Single-frequency violet and blue laser emission from AlGaInN photonic integrated circuit chips.

Chip-based, single-frequency and low phase-noise integrated photonic laser diodes emitting in the violet (412 nm) and blue (461 nm) regime are demonstrated. The GaN-based edge-emitting laser diodes were coupled to high-quality on-chip micro-resonators for optical feedback and mode selection resulting in laser self-injection locking with narrow emission linewidth. Multiple group III-nitride (III-N) based photonic integrated circuit chips with different waveguide designs including single-crystalline AlN, AlGaN, and GaN were developed and characterized. Single-frequency laser operation was demonstrated for all studied waveguide core materials. The best side-mode suppression ratio was determined to be ∼36 dB at 412 nm with a single-frequency laser emission linewidth of only 3.8 MHz at 461 nm. The performance metrics of this novel, to the best of our knowledge, type of laser suggest potential implementation in next-generation, portable quantum systems.

Comparison of the functional properties of murine dendritic cells generated in vivo with Flt3 ligand, GM-CSF and Flt3 ligand plus GM-SCF.

Flt3 ligand (FL) and granulocyte-macrophage colony-stimulating factor (GM-CSF) are important growth factors for dendritic cells (DC). Substantial numbers of DC can be generated in vivo following the administration of either factor. We sought to extend our knowledge of the functional properties of these cells including their ability to prime naïve CD8(+) T cells. In addition, we compared the nature of the DC generated in vivo with the single cytokines to those generated with the combination of FL+polyethylene glycol-modified GM-CSF (pGM-CSF). Treatment with FL+pGM-CSF yielded greater numbers of both CD11b(low) and CD11b(high) DC than with either cytokine alone, and these DC were more efficient at antigen (Ag) capture. The FL+pGM-CSF-generated CD11b(low) DC lacked expression of CD8alpha. Following treatment with LPS in vivo, all DC subsets upregulated CD40, CD80, CD86, and MHC class II expression, but surprisingly Ag capture was not downregulated and some DC subsets retained expression of intracellular MHC class II vesicles. Thus, even after activation in vivo with LPS, DC retained Ag capture properties of immature DC, and Ag presentation/costimulation properties of mature DC. Though all DC subsets stimulated CD4(+) T cell proliferation equivalently, FL-generated DC were more efficient at priming Ag-specific CD8(+) cytolytic T cells than DC generated with either pGM-CSF alone or FL+pGM-CSF, and CD11b(high) DC were more efficient at priming CD8(+) T cells than CD11b(low) DC.