Fizeau Interferometery for THz-Waves' Frequency and Intensity Measurement

A terahertz-wave generator based on optical parametric oscillator principle, detection based on combination of Fizeau wedged interferometer and an electro-optical crystal ZnTe has been studied. The analytical solution based on the basic principle of operation of solid wedge Fizeau interferometer has been realized. The mathematical calculations for THz frequency and intensity measurement dependent on wedge angle and fringe spacing have been considered. The efficiency of THz wave detection depends upon optimized wedge angle has been also realized. The feasibility of detection of THz waves＇ frequency and intensity by solid Fizeau interferometer （THz-waves＇ range of 1 - 3 THz） has been studied. By optimization of other parameters like thickness of Fizeau film, refractive index, material of Fizeau film, we can proceed towards the design of Fizeau interferometer for required research plans as it is a simple and inexpensive interferometer.

Fiber Fabry-Perot Demodulation System Based on Dual Fizeau Interferometers

In this study,we present a dual-Fizeau-interferometer-based high-speed and wide-range fiber-optic Fabry-Perot(F-P)demodulation system.We employ two Fizeau interferometers with air cavity thickness satisfying the quadrature requirement to increase the demodulation speed and broaden the demodulation range in order to address the issues of the existing fiber F-P demodulation system's sluggish demodulation rate and limited range.In order to investigate the demodulation properties of the dual-Fizeau-interferometer-based demodulation system,we derive and create a theoretical model of the system.The theoretical model,which primarily consists of the structural design of the interferometer and the study of the center wavelength of the light sources and their bandwidth selection,is used to construct the optical structure of the demodulation system.According to the calculation results,the demodulated signal exhibits the best contrast ratio when the two light sources'respective center wavelengths are 780nm and 850nm,and their bandwidths are 28nm and 30 nm.Finally,we finish evaluating the demodulation system's demodulation performance,parameter calibration,and assembly debugging.The test results demonstrate the constant operation of the demodulation system,an update rate of 100kHz,a demodulation range of 4.74μm,and a cavity length resolution of approximately 5 nm.Additionally,the system can perform high speed demodulation thanks to the light emitting diode's(LED's)nanosecond level switching speed and the usage of a single point detector.

Tilted Wave Fizeau Interferometer for flexible and robust asphere and freeform testing

Tilted Wave Interferometry(TWI)is a measurement technique for fast and flexible interferometric testing of aspheres and freeform surfaces.The first version of the tilted wave principle was implemented in a Twyman-Green type setup with separate reference arm,which is intrinsically susceptible to environmentally induced phase disturbances.In this contribution we present the TWI in a new robust common-path(Fizeau)configuration.The implementation of the Tilted Wave Fizeau Interferometer requires a new approach in illumination,calibration and evaluation.Measurements of two aspheres and a freeform surface show the flexibility and also the increased stability in both phase raw data and surface measurements,which leads to a reduced repeatability up to a factor of three.The novel configuration significantly relaxes the tolerances of the imaging optics used in the interferometer.We demonstrate this using simulations on calibration measurements,where we see an improvement of one order of magnitude compared to the classical Twyman-Green TWI approach and the capability to compensate higher order error contributions on the used optics.

Absolute Measurement Fiber-optic Sensors inLarge Structural Monitoring

The security of civil engineering is an important task due to the economic, social and environmental significance. Compared with conventional sensors, the optical fiber sensors have their unique characteristics.Being durable, stable and insensitive to external perturbations,they are particular interesting for the long-term monitoring of civil structures.Focus is on absolute measurement optical fiber sensors, which are emerging from the monitoring large structural, including SOFO system, F-P optical fiber sensors, and fiber Bragg grating sensors. The principle, characteristic and application of these three kinds of optical fiber sensors are described together with their future prospects.