{"title":"Lightsabers (“laster swords”) for improving photodetector speed and responsivity","authors":"I. Hasan, J. Simpson","doi":"10.1109/USNC-URSI-NRSM.2013.6525093","DOIUrl":null,"url":null,"abstract":"The micrometer scale of optics is significantly larger than the nanometer scale of modern electronic devices. To produce photodiodes yielding both superior speed and responsivity, a critical challenge is to confine the incident light efficiently to an active region having a small (subwavelength) area. In recent years, plasmonics has been applied as a means to confine light to subwavelength areas. In this case, the plasmonic structure converts the incident (far-field) light into near fields in order to achieve the sub-wavelength confinement. However, the surface plasmons are a near-field phenomenon such that the electromagnetic energy does not penetrate deeply. Further, surface plasmon resonances are generated only over narrow range of frequencies. Thus, the question arises: can we avoid the conversion to near fields and propagate the light into the semiconductor over a sub-wavelength area? When desired, can we propagate broadband electromagnetic energy into the sub-wavelength area to provide efficient broadband photodiodes? The latter may especially be desirable if the common silicon semiconductor is replaced with a more broadband semiconductor such as graphene. Here, it is proposed that a propagating sub-wavelength beam of light called a photonic nanojet and resembling a lightsaber or “laser sword” can be used to focus light onto the small active area of a photodiode. Exploratory three-dimensional, Maxwell's equations finite-difference time-domain (FDTD) simulations are conducted and demonstrate that the nanojets can confine light to an area comparable to a nanostructured dipole antenna while propagating multiple wavelengths into the semiconductor, even over a broad range of frequencies when desirable.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"66 1","pages":"0"},"PeriodicalIF":0.0000,"publicationDate":"2013-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525093","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
The micrometer scale of optics is significantly larger than the nanometer scale of modern electronic devices. To produce photodiodes yielding both superior speed and responsivity, a critical challenge is to confine the incident light efficiently to an active region having a small (subwavelength) area. In recent years, plasmonics has been applied as a means to confine light to subwavelength areas. In this case, the plasmonic structure converts the incident (far-field) light into near fields in order to achieve the sub-wavelength confinement. However, the surface plasmons are a near-field phenomenon such that the electromagnetic energy does not penetrate deeply. Further, surface plasmon resonances are generated only over narrow range of frequencies. Thus, the question arises: can we avoid the conversion to near fields and propagate the light into the semiconductor over a sub-wavelength area? When desired, can we propagate broadband electromagnetic energy into the sub-wavelength area to provide efficient broadband photodiodes? The latter may especially be desirable if the common silicon semiconductor is replaced with a more broadband semiconductor such as graphene. Here, it is proposed that a propagating sub-wavelength beam of light called a photonic nanojet and resembling a lightsaber or “laser sword” can be used to focus light onto the small active area of a photodiode. Exploratory three-dimensional, Maxwell's equations finite-difference time-domain (FDTD) simulations are conducted and demonstrate that the nanojets can confine light to an area comparable to a nanostructured dipole antenna while propagating multiple wavelengths into the semiconductor, even over a broad range of frequencies when desirable.