Controlling single rare earth ion emission in an electro-optical nanocavity.

Rare earth emitters enable critical quantum resources including spin qubits, single photon sources, and quantum memories. Yet, probing of single ions remains challenging due to low emission rate of their intra-4f optical transitions. One feasible approach is through Purcell-enhanced emission in optical cavities. The ability to modulate cavity-ion coupling in real-time will further elevate the capacity of such systems. Here, we demonstrate direct control of single ion emission by embedding erbium dopants in an electro-optically active photonic crystal cavity patterned from thin-film lithium niobate. Purcell factor over 170 enables single ion detection, which is verified by second-order autocorrelation measurement. Dynamic control of emission rate is realized by leveraging electro-optic tuning of resonance frequency. Using this feature, storage, and retrieval of single ion excitation is further demonstrated, without perturbing the emission characteristics. These results promise new opportunities for controllable single-photon sources and efficient spin-photon interfaces.

Photonic integration of Er3+:Y2SiO5 with thin-film lithium niobate by flip chip bonding.

Rare earth ions are known as promising candidates for building quantum light-matter interface. However, tunable photonic cavity access to rare earth ions in their desired host crystal remains challenging. Here, we demonstrate the integration of erbium doped yttrium orthosilicate (Er3+:Y2SiO5) with thin-film lithium niobate photonic circuit by plasma-activated direct flip chip bonding. Resonant coupling to erbium ions is realized by on-chip electro-optically tuned high Q lithium niobate micro-ring resonators. Fluorescence and absorption of erbium ions at 1536.48 nm are measured in the waveguides, while the collective ion-cavity cooperativity with micro-ring resonators is assessed to be 0.36. This work presents a versatile scheme for future rare earth ion integrated quantum devices.

Mitigating photorefractive effect in thin-film lithium niobate microring resonators.

Thin-film lithium niobate is an attractive integrated photonics platform due to its low optical loss and favorable optical nonlinear and electro-optic properties. However, in applications such as second harmonic generation, frequency comb generation, and microwave-to-optics conversion, the device performance is strongly impeded by the photorefractive effect inherent in thin-film lithium niobate. In this paper, we show that the dielectric cladding on a lithium niobate microring resonator has a significant influence on the photorefractive effect. By removing the dielectric cladding layer, the photorefractive effect in lithium niobate ring resonators can be effectively mitigated. Our work presents a reliable approach to control the photorefractive effect on thin-film lithium niobate and will further advance the performance of integrated classical and quantum photonic devices based on thin-film lithium niobate.

High-fidelity cavity soliton generation in crystalline AlN micro-ring resonators.

Chip-scale mode-locked dissipative Kerr solitons have been realized on various materials platforms, making it possible to achieve a miniature, highly coherent frequency comb source with high repetition rates. Aluminum nitride (AlN), an appealing nonlinear optical material having both Kerr (χ3), and Pockels (χ2) effects, has immerse potential for comb self-referencing without the need for external harmonic generators. However, cavity soliton states have not yet been achieved in AlN microresonators. Here, we demonstrate mode-locked Kerr cavity soliton generation in a crystalline AlN microring resonator. By utilizing ultrafast tuning of the pump frequency through single-sideband modulation, in combination with an optimized wavelength scan and pump power-ramp patterns, we can deterministically elongate a ∼400 ns short-lived soliton to a time span as long as we wish to hold it.

Cd-free Cu-Zn-In-S/ZnS quantum dots@SiO2 multiple cores nanostructure: preparation and application for white LEDs.

The work reports the fabrication of Cu doped Zn-In-S (CZIS) alloy quantum dots (QDs) using dodecanethiol and oleic acid as stabilizing ligands. With the increase of doped Cu element, the photoluminescence (PL) peak is monotonically red shifted. After coating ZnS shell, the PL quantum yield of CZIS QDs can reach 78%. Using reverse micelle microemulsion method, CZIS/ZnS QDs@SiO2 multi-core nanospheres were synthesized to improve the colloidal stability and avoid the aggregation of QDs. The obtained multi-core nanospheres were dispersed in curing adhesive, and applied as a color conversion layer in down converted light-emitting diodes. After encapsulation in curing adhesive, the newly designed LEDs show artifically regulated color coordinates with varying the weight ratio of green QDs and red QDs, and the concentrations of these two types of QDs. Moreover, natural white and warm white LEDs with correlated color temperature of 5287, 6732, 2731, and 3309 K can be achieved, which indicates that CZIS/ZnS QDs@SiO2 nanostructures are promising color conversion layer material for solid-state lighting application.

Protection against influenza A virus by vaccination with a recombinant fusion protein linking influenza M2e to human serum albumin (HSA).

The highly conserved extracellular domain of M2 protein (M2e) of influenza A viruses has limited immunogenicity on its own. Hence, aiming to enhance immunogenicity of M2e protein, optimal approaches remain to be established. In this study, we created recombinant fusion protein vaccines by linking M2e consensus sequence of influenza A viruses with C-terminal domain of human serum albumin (HSA). Then HSA/M2e recombinant fusion protein was studied. Our results showed that HSA/M2e could induce strong anti-M2e specific humoral immune responses in the established mice model. Administration of HSA/M2e with Freund's adjuvant resulted in a higher number of IFN-γ-producing cells compared to HSA/M2e or M2e peptide emulsified in Freund's adjuvant. Furthermore, HSA/M2e was able to reduce viral load in the mice lungs and provide significant protection against lethal challenge with an H1N1 or an H3N2 virus compared to controls. In conclusion, this study has demonstrated a potential vaccine that could provide protection in preventing the threat of influenza outbreak because of rapid variation of the influenza virus.

Expression, purification and characterization of recombinant human beta-amyloid 1-42 in Pichia pastoris.

The human peptide rhA beta(1-42) was effectively produced through a novel expression system and purification procedure. The peptide rhA beta(1-42) was successfully expressed in Pichia pastoris, the methylotrophic yeast that has never been used as host. The cDNA encoding full-length hA beta(1-42) was synthesized with yeast bias codons and cloned into the pPICZ alpha A vector in frame with the yeast alpha-factor secretion signal under the transcriptional control of the AOX1 promoter and integrated into the secreting expression organism P. pastoris strain X33. Production of rhA beta(1-42) through fermentation was further optimized and scaled up in an 80 L fermentor. Secreted rhA beta(1-42) was purified using a two-step purification scheme: SP Sepharose ion exchange chromatography and source 30 RPC. The purification procedure is fast and efficient and reached a recovery of >93% without loss of activity. The purified rhA beta(1-42) was confirmed by Western blotting analysis and N-terminals amino sequencing analysis. This efficient and cost-effective expression system facilitates large-scale production and purification for recombinant rhA beta(1-42).

High-level expression, purification, and characterization of recombinant human basic fibroblast growth factor in Pichia pastoris.

Basic fibroblast growth factor [basic FGF (bFGF); FGF-2] is an important member of the FGF family, bFGF is a potent angiogenic molecule in vivo and in vitro stimulate smooth muscle cell growth, wound healing, and tissue repair. The full-length hbFGF coding sequence, gained by RT-PCR, was cloned into the pPICZalphaA vector in frame with the yeast alpha-factor secretion signal under the transcriptional control of the AOX promoter and integrated into Pichia pastoris strain X33, and the high level expression of rhbFGF has been achieved. SDS-PAGE and Western blotting assays of culture broth from a methanol-induced expression strain demonstrated that rhbFGF, an 18 kDa protein, was secreted into the culture medium. The growth conditions of the transformant strain were optimized in 50 ml conical tubes including methanol concentration, pH and inducing time. Under the optimal conditions, stable production of rhbFGF around 150 mg/l was achieved. The expressed rhbFGF was purified more than 94% purity using SP Sepharose ion exchange chromatography and source 30RPC. A preliminary biochemical characterization of purified rhbFGF was performed by biological activity analysis which was used by NIH/3T3 cell cultures, and the results demonstrated that the purified rhbFGF stimulated the growth of NIH/3T3 cells similarly to standard material.