A Novel Approach to Interface High-Q Fabry-P\'erot Resonators with Photonic Circuits

The unique benefits of Fabry-P\'erot resonators as frequency-stable reference cavities and as an efficient interface between atoms and photons make them an indispensable resource for emerging photonic technologies. To bring these performance benefits to next-generation communications, computation, and timekeeping systems, it will be necessary to develop strategies to integrate compact Fabry-P\'erot resonators with photonic integrated circuits. In this paper, we demonstrate a novel reflection cancellation circuit that utilizes a numerically optimized multi-port polarization-splitting grating coupler to efficiently interface high-finesse Fabry-P\'erot resonators with a silicon photonic circuit. This circuit interface produces spatial separation of the incident and reflected waves, as required for on-chip Pound-Drever-Hall frequency locking, while also suppressing unwanted back reflections from the Fabry-P\'erot resonator. Using inverse design principles, we design and fabricate a polarization-splitting grating coupler that achieves 55% coupling efficiency. This design realizes an insertion loss of 5.8 dB for the circuit interface and more than 9 dB of back reflection suppression, and we demonstrate the versatility of this system by using it to interface several reflective off-chip devices

Photonic chip-based low noise microwave oscillator

Numerous modern technologies are reliant on the low-phase noise and exquisite timing stability of microwave signals. Substantial progress has been made in the field of microwave photonics, whereby low noise microwave signals are generated by the down-conversion of ultra-stable optical references using a frequency comb. Such systems, however, are constructed with bulk or fiber optics and are difficult to further reduce in size and power consumption. Our work addresses this challenge by leveraging advances in integrated photonics to demonstrate low-noise microwave generation via two-point optical frequency division. Narrow linewidth self-injection locked integrated lasers are stabilized to a miniature Fabry-P\'{e}rot cavity, and the frequency gap between the lasers is divided with an efficient dark-soliton frequency comb. The stabilized output of the microcomb is photodetected to produce a microwave signal at 20 GHz with phase noise of -96 dBc/Hz at 100 Hz offset frequency that decreases to -135 dBc/Hz at 10 kHz offset--values which are unprecedented for an integrated photonic system. All photonic components can be heterogeneously integrated on a single chip, providing a significant advance for the application of photonics to high-precision navigation, communication and timing systems

Research on a Dual-Mode Infrared Liquid-Crystal Device for Simultaneous Electrically Adjusted Filtering and Zooming

A new dual-mode liquid-crystal (LC) micro-device constructed by incorporating a Fabry⁻Perot (FP) cavity and an arrayed LC micro-lens for performing simultaneous electrically adjusted filtering and zooming in infrared wavelength range is presented in this paper. The main micro-structure is a micro-cavity consisting of two parallel zinc selenide (ZnSe) substrates that are pre-coated with ~20-nm aluminum (Al) layers which served as their high-reflection films and electrodes. In particular, the top electrode of the device is patterned by 44 × 38 circular micro-holes of 120 μm diameter, which also means a 44 × 38 micro-lens array. The micro-cavity with a typical depth of ~12 μm is fully filled by LC materials. The experimental results show that the spectral component with needed frequency or wavelength can be selected effectively from incident micro-beams, and both the transmission spectrum and the point spread function can be adjusted simultaneously by simply varying the root-mean-square value of the signal voltage applied, so as to demonstrate a closely correlated feature of filtering and zooming. In addition, the maximum transmittance is already up to ~20% according the peak-to-valley value of the spectral transmittance curves, which exhibits nearly twice the increment compared with that of the ordinary LC-FP filtering without micro-lenses

Layer-dependent correlated phases in WSe₂/MoS₂ moiré superlattice

Electron correlation plays an essential role in the macroscopic quantum phenomena in the moiré heterostructure, such as antiferromagnetism and correlated insulating phases. Unlike the phenomena where the interaction involves only electrons in one layer, the interaction of distinct phases in two or more layers represents a new horizon forward, such as the one in the Kondo lattice model. Here, using interlayer excitons as a probe, we show that the interlayer interactions in heterobilayers of tungsten diselenide and molybdenum disulfide (WSe2/MoS2) can be electrically switched on and off, resulting in a layer-dependent correlated phase diagram, including single-layer, layer-selective, excitonic-insulator and layer-hybridized regions. We demonstrate that these correlated phases affect the interlayer exciton non-radiative decay pathways. These results reveal the role of strong correlation on interlayer exciton dynamics and pave the way for studying the layer-resolved strong correlation behaviour in moiré heterostructures.Agency for Science, Technology and Research (A*STAR)Ministry of Education (MOE)National Research Foundation (NRF)This work is supported by the Singapore National Research Foundation and A*STAR through their Competitive Research Program (award no. NRF-CRP22-2019-0004, award no. NRF-CRP23-2019-0002 and the Quantum Engineering Programme) and by the Singapore Ministry of Education (MOE2016-T3-1-006 (S))

A novel approach to interface high-Q Fabry–Pérot resonators with photonic circuits

The unique benefits of Fabry–Pérot resonators as frequency-stable reference cavities and as an efficient interface between atoms and photons make them an indispensable resource for emerging photonic technologies. To bring these performance benefits to next-generation communications, computation, and time-keeping systems, it will be necessary to develop strategies to integrate compact Fabry–Pérot resonators with photonic integrated circuits. In this paper, we demonstrate a novel reflection cancellation circuit that utilizes a numerically optimized multi-port polarization-splitting grating coupler to efficiently interface high-finesse Fabry–Pérot resonators with a silicon photonic circuit. This circuit interface produces a spatial separation of the incident and reflected waves, as required for on-chip Pound–Drever–Hall frequency locking, while also suppressing unwanted back reflections from the Fabry–Pérot resonator. Using inverse design principles, we design and fabricate a polarization-splitting grating coupler that achieves 55% coupling efficiency. This design realizes an insertion loss of 5.8 dB for the circuit interface and more than 9 dB of back reflection suppression, and we demonstrate the versatility of this system by using it to interface several reflective off-chip devices

Asia‐inclusive global development of pevonedistat: Clinical pharmacology and translational research enabling a phase 3 multiregional clinical trial

Abstract The investigational NEDD8‐activating enzyme inhibitor pevonedistat is being evaluated in combination with azacitidine versus single‐agent azacitidine in patients with higher‐risk myelodysplastic syndrome (higher‐risk MDS), higher‐risk chronic myelomonocytic leukemia (higher‐risk CMML), or low‐blast acute myeloid leukemia (AML) in a Phase 3 trial PANTHER. To support Asia‐inclusive global development, we applied multiregional clinical trial (MRCT) principles of the International Conference on Harmonisation E17 guidelines by evaluating similarity in drug‐related and disease‐related intrinsic and extrinsic factors. A PubMed literature review (January 2000–November 2019) supported similarity in epidemiology of higher‐risk MDS, AML, and CMML in Western and East Asian populations. Furthermore, the treatment of MDS/AML was similar in both East Asian and Western regions, with the same dose of azacitidine being the standard of care. Median overall survival in MDS following azacitidine treatment was generally comparable across regions, and the types and frequencies of molecular alterations in AML and MDS were comparable. Dose‐escalation studies established the same maximum tolerated dose of pevonedistat in combination with azacitidine in Western and East Asian populations. Pevonedistat clearance was similar across races. Taken together, conservation of drug‐related and disease‐related intrinsic and extrinsic factors supported design of an Asia‐inclusive Phase 3 trial and a pooled East Asian region. A sample size of ~ 30 East Asian patients (of ~ 450 randomized) was estimated as needed to demonstrate consistency in efficacy relative to the global population. This analysis is presented as an exemplar to illustrate application of clinical pharmacology and translational science principles in designing Asia‐inclusive MRCTs. Study Highlights WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? Azacitidine is the standard of care for myelodysplastic syndromes/low‐blast acute myeloid leukemia (AML) across Western and East Asian patients. The first‐in‐class small‐molecule inhibitor of NEDD8‐activating enzyme, pevonedistat, has been investigated as a single agent in multiple studies of hematologic and nonhematologic malignancies and in combination with azacitidine in elderly patients with untreated AML. WHAT QUESTION DID THIS STUDY ADDRESS? By applying clinical pharmacology and translational science and International Conference on Harmonisation E17 principles, this study designed an East Asian‐inclusive global pivotal Phase 3 trial of pevonedistat, taking into consideration drug‐related and disease‐related intrinsic and extrinsic factors. WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE? These analyses provide scientific rationale for Asia‐inclusive globalization of the pivotal, Phase 3 PANTHER trial and for pooling clinical data across the East Asian region for assessing consistency in efficacy. HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE? We developed a framework to facilitate efficient global clinical development of investigational therapies for rare cancers and orphan diseases in Asia‐inclusive multiregional clinical trials