Generation Of New Structured Light Fields And Their Applications In Optical Metrology

Structured light,also known as tailored or engineered light,usually refers to the spatial control of its amplitude,phase,and polarization.Over the past three decades,a broad variety of techniques have been proposed to generate structured light fields either with homogeneous(scalar)or nonhomogeneous(vector)polarization distribution.Significantly,such techniques evolved dramatically after the invention of spatial light modulators,which have made possible the unlimited control of light's spatial shape and polarization to generate arbitrary scalar or vectorial fields.Noteworthy,vector beams have gained popularity in recent times due to exotic properties,such as the nonseparability of their spatial and polarization DOFs,which mimics some of the properties of quantum entanglement.Nevertheless,structured light,either in its vector or scalar form,provides additional advantages over the Gaussian beams.It has,for example,enabled the development of novel applications in fields as diverse as optical metrology,quantum,classical communications,imaging,optical tweezers,among many others.As such,the demand for diversification of generation methods and characterization techniques and the search for novel practical applications have increased dramatically in recent times.To this end,one of the main results of this thesis is the proposal of a novel technique to generate arbitrary vector modes with high quality,relying on the polarization-insensitive property of Digital Micromirrors Devices(DMDs).Additionally,we complement this technique with a novel encoding scheme,known as random spatial multiplexing,to maximally exploit the high refresh rate of the DMDs in the generation of vector beams in arbitrary spatial bases,namely,cylindrical,elliptical,parabolic,amongst others.Another important result of this thesis is the theoretical proposal and experimental generation of new types of structured light modes,namely,Ince-,Mathieu-,and Parabolic-Gaussian vector modes.Remarkably,each class of vector beams features different novel properties.On one hand,Ince-Gaussian vector beams consist of a larger prominent family that provides a smooth transition between the Laguerre-and Hermite-Gaussian vector modes.On the other Mathieu-Gaussian vector beams form a family of non-diffracting vector beams,whose intensity and polarization distribution is invariant upon propagation.Finally,the Parabolic-Gaussian vector beams feature novel properties that up to now had remain hidden,namely,upon free-space propagation,they evolve from maximally mixed and locally non-separable to completely unmixes and locally separable.A third important result derived from this thesis was the actual application of vector modes in the field of optical metrology,more precisely,the development of a novel laser remote sensing technique to measure the velocity components of remote targets.To explain such technique,it is worth reminding that the traditional Doppler effect,which is based on the use of Gaussian beams,only allows directly measuring the velocity component along the line of sight,i.e.,the longitudinal component.Crucially,structured light enables the direct measurement of the transverse velocity component.Both velocity components can then be measured by sequentially illuminating the target with a Gaussian and a vortex beam.In this context,a single vector beam provides a tool to make the simultaneous measurement of both velocity components possible.The main idea resides in illuminating the target with a vector beam that encodes both the Gaussian and the vortex beam,encoded in orthogonal polarizations.A final result reported in this thesis also lies in the context of optical metrology,more precisely,in speckle metrology,which is the basis of several applications,such as data storage,optical tweezers.Here,previous reports suggested that the mean speckle size is affected by the structure of the illuminating source.The main result of this thesis is the experimental and theoretical demonstration that the internal structure of light does not influence the speckle size.The mean speckle size only depends on the spot size of the illuminating source,not its internal phase structure.