Tunability of terahertz random lasers with temperature based on superconducting materials

We theoretically demonstrate the tunabiltiy of terahertz random lasers composed of high temperature superconductorYBCO and ruby layers as active medium. The considered system is a one-dimensional disordered medium made of ruby grain and YBCO. Finite-difference time domain method is used to calculate the emission spectrum and spatial distribution of electric field at different temperatures. Our numerical results reveal that the superconductor based random lasers exhibit large temperature tunability in the terahertz domain. The emission spectrum is significantly temperature dependent, the number of lasing modes and their intensities increase with decreasing temperature. Also, we make some discussion to explain the reason for the observed tunability and the effect of temperature variation on the spatial distribution of the electric field in the disordered active medium

Resonant Light Scattering Toward Optical Fiber Humidity Sensors

Abstract The deposition of tetrakis (4-sulonatophenyl) porphyrin (TPPS) thin film on optical fibers presents many possibilities for sensing applications. The J-form aggregation with a narrow and sharp spectral feature at about 490 nm and its sensitivity to humidity have been discussed; a fast change of wavelength occurs according with variation in the humidity level. The reproducibility and high sensitivity of TPPS-coated fibers, along with the capabilities of optical fibers, suggest the device as a good candidate for humidity sensing in harsh environments

Composite patterns formed by paraxial vortex-beams propagation in one-dimensional multilayer plasma photonic crystals

Optical properties of twisted electromagnetic beam propagating in one-dimensional binary dielectric-plasma photonic crystal are investigated. Reflection and transmission spectra by using nonlinear Transfer Matrix Method of Degenerate Four-Wave Mixing are calculated. These characteristics are studied in low intensity, high temperature range of plasma, large Rayleigh range and neglecting the pumps depletion. In our calculation, the standard slowly varying field approximation is employed. The results show that the composite vortex patterns in the left of photonic crystal structure is dependent on the beam vortex charge number, the incident beam frequency and plasma temperature. Also, it is indicated that reflection and transmission may be more than unity for the sake of amplifying through the nonlinear medium. In fact, this structure can be exploited for characterization of phase conjugation in multilayer optical structures and optoelectronic

Effect of Low Power Laser on Incisional Wound Healing

INTRODUCTION: The effectiveness of low power lasers for incisional wound healing, because of conflicting results of previous research studies, is uncertain. Therefore, this study was carried out to evaluate low power laser effects on incisional wound healing. MATERIALS AND METHODS: Incisional wound was produced on thirty-six mature male guinea pigs under general and local anesthesia. In half of the cases, He-Ne laser radiations were used for five minutes and the rest were left untreated. Animals were divided into six groups of six animals each that were killed after 3, 5 and 14 days. After histopathology processing and H&E staining, specimens were examined for acute and chronic inflammations, epithelial cell migration, epithelial seal and barrier formation, fibroblast migration, fibrosis, clot formation and granulation tissue formation. Mann-Whitney U and the Wilcoxon tests were used for statistical analysis. RESULTS: Statistically significant differences were found between fibroblast migration, acute and chronic inflammation of radiated groups and the control group at 5 days interval (p<0.05). There was no statistically significant difference at 3 and 14 days between laser radiated and control groups. CONCLUSION: This study showed that He-Ne laser had beneficial effects on incisional wound healing particularly at 5 days interval; however, further research on chronic ulcers is recommended