Shuai-Peng Wang, Alberto Mercurio, Alessandro Ridolfo
et al.
Abstract The realization of strong nonlinear coupling between single photons has been a long-standing goal in quantum optics and quantum information science, promising wide impact applications, such as all-optical deterministic quantum logic and single-photon frequency conversion. Here, we report an experimental observation of the strong coupling between a single-photon and a two-photon Fock state in an ultrastrongly-coupled circuit-QED system. This strong nonlinear interaction is realized by introducing a detuned flux qubit working as an effective coupler between two modes of a superconducting coplanar waveguide resonator. The ultrastrong light–matter interaction breaks the excitation number conservation, and an external flux bias breaks the parity conservation. The combined effect of the two enables the strong one–two-photon coupling. Quantum Rabi-like avoided crossing is resolved when tuning the two-photon resonance frequency of the first mode across the single-photon resonance frequency of the second mode. Within this new photonic regime, we observe the thresholdless second harmonic generation for a mean photon number below one. Our results represent a key step towards a new regime of quantum nonlinear optics, where individual photons can deterministically and coherently interact with each other in the absence of any stimulating fields.
Abstract Higher-order topological insulators (HOTIs) can support boundary states at least two dimensions lower than the bulk, attracting intensive attention from both fundamental science and application sides. Lattice-based tight-binding models such as Benalcazar-Bernevig-Hughes model have driven significant advancements in realizing HOTIs across various physical systems. Here, beyond lattice model, we demonstrate that a cylinder with an arbitrary cross section, composed of a homogeneous electromagnetic medium featuring nontrivial second Chern numbers $${c}_{2}=\pm 1$$ c 2 = ± 1 in a synthetic five-dimensional space, can exhibit topologically protected HOTI-type hinge states in three-dimensional laboratory space. Interestingly, this hinge state is essentially a chiral zero mode arising from the interaction between Weyl arc surface states, guaranteed by a nontrivial $${c}_{2}$$ c 2 , and an effective magnetic field induced by the curvature of the cylinder surface. Compared to conventional schemes to generate HOTIs, our approach is more robust, as it is an intrinsic topological phase and therefore does not rely on additional symmetry protections such as time-reversal, parity, or chiral symmetry. We experimentally realize such a cylinder using a photonic metamaterial and confirm the existence of hinge states via microwave near-field measurements. Our work introduces the concept of boundary gauge fields and establishes the link between synthetic-space $${c}_{2}$$ c 2 and real-space HOTI states, thereby generalizing HOTIs to corner-less systems.
The relevance of modeling the interaction of electromagnetic waves with various materials exhibiting nonlinear properties is increasing every year. In this work, we studied the dynamics of laser beams propagating in a medium of single-walled carbon nanotubes with impurities, placed in a dielectric. By multilevel impurity, we mean an impurity whose energy levels are separated from the conduction band and valence band in carbon nanotubes and lie inside the band gap of the dielectric medium. The novelty of this work lies in the development of a model for the evolution of electromagnetic radiation in the infrared range is constructed using the Madelung transform for the nonlinear Schrödinger equation, the numerical implementation of which is carried out using the smoothed-particle hydrodynamics. The influence of impurity parameters on the laser beam propagation in a given medium, namely, the energy of electron transitions from impurity levels to the first and second sublattices of nanotubes, is analyzed.
Relying on paired synthetic data, existing learning-based Computational Aberration Correction (CAC) methods are confronted with the intricate and multifaceted synthetic-to-real domain gap, which leads to suboptimal performance in real-world applications. In this paper, in contrast to improving the simulation pipeline, we deliver a novel insight into real-world CAC from the perspective of Unsupervised Domain Adaptation (UDA). By incorporating readily accessible unpaired real-world data into training, we formalize the Domain Adaptive CAC (DACAC) task, and then introduce a comprehensive Real-world aberrated images (Realab) dataset to benchmark it. The setup task presents a formidable challenge due to the intricacy of understanding the target optical degradation domain. To this intent, we propose a novel Quantized Domain-Mixing Representation (QDMR) framework as a potent solution to the issue. Centering around representing and quantizing the optical degradation which is consistent across different images, QDMR adapts the CAC model to the target domain from three key aspects: (1) reconstructing aberrated images of both domains by a VQGAN to learn a Domain-Mixing Codebook (DMC) characterizing the optical degradation; (2) modulating the deep features in CAC model with DMC to transfer the target domain knowledge; and (3) leveraging the trained VQGAN to generate pseudo target aberrated images from the source ones for convincing target domain supervision. Extensive experiments on both synthetic and real-world benchmarks reveal that the models with QDMR consistently surpass the competitive methods in mitigating the synthetic-to-real gap, which produces visually pleasant real-world CAC results with fewer artifacts. Codes and datasets are made publicly available at https://github.com/zju-jiangqi/QDMR.
Advancements in quantum communication and sensing require improved optical transmission that ensures excellent state purity and reduced losses. While free-space optical communication is often preferred, its use becomes challenging over long distances due to beam divergence, atmospheric absorption, scattering, and turbulence, among other factors. In the case of polarization encoding, traditional silica-core optical fibers, though commonly used, struggle with maintaining state purity due to stress-induced birefringence. Hollow core fibers, and in particular nested antiresonant nodeless fibers (NANF), have recently been shown to possess unparalleled polarization purity with minimal birefringence in the telecom wavelength range using continuous-wave (CW) laser light. Here, we investigate a 1-km NANF designed for wavelengths up to the 2-$μ$m waveband. Our results show a polarization extinction ratio between ~-30 dB and ~-70 dB across the 1520 to 1620 nm range in CW operation, peaking at ~-60 dB at the 2-$μ$m design wavelength. Our study also includes the pulsed regime, providing insights beyond previous CW studies, e.g., on the propagation of broadband quantum states of light in NANF at 2 $μ$m, and corresponding extinction-ratio-limited quantum bit error rates (QBER) for prepare-measure and entanglement-based quantum key distribution (QKD) protocols. Our findings highlight the potential of these fibers in emerging applications such as QKD, pointing towards a new standard in optical quantum technologies.
The field of electron optics exploits the analogy between the movement of electrons or charged quasiparticles, primarily in two-dimensional materials subjected to electric and magnetic (EM) fields and the propagation of electromagnetic waves in a dielectric medium with varied refractive index. We significantly extend this analogy by introducing an electronic analogue of Fourier optics dubbed as Fourier electron optics (FEO) with massless Dirac fermions (MDF), namely the charge carriers of single-layer graphene under ambient conditions, by considering their scattering from a two-dimensional quantum dot lattice (TDQDL) treated within Lippmann-Schwinger formalism. By considering the scattering of MDF from TDQDL with a defect region, as well as the moiré pattern of twisted TDQDLs, we establish an electronic analogue of Babinet's principle in optics. Exploiting the similarity of the resulting differential scattering cross-section with the Fraunhofer diffraction pattern, we construct a dictionary for such FEO. Subsequently, we evaluate the resistivity of such scattered MDF using the Boltzmann approach as a function of the angle made between the direction of propagation of these charge-carriers and the symmetry axis of the dot-lattice, and Fourier analyze them to show that the spatial frequency associated with the angle-resolved resistivity gets filtered according to the structural changes in the dot lattice, indicating wider applicability of FEO of MDF.
Optical phenomena always display some degree of partial coherence between their respective degrees of freedom. Partial coherence is of particular interest in multimodal systems, where classical and quantum correlations between spatial, polarization, and spectral degrees of freedom can lead to fascinating phenomena (e.g., entanglement) and be leveraged for advanced imaging and sensing modalities (e.g., in hyperspectral, polarization, and ghost imaging). Here, we present a universal method to analyze, process, and generate spatially partially coherent light in multimode systems by using self-configuring optical networks. Our method relies on cascaded self-configuring layers whose average power outputs are sequentially optimized. Once optimized, the network separates the input light into its mutually incoherent components, which is formally equivalent to a diagonalization of the input density matrix. We illustrate our method with arrays of Mach-Zehnder interferometers and show how this method can be used to perform partially coherent environmental light sensing, generation of multimode partially coherent light with arbitrary coherency matrices, and unscrambling of quantum optical mixtures. We provide guidelines for the experimental realization of this method, paving the way for self-configuring photonic devices that can automatically learn optimal modal representations of partially coherent light fields.
K. Chaudhary, Michele Tamagnone, Xinghui Yin
et al.
Polaritons formed by the coupling of light and material excitations enable light-matter interactions at the nanoscale beyond what is currently possible with conventional optics. However, novel techniques are required to control the propagation of polaritons at the nanoscale and to implement the first practical devices. Here we report the experimental realization of polariton refractive and meta-optics in the mid-infrared by exploiting the properties of low-loss phonon polaritons in isotopically pure hexagonal boron nitride interacting with the surrounding dielectric environment comprising the low-loss phase change material Ge3Sb2Te6. We demonstrate rewritable waveguides, refractive optical elements such as lenses, prisms, and metalenses, which allow for polariton wavefront engineering and sub-wavelength focusing. This method will enable the realization of programmable miniaturized integrated optoelectronic devices and on-demand biosensors based on high quality phonon resonators. Here, the authors experimentally demonstrate a platform for tunable polariton refractive and meta-optics based on hexagonal boron nitride and phase change Ge3Sb2Te6. This combination has the advantage of the long-lived phonon-polariton with switchable refractive index of the phase change material.
Frequent exposure to volatile organic compounds (VOC) above the permissible limit can result in adverse health effects. Therefore, VOC detection and monitoring at trace levels are essential in both indoor and outdoor environments. A highly sensitive and accurate method is desired for this purpose and optical interferometry is a sensitive measurement technique useful for trace-level VOC sensing. We have fabricated and experimentally studied the sensing properties of the optical fiber Fabry–Perot interferometer polymer sensor cast on the fiber tip for acetone detection. Polystyrene, deposited at the end facet of the fiber act as the FP cavity. A significant shift in the interference pattern resonant dip positions is observed in the interaction of the FP cavity with acetone vapor due to changes in the properties of the polymer resulting in physical thickness variation and a change in refractive index. Emphasis has been put on studying the sensor performance over multiple measurement cycles to affirm the reproducibility of the results for repeated usage instead of one-time disposable measurements. Excellent repeatable sensing performance with a sensitivity of 5.78 pm/ppm is observed for 09 data sets recorded over 09 days consisting of 190 individual experimental studies.
Methods for measuring the refractive index of optically transparent dielectric materials are considered. Modified methods based on the methods of minimum deviation and constant deviation are proposed and allow determining the refractive index of triangular prisms with unknown apex angles. In the proposed methods, the angles of light deviation on three faces of the prism are measured, and the refractive index of the material and the prism angles are determined from the solution of a system of equations. To implement the proposed methods, a goniometric system is used. That system was designed to measure angles between the flat surfaces of objects in manual and automated modes. Reference prism samples made of N-SF 1 optical glass, and a hollow prism filled with distilled water are studied. The proposed methods are compared and the measurement error is estimated. It is shown that the modified methods can be used for high-precision measurements of the refractive index in cases where the angles of the prism are unknown, or their measurement is associated with technical difficulties.
Hlib Kupianskyi, Simon A. R. Horsley, David B. Phillips
When light propagates through a complex medium, such as a multimode optical fibre (MMF), the spatial information it carries is scrambled. In this work we experimentally demonstrate an all-optical strategy to unscramble this light again. We first create a digital model capturing the way light has been scattered, and then use this model to inverse-design and build a complementary optical system - which we call an optical inverter - that reverses this scattering process. Our implementation of this concept is based on multi-plane light conversion, and can also be understood as a diffractive artificial neural network or a physical matrix pre-conditioner. We present three design strategies allowing different aspects of device performance to be prioritised. We experimentally demonstrate a prototype optical inverter capable of simultaneously unscrambling up to 30 spatial modes that have propagated through a 1m long MMF, and show how this enables near instantaneous incoherent imaging, without the need for any beam scanning or computational processing. We also demonstrate the reconfigurable nature of this prototype, allowing it to adapt and deliver a new optical transformation if the MMF it is matched to changes configuration. Our work represents a first step towards a new way to see through scattering media. Beyond imaging, this concept may also have applications to the fields of optical communications, optical computing and quantum photonics.
Photothermal interferometry is an ultra-sensitive spectroscopic means for trace chemical detection in gas- and liquid-phase materials. Previous photothermal interferometry systems used free-space optics and have limitations in efficiency of light–matter interaction, size and optical alignment, and integration into photonic circuits. Here we exploit photothermal-induced phase change in a gas-filled hollow-core photonic bandgap fibre, and demonstrate an all-fibre acetylene gas sensor with a noise equivalent concentration of 2 p.p.b. (2.3 × 10−9 cm−1 in absorption coefficient) and an unprecedented dynamic range of nearly six orders of magnitude. The realization of photothermal interferometry with low-cost near infrared semiconductor lasers and fibre-based technology allows a class of optical sensors with compact size, ultra sensitivity and selectivity, applicability to harsh environment, and capability for remote and multiplexed multi-point detection and distributed sensing. Photothermal interferometry systems using free-space optics have limits in terms of light–matter interaction efficiency, size, optical alignment and integration. Here, Jin et al. use a gas-filled hollow-core photonic bandgap fibre to demonstrate an all-fibre gas sensor with ultrahigh sensitivity and dynamic range.
This study investigated the neural mechanisms located in the prefrontal cortex (PFC) involved in maintaining addictive-like eating behavior. Therefore, we aimed to fill a gap in the existing literature and help clarify the food addiction (FA) cycle by inspecting the relationship between the executive control and psychopathology involved in the FA cycle. Twenty-three students recruited from the University of Macau participated in this study. We investigated a hemodynamic response captured by NIRS recordings, activated during n-back, set-shifting, and go/no-go paradigms. Moreover, we investigated the FA symptoms through the YFAS clinical inventory to better understand the relationship between hemodynamic response and clinical symptomatology in college students. First, the hemodynamic findings confirm that altered cognitive control in executive function performance appears to be linked to addictive-like eating behaviors, which in turn confirms a circuit similarity between FA and the substance abuse population (SUD) as reported in previous fMRI studies. Secondly, the psychological findings confirm the significant association between the working memory deficits and symptoms severity which suggest the role of self-control and regulation in limiting the storage resources as a potential trigger to develop overconsumption episodes in the FA cycle. Our findings highlight how disrupted self-control and regulation of craving and negative affect induced by mental imagery might shape and overload the working memory storage as a potential trigger to develop binge eating episodes to maintain the FA cycle. In conclusion, the use of fNIRS in the context of eating disorders studies represents a valuable application, noninvasive, and patient-friendly tool, providing new insights into understanding the addiction cycle and treatment guidelines.
Hiroshi Ishiwata, Naoki Hasegawa, Yasuo Yonemaru
et al.
When an optical system and a digital image sensor are combined, it is known that pixel size of the sensor affects digital images. In particular, the DOF was not represented in a simple formula due to the influence of pixel size. To consider the effect of pixel size on digital images, we set the ratio, fC/fN, between the cut-off frequency of the optical system, fC, and the Nyquist frequency of the imaging device, fN, as the parameter expressing the effect of the pixel size. By using the parameter, we derived that the DOF can be expressed as a simple formula. For confirming the DOF formula, we measured the DOF of a microscope combined a digital image sensor. The values calculated from the DOF formula that we derived were consistent with the experimentally measured results.We propose our formula expressing the DOF when an optical system and a digital image sensor are combined
Roland E. Mainz, Giulio Maria Rossi, Fabian Scheiba
et al.
The availability of electromagnetic pulses with controllable field waveform and extremely short duration, even below a single optical cycle, is imperative to fully harness strong-field processes and to gain insight into ultrafast light-driven mechanisms occurring in the attosecond time-domain. The recently demonstrated parametric waveform synthesis (PWS) introduces an energy-, power- and spectrum-scalable method to generate non-sinusoidal sub-cycle optical waveforms by coherently combining different phase-stable pulses attained via optical parametric amplifiers. Significant technological developments have been addressed to overcome the stability issues related to PWS and to obtain an effective and reliable waveform control system. Here we present the main ingredients enabling PWS technology. The design choices concerning the optical, mechanical and electronic setups are justified by analytical/numerical modeling and benchmarked by experimental observations. In its present incarnation, the PWS technology enables the generation of field-controllable mJ-level few-femtosecond pulses spanning the visible to infrared range.
Shahab Abdollahi, Pablo Marin-Palomo, Martin Virte
Lasers designed to emit at multiple and controllable modes, or multi-wavelength lasers, have the potential to become key building blocks for future microwave photonic technologies. While many interesting schemes relying on optical injection have been proposed, the nonlinear mode coupling between different modes of a multi-wavelength laser and their dynamical behavior under optical injection remains vastly unexplored. Here, we experimentally and numerically study the effect of optical injection around the suppressed mode of a dual12 wavelength laser and the resulting interactions with the dominant mode. We highlight a wavelength shift of the dominant mode triggered by injection locking of the suppressed mode and report a strong impact of the mode suppression ratio on the locking range. Finally, we show numerically that the cross-coupling parameter between the two modes might have a key role in this effect.
We report experimental generation and manipulation of optical tornado waves (ToWs). By controlling the self-focusing length, total angular momentum, and foci deviation of ToWs, the propagation properties of optical ToWs, especially their angular velocity of the main intensity lobes, can be manipulated. We achieve controlling the accumulated rotation angle of the intensity lobes from 0 to 1100 degrees. Also, we confirm that ToWs get the highest angular velocity around the foci coincide situation. Our experimental results are in good agreement with numerical results.