Optical constants of lactose pumped by strong terahertz (THz) waves have been investigated. The sample was measured by a THz-pump/THz-probe system, in which the electric field strength of the pump-THz waves exceeds 120 kV/cm. When the lactose sample is pumped by strong THz pulses, its probed response signal lasts about 2 ps. With different delay time, the optical constants of lactose was also measured and discussed. The experimental results show that the optical properties of lactose molecules can be changed by high-intensity THz waves, and this change is related to the applied the interaction time, which is in the order of picosecond.
A sensitive, real-time seven core optical fiber based Mach-Zehnder interferometer (MZI) sensor for liquid refractive index detection is proposed, fabricated and characterized. A trapezoid body with an inverted wedge shape groove in the center is used to design the MZI. The two ends of the trapezoid body play the roles of micro-prisms, and the middle parts of the trapezoid body and the groove play the roles of reference and sensing arms. A series of performance tests were carried out by immersing the sensor in different kinds of solutions to verify the universal applicability of the sensor. The MZI sensor is as small as only 43 μm × 8 μm, and at the same time with sensitivity of 1616 nm/RIU. Nominally, we realized a completely integrated optical sensing system. And, this system actually could be the building block of more powerful integrated chemical sensing chip for health, security and industry application.
An optical refractive index sensor based on the Rayleigh anomaly of the gold grating is demonstrated in the terahertz (THz) wave band. A pronounced peak due to the Rayleigh anomaly of the gold grating is observed in the reflection spectrum, the center wavelength of which is sensitive to the environmental refractive index on the top of the grating. The wavelength of the Rayleigh anomaly reflection peak and the corresponding sensitivity are solely determined by the period of the gold grating, the larger the period, the longer the resonance wavelength and the higher the sensitivity. Therefore, a higher sensitivity can be achieved in the THz wave band. Both theoretical and experimental investigations show that the shape and intensity of the Rayleigh anomaly reflection peaks are determined by the duty cycle of the grating, for the value of the duty cycle about 0.4, the maximum intensity of the Rayleigh anomaly reflection peak was achieved.
Terahertz (THz) radiation is an under developing range in the electromagnetic spectrum. It has attracted a lot of
attentions due to its various potential applications. However, THz systems are difficult to be integrated into a smart size
due to the limitation of its long wavelength. In this presentation, we propose a new approach to design planar lenses with
a thickness of several hundred nanometers in the THz range. The fabricated lenses are characterized with a focal plane
imaging system and it is found that they can focus the THz light and image an object well. It is expected that this new
approach can pave a way for smart THz systems integration.
A simple analytical model was formulated to describe the coupling between the broadband particle plasmon resonance (PPR) and the narrowband waveguide resonance mode (WRM) in wave-guided metallic photonic crystals (MPCs). The PPR and the WRM are processed independently to enable direct examination of their interaction. The enhanced transmission resulting from the PPR-WRM coupling in wave-guided MPCs can be simply interpreted as the destructive interference between directly transmitted light with lower intensity and the diffraction of the waveguide propagation mode with higher intensity.
We investigate the influence of particle plasmon resonance of Au nanoislands structures on the exciplex emission in the
polymer blend of poly (9, 9'-dioctylfluorene-co-benzothiadiazole) (F8BT) and poly (9,9'-dioctylfluorene-co-bis-N,N'-
(4-butylphenyl)-bis-N,N'-phenyl-l,4-phenylenediamine) (PFB). The experimental results indicate that when the particle
plasmon resonance of the gold nanoisland structures overlaps the spectral range of the exciplex emission, significant
enhancement of the photoluminescence can be observed. Furthermore, longer lifetime has been measured for the
red-shift emission of the exciplex. We proposed that the localized field due to the particle plasmon resonance of the Au
nanoislands has modulated the mechanisms for the formation of exciplex, which may be related to the exciton diffusion,
charge transfer, and phase separation at the interface between the two materials.
In this paper, it is proposed to record the matched filter in the photorefractive crystal by using the synthetic discriminant function as the input. The synthetic discriminant function is generated by training a set of rotated object images. Multiple matched filters are stored by angle-multiplexing in the same volume. Due to the large difference among the optical throughouts of the images, a wavelet transform filter is directly introduced into the experimental setup to improve the object discrimination largely. Computer simulation and experimental results demonstrate that it is possible to achieve the rotation-invariant pattern recognition with the proposed method
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