Ultrathin Picoscale White Light Interferometer

White light interferometry is a well established technique with diverse precision applications, however, the conventional interferometers such as Michelson, Mach-Zehnder or Linnik are large in size, demand tedious alignment for obtaining white light fringes, require noise-isolation to achieve sub-nanometric stability and importantly, exhibit unbalanced dispersion causing uncertainty in absolute zero delay reference. Here, we demonstrate an ultrathin white light interferometer enabling picometer resolution by exploiting the wavefront division of a broadband incoherent light beam after transmission through a pair of micrometer thin identical glass plates. Spatial overlap between the two diffracted split wavefronts readily produce high-contrast and stable white light fringes, with unambiguous reference to absolute zero path-delay position. The colored fringes evolve when one of the ultrathin plates is rotated to tune the interferometer with picometric precision over tens of µm range. Our theoretical analysis validates formation of fringes and highlights self-calibration of the interferometer for picoscale measurements. We demonstrate measurement of coherence lengths of several broadband incoherent sources as small as a few micrometer with picoscale precision. Furthermore, we propose a versatile double-pass configuration using the ultrathin interferometer enabling a sample cavity for additional applications in probing dynamical properties of matter.

Effect analysis of surface metal layer on step height standard

In order to improve the measurement accuracy of the step height measuring instrument, a semiconductor process was used to prepare the step height standard for calibrating the instrument. Aiming at the problem of deviation in the white light interferometer measuring step height standard, the cause of the measurement deviation was theoretically analyzed, combining the optical theory and the principle of instrument. In addition, referring to the semiconductor sputtering process, a method of sputtering metal layer on the surface of the step structure was proposed, and a set of universal step height standards with a nominal value of [Formula: see text] nm were developed for the step height measuring instrument. Finally, the step height standards with the sputtered metal layer were compared and measured, using the white light interferometer and nanometer measuring machine (NMM). The measurement error of the white light interferometer can be effectively controlled within 1%, which is beneficial to verify the measurement capability of the step height measuring instrument.

GHz-SAM for Warped Samples using HiSA

GHz-SAM using toneburst transducers is a method currently lacking the possibility to measure warped samples easily because large parts of such samples are out of focus due to the limited depth of focus of these types of transducers. This paper shows an approach to use the already established HiSA (High Speed Axis) method to overcome this disadvantage. Therefore warpage of the sample is measured by a white-light interferometer. The detected bow is parametrized and submitted in the control electronics of the HiSA. With this data the HiSA is enabled to keep the distance between sample and transducer precisely constant. This allows eliminating the influence of the warpage on the performance of this method and therefore highly increases the image quality.