Extending the spectrum of fully integrated photonics to submicrometre wavelengths.

Integrated photonics has profoundly affected a wide range of technologies underpinning modern society1-4. The ability to fabricate a complete optical system on a chip offers unrivalled scalability, weight, cost and power efficiency5,6. Over the last decade, the progression from pure III-V materials platforms to silicon photonics has significantly broadened the scope of integrated photonics, by combining integrated lasers with the high-volume, advanced fabrication capabilities of the commercial electronics industry7,8. Yet, despite remarkable manufacturing advantages, reliance on silicon-based waveguides currently limits the spectral window available to photonic integrated circuits (PICs). Here, we present a new generation of integrated photonics by directly uniting III-V materials with silicon nitride waveguides on Si wafers. Using this technology, we present a fully integrated PIC at photon energies greater than the bandgap of silicon, demonstrating essential photonic building blocks, including lasers, amplifiers, photodetectors, modulators and passives, all operating at submicrometre wavelengths. Using this platform, we achieve unprecedented coherence and tunability in an integrated laser at short wavelength. Furthermore, by making use of this higher photon energy, we demonstrate superb high-temperature performance and kHz-level fundamental linewidths at elevated temperatures. Given the many potential applications at short wavelengths, the success of this integration strategy unlocks a broad range of new integrated photonics applications.

Integrated Photonic Platform for Rare-Earth Ions in Thin Film Lithium Niobate.

Rare-earth ion ensembles doped in single crystals are a promising materials system with widespread applications in optical signal processing, lasing, and quantum information processing. Incorporating rare-earth ions into integrated photonic devices could enable compact lasers and modulators, as well as on-chip optical quantum memories for classical and quantum optical applications. To this end, a thin film single crystalline wafer structure that is compatible with planar fabrication of integrated photonic devices would be highly desirable. However, incorporating rare-earth ions into a thin film form-factor while preserving their optical properties has proven challenging. We demonstrate an integrated photonic platform for rare-earth ions doped in a single crystalline thin film lithium niobate on insulator. The thin film is composed of lithium niobate doped with Tm3+. The ions in the thin film exhibit optical lifetimes identical to those measured in bulk crystals. We show narrow spectral holes in a thin film waveguide that require up to 2 orders of magnitude lower power to generate than previously reported bulk waveguides. Our results pave the way for scalable on-chip lasers, optical signal processing devices, and integrated optical quantum memories.

Synthetic Gauge Field for Two-Dimensional Time-Multiplexed Quantum Random Walks.

Temporal multiplexing provides an efficient and scalable approach to realize a quantum random walk with photons that can exhibit topological properties. But two-dimensional time-multiplexed topological quantum walks studied so far have relied on generalizations of the Su-Shreiffer-Heeger model with no synthetic gauge field. In this work, we demonstrate a two-dimensional topological quantum random walk where the nontrivial topology is due to the presence of a synthetic gauge field. We show that the synthetic gauge field leads to the appearance of multiple band gaps and, consequently, a spatial confinement of the quantum walk distribution. Moreover, we demonstrate topological edge states at an interface between domains with opposite synthetic fields. Our results expand the range of Hamiltonians that can be simulated using photonic quantum walks.

Nanostructure-Induced Distortion in Single-Emitter Microscopy.

Single-emitter microscopy has emerged as a promising method of imaging nanostructures with nanoscale resolution. This technique uses the centroid position of an emitter's far-field radiation pattern to infer its position to a precision that is far below the diffraction limit. However, nanostructures composed of high-dielectric materials such as noble metals can distort the far-field radiation pattern. Previous work has shown that these distortions can significantly degrade the imaging of the local density of states in metallic nanowires using polarization-resolved imaging. But unlike nanowires, nanoparticles do not have a well-defined axis of symmetry, which makes polarization-resolved imaging difficult to apply. Nanoparticles also exhibit a more complex range of distortions, because in addition to introducing a high dielectric surface, they also act as efficient scatterers. Thus, the distortion effects of nanoparticles in single-emitter microscopy remains poorly understood. Here we demonstrate that metallic nanoparticles can significantly distort the accuracy of single-emitter imaging at distances exceeding 300 nm. We use a single quantum dot to probe both the magnitude and the direction of the metallic nanoparticle-induced imaging distortion and show that the diffraction spot of the quantum dot can shift by more than 35 nm. The centroid position of the emitter generally shifts away from the nanoparticle position, which is in contradiction to the conventional wisdom that the nanoparticle is a scattering object that will pull in the diffraction spot of the emitter toward its center. These results suggest that dielectric distortion of the emission pattern dominates over scattering. We also show that by monitoring the distortion of the quantum dot diffraction spot we can obtain high-resolution spatial images of the nanoparticle, providing a new method for performing highly precise, subdiffraction spatial imaging. These results provide a better understanding of the complex near-field coupling between emitters and nanostructures and open up new opportunities to perform super-resolution microscopy with higher accuracy.

A topological quantum optics interface.

The application of topology in optics has led to a new paradigm in developing photonic devices with robust properties against disorder. Although considerable progress on topological phenomena has been achieved in the classical domain, the realization of strong light-matter coupling in the quantum domain remains unexplored. We demonstrate a strong interface between single quantum emitters and topological photonic states. Our approach creates robust counterpropagating edge states at the boundary of two distinct topological photonic crystals. We demonstrate the chiral emission of a quantum emitter into these modes and establish their robustness against sharp bends. This approach may enable the development of quantum optics devices with built-in protection, with potential applications in quantum simulation and sensing.

Humidity-Induced Photoluminescence Hysteresis in Variable Cs/Br Ratio Hybrid Perovskites.

Hybrid organic-inorganic perovskites containing Cs are a promising new material for light-absorbing and light-emitting optoelectronics. However, the impact of environmental conditions on their optical properties is not fully understood. Here, we elucidate and quantify the influence of distinct humidity levels on the charge carrier recombination in Cs xFA1- xPb(I yBr1- y)3 perovskites. Using in situ environmental photoluminescence (PL), we temporally and spectrally resolve light emission within a loop of critical relative humidity (rH) levels. Our measurements show that exposure up to 35% rH increases the PL emission for all Cs (10-17%) and Br (17-38%) concentrations investigated here. Spectrally, samples with larger Br concentrations exhibit PL redshift at higher humidity levels, revealing water-driven halide segregation. The compositions considered present hysteresis in their PL intensity upon returning to a low-moisture environment due to partially reversible hydration of the perovskites. Our findings demonstrate that the Cs/Br ratio strongly influences both the spectral stability and extent of light emission hysteresis. We expect our method to become standard when testing the stability of emerging perovskites, including lead-free options, and to be combined with other parameters known for affecting material degradation, e.g., oxygen and temperature.

Socio-demographic Correlates of Rhinosporidiosis: A Hospital-Based Epidemiologic Study in Purulia, India.

The present paper attempts to explore the socio-demographic profile of patients with rhinosporidiosis in an endemic area. A cross-sectional study was carried out in a tertiary-care hospital in Purulia district, India, including consecutive patients with histologically-proved rhinosporidiosis. Their socio-demographic profiles were obtained through a pre-designed proforma with given epidemiologic parameters. Data was statistically analyzed with inputs from literature review. Of the 39 patients included, 87 % were fresh/new cases. The age-group of 10-20 years was mostly involved, with multiple peaks around 50. About 82 % were from rural background, commonly involved in cattle farming and agriculture, with a universal habit of pond-bathing. There was a male preponderance; however women were being increasingly affected. Nasal cavity was the predominant site involved; nasal obstruction and epistaxis were the primary complaints. About 13 % had recurrent lesions that were statistically related to higher age-group (≥15 years) and occupation (agriculture, labor). Rhinosporidiosis is predominantly the disease of young rural adults engaged in field activities and habituated to pond-bathing. A bimodal age distribution was noticed. The present article provides an update on the socio-demographic perspectives of rhinosporidiosis in an endemic zone. It also summarizes the factors that would identify the vulnerable population and help formulate preventive measures.

Mucosal cavernous hemangioma of the maxillary sinus.

Mucosal cavernous hemangiomas of maxillary sinus and the lateral nasal wall are seldom encountered and difficult to diagnose with misleading radiologic features like bone erosion and heterogeneity due to patchy contrast uptake. The overall picture mimicking sinonasal malignancy, it is unclear whether there is true breach in the bone or remodeling due to the lesion's chronicity. Interestingly, it often does not bleed as expected during surgery, questioning the use of therapeutic embolization and pre-intervention vascular shrinkage. The clinical presentation and management protocol of sinonasal cavernous hemangiomas seem greatly individualized. We here present a patient with cavernous hemangioma of maxillary sinus and discuss the distinguishing clinical, histologic and imaging characteristics and subsequent management options, and attempt to establish the findings as the basis of considering it as an important differential diagnosis of radiologically heterogeneous sinonasal mass with suspected bone erosions presenting with nasal obstruction and epistaxis, mostly in young women.

Ameloblastic carcinoma of mandible: facts and dilemmas.

Ameloblastic carcinoma is a rare malignant odontogenic tumor and is considered as the malignant counterpart of ameloblastoma with features of both benign and malignant histology. It may arise de novo or from a long-standing ameloblastoma and is locally aggressive with a propensity for metastasis. With limited documentation, little is known about its pathobiogenesis, with no universal guidelines for management. For clinicians, differentiating ameloblastic carcinoma from ameloblastoma and malignant ameloblastoma in a patient presenting with a suspicious jaw tumor is a challenge due to overlapping clinical features, inconclusive cytology/biopsy reports, different management approaches and inadequate follow-up. Proper knowledge of the disease entity and a high index of suspicion are essential. Here we elaborate the dilemmas in diagnosis and management of ameloblastic carcinoma through presentation of a representative case in a 56-year-old man presenting with a tumor in the mandible.