Imaging through opaque media and photodetection using engineered nanoparticles and nanostructures
| dc.contributor.advisor | Halas, Naomi J | |
| dc.creator | Tanzid, Mehbuba | |
| dc.date.accessioned | 2019-05-17T14:47:40Z | |
| dc.date.available | 2019-05-17T14:47:40Z | |
| dc.date.created | 2018-05 | |
| dc.date.issued | 2018-04-20 | |
| dc.date.submitted | May 2018 | |
| dc.date.updated | 2019-05-17T14:47:41Z | |
| dc.description.abstract | Extending our capabilities to image through opaque media can be highly significant for a wide range of applications: from bioimaging to seeing through fog or rain. We consider narrowband resonant nanoparticles, as well as broadband scatterer and absorber nanoparticles-constituent media, to characterize the properties of image transmission through complex media. Metallic nanoparticles can create narrowband opaque media possessing plasmon resonances with strongly frequency-dependent absorption and scattering cross-sections. We show that perceived image quality through plasmonic media, as well as the spatial resolution of the image both depend on the scattering and absorption cross-sections of the constituent nanoparticles. A nonlinear dependence of image quality is observed on optical density by varying optical pathlength and nanoparticle concentration. This approach should prove useful for evaluating object visualization through media consisting of subwavelength nanostructures as well as in the assessment of plasmonic optical imaging systems. We also examined the image transmission through opaque media consisting of broadband scattering and absorbing nanoparticles. We show both experimentally and computationally that image resolution through scattering media can be enhanced with the addition of absorbers where scattered photons having a longer pathlength are absorbed preferentially compared to ballistic photons. The increase in ballistic-to-scattered photon ratio enhances the image resolution. However, this image enhancement varies significantly depending on the absorption and scattering coefficients and the anisotropy factor of the scattering medium. We demonstrate that the addition of absorbers to a forward-scattering medium (e.g., biological tissue) has a negligible effect on image quality as compared to an isotropic scattering medium. However, we show that a medium which is forward-scattering in visible wavelength can be converted to an isotropic-scattering medium in near-infrared (NIR) wavelength depending on the size of the scatterers. For the same scattering medium, substantial image resolution enhancement is achieved in the NIR wavelength regime compared to visible wavelength. This work leads to an additional control for absorption-induced image resolution enhancement in scattering media by varying imaging wavelength, especially in the NIR wavelength window ideal for various imaging applications. Subsequently, we developed an NIR plasmonic photodetector which could provide us with a room temperature Si-based cost-effective narrowband imaging sensor. To achieve the enhanced responsivity of this photodetector, we used plasmonic nanostructures on highly-doped p-type Si substrate which combines two different detection mechanisms: plasmonic hot carrier generation and free carrier absorption (FCA) in highly doped Si. Using Au and Pd gratings on p-type Si substrate, we obtained >1 A/W responsivity at a low bias of 275 mV and 93 mV, respectively making the plasmonic narrowband photodetector performance comparable to the commercially available non-Si-based photodetectors. | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.citation | Tanzid, Mehbuba. "Imaging through opaque media and photodetection using engineered nanoparticles and nanostructures." (2018) Diss., Rice University. <a href="https://hdl.handle.net/1911/105713">https://hdl.handle.net/1911/105713</a>. | |
| dc.identifier.uri | https://hdl.handle.net/1911/105713 | |
| dc.language.iso | eng | |
| dc.rights | Copyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder. | |
| dc.subject | Imaging | |
| dc.subject | Scattering | |
| dc.subject | Absorption | |
| dc.subject | NIR | |
| dc.subject | Narrowband | |
| dc.subject | Plasmonic Hot Carrier | |
| dc.subject | Free Carrier Absorption | |
| dc.title | Imaging through opaque media and photodetection using engineered nanoparticles and nanostructures | |
| dc.type | Thesis | |
| dc.type.material | Text | |
| thesis.degree.department | Electrical and Computer Engineering | |
| thesis.degree.discipline | Engineering | |
| thesis.degree.grantor | Rice University | |
| thesis.degree.level | Doctoral | |
| thesis.degree.major | Photonics, Electronics and Nanodevices | |
| thesis.degree.name | Doctor of Philosophy |
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