Synchronized time lens based temporal magnifier assisted by the phase lock loop.

We propose a synchronized time lens based temporal magnifier for the characterization of an ultrafast pulse, which is assisted by the phase lock loop (PLL) to actively lock the repetition rates of the pump laser and signal laser. A feedback control system combining a proportional-integral (PI) circuit and a piezoelectric transducer (PZT) inside the signal laser cavity is used to synchronize the repetition rates between the pump and signal lights. Benefitting from the PLL technique, the temporal position of the signal pulse remains as the numerical aperture of the time lens system, and therefore it has a high short-time stability for pulse measurement. This synchronized time lens based temporal magnifier can record single-shot pulses within continuous round trips. By engineering the dispersion of the pump, signal, and idler lights, we demonstrate a 200× magnification of the signal pulse. Our technique offers a simple synchronized method in a time lens system for ultrafast temporal characterization, which provides new insights into the observation of the fiber laser dynamics.

Highly coherent, flat, and broadband time-stretched swept source based on extra-cavity spectral shaping assisted by a booster semiconductor optical amplifier.

We demonstrate a flat broadband time-stretched swept source based on extra-cavity spectral shaping. By adjusting the polarization-dependent gain profile and driving current of the booster optical amplifier (BOA), extra-cavity spectral shaping is optimized to generate output with a 1-dB bandwidth of ∼100 nm, 3-dB bandwidth of ∼140 nm and output power of ∼21.4 mW. The short-term and long-term stabilities are characterized. The average cross correlation of 183,485 round trips is 0.9997 with a standard deviation of 2×10-5, indicating high single-shot spectral similarity and high coherence. The noise floor of relative spectral energy jitter is -141.7 dB/Hz, indicating a high short-term spectral energy stability. The proposed highly stable flat broadband time-stretched swept source is applied to an optical coherence tomography (OCT) system. The axial resolution is 10.8 µm. The proposed swept source can serve as excellent light sources in ultra-fast coherent detection systems for high precision sensing and imaging.

Fourier Domain Mode Locked Laser and Its Applications.

The sweep rate of conventional short-cavity lasers with an intracavity-swept filter is limited by the buildup time of laser signals from spontaneous emissions. The Fourier domain mode-locked (FDML) laser was proposed to overcome the limitations of buildup time by inserting a long fiber delay in the cavity to store the whole swept signal and has attracted much interest in both theoretical and experimental studies. In this review, the theoretical models to understand the dynamics of the FDML laser and the experimental techniques to realize high speed, wide sweep range, long coherence length, high output power and highly stable swept signals in FDML lasers will be discussed. We will then discuss the applications of FDML lasers in optical coherence tomography (OCT), fiber sensing, precision measurement, microwave generation and nonlinear microscopy.

Zero-Dimensional MXene-Based Optical Devices for Ultrafast and Ultranarrow Photonics Applications.

In recent years, MXene has become a hotspot because of its good conductivity, strong broadband absorption, and tunable band gap. In this contribution, 0D MXene Ti3C2Tx quantum dots are synthesized by a liquid exfoliation method and a wideband nonlinear optical response from 800 to 1550 nm is studied, which have a larger nonlinear absorption coefficient ß of -(11.24 ± 0.14) × 10-2 cm GW-1. The carrier dynamic processes of 0D MXene are explored with ultrahigh time resolution nondegenerate transient absorption (TA) spectroscopy, which indicates that the TA signal reaches its maximum in 1.28 ps. Furthermore, 0D MXene is used to generate ultrashort pulses in erbium or ytterbium-doped fiber laser cavity. High signal-to-noise (72 dB) femtosecond lasers with pulse durations as short as 170 fs with spectrum bandwidth of 14.8 nm are obtained. Finally, an ultranarrow fiber laser based on 0D MXene is also investigated and has a full width at half maximum of only 5 kHz, and the power fluctuation is less than 0.75% of the average power. The experimental works prove that 0D MXene is an excellent SA and has a promising application in ultrafast and ultranarrow photonics.

NRAGE suppresses metastasis of melanoma and pancreatic cancer in vitro and in vivo.

We previously reported that human NRAGE could significantly alter the cellular skeleton and inhibit cell-cell adhesion, suggesting that human NRGAE play a potential role in cellular motility. Here, we report overexpression of human NRAGE in PANC-1 and B16-Bl6 cells could significantly suppress the metastasis of these cells in vitro and in vivo. Consistently, PANC-1 with stable silencing of NRAGE by RNA interference, exhibits a more metastatic phenotype than the native cell. Expression of epithelial proteins, including E-cadherin and beta-catenin is down regulated in siRNA-NRAGE PANC-1 cells. Further studies find that overexpression of human NRAGE suppresses the mRNA expression and activity of MMP2 significantly. Summary, our studies indicate for the first time that NRAGE could suppress metastasis of melanoma and pancreatic cancer probably through downregulation of MMP-2.

[Construction of recombinant adenovirus vector of hNRAGE gene and its effect on cell cycle of 293 cells].

AIM: To construct the recombinant adenovirus vector of hNRAGE gene and study its effect on the cell cycle of 293 cells. METHODS: hNRAGE gene was amplified by PCR and subcloned into the shuttle vector pAdTrack-CMV to construct a shuttle plasmid pAdTrack-CMV/hNRAGE. After sequencing, it was linearized with Pme I and cotransformed into E.coli BJ5183 cells with adenovirus genomic plasmid pAdEasy-1 by electroporation to achieve homologous recombination. After being digested with Pac I, the DNA of identified recombinant plasmid was transfected into QBI-293A cells by calcium phosphate transfection to package adenovirus. With the use of GFP gene expression in pAdTrack-CMV, the appearance of Ad-hNRAGE was observed and its concentration was measured. The expression of the target gene was detected by Western blot and its effect on cell cycle of 293 cells was examined by MTT colorimetry and FCM. RESULTS: The Ad-hNRAGE was successfully constructed and the expression of hNRAGE gene in 293 cells was proved by Western blot. After harvesting the virus particles, the concentration of Ad-hNRAGE was about 6.5x10(9) Ad/microL. The transfection of Ad-hNRAGE resulted in significantly lower proliferative rate of 293 cells compared with untransfected ones, with cell number of G0-G1 and G2-M phase increasing and that of S phase decreasing. CONCLUSION: hNRAGE gene can inhibit the growth of 293 cells.

Human NRAGE disrupts E-cadherin/beta-catenin regulated homotypic cell-cell adhesion.

Human NRAGE, a neurotrophin receptor p75 interaction MAGE homologue, confers NGF-dependent apoptosis of neuronal cells by inducing caspase activation through the JNK-c-jun-dependent pathway and arrests cell growth through the p53-dependent pathway. Our findings showed that human NRAGE could significantly alter the cell skeleton and inhibit homotypic cell-cell adhesion in U2OS cells. With further experiments, we revealed that human NRAGE disrupts colocalization of the E-cadherin/beta-catenin complex and translocates beta-catenin from the cell membrane into the cytoplasm and nucleus. Synchronously, NRAGE also decreases the total protein level of beta-catenin, especially when NRAGE expresses for a long time. More importantly, knock down of NRAGE by RNA interference in PANC-1 cell significantly reinforces E-cadherin/beta-catenin homotypic cell adhesion. The data demonstrate the importance of human NRAGE in homotypic cell-to-cell adhesion and illuminate the mechanism of human NRAGE in the process of inhibition of cell adhesion, which suggests that human NRGAE plays a potential negative role in cancer metastasis.