Litchi procyanidins inhibit colon cancer proliferation and metastasis by triggering gut-lung axis immunotherapy.

Litchi chinensis seed, as a valuable by-product of the subtropical fruit litchi (Litchi chinensis Sonn.), has been confirmed to be rich in procyanidins (LPC). The anticarcinogenic properties of procyanidins has been primarily attributed to their antioxidant and anti-inflammatory activities. However, there is a comparative paucity of information on if and how LPC inhibits colon cancer. Here, LPC significantly inhibited CT26 colon cancer cells proliferation and metastasis in vivo and in vitro. In CT26 lung metastatic mice, the anti-metastatic effect of LPC relied on its regulation of gut microbiota such as increase of Lachnospiraceae UCG-006, Ruminococcus, and their metabolites such as acetic acid, propionic acid and butyric acid. In addition, LPC significantly inhibited CT26 colon cancer cells metastasis through increasing CD8+ cytotoxic T lymphocytes infiltration and decreasing the number of macrophages. Antibiotics treatment demonstrated that the therapeutic effect of LPC depended on the gut microbiota, which regulated T cells immune response. Taken together, LPC had strong inhibitory effects on colon cancer pulmonary metastasis by triggering gut-lung axis to influence the T cells immune response. Our research provides a novel finding for the utilization of procyanidins in the future, that is, supplementing more fruits and vegetables rich in procyanidins is beneficial to the treatment of colon cancer, or it can be used as an adjuvant drug in clinical anti-tumor immunotherapy.

Photodarkening-resistance improvement of Yb3+/Al3+ co-doped silica fibers fabricated via sol-gel method.

Yb3+/Al3+ co-doped silica fibers (YDFs) with almost identical core glass compositions were prepared using the sol-gel and modified chemical vapor deposition (MCVD) methods. The photodarkening (PD) and laser performance before and after the PD process were tested under 974 nm pumping. The doping homogeneity of Yb3+ ions and clusters of Yb3+ ions in preform slices of these two fibers were investigated via optical absorption spectroscopy, photoluminescence emission spectra, electron probe microanalysis (EPMA), and low-temperature (4 K) electron paramagnetic resonance (EPR). It is known that the PD resistance of YDFs prepared via the sol-gel method is significantly better than that of YDFs prepared via MCVD under the same test conditions. EPMA mapping reveals that the doping homogeneity of Yb3+ ions in the sol-gel fiber core glass is better than that in the MCVD fiber. The low-temperature (4 K) EPR and cooperative luminescence spectra of Yb3+ ions indicate that the clustering degree of Yb3+ ions in the sol-gel fiber is lower than that in the MCVD fiber. In the absorption and emission spectra, small amounts of Yb2+ ions are observed in the preform slice from the sol-gel method. A model of the color-center generation in the PD process was proposed to explain the mechanism of PD resistance improvement for the YDFs fabricated via the sol-gel method.

Maintaining broadband gain in a Nd3+/Yb3+co-doped silica fiber amplifier via dual-laser pumping.

We report a 30 cm long Nd3+/Yb3+ co-doped silica glass fiber amplifier with well-maintained broadband gain through simultaneous dual-laser pumping at 808 and 975 nm. By controlling the ratio of the pump power at 975 (P975) and 808 nm (P808), the emission band of Yb3+/Nd3+ and the energy transfer efficiency of Nd3+→Yb3+ can be well controlled; thus, a tunable broadband and flat gain in the range of 1036-1080 nm are obtained. The theoretical calculation of the energy transfer efficiency of Nd3+→Yb3+ with dual-laser pumping of 808 and 975 nm explains well the mechanism of broadband and flat gain formation in the Nd3+/Yb3+ co-doped fiber.

Manipulating refractive index, homogeneity and spectroscopy of Yb3+-doped silica-core glass towards high-power large mode area photonic crystal fiber lasers.

Output power scaling of single mode large mode area (LMA) photonic crystal fiber (PCF) amplifiers urgently requires the low refractive index of Yb3+-doped silica glasses whilst maintaining high optical homogeneity. In this paper, we report on a promising alternative Yb3+/Al3+/F-/P5+-co-doped silica core-glass (YAFP), which is prepared by modified sol-gel method developed by our group and highly suitable for fabricating high power LMA PCF amplifiers. By controlling the doping combinations of Al3+/F-/P5+ in Yb3+-doped silica glass,it not only ensures low refractive index (RI) but also maintains the excellent optical homogeneity and spectroscopic properties of Yb3+. The spectroscopic properties of Yb3+ ions have not deteriorated by the co-doping of F- and P5+ in YAFP glass compared with that of Yb3+/Al3+ co-doped silica glass. A large-size (⌀5 mm × 90 mm) YAFP silica-core glass rod with low average RI difference of 2.6 × 10-4 (with respect to pure silica glass), and low radial and axial RI fluctuations of ~2 × 10-4, was prepared. A LMA PCF with 50 µm core diameter was obtained by stack-capillary-draw techniques using YAFP core glass. Its core NA is 0.027. An average amplified power of 97 W peaking at 1030 nm and light-light efficiency of 54% are achieved from a 6.5 m long PCF in the pulse amplification laser experiment. Meanwhile, quasi-single-mode transmission is obtained with laser beam quality factor M2 of 1.4.

Optical-power tunable dual-wavelength laser around 1 µm in Nd3+/Yb3+ co-doped phosphate glass fiber.

This work reports the generation of an optical-power tunable 1 µm dual-wavelength fiber laser in Nd3+/Yb3+ co-doped phosphate glass fiber under 970 nm and 808 nm laser diode pumping. A bidirectional free-space pump laser setup was adopted. An optical-power tunable dual-wavelength laser can be easily realized by the control of 808 nm pump power magnitude. Based on a series of laser tests under different pump conditions and theoretical calculation of the Nd3+→Yb3+ energy transfer efficiency, the control mechanism was found to be the stimulated emission modulation of Nd3+ on Yb3+ lasing. This property is helpful to enhance the knowledge of the Nd3+/Yb3+ co-doping system.

5 W output power from a double-clad hybrid fiber with Yb-doped phosphate core and silicate cladding.

For the first time, to the best of our knowledge, we report on the realization of a laser from a Yb-doped phosphate core/silicate cladding double-clad hybrid fiber. 5 W output power was extracted with 14.6% slope efficiency and a laser spectrum of a 1027 nm central wavelength from a 20 cm long single-mode fiber with a ∼10 µm core diameter in a 20%-4% laser cavity. The laser efficiency can be significantly enhanced by correspondingly adjusting and optimizing the laser oscillator.

50 µm core diameter Yb³âºAl³âº/F⁻ codoped silica fiber with M²<1.1 beam quality.

This paper reports, for the first time to our best knowledge, a nearly diffraction-limited output in a Yb(3+)/Al(3+)/F(-) codoped double cladding silica fiber with a 50 µm core diameter and 0.02 core NA. The core glass with a diameter >6 mm was fabricated through solgel process combined with high temperature sintering. Laser performances of this fiber at different bend diameters were studied. The mean M2<1.1 in this 50 µm core diameter fiber was achieved at a bend diameter of 0.35 m. The core glass with the refractive index nearly equal to pure silica glass is suitable for the fiber design, such as large-mode-area photonic crystal fiber.

Phosphate ytterbium-doped single-mode all-solid photonic crystal fiber with output power of 13.8†W.

Single-mode ytterbium-doped phosphate all-solid photonic crystal fiber (AS-PCF) with 13.8 W output power and 32% slope efficiency was reported. By altering the diameter of the rods around the doped core and thus breaking the symmetry of the fiber, a polarization-maintaining AS-PCF with degree of polarization of >85% was also achieved, for the first time to knowledge, in a phosphate PCF.

Yb/Er co-doped phosphate all-solid single-mode photonic crystal fiber.

An all-solid Yb(3+)/Er(3+) co-doped single-mode phosphate photonic crystal fiber (PCF) with Watt-level output power and 20 µm core diameter is demonstrated for the first time. A PCF whose refractivity of the active core is lower than that of the background glass is suggested and theoretically confirmed to be in single-mode operation at 40 µm core diameter.

Thermal loading in laser diode end-pumped Yb3+/Er3+ codoped phosphate glass laser.

We investigate, based on laser performance, the fractional thermal loadings in a Yb(3+)/Er(3+) codoped phosphate glass laser. The results indicate that fractional thermal loading increases with Er(3+) doping concentration nonlinearly. Above an Yb(3+) doping level, the increase of Yb(3+) cannot promote laser performance but induces a more serious heat effect. We investigate the main factors that simultaneously affect laser and thermal performances. The results show that the ratio of laser output power to heat is sensitive to beam overlap efficiency, the laser extraction efficiency, especially to quantum efficiency of laser material. The optimized doping concentrations of Yb(3+) and Er(3+) are deduced.