Volume holographic printing using unconventional angular multiplexing for three-dimensional display.

We propose and demonstrate a volume holographic printing method for dynamic three-dimensional (3D) display with an expanded space-bandwidth product (SBP) using unconventional angular multiplexing techniques. By wavefront encoding of the 3D scene, with the help of computer-generated holography, the object beam is loaded onto a 2D phase spatial light modulator (SLM) with a limited SBP. The printing method then writes a single hologram through the interference of the object beam with a reference beam as a holographic element (hogel) in the volume holographic polymer.

Nanopillar array on a fiber facet for highly sensitive surface-enhanced Raman scattering.

A highly-sensitive optical fiber surface-enhanced Raman scattering (SERS) sensor has been developed by interference lithography. While one facet of the optical fiber is patterned with silver-coated nanopillar array as a SERS platform, the other end of the probe is used, in a remote end detection, to couple the excitation laser into the fiber and send the SERS signal to the spectrometer. SERS performance of the probe is characterized using trans-1,2-bis(4-pyridyl)-ethylene (BPE) monolayer and an enhancement factor of 1.

Direct molecule-specific glucose detection by Raman spectroscopy based on photonic crystal fiber.

This paper reports the first step toward the development of a glucose biosensor based on Raman spectroscopy and a photonic crystal fiber (PCF) probe. Historically, it has been very challenging to detect glucose directly by Raman spectroscopy due to its inherently small Raman scattering cross-section. In this work, we report the first quantitative glucose Raman detection in the physiological concentration range (0-25 mM) with a low laser power (2 mW), a short integration time (30 s), and an extremely small sampling volume (~50 nL) using the highly sensitive liquid-filled PCF probe.

Highly sensitive detection of proteins and bacteria in aqueous solution using surface-enhanced Raman scattering and optical fibers.

We report the detection of the proteins lysozyme and cytochrome c as well as the live bacterial cells of Shewanella oneidensis MR-1 in aqueous solutions with sensitivities order(s) of magnitude higher than those previously reported. Two highly sensitive surface-enhanced Raman scattering (SERS)-based biosensors using optical fibers have been employed for such label-free macromolecule detections. The first sensor is based on a tip-coated multimode fiber (TCMMF) with a double-substrate "sandwich" structure, and a detection limit of 0.

Channel analysis of the volume holographic correlator for scene matching.

A channel model of the volume holographic correlator (VHC) is proposed and demonstrated to improve the accuracy in the scene matching application with the multi-sample parallel estimation (MPE) algorithm. A quantity related to the space-bandwidth product is used to describe the recognition ability in the scene matching system by MPE. A curve is given to optimize the number of samples with the required recognition accuracy.

Portable fiber sensors based on surface-enhanced Raman scattering.

Two portable molecular sensing systems based on surface-enhanced Raman scattering (SERS) have been experimentally demonstrated using either a tip-coated multimode fiber (TCMMF) or a liquid core photonic crystal fiber (LCPCF) as the SERS probe. With Rhodamine 6G as a test molecule, the TCMMF-portable SERS system achieved 2-3 times better sensitivity than direct sampling (focusing the laser light directly into the sample without the fiber probe), and a highly sensitive LCPCF-portable SERS system reached a sensitivity up to 59 times that of direct sampling, comparable to the sensitivity enhancement achieved using fiber probes in the bulky Renishaw system. These fiber SERS probes integrated with a portable Raman spectrometer provide a promising scheme for a compact and flexible molecular sensing system with high sensitivity and portability.

[A spectrum signals detection method for surface enhanced Raman scattering under high fluorescence and background noise].

A spectrum signals detection method has been designed for surface enhanced Raman scattering (SERS) under high fluorescence and background noise. The components of the fluorescence and background noise in SERS spectrum signal were analyzed first. Then they were evaluated by some models, such as polynomial model and AR model.

High-sensitivity molecular sensing using hollow-core photonic crystal fiber and surface-enhanced Raman scattering.

A high-sensitivity molecular sensor using a hollow-core photonic crystal fiber (HCPCF) based on surface-enhanced Raman scattering (SERS) has been experimentally demonstrated and theoretically analyzed. A factor of 100 in sensitivity enhancement is shown in comparison to direct sampling under the same conditions. With a silver nanoparticle colloid as the SERS substrate and Rhodamine 6G as a test molecule, the lowest detectable concentration is 10(-10) M with a liquid-core photonic crystal fiber (LCPCF) probe, and 10(-8) M for direct sampling.

Matched spectral filter based on reflection holograms for analyte identification.

A matched spectral filter set that provides automatic preliminary analyte identification is proposed and analyzed. Each matched spectral filter in the set containing the multiple spectral peaks corresponding to the Raman spectrum of a substance is capable of collecting the specified spectrum into the detector simultaneously. The filter set is implemented by multiplexed volume holographic reflection gratings.

Molecular fiber sensors based on surface enhanced Raman scattering (SERS).

Molecular sensors based on surface enhanced Raman scattering (SERS) and optical fibers have been widely used in biological, environmental and chemical detection procedures due to their unique advantages, such as molecular specificity, high sensitivity and flexibility. In this paper, we review the development and highlight some of the important milestones of SERS fiber sensor development with emphasis on recent work to improve the sensitivity of the fiber sensors. In particular in the area to increase the sensitivity, we've reviewed various methods of sample preparation as well as different fiber SERS sensors.

Novel index-guided photonic crystal fiber surface-enhanced Raman scattering probe.

We demonstrate a novel index-guided (IG) photonic crystal fiber (PCF) surface-enhanced Raman probe. Different from a regular PCF, the IGPCF has four big air holes inserted between the solid silica core and the photonic crystal cladding holes. The gold nanoparticles, serving as the surface enhanced Raman scattering (SERS) substrate, are either coated on the inner surface of the holes or mixed in the analyte solution in two separate experiments, respectively.

Manipulation and light-induced agglomeration of carbon nanotubes through optical trapping of attached silver nanoparticles.

A simple experimental method has been demonstrated for manipulating multi-walled carbon nanotube (MWCNT) bundles through the optical trapping of attached silver nanoparticles (SNPs). In our experiments, without the SNPs, the MWCNTs cannot be trapped due to their irregular shapes and large aspect ratio. However, when mixed with SNPs, the MWCNTs can be successfully trapped along with the SNPs using a TEM(00) mode laser at 532 nm.

Orthogonal polarization dual-channel holographic memory in cationic ring-opening photopolymer.

A dual-channel holographic recording technique and its corresponding memory scheme in the cationic ring-opening photopolymer are presented. In the dual-channel technique, a pair of holograms are recorded simultaneously with two orthogonal polarization channels in the common volume of the material, and are reconstructed concurrently with negligible inter-channel crosstalk. The grating strengths of these two channels are investigated and the relevant parameters for equal diffraction intensity readout are optimized.

Complete polarization controller based on magneto-optic crystals and fixed quarter wave plates.

We propose and demonstrate a polarization controller, which is a concatenation of three Faraday rotators based on magneto-optic crystals separated by two fixed quarter wave plates. Comparing with former schemes, this polarization controller is fast, accurate and stable because it is completely driven by electric signals and has no mechanically moving parts.It is simple-structured and low-cost.

Micro displacement sensor based on line-defect resonant cavity in photonic crystal.

A micro displacement sensor and its sensing technique based on line-defect resonant cavity in photonic crystals (PhCs) are presented. The line-defect resonant cavity is formed by a fixed and a mobile PhC segments. With a proper operating frequency, a quasi-linear measurement of micro-displacement is achieved with sensitivity of 1.

Strong phase-controlled fiber Bragg gratings for dispersion compensation.

Dispersion-compensating fiber Bragg gratings with approximately 99.9% reflectivity that are made by continuous apodization and phase control are demonstrated. These strong dispersion-compensating gratings provide precision second-order, third-order, or even more complex dispersion compensation, as well as sufficient transmission isolation to be used at add-drop stages without additional filtering.