Sacharia Albin

Coupled photonic crystal micro-cavities with ultra-low threshold power for stimulated Raman scattering.

We propose coupled cavities to realize a strong enhancement of the Raman scattering. Five sub cavities are embedded in the photonic crystals. Simulations through finite-difference time-domain (FDTD) method demonstrate that one cavity, which is used to propagate the pump beam at the optical-communication wavelength, has a Q factor as high as 
1.254×10⁸ and modal volume as small as 0.03 μm3 (0.3192(λ/n)3). These parameters result in ultra-small threshold lasing power~17.7 nW and 2.58 nW for Stokes and anti-Stokes respectively. The cavities are designed to support the required Stokes and anti-Stokes modal spacing in silicon. The proposed structure has the potential for sensor devices, especially for biological and medical diagnoses.

Resorcinarene amine stabilized nanodiamond dispersions in organic solvents: applications in diamond film growth

Nanodiamonds of widely differing sizes (4 to >100 nm), shapes, and origin could be extracted from aqueous dispersions into toluene by a multidentate resorcinarene amine surfactant, in the absence of any elaborate covalent functionalization or extreme conditions. Resorcinarene amine encapsulated nanodiamonds displayed excellent dispersion stability in non-polar organic solvents for several months. The IR spectral analysis of these extracted and further precipitated nanodiamonds suggests that the carboxylic acid groups present on the nanodiamond surfaces are electrostatically stabilized by the resorcinarene amine surfactant. Such nanodiamond dispersions can also act as nucleation sources for the fabrication of continuous diamond films by CVD growth. Notably, this process resulted in diamond films with better uniformity, smaller grain size and reduced surface roughness when compared to the films prepared with unmodified nanodiamonds as nucleating agents.

Anthracene Fibers Grown in a Microstructured Optical Fiber for X-ray Detection

Anthracene fibers are grown inside a microstructured quartz matrix to form a multicore optical fiber for X-ray detection. A modified fiber growth method for single crystal anthracene from the melt via the Bridgman-Stockbarger technique is presented. The anthracene fiber is characterized by using spectrophotometry, Raman spectroscopy, and X-ray diffraction. These results show the anthracene grown in fiber has high purity and a crystal structure similar to anthracene grown from liquid, vapor, and melt techniques. As an X-ray detector, the output is 12%–16% efficient between the energy ranges of 40 and 10 keV. The effect of materials and fiber processing are discussed.

A new method to improve the sensitivity of THz sensor based on combined photonic crystal microcavities

A new mode matching method that can significantly increase the sensitivity of photonic crystal THz detector is proposed. The new design introduces less energy loss and is easy for device fabrication.

Selective growth of nanodiamond films in microwave plasma

A patterned nanodiamond film is grown using microwave plasma-enhanced chemical vapor deposition. A selective growth method compatible with traditional silicon processing is described. A diamond pattern of high quality and moderate resolution is achieved. The process utilized is simple to generate patterns without etching diamond. A rectifying junction is demonstrated using a p-type nanodiamond and p-type silicon heterojunction with rectifying ratio of two orders of magnitude. This simple patterning technique could be applied in the fabrication of diamond electronic and mechanical devices and biological sensors. The plasma emission spectra indicate the presence of both CH and C2 species, which are responsible for diamond growth.