Der-Chin Su’s research while affiliated with National Yang Ming Chiao Tung University and other places

... In the laboratory, spectroscopic methods [13] are often used. Spectroscopic methods mainly use light refraction [14], interference [15], diffraction [16] and other characteristics to measure solution concentration indirectly. Although the technology of these methods is relatively mature, this approach often needs complex experimental equipment and is expensive. ...

Reference:

A instrument for measuring solution concentration

... In this paper, we propose a new method for accurately measuring the geometrical thickness of a transparent plate by using the heterodyne central fringe identification technique [11]. In a modified Twyman-Green interferometer with a polarization beam splitter (PBS), a high-precision translation stage (TS) is used to displace the reference mirror in one arm and a long working distance MO is located with the test transparent plate in the other arm. ...

Reference:

High-accuracy thickness measurement of a transparent plate with the heterodyne central fringe identification technique

... The authors concluded that aberrations adversely affect self-images, especially those located at higher-order Talbot planes; even the contrast inversion in fringes is observed. Toward resolving the issues stated above, researchers investigated gratings/structures other than the "linear," such as dual-field, evolute, spiral, triangular, and circular [25][26][27][28][29][30][31], for improved accuracy. ...

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MSE-based analysis of circular grating self-images for testing beam collimation

... Conventionally, the Jamin-Lebedeff interferometer uses orthogonal linear polarization states and is able to determine refractive indices of crystals and biological materials [3,6], improve the contrast in microscopic imaging [7,8] and measure refractive indices of metallic nanostructures [9]. Common-path interferometers exist that take advantage of circularly polarization states and that are able to measure not only conventional refractive indices [10][11][12], but also the circular birefringence, i.e. the difference (n L -n R ) [13]. However, an interferometer that can determine the circular-polarization (CP) dependent refractive indices n L and n R has, to the best of our knowledge, not been reported. ...

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Circular polarization interferometry: circularly polarized modes of cholesteric liquid crystals

... They are potentially easier to fabricate than the thin-film filters, and, when they are incorporated into planar configurations, alignment problems are greatly alleviated. [5][6][7][8][9] Most of these configurations involve two gratings, one grating for dispersing and separating wavelength channels and an output grating for coupling the light outward. In general, such grating-based configurations have either nonuniform throughput light efficiency among different wavelength channels or gradual roll-off rather than a cutoff spectral profile. ...

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Formation of a planar coarse wavelength-division multiplexer and demultiplexer with reflection volume phase gratings

... Biological applications of ellipsometry include the measurement of the thickness of macaque retinal nerve layers [19], which was measured to be between about 20 µm and about 215 µm. A related technique called circular heterodyne interferometry uses the reflection of a rotating linear polarisation and detection of the angle of maximum transmission through an analyser to retrieve thickness and refractive index by measuring at two analyser angles [20]. Spectroscopic ellipsometry, combining measurements at multiple wavelengths, has been employed to determine the thickness and (by studying absorption bands) the chemical composition of silane films several hundred nanometres thick [21], as well as to measure the thickness and electric permittivity of nanometric tellurium layers and decananometric polypyrrole layers [22]. ...

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Simultaneous microscopic imaging of thickness and refractive index of thin layers by heterodyne interferometric reflectometry (HiRef)

... In addition to the above several configurations, according to the optical path structure and the position of the microscope, the commonly used microscopic interferometry systems can be divided into three types: Michelson type [16][17][18][19], Mirau type [20][21][22][23][24] and Linnik type [25][26][27][28][29][30][31][32][33]. For example, Wiersma, J.T. used the Michelson microscopic system and synchronous phase sensor to realize high precision and repeatable measurement of common vibration [19]; Schmit, J. proposed an improved Mirau interferometer, which can generate orthogonally polarized output beams, and can obtain better fringe contrast by introducing achromatic phase shift [21]; Somekh, M.G. realized a plasmon microscope with sub-micron resolution by using the Linnik interferometer with speckle illumination [26]; Li, X.D. of Tsinghua University measured the thermal deformation of copper microbridges with different sizes (the maximum size is 2175 µm × 1009 µm) in real time using the Linnik microscopic interferometry system, and the accuracy reached submicron level [33]. ...

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An Improved Large-Field Microscopic Speckle Interferometry System for Dynamic Displacement Measurement of MEMS

... Although the relative thickness and the refractive index of the sample can be obtained directly, it takes a long time to finish a whole testing or it is very difficult to adjust the optical components precisely. In recent years, the He-Ne laser is often used as the laser source in the heterodyne interferometry [7][8][9], and the light beam is often incident on the front surface and reflected by the sample in such an interferometer system. So only the related information of the surface profiles of the sample can be obtained. ...

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Fiber-coupled near-infrared laser heterodyne interferometer with fast optical scanning

... For convenience, the +z axis is set as the light propagation direction and the +x axis is set as perpendicular to the paper plan. When the circularly polarized heterodyne light source that consists of a tunable laser, an electro-optic modulator (EO) (with fast axis lying at 45°), a function generator FG, linear voltage amplifier (LVA), and a quarter wave plate Q (with the fast axis lying along the xaxis), as shown in Fig. 2 [14,15], passes through a cholesteric liquid crystal cell with a thickness of d, its Jones vector E 1 of electric field can be written as ...

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Simple method for the measurement of small wavelength differences by optical activity of cholesteric liquid crystal and heterodyne interferometer

... Several refractometers were presented to measure the refractive index of liquids [1][2][3][4][5][6][7][8][9][10][11]. The principles of operation are in general based on the concepts of geometrical optics or wave optics. ...

Reference:

An imaging refractometer