CONTEMPORARY OPTICAL TECHNOLOGIES

Contemporary Optical Technologies

Summary

Optical Tweezers                               
            The extremely high gradient electric field (produced near the beam waist of a tightly focused laser beam) creates forces sufficient to trap
            micron-sized dielectric particles in three dimensions.

            The technique enables particles to be picked up and moved at will using a beam of visible light and hence was christened optical tweezers.
            Initially applicable to trap only  large size objects (large viruses like the tobacco mosaic virus.) This is due to the diffraction limits affecting the
            size of an optical beam. The latter allows to trap viruses 25 nm in size.

            In contrast, plasmonic trapping takes advantage of local field enhancement in the vicinity of nanometer sized apertures in metal sheets to
            overcome the diffraction limit. 

            Steven Chu,  and                                     Nobel Prize in Physics 1997
            Claude Cohen-Tannoudji                   "for development of methods to cool and trap atoms with laser light."
            William D. Phillips

            Arthur Ashkin,                                        Nobel Prize in Physics 2018
            Gérard Mourou                                     "for groundbreaking inventions in the field of laser physics"
            Donna Strickland                                  One half to Arthur Ashkin "for the optical tweezers and their application to   biological systems",
                                                                                      the other half to G. Mourou and D. Strickland "for their method  of generating high-intensity, ultra-short optical pulses."

                                                                                      J. E. Molloy  and M. J. Padgett;  Lights, action: optical tweezers; Contemporary Physics 43, 241 (2002).
                                                                                      J. Burkhartsmeyer et al, Optical Trapping, Sizing, and Probing Acoustic Modes of a Small Virus; Appl. Sci. 10, 394 (2020) 
                                                                                      doi:10.3390/app10010394
                                                                                      Video  Optical Tweezer Fundamentals

Metal Optics     (see the last 4 slides, in particular)                                                                                                       
            Objective:                                                   High data rates AND high packing densities (nano sized) devices   

            Why not Electronics?                           Electrical interconnects become progressively limited by RC-delay (too much capacitance lowers the bandwidth.)
            Why not Photonics?                              Light propagation is fast BUT subjected to diffraction (thus interconnects can not be made too small in size). Photonics
                                                                                      is diffraction- limited.

            Alternative                                                Plasmonics
                                                                                      Surface plasmons  wavelengths can reach nanoscale at optical frequencies! (SPPs are “x-ray wavelength” with
                                                                                      optical frequencies.)
                                                                                      Plasmonics naturally interfaces with similar size electronic components
                                                                                      Plasmonics interfaces well  with similar operating speed photonic networks
                                                                                      (La Rosa) Bio-applications of surface plasmons  (See Section 4.5, page 36   )

Non-Linear Optics                                                                                                                                                                        
            Birefringent crystal to generate entangled photons via spontaneous parametric down-conversion.
            Application:  Implementation of quantum entangles states  and quantum teleportation.

                                                                                      (La Rosa) Quantum-entanglement  and Quantum-teleportation 
                                                                                      Apparatus to produce polarization-entangled photons  (see Fig.4)
                                                                                      Single photon interference (see Figures 1 and 2)
                                                                                      Jesse Catalano, "Spontaneous Parametric Down-Conversion and Quantum Entanglement" (2014). University 
                                                                                      Honors Theses.  Portland State University Paper 474.    https://doi.org/10.15760/honors.474
                                                                                      Multiple-entangled photons from a spontaneous parametric down-conversion source    

Diffraction Limited Resolution
            Conventional Optical  Microscopy (also called Far-field Optical Microscopy.)
            Illumination spot size can not be made smaller than the wavelength; hence the name diffraction limited resolution.

High Resolution imaging  
            Eric Betzig                                                    Nobel Prize in Chemistry 2014 
            Stefan W. Hell                                             "for the development of super-resolved fluorescence microscopy."
            William E. Moerner

                                                                                      Near-field Scanning Optical Microscopy. (An alternative to far-field optics; overcoming the limitations imposed by diffraction
                                                                                      effects.)  

                                                                                      Eric Betzig Photo Activated Localization Microscopy (PALM)    
                                                                                      Method for isolation of single molecules at high densities (up to~ 10E5/(micronE2) based on the serial photoactivation and
                                                                                      subsequent bleaching of numerous sparse subsets of photoactivatable fluorescent protein (PA-FP) molecules within a sample. 

                                                                                       Stefan W. Hell Far-Field Optical Nanoscopy 
                                                                                      It discusses the physical concepts that have pushed fluorescence microscopy to the nanoscale, once the
                                                                                      prerogative of electron and scanning probe microscopes.