# Programmable photonics

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{{Short description|Study of photonic circuits for computation}}

'''Programmable photonics''' is a subfield of [photonics](/source/photonics) and [optical computing](/source/optical_computing) that studies the development of [photonic integrated circuits](/source/photonic_integrated_circuits) (PICs) for computation whose circuits can be altered at runtime to run different programs, rather than manufacturing each PIC for a specific program. Almost all modern electronic [integrated circuits](/source/integrated_circuits) are programmable and thus programmable photonics is an important step in making optical computing mainstream; a non-programmable electronic integrated circuit (analogous to a non-programmable [PIC](/source/photonic_integrated_circuits)) would be e.g. an [ASIC](/source/ASIC) that can only run inference of a specific [LLM](/source/Large_Language_Model).

Programmable PICs most frequently alter their circuits at runtime by using electronics to manipulate the [refractive index](/source/refractive_index) of specific regions/features in the lens via thermal changes, relying on the [thermo-optic coefficient](/source/thermo-optic_coefficient) of the lens material.<ref>{{cite journal |last1=Bogaerts |first1=Wim |last2=Pérez |first2=Daniel |last3=Capmany |first3=José |last4=Miller |first4=David A. B. |last5=Poon |first5=Joyce |last6=Englund |first6=Dirk |last7=Morichetti |first7=Francesco |last8=Melloni |first8=Andrea |title=Programmable photonic circuits |journal=Nature |date=October 2020 |volume=586 |issue=7828 |pages=207–216 |doi=10.1038/s41586-020-2764-0 |pmid=33028997 |bibcode=2020Natur.586..207B |url=https://www.nature.com/articles/s41586-020-2764-0 |language=en |issn=1476-4687|hdl=1854/LU-8681996 |hdl-access=free }}</ref> The circuits themselves usually are formed by [Mach–Zehnder interferometer](/source/Mach%E2%80%93Zehnder_interferometer) arrays that can perform arbitrary [linear](/source/linear) operations, e.g. [Fourier transforms](/source/Fourier_transforms);<ref>{{cite journal |last1=Ribeiro |first1=Antonio |last2=Ruocco |first2=Alfonso |last3=Vanacker |first3=Laurent |last4=Bogaerts |first4=Wim |title=Demonstration of a 4 × 4-port universal linear circuit |journal=Optica |date=20 December 2016 |volume=3 |issue=12 |pages=1348 |doi=10.1364/OPTICA.3.001348|bibcode=2016Optic...3.1348R |hdl=1854/LU-8504296 |hdl-access=free }}</ref> other operations, such as logic gates, require [nonlinear optics](/source/nonlinear_optics) techniques like [second-harmonic generation](/source/second-harmonic_generation).<ref>{{cite journal |last1=Bogoni |first1=Antonella |last2=Wu |first2=Xiaoxia |last3=Bakhtiari |first3=Zahra |last4=Nuccio |first4=Scott |last5=Willner |first5=Alan E. |title=640 Gbits/s photonic logic gates |journal=Optics Letters |date=1 December 2010 |volume=35 |issue=23 |pages=3955–3957 |doi=10.1364/OL.35.003955 |pmid=21124577 |bibcode=2010OptL...35.3955B |url=https://opg.optica.org/ol/abstract.cfm?uri=ol-35-23-3955 |language=EN |issn=1539-4794|url-access=subscription }}</ref>

== References ==
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Category:Photonics

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Adapted from the Wikipedia article [Programmable photonics](https://en.wikipedia.org/wiki/Programmable_photonics) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Programmable_photonics?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.