Active tuning of dispersive waves in Kerr soliton combs.

Kerr soliton combs operate in the anomalous group-velocity dispersion regime through the excitation of dissipative solitons. The generated bandwidth is largely dependent on the cavity dispersion, with higher-order dispersion contributing to dispersive-wave (DW) generation that allows for power enhancement of the comb lines at the wings of the spectrum. However, the spectral position of the DW is highly sensitive to the overall cavity dispersion, and the inevitable dimension variations that occur during the fabrication process result in deviations in the DW emission wavelength. Here, we demonstrate active tuning of the DW wavelength, enabling post-fabrication spectral shaping of the soliton spectrum. We control the DW position by introducing a wavelength-controllable avoided mode crossing through actively tuning the resonances of a silicon nitride coupled microresonator via integrated heaters. We demonstrate DW tuning over 113 nm with a spectral power that can exceed the peak soliton spectral power. In addition, our modeling reveals buildup and enhancement of the DW in the auxiliary resonator, indicating that the mode hybridization arising from the strong coupling between the two resonators is critical for DW formation.

Frequency-Domain Quantum Interference with Correlated Photons from an Integrated Microresonator.

Frequency encoding of quantum information together with fiber and integrated photonic technologies can significantly reduce the complexity and resource requirements for realizing all-photonic quantum networks. The key challenge for such frequency domain processing of single photons is to realize coherent and selective interactions between quantum optical fields of different frequencies over a range of bandwidths. Here, we report frequency-domain Hong-Ou-Mandel interference with spectrally distinct photons generated from a chip-based microresonator. We use four-wave mixing to implement an active "frequency beam splitter" and achieve interference visibilities of 0.95±0.02. Our work establishes four-wave mixing as a tool for selective high-fidelity two-photon operations in the frequency domain which, combined with integrated single-photon sources, provides a building block for frequency-multiplexed photonic quantum networks.

Turn-key, high-efficiency Kerr comb source.

We demonstrate an approach for automated Kerr comb generation in the normal group-velocity dispersion (GVD) regime. Using a coupled-ring geometry in silicon nitride, we precisely control the wavelength location and splitting strength of avoided mode crossings to generate low-noise frequency combs with pump-to-comb conversion efficiencies of up to 41%, which is the highest reported to date for normal-GVD Kerr combs. Our technique enables on-demand generation of a high-power comb source for applications such as wavelength-division multiplexing in optical communications.

Synchronization of nonsolitonic Kerr combs.

Synchronization is a ubiquitous phenomenon in nature that manifests as the spectral or temporal locking of coupled nonlinear oscillators. In the field of photonics, synchronization has been implemented in various laser and oscillator systems, enabling applications including coherent beam combining and high-precision pump-probe measurements. Recent experiments have also shown time-domain synchronization of Kerr frequency combs via coupling of two separate oscillators operating in the dissipative soliton [i.e., anomalous group velocity dispersion (GVD)] regime. Here, we demonstrate all-optical synchronization of Kerr combs in the nonsolitonic, normal GVD regime in which phase-locked combs with high pump-to-comb conversion efficiencies and relatively flat spectral profiles are generated. Our results reveal the universality of Kerr comb synchronization and extend its scope beyond the soliton regime, opening a promising path toward coherently combined normal GVD Kerr combs with spectrally flat profiles and high comb-line powers in an efficient microresonator platform.

Demonstration of chip-based coupled degenerate optical parametric oscillators for realizing a nanophotonic spin-glass.

The need for solving optimization problems is prevalent in various physical applications, including neuroscience, network design, biological systems, socio-economics, and chemical reactions. Many of these are classified as non-deterministic polynomial-time hard and thus become intractable to solve as the system scales to a large number of elements. Recent research advances in photonics have sparked interest in using a network of coupled degenerate optical parametric oscillators (DOPOs) to effectively find the ground state of the Ising Hamiltonian, which can be used to solve other combinatorial optimization problems through polynomial-time mapping. Here, using the nanophotonic silicon-nitride platform, we demonstrate a spatial-multiplexed DOPO system using continuous-wave pumping. We experimentally demonstrate the generation and coupling of two microresonator-based DOPOs on a single chip. Through a reconfigurable phase link, we achieve both in-phase and out-of-phase operation, which can be deterministically achieved at a fast regeneration speed of 400 kHz with a large phase tolerance.

Molecular design, synthesis, and hypoglycemic and hypolipidemic activities of novel pyrimidine derivatives having thiazolidinedione.

We previously reported the synthesis and biological activity of novel substituted pyridines and purines having thiazolidinedione with hypoglycemic and hypolipidemic activities. We now report the synthesis and antidiabetic activity of novel substituted pyrimidines having thiazolidinedione moiety. These compounds (entry No. 5a-i, 10a-d and 16) were evaluated for their glucose and lipid lowering activity in KKA(y) mice. From the results, novel compounds, 5c and 5g, exhibited considerably more potent biological activity than that of the reference compounds, pioglitazone and rosiglitazone, respectively.

Synthesis and biological activity of novel substituted pyridines and purines containing 2,4-thiazolidinedione.

A series of substituted pyridines and purines containing 2,4-thiazolidinedione were designed and synthesized from their corresponding pyridines and purines. These synthesized compounds (entry no. 6a-d, 12a-e, 18a-d, 23a-c) were evaluated for their effect on triglyceride accumulation in 3T3-L1 cells in vitro and their hypoglycemic and hypolipidemic activity in the genetically diabetic KKA(y) mice in vivo. On the basis of their biological activities, 5-(4-[2-[N-methyl-(5-phenyl-pyridin-2-yl)amino]ethoxy]benzyl)thiazolidine-2,4-dione (6d) was selected as a candidate for further pharmacological studies.

Synthesis and antihyperglycemic activity of erythrose, ribose and substituted pyrrolidine containing thiazolidinedione derivatives.

A series of erythrose, ribose, and substituted pyrrolidine containing 2,4-thiazolidinediones were synthesized. Among them, thirteen unsaturated thiazolidinediones, six saturated thiazolidinediones and two unsaturated malonates were evaluated for their ability to enhance glucose utilization in cultured L6 myocytes. On the basis of the in vitro activity, 5-[4-[2-(1-benzyl-3,4-bis-benzyloxypyrrolidin-2-yl)ethoxy]benzylidene]thiazolidine-2,4-dione 24b was selected as the candidate for further pharmacological studies.