Nonlinear optics (NLO) is the branch of optics that describes the behavior of light in "nonlinear media", that is, media in which the dielectric polarization P responds nonlinearly to the electric field E of the light.
 The nonlinearity is typically observed only at very high light intensities (values of the electric field comparable to interatomic electric fields, typically 10 V/m) such as those provided by lasers. Above the Schwinger limit, the vacuum itself is expected to become nonlinear.
 In nonlinear optics, the superposition principle no longer holds.
Mazur studied physics and astronomy at Leiden University.
 He passed his "doctoraal examen" (equivalent to a master's degree) in 1977 and continued his graduate studies at the same institution.
 In 1981 he obtained his Ph.D on a thesis entitled "The structure of non-equilibrium angular momentum polarizations in polyatomic gases".
 Although he intended to go on to a career in industry with Philips N.V. in Eindhoven, he left Europe at the urging of his father, Peter Mazur, to pursue a postdoctoral study with recent Nobel laureate Nicolaas Bloembergen at Harvard University.
Robert Alfano is an Italian-American experimental physicist.
 He is a Distinguished Professor of Science and Engineering at the City College and Graduate School of New York of the City University of New York, where he is also the founding Director of the Institute for Ultrafast Spectroscopy and Lasers (1982).
 He is a pioneer in the fields of Biomedical Imaging and Spectroscopy, Ultrafast lasers and optics, tunable lasers, semiconductor materials and devices, optical materials, biophysics, nonlinear optics and photonics; he has also worked extensively in nanotechnology and coherent backscattering.
 His discovery of the white-light supercontinuum laser is at the root of optical coherence tomography, which is breaking barriers in ophthalmology, cardiology, and oral cancer detection (see "Better resolution with multibeam OCT," page 28) among other applications.
 He initiated the field known now as Optical Biopsy
Sum frequency generation spectroscopy (SFG) is a technique used to analyze surfaces and interfaces.
 This nonlinear laser spectroscopy method was developed in 1987 and rapidly applied to deduce the composition, orientation distributions, and some structural information of molecules at gas–solid, gas–liquid and liquid–solid interfaces.
 In a typical SFG setup, two laser beams mix at a surface and generate an output beam with a frequency equal to the sum of the two input frequencies.
 SFG has advantages in its ability to be monolayer surface sensitive, ability to be performed in situ (for example aqueous surfaces and in gases), and not causing much damage to the sample surface.
 SFG gives complementary information Infrared and Raman spectroscopy.
Chinese Optics Letters is a monthly peer-reviewed scientific journal focusing on optics.
 Established in 2003, it covers optics research originating in the People's Republic of China as well as coverage from groups outside the country.
 According to the "Journal Citation Reports", the journal has a 2014 impact factor of 1.851.
 Although the journal is sponsored by the Chinese Optical Society, it is published in English by the Optical Society.
 The editor-in-chief is Zhizhan Xu (Chinese Academy of Sciences).
 Subject coverage includes fiber optics and optical communications, lasers and laser optics, nonlinear optics, integrated optics, materials, quantum optics, ultrafast optics, image processing, instrumentation, measurement and metrology.
Applied Physics B: Lasers & Optics is a peer-reviewed scientific journal published by Springer Science+Business Media.
 The editor-in-chief is Dieter Meschede (University of Bonn).
 Topical coverage includes laser physics, optical & laser materials, linear optics, nonlinear optics, quantum optics, and photonic devices.
 Interest also includes laser spectroscopy pertaining to atoms, molecules, and clusters.
 The journal publishes original research articles, invited reviews, and rapid communications.
Yuen-Ron Shen (沈元壤) is a professor emeritus of physics at the University of California, Berkeley, known for his work on non-linear optics.
 He was born in Shanghai and graduated from National Taiwan University.
 He received his Ph.D. in Applied Physics from Harvard under physicist and Nobel Laureate Nicolaas Bloembergen in 1963, and joined the department of physics at Berkeley in 1964.
 In the early years, Dr. Shen was probably best known for his work on self-focusing and filament propagation of laser beams in materials.
 These fundamental studies enabled the creation of ultrafast supercontinuum light sources.
 In the 1970s and 1980s, he collaborated with Yuan T. Lee on the study of multiphoton dissociation of molecular clusters.
 The molecular-beam photofragmentation translational spectroscopy that they developed has clarified much of the initial confusion concerning the dynamics of infrared multiphoton dissociation processes.
 In the 1980s and 1990s, Professor Shen developed various nonlinear optics methods for the study of material surfaces and interfaces.
 Among these techniques, second-harmonic generation and sum frequency generation spectroscopy are best known and now widely used by scientists from various fields.
 He has collaborated with Gabor Somorjai on the use of the technique of Sum Frequency Generation Spectroscopy to study catalyst surfaces.
 He is the author of the book "The Principles of Nonlinear Optics".
 Professor Shen belongs to the prolific J. J. Thomson academic lineage tree.
 Currently, Professor Shen works in U. C. Berkeley and Fudan University in Shanghai.
In nonlinear optics z-scan technique is used to measure the non-linear index n (Kerr nonlinearity) and the non-linear absorption coefficient Δα via the "closed" and "open" methods, respectively.
 As nonlinear absorption can affect the measurement of the non-linear index, the open method is typically used in conjunction with the closed method to correct the calculated value.
 For measuring the real part of the nonlinear refractive index, the z-scan setup is used in its closed-aperture form.
 In this form, since the nonlinear material reacts like a weak z-dependent lens, the far-field aperture makes it possible to detect the small beam distortions in the original beam.
 Since the focusing power of this weak nonlinear lens depends on the nonlinear refractive index, it would be possible to extract its value by analyzing the z-dependent data acquired by the detector and by cautiously interpreting them using an appropriate theory.
 To measure the imaginary part of the nonlinear refractive index, or the nonlinear absorption coefficient, the z-scan setup is used in its open-aperture form.
 In open-aperture measurements, the far-field aperture is removed and the whole signal is measured by the detector.
 By measuring the whole signal, the beam small distortions become insignificant and the z-dependent signal variation is due to the nonlinear absorption entirely.
Nicolaas "Nico" Bloembergen (March 11, 1920 – September 5, 2017) was a Dutch-American physicist and Nobel laureate, recognized for his work in developing driving principles behind nonlinear optics for laser spectroscopy.
 During his career, he was a professor at both Harvard University and later at the University of Arizona.
Chen Yung-Jui received his BS in Physics from National Tsing Hua University in 1969 and Ph.D. in Physics at the University of Pennsylvania (1976).
 After a brief postdoctoral period at Penn, he joined the Advanced Microelectronic Laboratory at McDonnell Douglas Astronautics Co. in 1977.
 From 1980 to 1987, Dr. Chen conducted fiber optical communications related research at GTE Laboratories.
 During the ten years in industry, he worked on MOS/MNOS VLSI technology, wafer scale integration, Ultra-fast optical spectroscopy, nonlinear optics of semiconductors and organic polymers, integrated optics and optoelectronic devices.
 In 1987, he moved to academe and became one of the founding faculty members of the Department of Electrical Engineering at University of Maryland, Baltimore County.

Question: Eric Mazur left Europe to pursue a postdoctoral study with which Nobel laureate recognized for his work i ndeveloping driving principles behind nonlinear optics for laser spectroscopy?
Answer: Nicolaas "Nico" Bloembergen