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SUMMARY:Nanostructured meta-surfaces for arbitrarily structured twisted li
 ght
DTSTART;VALUE=DATE-TIME:20210726T093000Z
DTEND;VALUE=DATE-TIME:20210726T094500Z
DTSTAMP;VALUE=DATE-TIME:20260813T215645Z
UID:indico-contribution-7094@events.saip.org.za
DESCRIPTION:Speakers: Bereneice Sephton (University of the Witwatersrand)\
 nStructuring materials to exhibit phenomena such as negative refractive in
 dices and near-zero indices has given rise to an exciting class of materia
 ls\, known as metamaterials and their 2D counterparts\, metasurfaces. Due 
 to these unique properties and the ability to control the size\, shape\, d
 ensity and orientations of these materials\, one is able to have unprecede
 nted control of their impact on light striking these structures. Controlli
 ng light with subwavelength-designed metasurfaces (MSs) has thus allowed f
 or the arbitrary creation of structured light by precisely engineering bot
 h the material and composite structures formed from them.  With structured
  light modes such as those carrying orbital angular momentum (OAM) taking 
 hold in many fields from communications\, cryptography and optical trappin
 g to metrology\, it follows that arbitrary generational control and easily
  employed devices such as these can form an important part in helping deve
 lop these fields. \n\nAs such\, we characterize both the purity and conver
 sion efficiency of such MSs\, designed to generate hybrid twisted light mo
 des\, which exemplify the versatility of the imparted properties that are 
 possible. Here we used a recently reported method to design and fabricate 
 meta-surfaces that exploit generalized spin-orbit coupling and propagation
  phase to produce vector OAM or twisted states with asymmetric superpositi
 ons\; this allowing for one to break the symmetrical restrictions imposed 
 by previous classes of such devices. Here\, the symmetrical restrictions a
 re broken both in the input spin states required for the modal patterning 
 as well as the OAM values paired in each device. For example\, asymmetrica
 l charges of 1 and 5 are coupled to linear and circular polarization state
 s in addition to fractional vector OAM states with charges of 3.5 and 6.5 
 being generated on the same device. The common symmetrical conjugate spin 
 and OAM of 1 is also demonstrated as reported in previously restricted spi
 n-orbit coupling devices.  The generated structures of the resulting beams
  are quantitatively studied here\, by exploiting the reciprocal nature of 
 light. We thus establish both the purity and conversion efficiency with co
 nversion efficiencies exceeding 75% and purities in excess of 95%\, yieldi
 ng good modal quality.\n\nhttps://events.saip.org.za/event/206/contributio
 ns/7094/
LOCATION:North-West University Potchefstroom Campus
URL:https://events.saip.org.za/event/206/contributions/7094/
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