Stable optical trapping and sensitive characterization of nanostructures using standing- wave Raman tweezers

Optical manipulation and label-free characterization of nanoscale structures open up new possibilities for assembly and control of nanodevices and biomolecules. Optical tweezers integrated with Raman spectroscopy allows analyzing a single trapped particle, but is generally less effective for individual nanoparticles. The main challenge is the weak gradient force on nanoparticles that is insufficient to overcome the destabilizing effect of scattering force and Brownian motion. Here, we present standing-wave Raman tweezers for stable trapping and sensitive characterization of single isolated nanostructures with a low laser power by combining a standing-wave optical trap with confocal Raman spectroscopy. This scheme has stronger intensity gradients and balanced scattering forces, and thus can be used to analyze many nanoparticles that cannot be measured with single-beam Raman tweezers, including individual single-walled carbon nanotubes (SWCNT), graphene flakes, biological particles, SERS-active metal nanoparticles, and high-refractive semiconductor nanoparticles. This would enable sorting and characterization of specific SWCNTs and other nanoparticles based on their increased Raman fingerprints

300-GHz Step-Profiled Corrugated Horn Antennas Integrated in LTCC

This paper presents 300-GHz step-profiled corrugated horn antennas, aiming at their integration in low-temperature co-fired ceramic (LTCC) packages. Using substrate integrated waveguide technology, the cavity inside the multi-layer LTCC substrate and a surrounding via fence are used to form a feeding hollow waveguide and horn structure. Owing to the vertical configuration, we were able to design the corrugations and stepped profile of horn antennas to approximate smooth metallic surface. To verify the design experimentally, the LTCC waveguides and horn antennas were fabricated with an LTCC multi-layer process. The LTCC waveguide exhibits insertion loss of 0.6 dB/mm, and the LTCC horn antenna exhibits 18-dBi peak gain and 100-GHz bandwidth with more than 10-dB return loss. The size of the horn antenna is only, 5 x 5 x 2.8 mm(3) which makes it easy to integrate it in LTCC transceiver modules.112826sciescopu

Terahertz Frequency-Domain Spectrometer Based on Photodiode and Low-Temperature-Grown GaAs Photoconductor at 1.55 μm

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Tomographic Imaging Using Photonically Generated Low-Coherence Terahertz Noise Sources

Three-dimensional (3D) terahertz (THz) imaging or THz tomography has recently proven to be powerful for non-destructive testing of industrial materials and structures. In order to reduce complexity and cost of conventional THz tomography systems, we propose a new approach using broadband THz noise sources based on amplified spontaneous emission noise, which is analogous to the optical coherence tomography (OCT) using broadband infrared sources. We have experimentally demonstrated a 3D imaging system with depth and spatial resolutions of 1 and 2 mm, respectively, by 280-380 GHz band noise signals.111317Nsciescopu

Application of High-Power Photodiode-Arrays to 300 GHz-Band Wireless Link

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Multi-Gigabit Wireless Data Transmission at over 200-GHz Band

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Millimeter- and THz-wave photonics toward 100 Gbps wireless transmission

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24 Gbit/s data transmission in 300 GHz band for future terahertz communications

Presented is 24 Gbit/s wireless data transmission at 300 GHz using a uni-travelling carrier photodiode (UTC-PD) emitter and Schottky barrier diode detector, which were designed and fabricated for larger bandwidth. Both the emitter and the detector were fabricated on the same epi-layer of the UTC-PD. At the link distance of around 50 cm, a bit error rate of less than 1 x 10(-10) has been achieved with the transmitted power from the UTC-PD of less than 200 mu W and effective antenna gains of 40 and 35 dBi in the emitter and detector sides, respectively.11105112sciescopu