Lin Pang

High-resolution surface plasmon resonance sensor based on linewidth-optimized nanohole array transmittance

A high spectral resolution, 2D nanohole-array-based surface plasmon resonance sensor that operates at normal or near normal incidence--facilitating high spatial resolution imaging--is presented. The angular and spectral transmittance of the structure is modified from a Fano type to a pure Lorentzian line shape with a parallel and orthogonal polarizer-analyzer pair. This change leads to a linewidth narrowing that maximizes the sensor resolution, which we show to be of O(10(-5)) refractive index units (RIU). We estimate the potential of this system of O(10(-6)) RIU under optimal conditions.

Engineered materials for all-optical helicity-dependent magnetic switching

The possibility of manipulating magnetic systems without applied magnetic fields have attracted growing attention over the past fifteen years. The low-power manipulation of the magnetization, preferably at ultrashort timescales, has become a fundamental challenge with implications for future magnetic information memory and storage technologies. Here we explore the optical manipulation of the magnetization in engineered magnetic materials. We demonstrate that all-optical helicity-dependent switching (AO-HDS) can be observed not only in selected rare earth-transition metal (RE-TM) alloy films but also in a much broader variety of materials, including RE-TM alloys, multilayers and heterostructures. We further show that RE-free Co-Ir-based synthetic ferrimagnetic heterostructures designed to mimic the magnetic properties of RE-TM alloys also exhibit AO-HDS. These results challenge present theories of AO-HDS and provide a pathway to engineering materials for future applications based on all-optical control of magnetic order.

Form-birefringent space-variant inhomogeneous medium element for shaping point-spread functions.

We experimentally characterize the properties of an element that generates a doughnutlike point-spread function by converting the linearly polarized incident field to radially or azimuthally polarized light utilizing space-variant inhomogeneous medium (SVIM) form-birefringent subwavelength structures. To fabricate the high-aspect-ratio SVIM structures, we developed a chemically assisted ion-beam-etching process that permits control of the fabricated form-birefringent structure profile to optimize the effect of birefringence and the impedance mismatch on the substrate-air interface. Fabricated elements perform efficient polarization conversion for incident angles as large as 30 degrees, where the extinction ratio is found to be better than 4.5. The intensity distribution in the far field shows that our SVIM device generates a doughnut point-spread function that may prove useful for various applications.

Reconfigurable large area metallic nanohole array and its application in bio-sensing

A novel fabrication method of large area surface plasmon resonance (SPR) 2-D metallic nanohole array sensor is presented to give controllable linewidth by metal deposition. The device is used to monitor real-time, label-free biomolecular binding.

Fabrication techniques for long range surface plasmon waveguides

We present different techniques for fabricating long-range plasmonic waveguides. Due to the requirement of symmetric cladding, fabrication is highly dependent on the material system used. Results are given for materials such as SU8 and polydimethylsiloxane.

Optofluidics for adaptation and sensing

The paper presents some of their recent works on optofluidics for adaptation and sensing applications. Demonstrated microfluidic-based adaptive optical devices are all optical switch based on control of total internal reflection (TIR) and microring resonator device (MRD)

Design, Fabrication and Characterization of Artificial Dielectrics for Polarization Transformations and Beam Shaping Applications

We report the design, fabrication and characterization of artificial dielectric components for polarization transformations and beam shaping applications. The devices are realized by deep etching of subwavelength gratings with space variant orientation into semiconductor substrate.