A guided-wave surface plasmon resonance based sensor using graphene layer for detect the biomolecules has been analyzed. The use of waveguide layer between the gold film and graphene significantly improves the penetration depth and increases the sensitivity, then graphene layer is used to enhance the adsorption of the biomolecules. The thickness and materials of waveguide layer along with the number of graphene layer have been optimized to achieve the best performance of the sensor in terms of sensitivity. The highest sensitivity with 228.8°/RIU is obtained for visible wavelength with optimized thickness of gold and waveguide layer as 45nm and 10nm respectively while the materials of waveguide layer is chosen as zinc oxide and the optimum number of graphene layers is 2.We believe that this sensor could find potential applications in biological detection.
In order to explore the key factors of the SPR effect, such as sensitive material, thickness of sensitive metal film, incident angle and wavelength, especially the affection of the incident light wavelength on the modulated reflectivity, calculations and analyses are carried out in this paper. Simulation results show that Ag has the lowest reflectivity when the incident light with shorter wavelength in visible wave band, Au has the lowest reflectivity with red light, and Cu has the best effect from 600 nm to infrared band. The ranges of thickness measurement for thin films can be obtained when the light source wavelength and incidence angle are fixed with the adopted metal sensitive material. Moreover, there is a special range of incidence angle that can put up a significant SPR effect phenomenon when there are definite metal films and wavelength of incident light.
In this paper, the impacts of surface plasmon resonance (SPR) on the angular spin splitting of light are investigated theoretically. The expression for the angular spin splitting shifts is derived, and the angular shifts as the function of the angle of incidence under different metal film thicknesses are calculated. The simulation results manifest that the angular spin splitting is significantly enhanced when surface plasmons are strongly excited. Under the optimal parameter conditions, the largest angular shift is up to 4.493×10-5 rad. It is also found that the directions of spatial propagation of photons in the out-of-plane can be switched by adjusting the angle of incidence under certain conditions. These findings may provide a new way for photon manipulation and open another possibility for the development of new nano-photonic devices.
In this letter, we theoretically investigate the impact of the incident light polarization on photonic spin splitting induced by the photonic spin Hall effect when a linearly polarized Gaussian beam is reflected from an air-glass interface around the Brewster angle. We calculate the spin splitting shift as a function of the incident light polarization under different incident angles. We find that a tiny variation of the incident light polarization can result in a dramatic change of the spin splitting shift, and the highest sensitivity is up to 6.8 μm/deg . The largest splitting shift can reach 5.3 μm, which is larger than the previously reported values. We also find that the direction of spin accumulation of photons with different spin directions can be switched by adjusting the incident angle around the Brewster angle when the incident light polarization is near the p-polarization. These findings may be useful for precise polarization metrology and photon modulation.
A mathematic model based on surface plasmon resonance (SPR) effect is presented to measure the nano metallic film
thickness with the coupling device of Kretschmann configuration composed of K9 prism-gold film-air. Four modulation
modes of SPR method, such as intensity, phase, wavelength and angle, are numerically analyzed. Their detection
principles, the measurement range and sensitivity of different modulation type sensors are discussed. The simulation
results show that the SPR intensity detection method has the highest measurement range and the SPR phase detection
method has the highest sensitivity. In practical applications, not only the measurement range and sensitivity, but the
optical signal processing mode, experiment devices, the complexity of the algorithm and cost factors should be
considered to research and develop the appropriate thin metallic film's thickness measurement SPR sensor with higher
sensitivity and stability.
The evanescent wave, occurred when the incident light generates total internal reflection on the interface between glass and metallic film, can raise the surface plasmon (SP) on the metallic film. SP and evanescent wave can resonate under certain angle of incidence when they have the same frequency and wave number. In this case, the power of reflection beam decreases dramatically, and the resonance peak appears in the reflection spectroscopic. The positions of resonance peaks are different when the refraction indexes of medium on the metallic film or the thicknesses of the metallic film are different. And it is found that the phase position of p-component of reflected light changes with the metal film thickness, while the phase position of s-component almost doesn’t change in the Surface Plasmon Resonance effect. S-polarized light is taken as reference and interferometry is adopted to turn the change of the phase position into the change of interference fringes position in the paper, and the film thickness can be derived from it. The simulation results indicated that, through making use of piecewise quadratic fitting on the phase data, the inaccuracy with the range of film thickness is between 30 and 80 nanometers is not more than 0.33 nm.
In the three-dimensional angle measurement, yaw and pitch angle can be detected easily by several convention optical devices. While the roll angle is difficult to measure since its rotation axis is parallel to the incident plane. This work is based on the application of the Talbot effect with a Ronchi grating. The period of Moiré fringes which generated by two gratings will be changed with small rotation. The roll angle can be calculated by the width change of fringes.
To improve dynamic measurement performance and resolution, an optimum design on two-dimensional (2D) micro-angle
sensor based on optical internal-reflection method via critical-angle refractive index measurement is presented in
the paper. The noise signals were filtered effectively by modulating laser-driven and demodulating in signal proceeding.
The system's accuracy and response speed are improved further by using 16-bit high-precision AD converter and
MSP430 CPU which present with a high-speed performance during signals processes such as fitting angle-voltage curve
through specific arithmetic, full range and zero point calibration, filter, scaling transformation etc. The experiment
results indicated that, dynamic signal measurement range can be up to ±600arcsec, the measurement resolution can be
better than 0.1arcsec, and the repeatability could be better than ±0.5arcsec.
In this paper, tunneling phenomena of tunneling junctions are studied and analyzed. Tunneling junction is the basic
structure of single electric transistor (SET) and other nano devices. Ultra fine oxidized titanium (Ti) lines are formed on
the Ti layer, which is 3nm thick and sputtered on a SiO2 substrate by magnetron sputtering. The atomic force microscope
(AFM)'s tip is used as a selective anodization electrode to oxidate the Ti film between electrode structures that are
formed by photo lithography. Ti-TiOx-Ti forms metal-insulator-metal (MIM) tunneling junction, and TiOx works as an
energy barrier for the electron. Different number of TiOx lines is fabricated between two electrodes by controlling
fabrication condition and environment at the same value. And then, the I-V characteristics of tunneling junctions with
different number of TiOx lines are measured. The results indicate that the tunneling phenomena of tunneling junctions
with different number of TiOx lines are different.
Titanium film with about 3nm thickness is deposited on SiO2-Si substrate with dual facing targets sputtering method. Nano-oxidation lines are fabricated on this Ti film with various biased voltages and for the first time, current monitoring is performed during the oxidation process using a contact-mode AFM. In the cases of all lines, a flow of current began immediately when the biased voltage was applied and it kept almost unchanged as each of the oxide line was growing. The level of detected currents during the fabrication of oxide lines on Ti film is in the microampere (μA) level. The detected currents increase linearly with the biased voltages, which indicates that the detected current is mainly tunneling current. Thus, the process of nano-oxidation of Ti film is controlled either by the tunneling of electrons or holes through the Ti/water interface.
In this paper, the principle and characteritics of an optical critical angle sensor based on the internal-reflection effect are introduced. Then, the method to design the optical parameters of the critical angle prisms and the relationship between these parameters and the system character are discussed with analytical and simulation results. These parameters include the initial angle of incidence, non-parallelism errors of the two parallel faces, and the surface flatness of the reflection faces. A pair of custom-built critical angle prisms providing three internal-reflections is used in our simulation. With the initial angle error is 20 arcsec, the matched non-parallelism errors of the prisms are 30 arcsec and the surface flatness is λ/8, the sensitivity of the system is better than 0.05 arcsec and the nonlinearity is less than 0.3%.
With the development and application of nanofabrication on nano photoelectron device, the completely oxidized thin metal film such as titanium film by Atomic Force microscope (AFM) tip induced oxidation method has been used to make various nano electric devices. It is more and more important to study the process mechanism for improving the operational stability and reliability of such nano devices. In this paper, the mechanism of AFM tip induced oxidation is analyzed with several aspects. According to the experimental results of AFM tip induced oxidation of titanium under various voltage biases and scanning speeds, we find that the height of the titanium oxidation is linear with the voltage bias and with the negative log of the scanning speed. Based on the formers’ theories, the mechanism and the theoretical modeling of AFM tip induced oxidation are improved. By setting the proper conditions such as voltage bias of 8V and
scanning speed of 0.1μm/s, good nanofabrication results with AFM oxidation of titanium are got and the oxide lines are with good aspect ratio and good continuity.