Differential interference in a polymer waveguide

Abstract

Abstract. The paper presents the results of investigations concerning the measurement of the refractive index and the thickness of planar waveguide structures, obtained by photo polymerization of the polymer SU8. In the paper the mode sensitivity has been calculated as a function of the thickness in a single-mode structure. The thickness of the layer has been determined in the case when the interferometer is most sensitive to changes of the refractive index.

The Sensitivity of Composite Bimodal Waveguide SU-8

“…In the waveguide two modes are excited, and a change of the refractive index of the cover involves changes of the eective refractive indices of the guided modes. The sensitivity of the dierential interferometer S D {n C } can be determined as dierences of the mode sensitivity S i {n C } and S j {n C } of the guided modes [7]:…”

Bimodal Layers of the Polymer SU8 as Refractometer

“…In the waveguide two modes are excited, and a change of the refractive index of the cover involves changes of the effective refractive indices of the guided modes. The sensitivity of the differential interferometer S D {n C } can be determined as differences of the mode sensitivity S i {n C } and S j {n C } of the guided modes [9]: In the range of thicknesses of the waveguide layer from 0.94μm to 1.54μm the three-layer structure is a bimodal structure for the polarizations TE and TM. In such a structure the modes TE 0 , TE 1 , TM 0 , TM 1 In the course of recent years the application of various orders in the construction of a differential interferometer has been suggested [15][16][17][18].…”

“…In order to determine the refractive index of a step-index waveguide structure, based on the polymer SU8, the numerical method was applied, requiring the determination of the effective refractive indices for each observed mode. By means of mode spectroscopy a set of effective refractive indices was determined for the wavelength 633nm, concerning the planar waveguides [9][10]. The synchronic angle was measured for the polymer waveguides obtained at rotational speeds of 2000rpm, 3000rpm and 5000rpm.…”

Spectropolarimetric analyses of optical single mode SU8 waveguide layers

“…Almost always the reading system works on the following principle: a change of the measured parameter is converted to a change of the properties of the optical beam in the measurement system, leading to changes in the intensity of light recorded by the detector. One of the commonly used sensor systems is the differential interferometer, based on planar waveguides [8][9][10][11].…”