Abstract Reflections from on-chip components pose significant challenges to stable laser operation in photonic integrated circuits (PICs). Quantum dot (QD) lasers, with low linewidth enhancement factors and high damping rates, are promising for isolator-free integration, yet earlier feedback studies were capped near −10 dB feedback and never reached coherence collapse (CC). As a result, one could only conclude that QD lasers tolerate feedback up to –10 dB, leaving open whether they remain reliable in practical PICs where lower coupling losses allow much stronger feedback. Here, we optimized QD lasers through advanced epitaxial growth and fabrication and developed a setup that delivers feedback up to 0 dB. Under these conditions, we observed CC at −6.7 dB (21.4% feedback), extending the feedback tolerance by tens of decibels beyond quantum-well (QW) lasers. We further demonstrated penalty-free 10 Gbps operation, robust thermal stability with ±0.5 dB drift across 15–45 °C, >100 h continuous testing, and ~±0.3 dB reproducibility across devices. Modeling indicates even stronger tolerance in realistic PIC cavities, and benchmarking shows our device rivals hybrid DFB–resonator platforms while outperforming other QW, QD, and VCSEL lasers. Together, this work provides the most comprehensive assessment of QD laser feedback tolerance to date and establishes practical design rules for isolator-free PICs.
Abstract Formation and dynamic control of strong coupling among cavities are essential to realize advanced functional photonic and quantum circuits. Especially for cavities at distant distance or arbitrary locations. Conventional approaches suffer from short coupling distance, poor controllability, fixed locations and low wavelength uniformity, significantly restricting the scalability of photonic and quantum networks. Here, we exploit the intrinsic advantages of optical bound state in the continuum (BIC) and demonstrate an all-in-one solution for long-range coupled cavities. BIC metasurface can support a series of finite-sized quasi-BIC microlasers at arbitrary locations. The quasi-BICs microlasers have the same wavelength and are inherently connected through BIC metasurface. Consequently, the coupling distances in experiment increase significantly from subwavelength to tens of micrometers. Such long-range interaction in BIC metasurface enables scaling to two-dimensional architectures and ultrafast control of internal laser actions, e.g., non-Hermitian zero-mode lasing. This research shall facilitate the advancement of scalable and reconfigurable photonic networks.
In this article, we review the history, current status, physical mechanisms, experimental methods, and applications of nonlinear magneto-optical effects in atomic vapors. We begin by describing the pioneering work of Macaluso and Corbino over a century ago on linear magneto-optical effects (in which the properties of the medium do not depend on the light power) in the vicinity of atomic resonances, and contrast these effects with various nonlinear magneto-optical phenomena that have been studied both theoretically and experimentally since the late 1960s. In recent years, the field of nonlinear magneto-optics has experienced a revival of interest that has led to a number of developments, including the observation of ultra-narrow (1-Hz) magneto-optical resonances, applications in sensitive magnetometry, nonlinear magneto-optical tomography, and the possibility of a search for parity- and time-reversal-invariance violation in atoms.
Light focusing plays a central role in biomedical imaging, manipulation, and therapy. In scattering media, direct light focusing becomes infeasible beyond one transport mean free path. All previous methods1–3 to overcome this diffusion limit lack a practical internal “guide star.”4 Here we proposed and experimentally validated a novel concept, called Time-Reversed Ultrasonically Encoded (TRUE) optical focusing, to deliver light into any dynamically defined location inside a scattering medium. First, diffused coherent light is encoded by a focused ultrasonic wave to provide a virtual internal “guide star”; then, only the encoded light is time-reversed and transmitted back to the ultrasonic focus. The TRUE optical focus–defined by the ultrasonic wave–is unaffected by multiple scattering of light. Such focusing is especially desirable in biological tissue where ultrasonic scattering is ~1000 times weaker than optical scattering. Various fields including biomedical and colloidal optics can benefit from TRUE optical focusing.
Light propagation is usually reciprocal. However, a static magnetic field along the propagation direction can break the time-reversal symmetry in the presence of magneto-optical materials. The Faraday effect in magneto-optical materials rotates the polarization plane of light, and when light travels backward the polarization is further rotated. This is applied in optical isolators, which are of crucial importance in optical systems. Faraday isolators are typically bulky due to the weak Faraday effect of available magneto-optical materials. The growing research endeavour in integrated optics demands thin-film Faraday rotators and enhancement of the Faraday effect. Here, we report significant enhancement of Faraday rotation by hybridizing plasmonics with magneto-optics. By fabricating plasmonic nanostructures on laser-deposited magneto-optical thin films, Faraday rotation is enhanced by one order of magnitude in our experiment, while high transparency is maintained. We elucidate the enhanced Faraday effect by the interplay between plasmons and different photonic waveguide modes in our system. The Faraday effect rotates the polarization plane of light in magneto-optical materials and is used for optical isolators blocking unwanted backscattering of light. Usually a small effect, Chin et al. have observed a large enhancement of the optical rotation by magneto-plasmonics.
Exquisite polarization control using optical metasurfaces has attracted considerable attention thanks to their ability to manipulate multichannel independent wavefronts with subwavelength resolution. Here we present a new class of metasurface polarization optics, which enables imposition of two arbitrary and independent amplitude profiles on any pair of orthogonal states of polarization. The implementation method involves a polarization-dependent interference mechanism achieved by constructing a metasurface composed of an array of nanoscale birefringent waveplates. Based on this principle, we experimentally demonstrate chiral grayscale metasurface and chiral shadow rendering of structured light. These results illustrate a general approach interlinking amplitude profiles and orthogonal states of polarization and expands the scope of metasurface polarization shaping optics.
The precise engineering of materials and surfaces has been at the heart of some of the recent advances in optics and photonics. These advances related to the engineering of materials with new functionalities have also opened up exciting avenues for designing trainable surfaces that can perform computation and machine-learning tasks through light–matter interactions and diffraction. Here, we analyze the information-processing capacity of coherent optical networks formed by diffractive surfaces that are trained to perform an all-optical computational task between a given input and output field-of-view. We show that the dimensionality of the all-optical solution space covering the complex-valued transformations between the input and output fields-of-view is linearly proportional to the number of diffractive surfaces within the optical network, up to a limit that is dictated by the extent of the input and output fields-of-view. Deeper diffractive networks that are composed of larger numbers of trainable surfaces can cover a higher-dimensional subspace of the complex-valued linear transformations between a larger input field-of-view and a larger output field-of-view and exhibit depth advantages in terms of their statistical inference, learning, and generalization capabilities for different image classification tasks when compared with a single trainable diffractive surface. These analyses and conclusions are broadly applicable to various forms of diffractive surfaces, including, e.g., plasmonic and/or dielectric-based metasurfaces and flat optics, which can be used to form all-optical processors. Layers of materials that diffract light with variable spacing between them can be adjusted or “trained” to perform information-processing tasks using light alone. Diffraction is the alteration of the propagation of light waves by structural features of the materials they encounter. Aydogan Ozcan and colleagues at the University of California, Los Angeles, USA, performed an analysis of optical neural networks composed of spatially engineered diffractive surfaces. They explored the power of multilayered networks to perform optical processing tasks, including image recognition and classification. They also determined mathematical rules describing the performance limits of the networks in relation to the number of diffractive surfaces they contained. Their work is relevant to various diffractive surfaces, including metasurfaces patterned with features smaller than the wavelength of light, and plasmonic materials governed by the coherent behavior of surface electrons.
AbstractTransparent objects are invisible to traditional cameras because they can only detect intensity fluctuations, necessitating the need for interferometry followed by computationally intensive digital image processing. Now it is shown that the necessary transformations can be performed optically by combining machine learning and diffractive optics, for a direct in-situ measurement of transparent objects with conventional cameras.
The theory of Hawking radiation can be tested in laboratory analogues of black holes. We use light pulses in nonlinear fiber optics to establish artificial event horizons. Each pulse generates a moving perturbation of the refractive index via the Kerr effect. Probe light perceives this as an event horizon when its group velocity, slowed down by the perturbation, matches the speed of the pulse. We have observed in our experiment that the probe stimulates Hawking radiation, which occurs in a regime of extreme nonlinear fiber optics where positive and negative frequencies mix.
Shaka O. Samuel, M. Frank Lagbegha-ebi, E.P. Ogherohwo
et al.
The electrochemical deposition was used to synthesize zirconium-doped strontium sulphide materials at varying dopant concentrations of 0.01 to 0.03 mol. The surface micrograph of the zirconium doped films is well structured on the surface of the FTO used for the synthesis without any crack or lattice strain. The spectrum is polycrystalline with a cubic structure and a prominent peak at (111) orientation for SrS film. At the introduction of the zirconium dopant 0.01 mol, the peak intensity increases with a prominent peak at (211) which indicate acceptance of zirconium dopant in the precursor and as the dopant concentration rises the peak intensity decreases which depicts that a higher concentration of zirconium reduces the peak intensity of the films. The Williamson-Hall plot's slope increases as the dopant concentration increases. The materials exhibit a thickness increase of 121.32 to 126.13 nm and a decrease in film resistivity from 1.12 × 109 to 1.32 × 109 O.m, which further led to an increase in conductivity from 7.57 × 108 to 8.26 × 108 S/m. The bandgap energy of SrS is 1.50 eV while SrS-doped zirconium is 1.35 eV–2.52 eV.
Carbon dots have many new and interesting phenomena and the concentration‐dependent luminescence wavelength is an intriguing one. Luminescent carbon dots have recently gained interest due to their new and interesting phenomena such as its concentration‐dependent peak emission. While there have been reports and discussions on this phenomenon, the mechanism continues to be poorly understood. Herein, new observations on nitrogen–sulfur codoping carbon dots (NSCDs) diluted at different concentrations show that the high concentration of G‐NSCDs (0.2 mg mL−1) emits green fluorescence while the low concentration of B‐NSCDs (0.01 mg mL−1) emits blue fluorescence. It is found that the carbon dot size changes with the particle concentration: the high concentration of G‐NSCDs is about 37 nm in size while the low concentration of B‐NSCDs is only about 1.8 nm in size. Therefore, it is clearly demonstrated that the emission wavelength is related to the particle size. These interesting behaviors open a door for the exploration of new materials with novel potential.
Optogenetics promises precise spatiotemporal control of neural processes using light. However, the spatial extent of illumination within the brain is difficult to control and cannot be adjusted using standard fiber optics. We demonstrate that optical fibers with tapered tips can be used to illuminate either spatially restricted or large brain volumes. Remotely adjusting the light input angle to the fiber varies the light-emitting portion of the taper over several millimeters without movement of the implant. We use this mode to activate dorsal versus ventral striatum of individual mice and reveal different effects of each manipulation on motor behavior. Conversely, injecting light over the full numerical aperture of the fiber results in light emission from the entire taper surface, achieving broader and more efficient optogenetic activation of neurons, compared to standard flat-faced fiber stimulation. Thus, tapered fibers permit focal or broad illumination that can be precisely and dynamically matched to experimental needs.
Yuji Sasaki, Kenji Yamazaki, Naoshi Murakami
et al.
Wavefront shaping of structured light beams is attracting considerable attention in optics and related technologies. Due to the potential benefits, it is crucial to develop versatile methods for controlling the wavefront in a compact space with the capacity for high‐throughput parallel processing. Herein, a unique concept is introduced for converting the wavefront of multiple structured light beams, which are periodically packed in a microscopic area. An experimental demonstration is provided by using transmissive planar optical elements consisting of a microarray of geometric phase based on nematic liquid crystals. The periodic microstructure is fabricated by the directed self‐organization of topological defects present in a nanoscale relief obtained by area‐selective surface modification. The conversion of multiple wavefronts is realized by using the Talbot self‐imaging effect of the microarray. The integrated geometric phase microarray has potential applications in vortex beam emitters to harness structured light, such as for optical manipulation and lithography.
We demonstrate a dynamic synthesis deep learning framework to adaptively adjusts model weights and adapts to different scattering conditions, which opens up a new paradigm for adaptive computational imaging.
Today, the on-board Spacecraft (SC) communication requires an impressive network of massive wires, both in flight and in the Assembly Integration and Test (AIT) phase. Here, we present the design and the experimental characterization of novel Optical Wireless Communication (OWC) transceivers compatible with MIL-STD-1553B, which is the shared bus predominantly deployed in SCs. Each transceiver works as an interface that transports the bipolar Manchester-coded signal by converting it to/from the optical domain. These OWC interfaces can effectively reduce the overall weight and cost of the SC and can also largely decrease the AIT time. Since they are fully analog and do not need any microprocessors or Digital Signal Processing, they have a small footprint and a very low power consumption. We initially characterize the transceivers using a non-return-to-zero (NRZ) signal, then we used them to replace a cable and connect a pair of test units, transmitting MIL-STD-1553B signals: the measurements show that our solution has a good power budget (+65dB), which will allow the interoperability with MIL-STD-1553B boards in a wide range of scenarios. Furthermore, it is realized by means of commercially available components; it could also be implemented by using proven space-graded devices.
Material loss, especially in metal and 2D materials, is the bottleneck for high‐performance integrated optical devices. Here, a novel concept by utilizing the high‐loss materials in a non‐Hermitian system instead of avoiding the loss materials. It is theoretically analyzed how the complex refractive index affects the loss of optical devices based on a two‐waveguide‐coupled non‐Hermitian system. The results reveal that the loss of optical devices can be improved by increasing the loss of materials or the difference in real refractive indexes. It is experimentally verified that a high loss material can be placed close to the optical waveguide without introducing non‐negligible loss to the optical devices, by demonstrating a thermo‐optic phase shifter with a metallic heater placed very close to the silicon waveguide. As a result, the insertion loss is only 0.1 dB for the 100 μm long heater with a gap of 400 nm, and the largest bandwidth for the metallic heater reaches up to 280 kHz. The finding offers a way to realize high‐performance optical devices with high‐loss materials, contributing to the practical applications of strongly absorbing materials based on non‐Hermitian optics.
A highly sensitive optical sensor is presented. This sensor is having multilayer structure that is designed and optimized theoretically by using Zinc Sulfide (ZnS) and Polyvinylpyrrolidone (PVP). The optical sensor proposed here is based on Surface Plasmon Resonance (SPR) technique by using Kretschmann configuration. This SPR sensor is designed with BK-7 prism which is coated with silver (Ag), overlayers ZnS and PVP in sequence. Silver is the plasmonic metal, PVP and ZnS are polymer and dielectric respectively and they perform the interaction with analyte and sensitivity enhancement however ZnS contributes more to enhance the sensitivity. For the characterization of multilayer Ag/ZnS/PVP structure of optical sensor, spectral interrogation mode is used. The surface plasmon resonance wavelength was calculated for each concentration. It shifts linearly towards higher wavelength with the increasing concentration of the analytes from 1.33 to 1.35 refractive index when interact with sensing surface. The sensitivity of the sensor is found to be 8537.06 nm/RIU throughout. The spectral range of proposed sensor is Visible-Near Infra Red (VIS-NIR) region from 600 to 1050 nm. The detection accuracy (DA) decreases with increasing concentration of analytes. Figure of merit (FOM) is also having same nature as DA. The sensitivity of the proposed sensor is quite high in comparison to other sensors. The proposed sensor will be useful to sense the chemical and biological compounds within its detection range (from 1.33 to 1.35 refractive index) in VIS-NIR region from experimental point of view.
Ibrutinib, a Bruton’s tyrosine kinase that plays an essential role in the B-cell development and cancer cells, has been recently approved to treat chronic, lymphocytic, and other types of leukemia. This study focused on investigating ibrutinib by its electronic transitions, vibrational frequencies, and electrospray mass spectra. The experimental peaks for electronic spectrum were found at 248.0 and 281.0 nm, whereas the νC = 0 stretching frequency was found at 1652.4 and 1639.19 cm−1. These experimental properties were compared with the corresponding theoretical calculations in which density functional theory was applied. The optimized structure was obtained with the calculations using a hybrid function (B3LYP) and high-level basis sets [6-311G++(d,p)]. Most of the calculated vibrational frequencies showed a relatively good agreement with the experimental ones. The electronic transitions of ibrutinib calculated using time-dependent DFT method were performed at two different solvation methods: PCM and SMD. The mass spectrum of ibrutinib, its fragments, and its isotopic pattern agreed well with the expected spectra.
Abstract In recent years, the integration of graphene and related two-dimensional (2D) materials in optical fibers have stimulated significant advances in all-fiber photonics and optoelectronics. The conventional passive silica fiber devices with 2D materials are empowered for enhancing light-matter interactions and are applied for manipulating light beams in respect of their polarization, phase, intensity and frequency, and even realizing the active photo-electric conversion and electro-optic modulation, which paves a new route to the integrated multifunctional all-fiber optoelectronic system. This article reviews the fast-progress field of hybrid 2D-materials-optical-fiber for the opto-electro-mechanical devices. The challenges and opportunities in this field for future development are discussed.