Dynamic Behaviors of PbS Irradiated by Laser Pulse

Abstract-PbS detector is known as an important infrared (IR) detector which is widely used. The study of laser irradiation on PbS is important in military and commercial area. When the PbS sample is irradiated by laser pulse, the temperature rises in the sample. As the power density of the laser pulse increases, transient phase transformation may occur. In this paper, we will simulate the temperature field in PbS, and discuss the dynamic behaviors of PbS irradiated by laser pulse

Optically tunable guide-mode resonance grating based on VO2 phase transition material

In this paper, highly efficient tunable guide-mode resonance (GMR) grating patterned on top of a film of the phase transition material, vanadium dioxide (VO2), is demonstrated. The optimal optical transmission and tuning can be achieved by optimizing the device structure. Based on the large insulator-to-metal transition (IMT) characteristic tuned by thermally driven of VO2 in the near-infrared range, we show that the full width at half maximum (FWHM) of about 100 nm of the transmittance resonance spectra of the dielectric GMR in VO2 grating offers remarkable extinction modulation depths (68%) at 1535 nm for tunability. The tunability is accompanied by a hysteresis-like behavior that can be exploited for versatile memory effects. In addition, we experimentally demonstrate tuning of the reflection phase over 20°. This work further improves the research topic of GMR and expands the design of novel reconfigurable devices for photonics

Nanocrystalline Cr²⁺-doped ZnSe Nanowires Laser

By using femtosecond laser pulses to ablate microsized targets that are dispersed in liquid media, nanocrystalline Cr²⁺-doped ZnSe nanowires have been successfully fabricated for the first time. The phase and stoichiometries of the original materials are preserved while the sizes are reduced down to 30–120 nm for these nanowires. X-ray diffraction results show that the products are nanocrystalline ZnSe with cubic sphalerite structure. Scanning electron microscope results indicate that the products be ZnSe nanowires. The nanowires are usually 30–120 nm in diameter and several tens of micrometers in length. Photoluminescence of the nanocrystalline Cr²⁺-doped ZnSe nanowires shows strong emission at around 2000–2500 nm under excitation of 1300–2250 nm wavelength at room temperature. By using the Cr²⁺-doped ZnSe multiple nanowires as the gain medium, mid-infrared oscillation at 2194 nm has been established. The oscillation wavelength of the multiple nanowires laser is 150 nm shifted to shorter wavelengths in comparison with that of microsized powder random laser

Dynamic measurement of 2D refractive index distribution of NaCl solutions

<p>We demonstrate a simple and reliable method for measuring the two-dimensional refractive index (RI) distribution of transparent liquids, either homogeneous or inhomogeneous. The RI variation and the RI over the laser incident surface are measured by computing the phase shift of the interferograms as the optical path difference between the two beams passing through the sample liquid and air is changing. The phase shift is calculated by analyzing the interferograms by fast Fourier transform and a fringe shift counter. The RI change of the NaCl–water in the dissolving process was successfully measured by our method. This algorithm is stable, fast, efficient and of high accuracy up to 10⁻⁴. It holds potential for some applications that requires noncontact, and particularly for inhomogeneous transparent mediums.</p

Narrow-Linewidth Tunable Fiber Laser Based on Laser-Induced Graphene Heated Fiber Bragg Grating with Low Voltage

In this paper, we demonstrate a narrow-linewidth tunable fiber laser based on laser-induced graphene (LIG) paper-heated fiber Bragg grating (FBG) with low voltage. A linewidth of less than 600 Hz is achieved by the combination of a piece of unpumped Er-doped fiber and an FBG. Changing the temperature of the FBG will result in the central transmission spectrum shifting, and hence the laser wavelength tuning. LIG-heated (LIG-H) fabrication on polyimide (PI) paper by CO2 laser is used to offer temperature control of the FBG. By adjusting the voltage of the LIG-H from 0 to 5 V, the temperature of the LIG-H can be changed from room temperature up to 220 &deg;C, while the central wavelength of the output laser can be continuously adjusted from 1549.5 nm to 1552 nm with a full range of 2.5 nm. The proposed technique by electric control of LIG-H can provide a low-cost and compact wavelength tunable laser design

Fano-Like Resonance of Heat-Reconfigurable Silicon Grating Metasurface Tuned by Laser-Induced Graphene

We propose a heat-reconfigurable metasurface composed of the silicon-based gold grating. The asymmetric Fano-like line shape is formed due to the mutual coupling of the local surface plasmon (LSP) in the gap between the two layers of Au gratings and the surface propagating plasmon (SPP) on the surface of the Au gratings. Then, we effectively regulate the Fano resonance by applying a bias voltage to laser-induced graphene (LIG), to generate Joule heat, so that the resonant dip of one mode of the Fano resonance can shift up to 28.5 nm. In contrast, the resonant dip of the other mode barely changes. This effectively regulates the coupling between two resonant modes in Fano resonance. Our study presents a simple and efficient method for regulating Fano-like interference in the near-infrared band