Vapor phase detection of explosives by surface enhanced Raman scattering under ambient conditions with metal nanogap structures.

Non-invasive and passive detection of explosives in the vapor phase is advantageous for military, counter-terrorism, and homeland security applications. Detection of explosives using SERS has been an active research topic. However, the vapor pressures of most explosives are low at room temperature, and consequently, the vapor phase detection by SERS is highly challenging without intentionally heating explosive powder to increase the vapor pressure.

Design of a bidirectional TM01(TE01)-LP01 mode converter with a metasurface-on-fiber.

Mode conversion is crucial for coupling a light source to a desired waveguide. While traditional mode converters such as fiber Bragg gratings and long-period fiber gratings exhibit high transmission and conversion efficiency, the mode conversion of two orthogonal polarizations remains challenging. Here, we present a bidirectional metasurface mode converter that can convert the transverse electric (TE)01 or transverse magnetic (TM)01 mode to the fundamental mode (LP01) with orthogonal polarization, and vice versa.

Dynamics of surface-plasmon lasing in planar metal gratings on semiconductor.

We investigate the dynamics of surface plasmon (SP) lasing in Au gratings fabricated on InGaAs with a period of around 400 nm, which locates the SP resonance near the semiconductor energy gap and facilitates efficient energy transfer. By optically pumping the InGaAs to reach the population inversion required for the amplification and the lasing, we observe SP lasing at specific wavelengths that satisfy the SPR condition depending on the grating period. The carrier dynamics in semiconductor and the photon density in the SP cavity was investigated from the time-resolved pump-probe measurement and the time resolved photoluminescence spectroscopy, respectively.