Papers by Keyword: Fabry-Perot Interferometer

Abstract: We studied numerically and experimentally the possibility of the development of a novel probe based on the fiber Fabry-Perot interferometer with an evanescent light source protruding directly toward the sample. It was shown that such probe provides a spatial resolution ~λ/40 for λ=1550 nm. The fabrication process of such a probe is described in detail.

Abstract: This paper presents a polymer diaphragm based Fabry-Perot (F-P) sensor system for aeroacoustic measurement in air. The diaphragm of a novel polymer material poly phthalazinone ether sulfone ketone (PPESK) is used as the sensing element. The effective dimension of the diaphragm is 1.0mm in diameter and 6μm in thickness. Thanks to the good mechanical feature of the material and the interferometric-intensity demodulation mechanism, the sensor diaphragm shift sensitivity of 0.72 nm/Pa, correspond to an acoustic pressure to voltage sensitivity of 5.56mV/Pa has been achieved. Experimental results showed that the characteristics of the sensor system is comparable with traditional electrical microphone in frequency range 100Hz to 1kHz and the sensor has the potential to be used as an optical microphone.

Abstract: The possibility of constructing terahertz Fabry-Perot interferometer using metallic meshes with micrometer period and high ratio of linewidth/period is investigated, and the effectivity of traditional equivalent circuit method is verified by FDTD method. Simulation shows that the reflectance and transmittance of this kind of meshes calculated by equivalent circuit method have considerable deviation from those obtained by vector analysis of FDTD, so equivalent circuit method can be used to roughly evaluate the properties of this kind of metallic meshes. By using a metallic mesh with the period of 5 micrometers and the ratio of linewidth/period of 0.8, a finesse larger than 1100 can be achieved while the peak transmittance is still larger than 0.2 for a Fabry-Perot interferometer. It is therefore concluded that a high-quality terahertz Fabry-Perot interferometer can be constructed by using metallic meshes with micrometer period and high ratio of linewidth/period.

Abstract: The construction of Fabry-Perot interferometer is very simple and it has been already utilized in different measurement systems. The result of displacement measurement is obviously influenced by the tilt angles of measurement mirror, if a Fabry-Perot interferometer is utilized for displacement measurement. Hence, the measuring range of current systems is rather small (less than 1 mm). The goal of this investigation is to develop a Fabry-Perot interferometer for large travelling range (till 60 mm) by aid of compensation of tilt angles with an angular sensor, piezo translators, control mechanism and self-designed software. To verify the measuring characteristic of the self-developed Fabry-Perot interferometer, some comparison measurements have been performed. A commercial laser interferometer serves as reference standard and the differences between Fabry-Perot interferometer and the commercial Laser interferometer are measured. Through experimental tests, the differences are less than 0.3 m in the full measurement range. The results show that the Fabry-Perot interferometer can meet the measuring requirement with high accuracy of sub-micrometer order and large measurement range.

Abstract: A Fabry-Perot self-collimation interferometer (FPSI) constructed in a two-dimensional photonic crystal (2D PhC) by liquid crystal infiltration has been proposed and demonstrated theoretically. The resonant cavity of FPSI is infiltrated with a nematic liquid crystal (LC) 5CB with ordinary and extraordinary refractive indices 1.522 and 1.706, respectively. The transmission spectrum of the FPSI has been investigated with the 2D finite-difference time-domain method. Calculation results show that resonant transmission peaks have nearly equal frequency spacing 0.0090c/a. When the effective refractive index neff of the liquid crystal is increased from 1.522 to 1.706, the peaks shift to the lower frequencies over 0.0071c/a while the peak spacing is almost kept unchanged. Thus this FPSI by LC infiltration can work as a tunable attenuator or an optical switch. For the central operating wavelength around 1.55m, its dimensions are only about tens of microns. Thus this device may be applied to photonic integrated circuits.

Abstract: Contact type detection, one of UT for the detection of defects in welding area, has several weak-points. Proximity type ultrasonic inspection using laser is being studied these days to make up for the weak points of contact type ultrasonic inspection. In this paper, automatic inspection system of the welding area of spiral welding pipe has been developed, of which mechanical characteristic is better than that of circular directional pipes, and executed the proximity ultrasonic inspections using laser. The usefulness of proximity ultrasonic inspection using laser will be verified in this paper through the analysis of the inspection results.