In this paper, an optical fiber biosensor based on multiple total internal reflections in heterodyne interferometry is
proposed. The sensor is made of a long U-shaped multimode optical fiber which cladding is removed from the sensing
portion of the fiber. With the optical fiber biosensor the phase shift difference due to the multiple total internal
reflections (MTIR) effect between the P and S-polarizations is measured by using heterodyne interferometry with the
optical fiber biosensor. Substituting the phase shift difference into Fresnel's equations, the refractive index for the tested
medium can be calculated. The resolution of the sensor can reach 1.58×10-6 refractive index unit (RIU). The optical
fiber biosensor could be valuable for chemical, biological and biochemical sensing. It has some merits, such as, high
resolution and stability, small size and real-time measurement.
A new idea for a D-type optical fiber sensor based on Kretschmann's configuration is proposed. The sensing device is a D-type single mode fiber with a half-polished core, and a thin film layer of gold deposited on the flat side of the sensor. In order to achieve the best sensitivity of the D-type optical fiber sensor, we must choose suitable parameters, e.g., the thickness of the thin film layer of gold and the length of the sensor. We found that the experimental results are in good correspondence with theoretical results. The sensor's sensitivity can reach 2×10–4 refractive index unit (RIU) at least. Because the sensor has some merits, e.g., small size, less costly, smaller sample volume, easy measurement, and suitability for in vivo testing, etc., the D-type optical fiber sensor is valuable for chemical, biological, and biochemical sensing.
A heterodyne dispersion meter based on total-internal reflection effects and common-path configuration is presented. It is used to measuring the dispersion power of an optical material or component for many applications in industries. The phase difference between S and P-polarizations at the total-internal reflection condition can be extracted and measured accurately by using heterodyne interferometry. The constants of dispersion formulas built by traditional ways could be revised by this method. It has some merits, such as, high resolution and stability, easy to operate, and real-time measurement.
A new method for measuring a very small displacement is presented. The principles of the measurement are based on the critical angle method and confocal technology. It will increase the lateral and longitudinal resolutions higher than 0.3μm and 5nm, respectively, and the maximum displacement could be above 12μm. This optical structure could be applied to measure some messages for optical surface, bio-medical science, and nanotechnology in the future. The new technique has some merits, such as a simple and compact optical setup, high sensitivity, and high resolution.
A new type of fiber optical liquid refractometer based on total-internal reflection heterodyne interferometry (TIRHI) is proposed. The phase shift difference due to the TIR effects between the P and S-polarizations is measured using heterodyne interferometry with a D-type fiber sensor. Substituting the phase shift difference into Fresnel's equations, the refractive index can be calculated. It has some merits, such as, high sensitivity and stability, small size and real-time measurement.
As for our knowledge, a simplest real-time system for measuring dynamic optical phase perturbation is proposed and demonstrated. In this system a 1% weight Fe:LiNbO3 is used to record the self-interference grating by the incident light. The interferometer is a new kind of double-exposure one. The speed of the interferometer is as fast as that of the dynamic phase perturbations.
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