Terahertz Molecular Imaging and Sensing Applications
Date Issued
2007
Date
2007
Author(s)
Lu, Ja-Yu
DOI
en-US
Abstract
Recently THz imaging and sensing techniques become focusing in THz technology and the main driven force of THz generation and detection. Due to the unique capability of direct molecular identification differed from other EM waves (optical waves and microwaves), it enables noninvasive and label-free molecular imaging and sensing based on THz waves. In order to develop THz imaging and sensing technique or system with high sensitivity, low loss, ease of control and high flexibility for various practical applications, many researchers have made lots effort on it. In this thesis, we provide other alternatives for THz imaging and sensing application.
Based on an optoelectronic THz photonic transmitter with ultra high conversion efficiency, we demonstrate a compact THz molecular imaging system with extremely low driven power (<5mW optical pump, 15V bias). Based on the micron-sized photonic transmitter operating at room temperature, an improved signal-to-noise ratio with a reasonable spatial resolution and high penetration depth (>3cm) can be achieved. Biomedical THz imaging has been demonstrated by scanning a dried seahorse and a fresh flower, which were hidden in plastic sample holders and were invisible. Tissue and water distributions of distinct regions of the bio-samples were clearly resolved, showing the high imaging contrasts of the demonstrated system. These results reveal the possibility to construct a compact and high-sensitivity THz imaging system with less than 1-mW optical excitation which is promising in the future clinical application and sensing of hidden objects such as explosives and viruses.
By planar integrating a THz micro-source into a glass-substrated microchip within a THz near-field distance, we demonstrate a compact, label-free, noninvasive, and sensitive micro-biosensing system with low-power consumption. The demonstrated THz microchip allows us to locally specify various illicit drug powders with weights on the order of nanograms. Our demonstration shows the possibility to integrate optoelectronic photonic transmitters with the current biochip technology for various biosensing applications, including DNA sequencing, explosive and virus detections, and rapid identification of the static status or even the dynamics of various biomolecules.
To efficiently transmit THz waves for achieving THz imaging and sensing with high SNR, is another important issue in THz technology. In this thesis, we develop an air-core microstructure fiber (AMF) for THz transmission. The novel THz-AMF has advantages of with extremely low loss and tunable guiding wavelength by scaling the size of MF. In addition, most THz field is concentrated inside the central hollow air-core and guided without outside interference. We will introduce the design and fabrication of THz-AMF and discuss the waveguiding mechanism. The demonstrated THz-AMF is ideal for various THz applications, including low-dispersion high THz power transmission for nonlinear applications, THz sensing, and THz optical communication for avoiding the interference from surroundings.
A THz subwavelength plastic fiber has been previously developed by our labs for low loss waveguiding. Due to most THz field guided outside the fiber core which is different from the traditional optical fiber, resulting in great decrease of dielectric absorption and thus could guide for a long distance (more than one meter). In this thesis, we further explore the feasibility on imaging by using THz subwavelength fiber on which THz wave is loosely guided. We study its bending loss, energy transfer ratio, and modal spot quality. Furthermore, we also construct a compact room-temperature transmitted fiber scanning THz imaging system based on a low-loss subwavelength plastic fiber. Various biological images have been acquired by direct scanning of a THz subwavelength fiber in a large area, and it reveals that the subwavelength plastic fiber enables high SNR imaging with reasonable spatial resolution (close to diffraction limit). Finally, we first ever demonstrate a THz endoscope based on the subwavelength THz fiber, and apply it for imaging of biological specimen and metal pattern without focusing system. The measured images not only reflected the 2D molecular distribution, but revealed the depth variation and thus showed the surface profile or morphology of imaged object. This novel THz endoscope is especially suitable for water-rich biological specimen, because it overcomes the limitation of water absorption which becomes restriction in the conventional transmitted THz imaging system.
Subjects
兆赫波
次毫米波
兆赫波影像
兆赫波波導
內視鏡
光纖
Terahertz
submillimeter wave
THz imaging
THz waveguide
endoscope
fiber
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-96-D91941004-1.pdf
Size
23.31 KB
Format
Adobe PDF
Checksum
(MD5):12467e95a75b408866fac69f6c0c3976