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A coronagraph designed for high contrast imaging applications has been experimentally tested using coherent laser light and a vortex mask of topological charge m=2. Intensity contrast values of 95% were achieved in this first verification of the scheme. Improvements for approaching the theoretical value of 100% are suggested.

The enhanced infrared spectra of Langmuir-Blodgett (LB) monolayers deposited on rough metal island films are presented. The nature and properties of surface-enhanced infrared (SEIR) spectra are discussed and compared with those of surface-enhanced Raman scattering (SERS). The geometry and polarization properties of the SEIR experiment were investigated. For practical applications, it is shown that a single sample can be prepared to obtain SERS and SEIR spectra. The use of different metals for SERS and SEIR, in keeping with the requirement of the appropriate optical constants for electromagnetic enhancement, is also discussed.

In this work we experimentally demonstrated an underwater wireless optical communications (UWOC) link over a 2.96 m distance with two 445-nm fiber-pigtailed laser diodes employing Orbital Angular Momentum (OAM) to allow for spatial multiplexing. Using an on-off keying, non-return-to-zero (OOK-NRZ) modulation scheme, a data rate of 3 Gbit/s was achieved in water with an attenuation coefficient of 0.4128 m^-1 at an average bit error rate (BER) of 2.073 × 10^-4, well beneath the forward error correction (FEC) threshold.