Broadband absorption bio-inspired by the Fovea Centralis

Broadband absorption is important to various photonic devices. We examine light trapping that is based on the Fovea Centralis. The Fovea Centralis is a region in the retina composed of densely packed inverted cone photoreceptors and is responsible for our vision under bright light conditions. In this sense the Fovea Centralis resembles the functionality of the photovoltaic cell. In our lab we examine light trapping based on metamaterials composed of  light-funnel (LF) arrays that is bio-inspired by the Fovea Centralis. A LF is an inverted structure with respect to the incoming illumination. The research involves electromagnetic calculations, near-field microscopy, far-field spectroscopy, and sample and device fabrication.

Our relevant publications:

  1. H. Elisha, A. Prajapati, G. Shalev, 'Broadband Absorption in Thin Films Motivated by Strong Light Bending', Advanced Photonics Research, DOI: 10.1002/adpr.202000120

  2. A. Chauhan, A. Prajapati, C. Calaza, H. Fonseca, P. C. Sousa, J. Llobet, G. Shalev, 'Near-Field Optical Excitations in Silicon Subwavelength Light Funnel Arrays for Broadband Absorption of the Solar Radiation', Solar RRL(2021), DOI: 10.1002/solr.202100721 

  3. A. Chauhan, G. Shalev, 'Broadband solar absorption with silicon metamaterials driven by strong proximity effects', Nanoscale Advances, DOI:10.1039/c9na00711c. 

  4. G. Marko, A. Prajapati, G. Shalev, ‘Subwavelength nonimaging light concentrators for the harvesting of the solar radiation’, Nano Energy, 61, 275-283 (2019) .

  5. S. S. P. Konedana, E. Vaida, V. Viller, G. Shalev, ‘Optical absorption beyond the Yablonovitch limit with light funnel arrays’, Nano Energy, 59, 321 (2019).

  6. A. Prajapati, A. Chauhan, D. Keizman, G. Shalev, ‘Approaching the Yablonovitch limit with free-floating arrays of subwavelength trumpet non-imaging light concentrators driven by extraordinary low transmission’, Nanoscale, 11, 3681 (2019).

  7. A. Prajapati, Y. Nissan, T. Gabay, G. Shalev, ‘Broadband absorption of the solar radiation with surface arrays of subwavelength light funnels’, Nano Energy, 54, 447 (2018).

  8. G. Shalev, S.W. Schmitt, H. Embrechts, G. Brönstrup, and S. Christiansen, 'Enhanced photovoltaics inspired by the fovea centralis' Scientific Reports, 5, 8570 (2015).


Deep subwavelength structures for Light trapping enhancement

Light trapping in silicon thin films is of interest to various nanophotonic applications ranging from sensing, camouflaging and harvesting of the solar energy, for example. We explore the effect of deep-subwavelength structures on light trapping and the possibility of deterministic absorption enhancement. The research involves electromagnetic calculations, near-field microscopy, far-field spectroscopy, and sample fabrication.

Our relevant publications:

  1. A. Prajapati, J. Llobet, P. C. Sousa, H. Fonseca, C. Calaza, G. Shalev, 'Broadband and Omnidirectional Antireflection Surfaces Based on Deep Subwavelength Features for Harvesting of the Solar Energy', Solar RRL(2021), DOI: 10.1002/solr.202100548

  2. A. Prajapati, J. Llobet, M. Antunes, S. Martins, H. FonsecaC. Calaza, J. Gaspar, G. Shalev, 'Opportunities for enhanced omnidirectional broadband absorption of the solar radiation using deep subwavelength structures', Nano Energy 70, 104553 (2020).

  3. A. Prajapati, J. Llobet, M. Antunes, S. Martins, H. Fonseca, C. Calaza, J. Gaspar, G. Shalev, 'An efficient and deterministic photon management using deep
    subwavelength features', Nano Energy 70, 104521 (2020).

  4. Y. Faingold, S. Fadida, A. Prajapati, J. Llobet, M. Antunes, H. Fonseca, C. Calaza, J. Gaspar and G. Shalev, ‘Efficient light trapping and broadband absorption of the solar spectrum in nanopillar arrays decorated with deep-subwavelength sidewall features’, Nanoscale, 10, 18613 (2018).


Carrier extraction from subwavelength structures

Efficient carrier extraction is important to various optoelectronic devices such as sensors and photovoltaic devices. We explore geometry-driven management of carrier extraction and membrane-selectivity enhancement in subwavelength structures. The research involves electromagnetic and device calculations, development and fabrication of silicon devices, electrical measurements and near-field microscopy.

Our relevant publications:

  1. Ashish Prajapati, Gil Shalev, ‘Photo-voltage management based on enhanced excitation levels in surface arrays of subwavelength silicon formations’,  Solar RRL,  (2020), DOI: 10.1002/solr.202000514 

  2. A. Prajapati, G. Shalev, ‘Geometry-driven carrier extraction enhancement in photovoltaic cells based on arrays of subwavelength light funnels’, Nanoscale Advances, 12, 4755-4763 (2019).

  3. G. Shalev, ‘Addressing carrier extraction from optically-optimized nanopillar arrays for thin-film photovoltaics’, Nanoscale, DOI: 10.1039/C7NR05172G (2017).

  4. S. W. Schmitt, G. Brönstrup, G. Shalev, S. K. Srivastava, M.Y. Bashouti, G. H. Dohler and S.H. Christiansen, “Probing photo-carrier collection efficiencies of individual silicon nanowire diodes on a wafer substrate”, Nanoscale, 6, 7897 (2014).


Biosensing based on novel field-effect devices

The importance of specific and label-free detection of proteins via antigen-antibody interactions for the development of point-of-care testing devices has greatly influenced the search for a more accessible, sensitive, low cost and robust sensors. The vision of silicon field-effect transistor (FET)-based sensors has been an attractive venue for addressing the challenge as it potentially offers a natural path to incorporate sensors with the existing mature Complementary Metal Oxide Semiconductor (CMOS) industry; this provides a stable and reliable technology, low cost for potential disposable devices, the potential for extreme miniaturization, low electronic noise levels, etc. In our lab we explore novel designs of field-effect devices for biosensing. The research involves device 3D finite-difference numerical calculations, analytical modeling, device development and fabrication, device electrical measurements and sensing experiments.


Our relevant publications:

  1. Ie Mei Bhattacharyya, Izhar Ron, Ruth Shima-Edelstein, Evgeny Pikhay, Yakov Roizin, Gil Shalev,'A New Approach toward the Realization of Specific and Label-Free Biological Sensing Based on Field-Effect Devices', Advanced Electronic Materials (2022)

  2. I. M. Bhattacharyya, I. Ron, A. Chauhan, E. Pikhay, D. Greental, N. Mizrahi, Y. Roizin, G. Shalev, 'A new approach towards the Debye length challenge for specific and label-free biological sensing based on field-effect transistors', Nanoscale (2022),  DOI: 10.1039/D1NR08468B

  3. I. M. Bhattacharyya, G. Shalev, 'Electrostatically Governed Debye Screening Length at the Solution- Solid Interface for Biosensing Applications', ACS Sens. 5, 154−161 (2020).

  4.  I. M. Bhattacharyya, S. Cohen, A. Shalabny, M. Bashouti, B. Akavayov, G. Shalev, ‘Specific and label-free immunosensing of protein-protein interactions with silicon-based immunoFETs’, Biosensors and Bioelectronics, 132, 143 (2019)

  5. G. Shalev, Y. Rosenwaks and I. Levy, "Label-Free Biomarker Detection with Electrostatically-Formed Nanowire Transistor", Nature Asia Materials, 5, 1, doi:10.1038/am.2012.75 (2013).

  6. G. Shalev, Y. Rosenwaks and I. Levy, "The interplay between pH sensitivity and label-free protein detection in immunologically modified nano-scale field-effect transistor", Biosensors and Bioelectronics. 31, 510 (2012).

  7. O. Shaya, E. Halpern, B. Khamaisi, M. Shaked, Y. Usherenko, G. Shalev, A. Doron, I. Levy, Y. Rosenwaks, `Molecular gated transistors: Role of self-assembled monolayers`, Applied Surface Science, 256, 5789 (2010).

  8. G. Shalev, A. Cohen, A. Doron, A. Machauf, M. Horesh, U. Virobnik, D. Ullien and I. Levy, "Standard CMOS Fabrication of a Sensitive Fully Depleted Electrolyte-Insulator-Semiconductor Field Effect Transistor for Biosensor Applications", Sensors, 9, 4366 (2009).

  9. E. Halpern, B. Khamaisi, O. Shaya, G. Shalev, I. Levy, and Y. Rosenwaks, `Electrostatic properties of silane monolayers in an electrolytic environment`, Journal of Physical Chemistry C, 113, 16802 (2009).

  10. G. Shalev, E. Halpern, A. Doron, A. Cohen, Y. Rosenwaks, and I. Levy, "Surface chemical modification induces nanometer scale electron confinement in field effect device", Journal of Chemical Physics., 131, 024702 (2009).

  11. O. Shaya, M. Shaked, Y. Usherenko, E. Halpern, G. Shalev, A. Doron, I. Levy, and Y. Rosenwaks, `Tracing the Mechanism of Molecular Gated Transistors`, Jounral of Physical Chemistry C, 113, 6163 (2009).

  12. G. Shalev, A. Doron, U. Virobnik, A. Cohen, Y. Sanhedrai, and I. Levy, "Gain optimization in ion sensitive field-effect transistor based sensor with fully depleted silicon on insulator", Applied Physics. Letters, 93, 083902 (2008).