Application of GRIN-lens-based in-line digital holographic microscopy to automatic detection and localization of particles released from a MEMS device.

Recently, we developed a compact and easy-to-implement in-line digital holographic microscope (DHM) using a GRIN rod lens, which provides better resolution (1.3 µm) compared with commonly used pinhole-based DHM setups. Here, we employ this microscope to acquire 3D holographically reconstructed images of silica microparticles, within the 10-300 µm size range, launched/released from a microelectro-mechanical systems (MEMS) device.

GRIN-lens-based in-line digital holographic microscopy.

In-line digital holographic microscopy (DHM) provides three-dimensional images with large fields of view and depths of field and micrometer-scale resolution, using a compact, cost-effective, and stable setup. Here, we develop the theoretical background and experimentally demonstrate an in-line DHM based on a gradient-index (GRIN) rod lens. In addition, we develop a conventional pinhole-based in-line DHM with different configurations to compare the resolution and image quality of both GRIN-based and pinhole-based systems.

Hexagonal arrays of gold triangles as plasmonic tweezers.

We present theoretical and experimental studies of the plasmonic properties of hexagonal arrays of gold triangles, fabricated by angle-resolved nanosphere lithography method. Our numerical and experimental results both show that a change in the angle of gold deposition affects the size and the distance between the triangles, leading to a controlled shift in their absorption and scattering spectra. We calculate the force exerted on the polystyrene particles of 650 nm radii numerically while passing above the hexagonal arrays.

Moiré deflectometry-based position detection for optical tweezers.

Optical tweezers have proven to be indispensable tools for pico-Newton range force spectroscopy. A quadrant photodiode (QPD) positioned at the back focal plane of an optical tweezers' condenser is commonly used for locating the trapped object. In this Letter, for the first time, to the best of our knowledge, we introduce a moiré pattern-based detection method for optical tweezers.

Nanometer displacement measurement using Fresnel diffraction.

We introduce a relatively simple and efficient optical technique to measure nanoscale displacement based on visibility variations of the Fresnel diffraction fringes from a two-dimensional phase step. In this paper we use our technique to measure electromechanical expansions by a thin piezoelectric ceramic and also thermal changes in the diameter of a tungsten wire. Early results provide convincing evidence that sensitivity up to a few nanometers can be achieved, and our technique has the potential to be used as a nanodisplacement probe.