Optics (physics.optics)

Abstract: We experimentally explored novel behaviors of non-reciprocal absorption and almost zero reflection in a dual photon resonator system, which is physically separated and composed of two inverted split ring resonators (ISRRs) with varying inter-distances. We also found that an electromagnetically-induced-transparency (EIT)-like peak at a specific inter-distance of d = 18 mm through traveling waves flowing along a shared microstrip line to which the dual ISRRs are dissipatively coupled. With the aid of CST-simulations and analytical modeling, we found that destructive and/or constructive interferences in traveling waves, indirectly coupled to each ISRR, result in a traveling-wave-induced transparency peak within a narrow window. Furthermore, we observed not only strong non-reciprocal responses of reflectivity and absorptivity at individual inter-distances exactly at the corresponding EIT-like peak positions, but also nearly zero reflection and almost perfect absorption for a specific case of d = 20 mm. Finally, the unidirectional absorptions with zero reflection at d = 20 mm are found to be ascribed to a non-Hermitian origin. This work not only provides a better understanding of traveling-wave-induced indirect coupling between two photonic resonators without magnetic coupling, but also suggests potential implications for the resulting non-reciprocal behaviors of absorption and reflection in microwave circuits and quantum information devices.

Abstract: We report a near two-octave spanning supercontinuum (SC) from 790 nm to 2900 nm in a nanostructured tellurite graded-index multimode fiber with a nanostructured core. We study the SC dynamics in different dispersion regimes and observe near-single mode spatial intensity distribution at high input energy values. Numerical simulations of the (3+1)D generalized nonlinear Schr\"odinger equation are in good agreement with our experiments. Our results open a new avenue for the generation of high-power mid-infrared SC sources in soft glass fibers.

Abstract: Modelling the scattering of focused, coherent light by nano-scale structures is oftentimes used to reconstruct or infer geometrical or material properties of structures under investigation in optical scatterometry. This comprises both periodic and aperiodic nano-structures. Coherent Fourier scatterometry with focused light exploits the diffraction pattern formed by the nano-structures in Fourier plane. While the scattering of a focused beam by a spatially isolated scatterer is a standard modelling task for state-of-the art electromagnetic solvers based, e.g., on the finite element method, the case of periodically structured samples is more involved. In particular when the focused light covers several grating periods of as it is commonly the case. We will present a coherent illumination model for scattering of focused beams such as Gaussian -- and Bessel -- beams by periodic structures such as line gratings. The model allows to take into account optical wavefront aberrations in optical systems used for both, the illumination and detection of the scattered fields. We compare the model with strategies implemented on large-scale super-cells and inverse Floquet-transform strategies to superimpose both near- and far- fields coherently.

Abstract: Semiconductor quantum dots are promising candidates for the generation of nonclassical light. Coupling a quantum dot to a device capable of providing polarization-selective enhancement of optical transitions is highly beneficial for advanced functionalities such as efficient resonant driving schemes or applications based on optical cyclicity. Here, we demonstrate broadband polarization-selective enhancement by coupling a quantum dot emitting in the telecom O-band to an elliptical bullseye resonator. We report bright single-photon emission with a degree of linear polarization of 96%, Purcell factor of 3.9, and count rates up to 3 MHz. Furthermore, we present a measurement of two-photon interference without any external polarization filtering and demonstrate compatibility with compact Stirling cryocoolers by operating the device at temperatures up to 40 K. These results represent an important step towards practical integration of optimal quantum dot photon sources in deployment-ready setups.

Abstract: Photonic integrated circuits are paving the way for novel on-chip functionalities with diverse applications in communication, computing, and beyond. The integration of on-chip light sources, especially single-mode lasers, is crucial for advancing those photonic chips to their full potential. Recently, novel concepts involving topological designs introduced a variety of options for tuning device properties such as the desired single mode emission. Here we introduce a novel cavity design that allows to amplify the topological interface mode by deterministic placement of gain material within the topological lattice. The proposed design is experimentally implemented by a selective epitaxy process resulting in Si and InGaAs nanorods embedded within the same topological lattice. This results in the first demonstration of a single-mode laser in the telecom band using the concept of amplified topological modes.

Abstract: We have developed a cryogenic characterization platform for ultrafast photodiodes, whose time domain responses are extracted by electro-optic sampling using femtosecond laser pulses in a pump-probe configuration. The excitation of the photodiodes with the pump beam and the electro-optic sampling crystals with the probe beam are realized in a fully fiber-coupled manner. This allows us to place the characterization platform in almost any temperature environment. As application example, we characterize the time-domain response of commercial p-i-n photodiodes with a nominal bandwidth of 20 GHz and 60 GHz at temperatures of 4 K and 300 K and in a large parameter range of photocurrent and reverse bias. For these photodiodes, we detect frequency components up to approximately 250 GHz, while the theoretical bandwidth of our sampling method exceeds 1 THz. Our measurements demonstrate a significant excitation power and temperature dependence of the photodiodes' ultrafast time responses, reflecting, most likely, changes in carrier mobilities and electric field screening. Since our system is an ideal tool to characterize and optimize the response of fast photodiodes at cryogenic temperatures, it has direct impact on applications in superconducting quantum technology such as the enhancement of optical links to superconducting qubits and quantum-accurate waveform generators.

Abstract: High-harmonic generation in solids allows probing and controlling electron dynamics in crystals on few femtosecond timescales, paving the way to lightwave electronics. In the spatial domain, recent advances in the real-space interpretation of high-harmonic emission in solids allows imaging the field-free, static, potential of the valence electrons with picometer resolution. The combination of such extreme spatial and temporal resolutions to measure and control strong-field dynamics in solids at the atomic scale is poised to unlock a new frontier of lightwave electronics. Here, we report a strong intensity-dependent anisotropy in the high-harmonic generation from ReS$_2$ that we attribute to angle-dependent interference of currents from the different atoms in the unit cell. Furthermore, we demonstrate how the laser parameters control the relative contribution of these atoms to the high-harmonic emission. Our findings provide an unprecedented atomic perspective on strong-field dynamics in crystals and suggest that crystals with a large number of atoms in the unit cell are not necessarily more efficient harmonic emitters than those with fewer atoms.

Abstract: The development of X-ray scintillators with ultrahigh light yields and ultrafast response times is a long sought-after goal. In this work, we theoretically predict and experimentally demonstrate a fundamental mechanism that pushes the frontiers of ultrafast X-ray scintillator performance: the use of nanoscale-confined surface plasmon polariton modes to tailor the scintillator response time via the Purcell effect. By incorporating nanoplasmonic materials in scintillator devices, this work predicts over 10-fold enhancement in decay rate and 38% reduction in time resolution even with only a simple planar design. We experimentally demonstrate the nanoplasmonic Purcell effect using perovskite scintillators, enhancing the light yield by over 120% to 88 $\pm$ 11 ph/keV, and the decay rate by over 60% to 2.0 $\pm$ 0.2 ns for the average decay time, and 0.7 $\pm$ 0.1 ns for the ultrafast decay component, in good agreement with the predictions of our theoretical framework. We perform proof-of-concept X-ray imaging experiments using nanoplasmonic scintillators, demonstrating 182% enhancement in the modulation transfer function at 4 line pairs per millimeter spatial frequency. This work highlights the enormous potential of nanoplasmonics in optimizing ultrafast scintillator devices for applications including time-of-flight X-ray imaging and photon-counting computed tomography.

Abstract: Development of advanced optical data storage, information encryption, and security labeling technologies requires low-cost materials exhibiting local, pronounced, and diverse modification of their structure-dependent optical properties under external excitation. Herein, for these purposes, we propose and develop a novel platform relying on layered lead halide Ruddlesden-Popper (quasi-2D) phases that undergo a light-induced transition towards bulk (3D) halide perovskite and employ this phenomenon for the direct optical writing of various multicolor patterns. This transition causes the weakening of quantum confinement, and hence the bandgap reduction in these photoluminescent thin films. To significantly extend the color gamut of evolving photoluminescence, we make use of mixed-halide compositions exhibiting photoinduced halide segregation. As a result, the emission wavelength of the resulting films can be widely tuned across the entire 450-600 nm range depending on the illumination conditions. We show that pulsed near-infrared femtosecond laser irradiation provides high-resolution direct writing, whereas continuous-wave ultraviolet exposure is suitable for fast recording on larger scales. The luminescent micro- and macro-scale images created on such quasi-2D perovskite films can be erased during the visualization process, by which the persistence of these images to UV light exposure can be controlled and increased further with the increasing number of octahedral layers used in the perovskite stacks. This makes the proposed writing/erasing perovskite-based platform suitable for the manufacturing of both inexpensive optical data storage devices and light-erasable security labels.