How to improve the sensitivity of new pattern of gyroscope which is based on micro ring resonator is widely researched. And periodically modulating coupling coefficient and area are the two most common schemes. Moreover, when the area of the square difference is large enough, the precision of gyroscope of the latter is higher than that of the former by 1 to 2 orders of magnitude. But increasing modulation area will narrow the transmission band, it will impact on our measurement of the inertial rotation. What’s more, this modulation method is very sensitive to the coupling coefficient between the micro rings. Simultaneously, the slope of the center resonance peak will be quickly decayed with the increase of the coupling coefficient. Generally, there's no sense to our modulation when the coupled coefficient is over 0.1. In this paper, we use the way of combining the two schemes to study the performance of the gyroscope which includes it's precision and how to reduce interference when it applied to devices. We found that the accuracy of rotation produced by our scheme is higher than that of simply modulating coupling coefficient or coupling area. And the sensitivity of gyroscope achieved by the new method is times higher than that of the general of coupled resonator optical waveguide, and there is almost no limit to the coupled coefficient based on our coupling scheme. What’s more, the steepest transmission resonance of the transmission band appears at Ω = 0 and other resonance peaks around the center resonance are completely suppressed because of the effective superlattice structure, which will effectively reduce the interference during our measurement.
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.
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.
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.
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.
Infrared thermograph technology in the research of laser-matter interaction was discussed. The formation of molten pool and heat transfer and matter transfer in laser repairing cracks of components were investigated using infrared thermal imaging system. Because the software system of HWRX-3 thermovision is not compatible with the present computer and operation system, we discussed several methods, where the compatibility has been solved and the image processing system can be transformed to windows operation system by the redesign software. The friendly user interface and very high visibility of the optimized software have been testified during laser repairing cracks of components processing. One practical method of digital process for the investigation on heat transfer and matter transfer in laser repairing cracks of components has been developed.