The increasing of demands for high precision positioning and length measuring tasks needs improved solutions for the length metrology. Laser interferometers are established instruments for measurements of the displacement, angles, straightness and vibration with lowest uncertainty and high resolution.
The talk gives an overview over the current achievements in the field of the laser interferometry and shows applications of the interferometric method of measurements for applications with highest demands on precision and ultra-stability.
Multi-beam laser interferometers play an increased role in the length metrology and allow compensation of the geometrical errors of the measuring application. A one common coherent laser used for all interferometric channels is a basis for reliable and traceable results. The highest stability of the measurements can be achieved if optical setup of the system is based on the differential principle. In this case a part of the light path in air can be optically compensated and is not influenced by the fluctuations of the air refractive index.
The presentation will show, based on the physical background of the laser interferometry, measuring arrangements of the multi-beam interferometers for simultaneous measurements of several degrees of freedom of the displacement as well the achievable results for the setups based on differential principal of laser interferometry.

1988 to 1994: Study of the measuring technology at the National Technical University in Kiew, Ukraine
1995 to 2001 PhD work at the Technical University of Ilmenau, Germany at the field of laser vibrometry
2002 - 2010 Project manager and R&D engineer at SIOS Messtechnik
2010 - 2016 Director of Research and Developments of SIOS Messtechnik GmbH
Since 2016: Managing director of SIOS Messtechnik GmbH

The continued shrink in semiconductor devices drives lithography requirements to extreme levels that results in the need for a robust control of the patterning process. This asks for continued improvements of metrology of CD and overlay in terms of speed, robustness, precision and accuracy. In this talk we will present some of the optical metrology techniques that are being used today. We will discuss the challenges that metrology is facing today and we will give an overview of the progress that is being made in dealing with these challenges.

Arie den Boef worked at Philips Research Laboratories from 1979 till 1992 in the area of laser diodes and optical interferometry. In 1991 he received a Ph.D. degree from the University of Twente with a thesis titled “Scanning Force Microscopy using Optical Interferometry”. From 1992 till 1995 den Boef worked at Philips Medical Systems on Magnetic Resonance Imaging and in 1995 he worked as system engineer on CD-Recordable systems. In 1997 he joined ASML where he started exploring optical sensors with emphasis on wafer alignment sensors and scatterometry for CD and overlay metrology. Den Boef was appointed part-time full professor in 2016 at the Vrije Universiteit of Amsterdam in the area of “nano-lithography and metrology”. At the university he is teaching a course on optical wafer metrology techniques and he has set-up a small research group that explores new optical techniques for metrology.

The identification of the authenticity, brand, age of Chinese liquors objectively and accurately through scientific method is an urgent need for the market supervision. The spectroscopic technology is introduced in the detection of Chinese liquors. However, the spectral complexity of the multiple-component system limits the direct analysis. We use a variety of mathematics algorithms, wavelet transformation, parallel factor analysis, non-negative matrix decomposition, partial least squares, to realize the spectral data matrix decomposition and reconstitution. The fingerprint spectra and characteristic database of Chinese liquors are established. Artificial neural network is used to find the nonlinear relationship between the spectral characteristics and the information of the Chinese liquors. The support vector machine, the Euclidean distance and the threshold determination algorithm are also used for accurate identification of Chinese liquors.

Prof. Chen is the dean of School of Science, Jiangnan University and the president of Wuxi Physical and Mathematical Society. He has been long involved in research on the application of spectroscopic technology in food safety. Up to now, Prof. Chen has led and participated as the backbone member in 10 projects funded by the NSFC, National Key R&D Program of China and other provincial and ministerial foundation Meanwhile, Prof. Chen has already published 10 textbooks and more than 100 academic papers so far, most of which are SCI and EI indexed. 6 inventive patents have been granted. Moreover, Prof. Chen has received awards of third prize in Science and Technology Progress in Wuxi, and second prize for Science and Technology Progress of China National Light Industry Council.

Imaging through multiple-scattering media, or turbid media, is scientifically challenging but very attractive for numerous applications. For example, diffuse optical tomography is becoming a potential imaging modality for breast cancer early detection. We have been developing new approaches that addressed fundamental challenges of acquiring more useful information from diffusive photons and solving inverse problem of light transport in turbid media. The integrated image reconstruction framework leverages on the power of data-driven machine learning techniques and physics-driven regularization techniques, built upon big data collected from practical imaging systems, which performs Laplace domain optical measurements directly to enhance the signal to noise ratio and image quality.

Dr. Chen Nanguang is currently an Associate Professor of Biomedical Engineering at the National University of Singapore (NUS). He received his PhD in Biomedical Engineering in 2000 from Tsinghua University. He also received his MSc in Physics and BSc in Electrical Engineering in 1994 (Peking University), and 1988 (Hunan University), respectively. He joined the Optical and Ultrasound Imaging Lab at the University of Connecticut in 2000 as a postdoctoral fellow and then became an Assistant Research Professor in 2002. Since 2004, he has been a faculty member with NUS. His research interests include diffuse optical tomography, optical coherence tomography, and novel fluorescence microscopic imaging methods. He has published more than 70 papers in international leading journals and holds 5 international patents.

Optical scatterometry is one of the most important techniques for measuring the critical dimension and overlay of nanostructures in current semiconductor manufacturing due to its inherent noncontact, nondestructive, time-effective, and relatively inexpensive merits over other metrology techniques, such as scanning electron microscopy and atomic force microscopy. Along with the advantages of optical scatterometry, there are some challenges or limitations to this technique with the ever-decreasing dimensions of advanced technology nodes, such as the parameter correlation issue. In addition, optical scatterometry is mostly suitable for measuring repetitive dense structures while infeasible for the measurement of isolated or the general non-periodic structures. To address the challenges or limitations in conventional optical scatterometry, we have recently developed a novel instrument called the tomographic Mueller-matrix scatterometer (TMS). The TMS illuminates sequentially a sample by a plane wave with varying illumination directions (incidence angles 0~65.6° and azimuthal angles 0~360°) and records, for each illumination direction, the polarized scattered filed along various directions of observation (scattering angles 0~67°) in form of scattering Mueller matrices. Due to the rich scattering information collected by the developed instrument, it is expected that the TMS would gain wide applications in the metrology of not only periodic nanostructures but also isolated or the general non-periodic structures. It is also expected that the TMS would gain applications in the inspection of defects in nanostructures.

Xiuguo Chen received his PhD degree in Mechanical Engineering from Huazhong University of Science and Technology (HUST) in 2013. From 2013 to 2015, he was working as a Postdoc at the School of Mechanical Science and Engineering in the same university. From 2016 to 2018, he was working a JSPS Research Fellow at the Department of Nanomechanics, Tohoku University (Sendai, Japan). He is now an associate professor at HUST. He has authored/co-authored more than 60 peer-reviewed journal papers and held more than 20 patents related with theory, instrumentation and application of ellipsometry, especially Mueller matrix (imaging) ellipsometry, for nanoscale characterization.

Weak measurement, first proposed by Aharonov, Al¬bert, and Vaidman in 1988, is a concept primarily studied in conjunction with quantum measurement theory and has remained by and large a laboratory curiosity until recent years. It has attracted interest due to the attendant mechanism of weak value amplification (WVA) as a signal enhancement methodology, offering tantalizing promise of augmenting the detectable signal by several orders of magnitude without a concurrent amplification of technical noise. Its potential in pre¬cision measurement of variation of physical parameters in the presence of noise that overwhelms the useful signal, as in most practical cases of optical phase determination, has been recognized, and demonstrated in a number of scenarios using bulk optical components. To transform a WVA measurement system from a collection of bulk optical components mounted on an optical table to a fieldable sensor capable of measuring unprecedently small variations of such physical quantities as displacement, pressure, electric and magnetic fields, and gravity, requires the fiberization and modularization of the setup. In this talk I report on our first attempt at such an endeavor. Using a prototypical interferometric fiber optic hydrophone as an ex¬ample, we have explored the possibility of measuring small changes in the optical phase of the fiber interferometer, via the WVA technique. We experimentally demonstrated the anticipated improved performance for detecting small phase change (more than two orders of magnitude better than traditional fiber-optic hydrophone based on an interferometer) induced by minute variation of hydro-pressure.

Hong-Liang Cui received his undergraduate education from Changchun Institute of Optics and Fine Mechanics, obtaining a BE in laser physics in 1982, and his Ph.D. degree in theoretical physics from Stevens Institute of Technology in 1987. He is currently a chaired professor at Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Science, and Jilin University. He was previously a professor of physics and engineering physics at Stevens Institute of Technology, and a professor of applied physics at New York University. His research efforts have been concentrated in areas of solid-state electronics, fiber optical communications and sensing, high-frequency electromagnetic wave propagation and interaction with matter, and physics-based approaches to modeling of semiconductor and molecular devices.

Wavefront aberration can reflect the performance of optical systems, the test of wavefront aberration is convenient to express in Zernike polynomials form. Transmission optical system wavefront changes with wavelength, testing at design wavelength is critical for the optical system, from now on only a few wavelength wavefront can be tested by laser interferometer. A new idea is put forward in this paper, transmission optical system wavefront can be calculated at any wavelength utilizing the relationship between transmitted wavefront Zernike coefficients and wavelength. The optical system was modeled and Zernike coefficients at different wavelength were collected by Zemax, then the coefficients were fitted by Matlab curve fitting tool, finally we found Conrady-Zernike formula. The maximum error of the calculated Zernike coefficients is within 1%. The results show that the Zernike coefficients and the wavelength are basically consistent with Conrady-Zernike formula.

Sen Han obtained his Ph.D.in Optical Engineering from University of Stuttgart, Germany. Dr. Han is a Professor of University of Shanghai for Science and Technology and one of Co-Founder of H&L Instruments. He is both a SPIE Fellow and an Adjunct Professor of University of Arizona, USA. Dr. Han won R&D 100 Awards twice in USA.

Based on Michelson interference principle, the homodyne or heterodyne laser interferometry has the advantages of direct traceability, high resolution, long range and high accuracy up to several nanometers. Laser Interferometry has already been widely used in the field of ultra-precision manufacturing. It plays important roles in manufacturing/metrology equipment. Recently, driven by the cutting-edge industries and astronomy, there are demands for next generation interferometry with sub-nm or deep sub-nm accuracy.
According to the error budget of laser interferometry, the key issues in developing next generation laser interferometry are enhancing laser wavelength accuracy, decreasing periodic error, enhancing phase resolution, etc. Over the past few years, our research group has conducted in-depth study on next generation laser interferometry. Firstly, with a water-cooling offset frequency locking method, the relative laser frequency accuracy/stability has been enhanced to 4.2×10^-10. Secondly, we have built heterodyne interferometers with spatially separated beams, in which the periodic nonlinearity error is under several tens of pico-meter. Lastly, different phase evaluate methods have been studied and optimized to achieve phase resolution as high as several pico-meter.

Prof. Pengcheng Hu is Professor of the instrument science & technology department at Harbin Institute of Technology (HIT). His professional interests are precision measurements and instrumentation, specialized in nm-level and dynamic laser interferometry for ultra-precision measurements and manufacture. He has joined the instrument science & technology department at Harbin Institute of Technology since 2008, and worked in PTB as a guest scientist from 2009 to 2010. During last decades he has published ~60 technical papers in peer-reviewed journals, ~10 presentations in conferences, and ~60 patents. He has been conferred a second-class honor in the 2013 National Technological Invention Award. He is currently secretary-general of CSM-MIC (Chinese Society of Measurement, Metrology Instrument Committee), senior member of CIE (Chinese Institute of Electronics), and senior member of IEEE (Institute of Electrical and Electronics Engineers). In 2019 Prof. Pengcheng Hu is supported National high level talents special support plan (outstanding young talents).

X-ray reflective optics have been widely used in many fields including photo-lithography, synchrotron radiation facility, high energy astronomy, and so on. The reflective optics consists of nanoscale multilayer coatings and high precision substrates, both of which require accurate metrology and characterization in order to manipulate the X-ray light efficiently and precisely. For the X-ray multilayer, each layer thickness is only a few nanometers, the interface and surface quality of these layers are crucial for achieving high reflectance. X-ray reflectometry is very sensitive in analyzing the layer thickness, interface width, and even the surface contamination. The layer morphology and composition can be measured by electron microscopy and spectroscopy techniques. To probe the layer structure inside nondestructively, spectroscopy techniques combined with standing wave has been developed. For the mirror substrate, nanometer figure accuracy is demanded by the perfect wavefront control. This is especially difficult for the measurement of a curved surface. A stitching interferometry method has been developed to solve this issue and low repeatability error of <0.4nm RMS has been achieved on a spherical mirror with 100m radius of curvature. The absolute accuracy of the measurement has been compared with other metrology tools.

Dr. Qiushi Huang has received his PhD degree in optics in Tongji University, 2012. He worked in the FOM institute (DIFFER) and University of Twente from 2012 to 2014 as a postdoc. In 2014, he joined the Institute of Precision Optics and Engineering in Tongji University as an assistant professor. He is currently an associate professor in Tongji University. He was sponsored by Shanghai Pujiang Program in 2015 and Shanghai Rising-Star Program in 2019. He has published more than 50 journal papers. His main research interests include extreme ultraviolet and X-ray multilayers, X-ray grating optics, high precision mirror metrology and manufacture.

The resolution and stability are two important technical specifications of optical instruments. It is more important for high precision optical measurement and metrology application up to sub-micron and nanometer scale.
Up to now, some methods used to measure the resolution and the stability are separately. Here we propose a specially designed reference material which can be used to determine the resolution and stability of the optical instruments at one time.
In this talk we will describe the principle of design of the patterns, the fabrication results and the application of this reference material.

Prof. Huang Wenhao was born on May 26,1944, graduated from Tsinghua Univ. in 1968 in the Department of Precision Instrumentation and Mechanics. Then he worked in a factory as a technician, and moved to USTC since 1978. 1989-1991 he worked as visiting scholar in STM lab in Universidad Autonoma de Madrid. He was Chairman of organizing committee of international forum on trends of nano-manufacturing in 2011, 2012, 2014, 2016. He was selected as fellow of ISNM.
Now he is the consultant expert in manufacturing and engineering field of Ministry of Science and Technology of China, and he is also an expert of TC 201 of ISO. His research directions: Micro and nano scale manufacturing and measurement technology, Scanning probe microscopy, Femto second laser micro-nano fabricating, Nano metrology and standardization.

Optical coherence tomography (OCT) provides noninvasive cross-sectional and real time images of biological tissues. The subcellular resolution form of OCT is termed Micro-OCT. Micro-OCT is capable of measuring microanatomic and even subcellular parameters which are critical for the diagnosis of human diseases, such as gastrointensitinal cancers and respiratory airway diseases. We demonstrate measurement of size of nuclei in gastrointestinal tracts and mucociliary activities in the respiratory airways. The results of the measurement results are validated with the gold standard methods.

Liu Linbo received B.Eng in Precision Instrument in 2001, and M. Eng. in Optical Engineering in 2004, from Tianjin University, China. He received PhD in Bioengineering in 2008 from National University of Singapore before his postdoctoral training in Wellman Center in Photomedicine, Harvard Medical School (HMS) and Massachusetts General Hospital (MGH) from 2008 -2011. He was promoted as an Instructor in Dermatology at HMS. Dr Liu is currently an Associate Professor in the School of Electrical and Electronic Engineering and School of Chemical and Biomedical Engineering in Nanyang Technological University. His research interests are mainly focused on development and validation of non-invasive, cellular and sub-cellular resolution imaging methods for disease diagnosis and life science research.

Raman scattering serves as a valuable contrast mechanism for label-free chemical analysis and imaging when performed in a microscopy modality. However, the ultra-low signal level of spontaneous Raman severely limits speed of imaging at a high spatial resolution. Stimulated Raman scattering (SRS), a coherent and nonlinear Raman process, can amplify the Raman signals “linearly” by a few orders of magnitude, enabling rapid Raman imaging with microseconds pixel dwell time. In this talk, fundamental and state-of-the-art of SRS microscopy technology will be introduced. A few interesting biomedical imaging applications of SRS microscopy for label-free and quantitative cancer tissue characterization, as well as for drug delivery imaging, will be presented.

Dr. Fake Lu is an assistant professor in the Department of Biomedical Engineering at the Binghamton University, State University of New York (SUNY). Binghamton University is one of the top public universities, ranked #32 in the United States (USNEWS 2019). Dr. Lu received his PhD in Bioengineering from the National University of Singapore in 2010. He then completed 5-year postdoc training at Harvard University in Boston. Dr. Lu's research interest focuses on developing multiphoton and nonlinear Raman microcopy technologies for biomedical and translational imaging applications. He has published on PNAS, JACS, Cancer Research, and Nature Communications. His research is being funded by NIH and other funding agencies.

Full-field swept source optical coherence tomography using an acousto-optically tuned external-cavity laser diode is proposed and demonstrated. The wavelength of the light source is controlled by diffraction in an acousto-optic modulator, instead of by mechanical motion. This allows tuning rates of over 100 kHz without mode hopping. For phase analysis, we used a continuous wavelet transform. This allows for accurate signal processing that reduces calculation error caused by the nonstationary features of an interference signal. We measured the two-dimensional thickness distribution of a thin glass plate at the tuning range of 68.9 nm, with a central wavelength of 832 nm. A complex Morlet wavelet was used as a mother wavelet in our calculations. The average thickness of the glass plate was found to be 147.0 μm.

Takamasa Suzuki received his BE and ME degrees in electrical engineering from Niigata University in 1982 and from Tohoku University in 1984, respectively, and his PhD degree in electrical engineering from Tokyo Institute of Technology in 1994. He is a professor of electronic, information and communication engineering program at Niigata University. His research interests include optical metrology and optical information processing.

We report the development and implementation of an intraoperative polarization-sensitive optical coherence tomography (PS-OCT) system for enhancing breast cancer detection. A total of 3440 PS-OCT images were intraoperatively acquired from 9 human breast specimens diagnosed by H&E histology as healthy fibro-adipose tissue (n = 2), healthy stroma (n = 2), or invasive ductal carcinoma (IDC, n = 5). A standard OCT-based metric (coefficient of variation (CV)) and PS-OCT-based metrics sensitive to biological tissue from birefringence (i.e., retardation and degree of polarization uniformity (DOPU)) were derived from 398 statistically different and independent images selected by correlation coefficient analysis. We found the standard OCT-based metric and PS-OCT-based metrics were complementary for the differentiation of healthy fibro-adipose tissue, healthy stroma, and IDC. While the CV of fibro-adipose tissue was significantly higher (p<0.001) than those of either stroma or IDC, the CV difference between stroma and IDC was minimal. On the other hand, stroma was associated with significantly higher (p<0.001) retardation and significantly lower (p<0.001) DOPU as compared to IDC. By leveraging the complementary information acquired by the intraoperative PS-OCT system, healthy fibro-adipose tissue, healthy stroma, and IDC can be differentiated with an accuracy of 89.4%, demonstrating the potential of PS-OCT as an adjunct modality for enhanced intraoperative differentiation of human breast cancer.

Dr. Jianfeng Wang is currently a Carle-Foundation Hospital – Beckman Institute Postdoctoral Fellow, working in Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign. His research focus on the development of polarization-sensitive optical coherence tomography, multiphoton microscopy and Raman spectroscopy for intraoperative breast tumor margin detection. He received his Ph.D. in biomedical engineering in 2017 from the National University of Singapore, and his M.Eng. in Optical Engineering in 2012 from Beijing Institute of Technology.

As the core equipment for integrated circuit manufacturing, lithography tool is the key to determining the feature size and integration level of integrated circuits. Its improvement in key performance index is the important driving force for the continuous development of integrated circuit to higher integration according to Moore’s law. Image quality is a key factor in determining the resolution and overlay of lithography tool. It is the continuous improvement of the image quality that enables the performance of the lithography tool to improve continually.
As the integrated circuit technology node enters below 130nm, the influence of wavefront aberration of projection lens of lithography tools on the imaging quality cannot be ignored. The high-accuracy measurement and control for wavefront aberration is an important guarantee for high-quality imaging. Our research group has been engaged in research work in the field of wavefront aberration measurement of projection lithography tools since 2002, and has achieved a series of innovative research results. This presentation systematically introduces these research work of our research group, including measurement techniques of primary image quality parameters, wavefront aberrations and polarization aberrations. The types of measurement techniques involved include exposure-based method, aerial-image-based method and interference-based method. The types of lithography tools involved include dry, immersion and EUV lithography tools.

Xiangzhao Wang received his BE degree in electric engineering from Dalian University of Technology, China, in 1982, and his ME and PhD degree in electric engineering from Niigata University, Japan, in 1992 and 1995, respectively. Now, he is a professor at the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences. His research interests include lithography imaging theory and technology and information optoelectronics.

Photoacoustic microscopy (PAM) has been extensively applied in biomedical studies because of its ability to visualize optical absorption contrast in vivo in three dimensions. However, maintaining high resolution over a large axial range remains a challenge because the lateral resolution decreases rapidly with distance from the focal plane. Here, we propose motionless volumetric spatially invariant resolution photoacoustic microscopy (SIR-PAM) via wavefront engineering technology. To realize motionless volumetric imaging, SIR-PAM combines two-dimensional Fourier-spectrum optical excitation with single-element depth-resolved photoacoustic detection. To achieve spatially invariant lateral resolution, propagation-invariant sinusoidal fringes are generated by a digital micromirror device with wavefront engineering technology. Further, SIR-PAM achieves 1.5 times finer lateral resolution than conventional PAM. We built an SIR-PAM prototype, achieving a 45-fold improvement in depth of field over the conventional-PAM counterpart. Its superior resolution-invariant axial range of 1.8 mm was demonstrated in both inanimate objects and in vivo animals. Our work opens new perspectives for various high-resolution volumetric imaging technologies in biomedical sciences.

Dr. Jiamiao Yang works as a postdoctoral scholar in Andrew and Peggy Cherng Department of Medical Engineering, California Institute of Technology. He got his PhD degree in Beijing Institute of Technology, China. His main research interests focus on optical wavefront shaping, photoacoustic microscopy, optical measurement, and optical instrument researching. He has published more than 10 peer-reviewed articles in journals as the first author, including Nature Communications, Optica, Applied Physics Letters, and Optical Letters.