The ultraviolet (UV) light wavelengths, typically defined to range from10-400nm, have proven to be useful for a number of applications, such as astronomy, biology, medicine and so on. It is important for us to study on the UV and related devices. In this paper, a novel and effective grating coupler for ultraviolet light was reported, which can couple efficiently ultraviolet light from fiber to waveguide at the wavelength of 300nm. The grating coupler was based on the oxide layer of silicon surface, because ultraviolet light can be transmitted pure silicon dioxide (SiO<sub>2</sub>) with low loss. Based on Bragg condition of grating, we use FDTD method to simulate and design the grating parameters operated under TM polarization. Using our optimization design parameters (period T, incident angle θ, filling factor f and etching height h) to optimize the mode matching between the fiber and the grating region, a relatively high coupling efficiency was obtained for the fiber and waveguide interface. In our design, filling factor f=0.55, period T=280nm etching height H=110nm, incident angle θ=11° can be realized in the process of manufacture. But coupling efficiency are sensitivity to the range of period of grating and incident angle θ, which increase the difficulty of processing and experiment, the process of technology and operation need high precision. Consequently, we the coupling efficiency can be largely increased and beyond 88.5% at center wavelength of 296nm and 1dB bandwidth, in which the theory analysis and the simulation results are in good agreement and coupling efficiency is the highest for this kind of coupler reported as we known. This kind submicron-sized SiO<sub>2</sub> waveguides that can be fabricated by mature CMOS-compatible processes are showing promise for realistic dense photonic integrated circuit (PIC) in various applications including optical communications, optical interconnects, signal processing and sensing. The gratings open the path to pure silicon dioxide for ultraviolet the enabling new nonlinear optical functions as well as new spectroscopic lab on-a chip approaches.
Retroreflective free-space optical communication is a new method of optical communication, it is achieved by using a multiple-quantum-well (MQW) modulator as a passive data transmitter. This work analyzes the polarization propagation of light in the MQW modulator, and the corresponding influence to a retroreflective link. Results show that, on the condition that the intensity and incident angle of the incident light remains to be constant, the polarization and intensity of the transmitted light varies markedly; if the polarization of the incident light is carefully considered for a specific MQW modulator, the retroreflective signals can be improved for a retroreflective free-space optical communication link.
With low radiation background of solar-blind UV and strong scattering of UV photons by atmospheric particles, UV
communication can be made use of to set up a non-line-of-sight (NLOS) free-space optical communication link. Polarization modulation, besides the traditional intensity modulation, is presented to enhance the data rate of the UV
communication system. The configuration and the working process of the dually modulated UV communication system
with intensity modulation and polarization, the theoretical evaluation of polarization modulation, and a numerical of the scattering matrix are presented, with the conclusion that polarization modulation is achievable. By adding the polarizing devices and changing the coding procedures, the existing singly-modulated UV communication systems with intensity modulation are easily modified to be dually-modulated ones with polarization modulation and intensity modulation. Ideally speaking, the data rate of the dually-modulated UV communication system is the product of the data rate of the singly modulated system and the number of polarization modulation.
The UV radiance of the missile plume is considered as gray body radiance, and transmission efficiency and backgroud
radiation of UV in atmosphere are obtained by Lowtran 7. The signal-to-noise ratios of missile plume UV radiation at
different altitudes are estimated seperately for the ground-based, air-based and space-based systems of missile precaution, results show that, the SNR of the ground-based system decreases, the SNR of the air-based system firstly increases and then decreases, and the SNR of the space-based system increases with the growth of the altitude of missile; The SNRs of the ground-based and air-based systems are both relatively large aroud 300nm while the SNR of the space-based system is relatively large at the band from 250nm to 290nm; The SNR of the ground-based reaches the maximum when the altitude of missile is below 5km , the SNR of the air-based system is at the maximum between 10km and 20km, and the SNR of the space–based system is at the maximum above 40km. The results can be applied to designing the integrated system of missile precaution from air to space.
As it contains the spectral and image information of targets, the hyperspectral image measured by the airborne CASI
imaging spectrometer can improve the accuracy of target identification effectively. Usually, the spectral matching
methods are used in identification by extracting spectral information from hyperspectral image. Two matching
algorithms, the spectral angle matching method and the binary encoding method, are investigated under the condition of
different spectral resolutions. Firstly the atmospheric correction, the spectral curve smoothing and re-sampling are
carried out in ENVI software. Then the different spectral resolutions are constructed by selecting spectral subsets from
the hyperspectral image. The matching result indicates that the spectral resolution threshold of the spectral angle
matching method is above the threshold of the binary encoding method. The result of this study has important guiding
significance to the use of the matching algorithm and the selection of spectral resolution.
Proc. SPIE. 8202, 2011 International Conference on Optical Instruments and Technology: Solid State Lighting and Display Technologies, Holography, Speckle Pattern Interferometry, and Micro/Nano Manufacturing and Metrology
A high-perform and compact subwavelength binary blazed grating optical switch was designed based on
TiO<sub>2</sub>-on-SiO<sub>2</sub>. By appropriate choice of grating parameters including thicknesses, periods, height, and fill factor, to
optimize the diffraction properties, a relative high diffraction efficiency and large diffraction angle was obtained
simultaneously. The diffraction efficiency of the first switching channel is about 80% with a 45° diffraction angle, and
the diffraction efficiency of the second channel is around 90% with a 30° diffraction angle. The device layout is simple,
feasible, one-step etch, and compatible with standard CMOS technology processing.
A novel signals' receiving and data processing approach is proposed for optical scattering signal transmitting. This
proposed approach consist of three steps: firstly, the signals are received by two detectors in terms of spacial diversity
synchronously, and then collected by high speed data collection card afterwards; Secondly, the 1.5 dimension spectrums
of the collected signals in step 1 are calculated; Finally, the cross-correlation of the 1.5 dimension spectrums is used to
decrease the non-gauss noise. In order to validate the proposed approach, an optical scattering signal receiving system
has been designed based on two detectors and other ordinary instruments. The experimental results indicate that the
designed system can demodulate the optical scattering signals accurately even if the noise-signal ratio (SNR) is as low as
-25dB. It proves to be effective and adequate in the secure optical scattering communication.
The detection of explosive agents is becoming more important and receiving much greater emphasis for homeland
defense. Raman spectroscopy is a well established tool for vibration spectroscopic analysis and can be applied to the
field of explosives identification and detection. The major bands of the Raman spectroscopy of industrial TNT
(Trinitrotoluene, CH<sub>3</sub>C<sub>6</sub>H<sub>2</sub>(NO<sub>2</sub>)<sub>3</sub>) are analyzed and seven prominent peaks, that is 1616.9cm<sup>-1</sup> (C=C aromatic
stretching vibration), 1533.9cm<sup>-1</sup> (NO<sub>2</sub> asymmetric stretching vibration), 1360.1cm<sup>-1</sup> (NO<sub>2</sub> symmetric stretching
vibration ), 1210.5cm<sup>-1</sup> (C<sub>6</sub>H<sub>2</sub>-C vibration), 822.9cm<sup>-1</sup> (nitro-group scissoring mode), 792.3cm<sup>-1</sup> (C-H out-of-plane bend),
and 326.7cm<sup>-1</sup> (framework distortion mode) are used to identify the TNT. The Raman spectroscopes of TNT solved in
acetone at different mass ratios are studied, and the TNT in the solution can be detected correctly according the relative
distance, intensity, and peak area of the seven peaks. The TNT prominent peaks appear clearly in high level solution (the
mass ration of TNT and acetone is more than 1:10). With the decrease of TNT concentration in solution, the signature of
TNT becomes more and more weak. The low detection limit of TNT is limited by the noise of the instrument (NXR
FT-Raman accessory module with Nicolet 5700 FT-IR spectrometer is used for our experiments. The low detection limit
in our experiments is mass ratio 1:200, which is about 4mg/mL). The prominent peak heights are discussed in
consideration of the TNT concentration. Taking one of the acetone's peaks (1716.9cm<sup>-1</sup>) as the internal standard line, the
relative height of the prominent TNT peaks is almost proportional to the concentration of the TNT in the solution. A
fitting curve for the relations of prominent peak height according to the concentration is proposed with multinomial
fitting method, which can be used to analyze the concentration of TNT more accurately.
Solar blind ultraviolet communication systems can provide short to medium range non line-of-sight and line-of-sight
links which are covert and insensitive to meteorological conditions. These unique properties endow solar blind
ultraviolet communication systems increasing applications. While optical filters are key components of these solar blind
ultraviolet communication systems. Although filters can be designed in different forms, thin-film interference narrow-band
filters are widely adopted. In this paper, we make use of NCNBIF, which was so-called nonconventional narrow-band
interference filters proposed by Jerzy Ciosek firstly, to design ultraviolet narrow-band interference filters.
Generally, classical narrow-band interference dielectric filters, such as Fabry-Pérot filters, have a half-wave-thickness
spacer layer. In contrast with a classical interference filter, the NCNBIF does not have a half-wave-thickness spacer
layer. This spacer layer of NCNBIF consists of two different materials. This new kind of film system (NCNBIF) is
synthesized by using needle optimization technique, and possesses desired spectral characteristics.
Ultraviolet (UV) communication is a new kind of communication method by realizing non
line-of-sight transmission of information, which overcomes disadvantages of line-of sight
communication in other free space optical communication, such as non-UV laser communication.
It will have a bright prospect of application. At present, there are more and more studies on UV
communication technology at home and abroad. As for the UV communication system of our
studies, we have researched deeply on one of the key technologies of UV communication that is
UV high reflectance coatings. Based on the traditional theories and arithmetic of design for
quarter-wavelength multilayer high reflectance coatings, the Needle method is improved greatly for
the coating design, thus a kind of solar blind UV high reflectance coatings is designed. Results of
calculation shows that this solar blind UV high-reflecting coating's reflectance is more than 97% at
the range of wavelength λ=250~280nm and the coating's reflectance is smaller than 3% at the
range of wavelength λ>300nm. Compared with Al coating and quarter- wavelength high reflective
multi-layers coating, the coating is more suitable to be used in the atmosphere UV communication
system, so the communication distance and the sensitivity of receiving system can be improved
greatly. This solar blind UV high-reflecting coating can also be used in other UV optical
technology and application, such as UV image, UV reconnaissance.
Model of non-line-of-sight (NLOS) UV transmission was introduced, NLOS UV transmission was simulated using
Monte-Carlo method. Impact of visibility, rainfall, wind speed, light source radiation power, detector sensitivity on
transmission range was debated. Results showed that visibility and rainfall had relative impact on transmission range,
while wind speed hardly had any influence, it was a main way to improve range by enhancing detector sensitivity, and it
weren't very effective to increase source radiation power.
In the paper, The importance of research in non-line-of sight(NLOS) ultraviolet(UV) propagation channel is first pointed
out, and then an experimental system based on Lock-In-Amplifier (LIA) technology is set up to explore the NLOS UV
propagation channel characteristics in the atmosphere, and the related experimental results are good helpful to design and
evaluate the NLOS UV communication system. The research results show that: firstly, the received energy decreases
much quickly with the distance enlarged, and it is also influenced by the emitting elevation angle and emitting field of
view angle; secondly, the visibility, wind force, rain rate and fog has little influence on the received power in the short
working distance, but with the propagation distance is getting longer, the fog play an very important role on the received
signal; finally, some effective methods to enlarge UV communication system distance are discussed, such as UV source
power, received antenna diameter and UV detector quality, and experimental data show that the best way to improve
UV communication system is to improve the detector sensitivity.
Ultraviolet communication is a new means of free space optical communication links developed since 1990's. In the paper, we first point out the low data rate drawback of the UV communication system using mercury lamp, and find the limitation arises because of the self trapping of the mercury atomic resonance radiation. Then the working principle and the max modulation speed o f the high data rate UV communication system are explained, at last the high date rate UV communication system which based on the low pressure iodine lamp is described in details. The high UV communication system includes an emitter, a receiver and light propagation channel. The light propagation channel is in the low air. Finally, the system has accomplished good voice and high data rate communication in short distance and its maximal communication rate is 48Kbps which decuple the data rate of the UV communication system made by GTE in 2000. Because of shorter wavelength of the iodine UV source, the whole communication system is more suitable for the security communication usage.
Ultraviolet light communication is a new means of optical information transmission technology developed since 1990’s. In this paper, some key technologies developed from the experiment will be described in detail. These technologies include the design of high speed UV source frequency modulator, the design of high sensitive optical receiver system and the design of weak signal detect and process modular, etc. The UV communication system has accomplished good voice and high speed digital data bidirectional communication in semi-duplex way and its maximal communication baud rate is up to 9600 bps which is twice as the baud rate of the UV communication system made by GTE Company for navy USA navy in 2000. Furthermore, in some distance the system can achieves a non-line-sight communication.