With the development of science and technology, all teachers in the college will face how to stimulate the undergraduate student’s ability and make them to be an excellent engineer. For solving these questions, a new scheme with three steps has been designed. First, students will participate in the class teaching activity not only teacher. It will encourage them to read many extracurricular books and articles. Second, they will be required to think and design more new experiments after complete all experiment about the textbook and join more competition of the innovation and entrepreneurship. Third, some students who have more time and ability can early enter into his advisor professor’s lab to join various science and technology project. By this scheme, it will be realized to improve student’s innovation ability and be a brilliant engineer.
The inverse Doppler effect in photonic crystal with negative refractive index had been proofed experimentally in our previous research. In this paper, we studied the spatial harmonics of Bloch wave propagating in such PhCs by FFT method. The lagging and front phase evolutions reveal that both backward wave and forward wave exist in these harmonics. Subsequently, we studied the double Doppler effect phenomenon that both the normal and inverse Doppler exist in one photonic crystal simultaneously by using the improved dynamic FDTD method which we made it suitable for dealing with moving objects. The simulative Doppler frequency shifts were consistent with the theoretical values. Our study provides a potential technology in measurement area.
The existence of Gravitational Wave (GW) is one of the greatest predictions of Einstein’s relative theory. It has played an important part in the radiation theory, black hole theory, space explore and so on. The GW detection has been an important aspect of modern physics. With the research proceeding further, there are still a lot of challenges existing in the interferometer which is the key instrument in GW detection especially the measurement of the super large radius optics. To solve this problem, one solution , Fizeau interference, for measuring the super large radius has been presented. We change the tradition that curved surface must be measured with a standard curved surface. We use a flat mirror as a reference flat and it can lower both the cost and the test requirement a lot. We select a concave mirror with the radius of 1600mm as a sample. After the precision measurement and analysis, the experimental results show that the relative error of radius is better than 3%, and it can fully meet the requirements of the measurement of super large radius optics. When calculating each pixel with standard cylinder, the edges are not sharp because of diffraction or some other reasons, we detect the edge and calculate the diameter of the cylinder automatically, and it can improve the precision a lot. In general, this method is simple, fast, non-traumatic, and highly precision, it can also provide us a new though in the measurement of super large radius optics.
The temperature-dependent reflection spectrums of ultrahigh order guided modes of symmetrical metal-cladding waveguide (SMCW) are measured in angular interrogation. The results show that the reflection spectrum is characterized by extremely narrow resonance dip, which agrees well with numerical calculation. Based on the falling or rising edge of resonance dip of ultrahigh order guided modes of SMCW, a temperature sensor with characteristic of high sensitivity is proposed. Meanwhile, by experimentally determine the linear character between the shift of resonance angle and the variation of temperature, a method of angle compensation is put forward to extend the sensing range. Owing to its characteristics of high sensitivity, low cost and easy fabrication, the temperature sensor based on SMCW will be a promising sensor in many fields.
The analysis of the temperature property of sensors based on symmetrical metal-cladding optical waveguide (SMCOW) is focused on analyzing the temperature property of reflectivity of SMCOW sensors, which is theoretically studied with single-factor investigation under spectral and angular interrogation scheme. There are mainly four factors influencing the temperature dependence of reflectivity, it is the temperature dependence of refractive index and thickness of guiding layer, along with the temperature dependence of the metal film thickness and metal-dielectric function. The simulation result shows that the effect of temperature on the reflectivity of SMCOW is mainly attributed to the temperature dependence of refractive index and thickness of guiding layeron the contrary, the temperature properties of metal film hardly contributes to the influence of temperature on the reflectivity. Based on the analysis, the sensitivities of SMCOW with guiding layer of different optical glasses are computed under both spectral and angular interrogation. This paper is supposed to provide direction in designing temperature-sensitive SMCOW structure sensors.
The paper is mainly concerned with the study of the PBG (Photonic Band Gap) in 2D photonic crystal which consists of a
hexagonal lattice of circular dielectric rods with Polyethylene. The result indicates that its PBG is very narrow.
According that, a narrow band filter has been obtained by choosing certain parameters of the photonic crystal.
A new kind of birefringence is found in a two-dimensional (2D) flat perfect photonic crystal (PhC). It is different from
the one in the normal biaxial crystal, but qualitative, and comes from the positive and negative refraction in the 2D flat
perfect PhC. The quantitative relationship between the refractive index and the incident angle are plotted, by the analysis
of the equal-frequent surface (EFS) of the perfect PhC. The plot is consisted of three branches---the main across 0° to
45.53° of the incident angle, the upper across 33.3° to 38.53° and the lower across 38.53° to 45.53°. The upper reveals the
positive refraction; the lower and the main reveal the negative ones. The finite-difference time-domain (FDTD)
simulations are performed, and the relevantly quantitative measurement validates the quantitative relationship by the
analysis of the EFS, but a 2.67° shift to the bigger incident angle.
A novel beam guiding is observed, which is resulted not from the guiding in a defect photonic crystal (PhC) but from the
negative refraction in a two-dimensional (2D) flat perfect PhC slab.
Many changes of various parameters in photonic crystal cause changes of band structure and thus cause changes of light propagation through photonic crystal. The paper is mainly concerned with the study of negative refraction phenomenon dependent on wave guide width in 2D photonic crystal which consists of a hexagonal lattice of circular dielectric rods with Si. It is separately carried on the elaboration from three aspects: along with the accretion of wave guide width in photonic crystal, how the incident light frequency range in which the negative refraction phenomenon presents is changed; under identical incident light frequency, if the negative refraction phenomenon presents, then what the transformation of corresponding negative refractive index is ; if the value of refractive index of -1 is obtained, what the trend of e incident light frequency is.
The paper is mainly concerned with the study of negative refraction phenomenon dependent on the incident light frequency in 2D photonic crystal which consists of a hexagonal lattice of circular dielectric rods with Si. The result indicates that along with the accretion of incident light frequency, the angle of refractive light and negative refractive index in absolute terms become smaller gradually. This law offers an application of differentiating two close incident light frequencies. And a sample has been made successfully to realize negative refraction phenomenon.
Based on unbalanced Mach-Zehnder interferometers, a novel electrooptical waveguide tunable filter is proposed and designed. By coupled-mode equations method and beam propagation method, the variation of the output light intensity versus applied voltage and frequency is analyzed for a single filter. Then several filters are combined to filtrate and route one of several frequencies, and a good result is obtained.