Search for: All records

Abstract Manipulating the frequency and bandwidth of nonclassical light is essential for implementing frequency-encoded/multiplexed quantum computation, communication, and networking protocols, and for bridging spectral mismatch among various quantum systems. However, quantum spectral control requires a strong nonlinearity mediated by light, microwave, or acoustics, which is challenging to realize with high efficiency, low noise, and on an integrated chip. Here, we demonstrate both frequency shifting and bandwidth compression of heralded single-photon pulses using an integrated thin-film lithium niobate (TFLN) phase modulator. We achieve record-high electro-optic frequency shearing of telecom single photons over terahertz range (±641 GHz or ±5.2 nm), enabling high visibility quantum interference between frequency-nondegenerate photon pairs. We further operate the modulator as a time lens and demonstrate over eighteen-fold (6.55 nm to 0.35 nm) bandwidth compression of single photons. Our results showcase the viability and promise of on-chip quantum spectral control for scalable photonic quantum information processing. 

Crystals are ubiquitous in nature and are at the heart of material research, solid-state science, and quantum physics. Unfortunately, the controllability of solid-state crystals is limited by the complexity of many-body dynamics and the presence of defects. In contrast, synthetic crystal structures, realized by, e.g.,  optical lattices, have recently enabled the investigation of various physical processes in a controllable manner, and even the study of new phenomena. Past realizations of synthetic optical crystals were, however, limited in size and dimensionality. Here we theoretically propose and experimentally demonstrate optical frequency crystal of arbitrary dimensions, formed by hundreds of coupled spectral modes within an on-chip electro-optic frequency comb. We show a direct link between the measured optical transmission spectrum and the density of states of frequency crystals in one, two, three, and four dimensions, with no restrictions to further expanding the dimensionality. We demonstrate that the generation of classical electro-optic frequency comb can be modeled as a process described by random walks in a tight-binding model, and we have verified this by measuring the coherent distribution of optical steady states. We believe that our platform is a promising candidate for exploration of topological and quantum photonics in the frequency domain. 

Lithium niobate (LN), an outstanding and versatile material, has influenced our daily life for decades—from enabling high-speed optical communications that form the backbone of the Internet to realizing radio-frequency filtering used in our cell phones. This half-century-old material is currently embracing a revolution in thin-film LN integrated photonics. The successes of manufacturing wafer-scale, high-quality thin films of LN-on-insulator (LNOI) and breakthroughs in nanofabrication techniques have made high-performance integrated nanophotonic components possible. With rapid development in the past few years, some of these thin-film LN devices, such as optical modulators and nonlinear wavelength converters, have already outperformed their legacy counterparts realized in bulk LN crystals. Furthermore, the nanophotonic integration has enabled ultra-low-loss resonators in LN, which has unlocked many novel applications such as optical frequency combs and quantum transducers. In this review, we cover—from basic principles to the state of the art—the diverse aspects of integrated thin-film LN photonics, including the materials, basic passive components, and various active devices based on electro-optics, all-optical nonlinearities, and acousto-optics. We also identify challenges that this platform is currently facing and point out future opportunities. The field of integrated LNOI photonics is advancing rapidly and poised to make critical impacts on a broad range of applications in communication, signal processing, and quantum information. 

Abstract High‐bandwidth metallic coaxial nanolasers are of high interest to investigate laser physics such as thresholdless coherence transitions, and have a large variety of promising applications enabled by their ultrasmall size and large spectral bandwidth. Optical coherence properties are commonly characterized in Hanbury‐Brown and Twiss experiments. However, those are difficult to perform in broadband lasers when the coherence time is an order of magnitude shorter than the temporal resolution of the single‐photon detectors, thus requiring significant spectral filtering. This paper demonstrates a new approach in investigating the temporal dynamics of the photon statistics associated with the nanolaser emission, obtained without the requirement of spectral filtering. While optically pumping the nanolasers with nanosecond pulses, time‐resolved second‐order coherence properties are evaluated over the time duration of the pump pulse. Coherence transitions from thermal emission to lasing are observed in the gathered time‐resolved photon statistics, linked to the temporal change in optical power of the nanosecond pump pulses. As nanolasers show better performance for the pulsed pumping scheme, the temporal envelope modulation of these pulses results in varying degrees of coherence within the nanolaser pulse envelope. This approach can also be readily applied to characterize a large variety of broadband lasers.