. The TOPO, whose oscillation threshold of pump power exceeds 7 W, can be easily triggered by marginally increasing the pump power as long as the OPO process occurs. The maximum idler powers are respectively 2.6 W (at 3896 nm) and 34 mW (at 4863 nm), and the corresponding signal powers are both nearly 100 mW.

10.
Opt Lett ; 49(20): 5799-5802, 2024 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-39404541

RESUMO

Based on quasi-phase-matching (QPM) theory, nonlinear photonic crystals (NPCs) are capable of realizing efficient spontaneous parametric downconversion (SPDC) for the generation of photonic entangled states. However, the traditional electric field poling techniques employed in NPC fabrication often result in non-negligible processing errors of a few hundred nanometers, thus impeding the production of quantum photon pairs as intended. In this work, we investigate the SPDC photon pairs generated in a laser-poled lithium niobate (LN) NPC. By using the recently developed laser poling technique, the processing error of the NPC is substantially reduced to approximately 15 nm. Consequently, the coincidence counts of the generated photon pairs in the experiment reach 83.6% of the designed value. Our result paves the way for on-demand production of high-quality quantum sources, which has potential applications in quantum communications and quantum computations.

11.
Phys Rev Lett ; 133(7): 073803, 2024 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-39213563

RESUMO

Non-Hermitian physics has greatly enriched our understanding of nonequilibrium phenomena and uncovered novel effects such as the non-Hermitian skin effect (NHSE) that has profoundly revolutionized the field. NHSE has been predicted in systems with nonreciprocal couplings which, however, are challenging to realize in experiments. Without nonreciprocal couplings, the NHSE can also emerge in systems with coexisting gauge fields and loss or gain (e.g., in Floquet non-Hermitian systems). However, such Floquet NHSE remains largely unexplored in experiments. Here, we realize the Floquet NHSEs in periodically modulated optical waveguides integrated on a silicon photonic platform. By engineering the artificial gauge fields induced by the periodical modulation, we observe various Floquet NHSE phases and unveil their rich topological transitions. Remarkably, we discover the transitions between the unipolar NHSE phases and an unconventional bipolar NHSE phase, which is accompanied by the directional reversal of the NHSEs. The underlying physics is revealed by the band winding in complex quasienergy space which undergoes a topology change from isolated loops with the same winding to linked loops with opposite windings. Our work unfolds a new route toward Floquet NHSEs originating from the interplay between gauge fields and dissipation effects, and thus offers fundamentally new ways for steering light and other waves.

12.
Phys Rev Lett ; 132(1): 016601, 2024 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-38242675

RESUMO

Topological photonic states provide intriguing strategies for robust light manipulations, however, it remains challenging to perfectly excite these topological eigenstates due to their complicated mode profiles. In this work, we propose to realize the exact eigenmode of the topological edge states by supersymmetric (SUSY) structures. By adiabatically transforming the SUSY partner to its main topological structure, the edge modes can be perfectly excited with simple single-site input. We experimentally verify our strategy in integrated silicon waveguides in telecommunication wavelength, showing a broad working bandwidth. Moreover, a shortcut-to-adiabaticity strategy is further applied to speed up the adiabatic pump process by inverse-design approaches, thus enabling fast mode evolutions and leading to reduced device size. Our method is universal and beneficial to the topology-based or complex eigenmodes systems, ranging from photonics and microwaves to cold atoms and acoustics.

13.
Phys Rev Lett ; 132(14): 143801, 2024 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-38640373

RESUMO

Photonic structures with Weyl points (WPs), including type I and type II, promise nontrivial surface modes and intriguing light manipulations for their three-dimensional topological bands. While previous studies mainly focus on exploring WPs in a uniform Weyl structure, here we establish Weyl heterostructures (i.e., a nonuniform Weyl lattice) with different rotational orientations in the synthetic dimension by nanostructured photonic waveguides. In this work, we unveil a transition between bound and extended modes on the interface of type-II Weyl heterostructures by tuning their rotational phases, despite the reversed topological order across the interface. This mode transition is also manifested from the total transmission to total reflection at the interface. All of these unconventional effects are attributed to the tilted dispersion of type-II Weyl band structure that can lead to mismatched bands and gaps across the interface. As a comparison, the type-I Weyl heterostructures lack the phase transition due to the untilted band structure. This work establishes a flexible scheme of artificial Weyl heterostructures that opens a new avenue toward high-dimensional topological effects and significantly enhances our capabilities in on-chip light manipulations.

14.
Inorg Chem ; 63(8): 3807-3814, 2024 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-38345921

RESUMO

Thorium-doped vacuum ultraviolet (VUV) transparent crystals is a promising candidate for establishing a solid-state nuclear clock. Here, we report the research results on high-concentration doping of 232Th:CaF2 single crystals. The structures, defects, and VUV transmittance performances of highly doped Th:CaF2 crystals are investigated by theoretical and experimental methods. The defect configurations formed by Th and the charge compensation mechanism (Ca vacancy or interstitial F atoms) located at its first nearest neighbor position are mainly considered and studied. The preferred defect configuration is identified according to the doping concentration dependence of structural changes caused by the defects and the formation energies of the defects at different Ca or F chemical potentials. The cultivated Th:CaF2 crystals maintain considerable high VUV transmittance levels while accommodating high doping concentrations, showcasing an exceptional comprehensive performance. The transmittances of 1-mm-thick samples with doping concentrations of 1.91 × 1020 and 2.76 × 1020 cm-3 can reach ∼62% and 53% at 150 nm, respectively. The VUV transmittance exhibits a weak negative doping concentration dependence. The system factors that may cause distortion and additional deterioration of the VUV transmittance are discussed. Balancing and controlling the impacts of various factors will be of great significance for fully exploiting the advantages of Th:CaF2 and other Th-doped crystals for a solid-state nuclear optical clock.

15.
Appl Opt ; 63(9): 2286-2293, 2024 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-38568584

RESUMO

A two-dimensional binary phase grating is proposed in this paper. Unlike a conventional transmission grating, in theory, the proposed phase grating can simultaneously eliminate the zero- and high-order diffraction along certain axes on the image plane, forming a pure sinusoidal transmission modulation that leaves only the first-order diffraction. The first-ever, to the best of our knowledge, theoretical model for achieving sinusoidal transmission modulation is suggested in this paper; then the theoretical calculation and experiment results are displayed to investigate the physical mechanism of the proposed grating. Moreover, the manipulation on the arrangement of grating design can disperse or concentrate the diffraction energy at a specific axis. Finally, almost first-order-only diffraction is achieved on a single axis by introducing random changes to certain geometrical parameters of the two-dimensional binary phase grating. Our work provides potential applications in optical science and engineering fields.

16.
Nano Lett ; 23(7): 2750-2757, 2023 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-36951420

RESUMO

An integrated way to generate and manipulate higher-order Poincaré sphere beams (HOPBs) is a sought-after goal in photonic integrated circuits for high-capacity communication systems. Here, we demonstrate a novel method for on-chip generation and manipulation of HOPBs through combining metasurface with optical waveguides on lithium niobate on insulator platform. With phase modulation by a diatomic geometric metasurface, guided waves are extracted into free space with a high signal-to-noise ratio in the form of two orthogonal circularly polarized optical vortices which are linearly superposed into HOPBs. Meanwhile, a dual-port waveguide crossing is established to reconfigure the output states into an arbitrary point on a higher-order Poincaré sphere based on in-plane interference of two guided waves. Our approach provides a promising solution to generate and manipulate the HOPBs in a compact manner, which would be further enhanced by employing the electro-optical modulation on a lithium niobate waveguide to access a fully tunable scheme.

17.
Opt Express ; 31(13): 21399-21406, 2023 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-37381239

RESUMO

Metasurface can be used in combination with singlet refractive lens to eliminate chromaticity, in which the metasurface usually works as a dispersion compensator. Such a kind of hybrid lens, however, usually has residual dispersion due to the limit of meta unit library. Here, we demonstrate a design method that considers the refraction element and metasurface together as a whole to achieve large scale achromatic hybrid lens with no residual dispersion. The tradeoff between the meta-unit library and the characteristics of resulting hybrid lenses is also discussed in detail. As a proof of concept, a centimeter scale achromatic hybrid lens is realized, which shows significant advantages over refractive lenses and hybrid lenses designed by previous methods. Our strategy would provide guidance for designing high-performance macroscopic achromatic metalenses.

18.
Opt Express ; 31(21): 33873-33882, 2023 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-37859157

RESUMO

Correction of chromatic aberration is an important issue in color imaging and display. However, realizing broadband achromatic imaging by a singlet lens with high comprehensive performance still remains challenging, though many achromatic flat lenses have been reported recently. Here, we propose a deep-learning-enhanced singlet planar imaging system, implemented by a 3 mm-diameter achromatic flat lens, to achieve relatively high-quality achromatic imaging in the visible. By utilizing a multi-scale convolutional neural network (CNN) imposed to an achromatic multi-level diffractive lens (AMDL), the white light imaging qualities are significantly improved in both indoor and outdoor scenarios. Our experiments are fulfilled via a large paired imaging dataset with respect to a 3 mm-diameter AMDL, which guaranteed with achromatism in a broad wavelength range (400-1100 nm) but a relative low efficiency (∼45%). After our CNN enhancement, the imaging qualities are improved by ∼2 dB, showing competitive achromatic and high-quality imaging with a singlet lens for practical applications.

19.
Opt Express ; 31(4): 6217-6227, 2023 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-36823883

RESUMO

Quantum imaging has non-negligible advantages in terms of sensitivity, signal-to-noise ratio, and novel imaging schemes. Based on metasurfaces, the information density and stability of the quantum imaging system can be further improved. Here we experimentally demonstrate that two patterns, simultaneously and independently superimposed on a high-efficiency dielectric metasurface, can be remotely switched via polarization-entangled photon pairs. Furthermore, using the time-correlated property of entangled photon pairs, the information carried by quantum light can be remarkably discriminated from background noise. This work confirms that the phase manipulation of quantum light with metasurfaces has a huge potential in the field of quantum imaging, quantum state tomography, and also promises real-world quantum metasurface devices.

20.
Opt Express ; 31(5): 8428-8439, 2023 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-36859957

RESUMO

The flexible photodetector is viewed as a research hotspot for numerous advanced optoelectronic applications. Recent progress has manifested that lead-free layered organic-inorganic hybrid perovskites (OIHPs) are highly attractive to engineering flexible photodetectors due to the effective overlapping of several unique properties, including efficient optoelectronic characteristics, exceptional structural flexibility, and the absence of Pb toxicity to humans and the environment. The narrow spectral response of most flexible photodetectors with lead-free perovskites is still a big challenge to practical applications. In this work, we demonstrate the flexible photodetector based on a novel (to our knowledge) narrow-bandgap OIHP of (BA)2(MA)Sn2I7, with achieving a broadband response across an ultraviolet-visible-near infrared (UV-VIS-NIR) region as 365-1064 nm. The high responsivities of 28.4 and 2.0 × 10-2 A/W are obtained at 365 and 1064 nm, respectively, corresponding to detectives of 2.3 × 1010 and 1.8 × 107 Jones. This device also shows remarkable photocurrent stability after 1000 bending cycles. Our work indicates the huge application prospect of Sn-based lead-free perovskites in high-performance and eco-friendly flexible devices.

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