A multi-core fiber includes multiple optical cores, and for each different core of a set of different cores of the multiple optical cores, a total change in optical length is detected. The total change in optical length represents an accumulation of all changes in optical length for multiple segments of that different core up to a point on the multi-core fiber. A difference is determined between the total changes in optical length for cores of the set of different cores. A twist parameter and/or a bend angle associated with the multi-core fiber at the point on the multi-core fiber is/are determined based on the difference.

An evaluation method of a silicon wafer allows non-destructive and non-contact inspection of a slip that affects the electrical properties of semiconductor devices, without being subjected to restrictions of the surface condition of silicon wafers or processing contents as much as possible. The evaluation method of a silicon wafer includes a step of section analysis where a surface of a single crystal silicon wafer after thermal processing is divided by equally-spaced lines into sections with an area of 1 mm.sup.2 or more and 25 mm.sup.2 or less and the existence of strain in each of the sections is determined based on a depolarization value of polarized infrared light, and a screening step where the wafer is evaluated as non-defective when the number of adjacent sections being determined to have strain by the section analysis step does not exceed a predetermined threshold value.

An evaluation method of a silicon wafer allows non-destructive and non-contact inspection of a slip that affects the electrical properties of semiconductor devices, without being subjected to restrictions of the surface condition of silicon wafers or processing contents as much as possible. The evaluation method of a silicon wafer includes a step of section analysis where a surface of a single crystal silicon wafer after thermal processing is divided by equally-spaced lines into sections with an area of 1 mm.sup.2 or more and 25 mm.sup.2 or less and the existence of strain in each of the sections is determined based on a depolarization value of polarized infrared light, and a screening step where the wafer is evaluated as non-defective when the number of adjacent sections being determined to have strain by the section analysis step does not exceed a predetermined threshold value.

Methods and systems for measuring optical properties of transistor channel structures and linking the optical properties to the state of strain are presented herein. Optical scatterometry measurements of strain are performed on metrology targets that closely mimic partially manufactured, real device structures. In one aspect, optical scatterometry is employed to measure uniaxial strain in a semiconductor channel based on differences in measured spectra along and across the semiconductor channel. In a further aspect, the effect of strain on measured spectra is decorrelated from other contributors, such as the geometry and material properties of structures captured in the measurement. In another aspect, measurements are performed on a metrology target pair including a strained metrology target and a corresponding unstrained metrology target to resolve the geometry of the metrology target under measurement and to provide a reference for the estimation of the absolute value of strain.

Provided herein are systems and methods for monitoring radial stresses in glass tubing. In some embodiments, a measurement system includes a light source delivering a light to a tube, and a polarizer receiving the light after the light is refracted through a wall of the tube. The measurement system may further include a detector receiving the light from the polarizer, the detector operable to capture a first image of the light at a first polarization state and a second image of the light at a second polarization state. The system may further include a controller operable to determine a retardation profile related to the stress profile of the wall of the tube by determining a retardation magnitude of the light refracted through the wall of the tube based on a difference between the first image of the light and the second image of the light.

Methods, devices and apparatus for measuring expansion/contraction properties of a material are described. According to an embodiment a method comprises: providing a device, said device comprising a sample comprising said material, said sample comprising a first surface and a second surface, a first substrate and a second substrate connected to said first surface and to said second surface of said sample, respectively, a reflective material attached to said second substrate, and two electrical contacts each independently in contact with said sample; applying voltage to said sample using said electrical contacts; illuminating said reflective material using a light source, such that said illumination comprises light having known and controllable polarization; collecting light reflected off said reflective material; measuring amplitude and phase of an oscillating change in polarization of the reflected light; and extracting parameters related to expansion/contraction from said reflected light measurement, thus evaluating said expansion/contraction properties of said material.

A polarization maintaining fiber array includes a substrate, a cover, and at least two polarization maintaining optical fibers. The substrate includes at least two main grooves, a first additional groove, and a second additional groove, wherein the main grooves are positioned between the first additional groove and the second additional groove. The fiber array includes at least two polarization maintaining optical fibers positioned in the at least two main grooves, a first dummy fiber positioned in the first additional groove, and a second dummy fiber positioned in the second additional groove. The cover is positioned such that it contacts the polarization maintaining optical fibers, the first dummy fiber, and the second dummy fiber.

A multi-core fiber includes multiple optical cores, and for each different core of a set of different cores of the multiple optical cores, a total change in optical length is detected. The total change in optical length represents an accumulation of all changes in optical length for multiple segments of that different core up to a point on the multi-core fiber. A difference is determined between the total changes in optical length for cores of the set of different cores. A twist parameter and/or a bend angle associated with the multi-core fiber at the point on the multi-core fiber is/are determined based on the difference.

The hybrid measurement system includes an evanescent prism coupling spectroscopy (EPCS) sub-system and a light-scattering polarimetry (LSP) sub-system. The EPCS sub-system includes an EPCS light source optically coupled to an EPCS detector system through an EPCS coupling prism. The LSP sub-system includes an LSP light source optically coupled to an optical compensator, which in turn is optically coupled to a LSP detector system via a LSP coupling prism. A support structure supports the EPCS and LSP coupling prisms to define a coupling prism assembly, which supports the two prisms at a measurement location. Stress measurements made using the EPCS and LSP sub-systems are combined to fully characterize the stress properties of a transparent chemically strengthened substrate. Methods of processing the EPCS and LSP measurements to improve measurement accuracy are also disclosed.

An optical apparatus includes a coherent light source; a transmission assembly configured to receive light emitted by the coherent light source, split the light into object light and reference light so that the object light and the reference light travel along different paths receive object light reflected by an object to be measured, and combine the object light reflected by the object to be measured and the reference light; and a photosensitive camera disposed at an output of the transmission assembly, and configured to receive combined light and process the combined light to record light intensity information capable of characterizing a spatial position of a surface of the object to be measured.