STUDY ON THE OPTICAL FLAT PROFILE HIGH PRECISION MEASURING TECHNOLOGY IN THE METHOD OF LASER DATUM

The physical datum method that uses the laser beam as the physical datum is proposed.A high accuracy of the straight movement on the line above 0.01 μm/100 mm is achieved through applying the method of the closed loop feedback control that uses the laser beam as the datum.The measuring accuracy above 0.05 μm is obtained by applying the self making electric eddy displacement sensor to detect the geometric accuracy of the optical flat.It proves that the laser beam datum method can achieve the high accurcy of the straight movement and has the huge advantage.

Revisiting Newton’s rings with a plasmonic optical flat for high-accuracy surface inspection

Two parallel optical surfaces often exhibit colorful fringes along the lines of equal thickness because of the interference of light.This simple phenomenon allows one to observe subwavelength corrugations on a reflective surface by simply placing on it a flat reference dielectric surface,a so-called optical flat,and inspecting the resultant interference pattern.In this work,we extend this principle from dielectric surfaces to two-dimensional plasmonic nanostructures.Optical couplings between an Au nanodisk array and an Au thin film were measured quantitatively using two different techniques,namely,the classical Newton’s rings method and a closed-loop nano-positioning system.Extremely high spectral sensitivity to the inter-surface distance was observed in the near-field coupling regime,where a 1-nm change in distance could alter the resonance wavelength by almost 10 nm,440 times greater than the variation in the case without near-field coupling.With the help of a numerical fitting technique,the resonance wavelength could be determined with a precision of 0.03 nm,corresponding to a distance precision as high as 0.003 nm.Utilizing this effect,we demonstrated that a plasmonic nanodisk array can be utilized as a plasmonic optical flat,with which nanometer-deep grooves can be directly visualized using a low-cost microscope.

Absolute surface form measurement of flat optics based on oblique incidence method

In this Letter, a test method based on oblique incidence is practically implemented in the interferometric measurement process. Three sets of wavefront data are achieved through cavity interference measurement with a Fizeau interferometer and one oblique incidence measurement. An iterative algorithm is applied to retrieve the absolute surface shape of the test flat. By adding two sets of measurements, the absolute surface error of the interferometer＇s reference flat can be obtained. The new method can not only calibrate the reference flat error of interferometer, but also provide the absolute measurement method for high precision optical components applied in high power laser systems.

Optical metalenses:fundamentals,dispersion manipulation,and applications

Metasurfaces,also known as 2D artificial metamaterials,are attracting great attention due to their unprecedented performances and functionalities that are hard to achieve by conventional diffractive or refractive elements.With their sub-wavelength optical scatterers,metasurfaces have been utilized to freely modify different characteristics of incident light such as amplitude,polarization,phase,and frequency.Compared to traditional bulky lenses,metasurface lenses possess the advantages of flatness,light weight,and compatibility with semiconductor manufacture technology.They have been widely applied to a range of scenarios including imaging,solar energy harvesting,optoelectronic detection,etc.In this review,we will first introduce the fundamental design principles for metalens,and then report recent theoretical and experimental progress with emphasis on methods to correct chromatic and monochromatic aberrations.Finally,typical applications of metalenses and corresponding design rules will be presented,followed by a brief outlook on the prospects and challenges of this field.

Planar liquid crystal polarization optics for augmented reality and virtual reality: from fundamentals to applications

Planar and ultrathin liquid crystal(LC)polarization optical elements have found promising applications in augmented reality(AR),virtual reality(VR),and photonic devices.In this paper,we give a comprehensive review on the operation principles,device fabrication,and performance of these optical elements.Optical simulations methods for optimizing the device performance are discussed in detail.Finally,some potential applications of these devices in AR and VR systems are illustrated and analyzed.

Wavevector Selective Metasurfaces and Tunnel Vision Filters

Metasurfaces offer unprecedented flexibility in the design and control of light propagation,replacing bulk optical components and exhibiting exotic optical effects.One of the basic properties of the metasurfaces,which renders them as frequency selective surfaces,is the ability to transmit or reflect radiation within a narrow frequency band that can be engineered on demand.Here we introduce and demonstrate experimentally in the THz domain the concept of wavevector selective surfaces–metasurfaces transparent only within a narrow range of light propagation directions operating effectively as tunnel vision filters.Practical implementations of the new concept include applications in wavefront manipulation,observational instruments,vision and free-space communication in light-scattering environments.