Optics Research:


Nanoantenna structure: we are investigating plasmonic nanoantennas and metasurfaces for bio- and -chemical sensing applications. When light is incident upon the sensor, nanoparticle resonances are excited, resulting in strongly enhanced electric fields at the sensor surface. These electric fields are highly sensitive to changes in the local dielectric environment, making it possible to detect small quantities of target analytes bound to the sensor which produce a shift in resonance wavelength.

Calculated electric field enhancement: we use simulation tools, such as CST Microwave Studio, to design and optimize the nanostructures for the target application. The electric field profile, resonance sensitivity (wavelength shift per change in refractive index) and resonance bandwidth (full width at half maximum) are considered in the design/optimization, as well as impacts of the surrounding environment, including temperature and bulk refractive index.

Fabrication images and reflection spectra: the nanostructures are fabricated either using top-down approaches, such as electron beam lithography (EBL), or bottom-up approaches, including nanoparticle printing, microfluidic alignment, and nanoisland thin film deposition. The optical properties are thoroughly characterized using microspectroscopy and variable-angle spectroscopic ellipsometry. Devices are then functionalized with target-specific recognition elements and tested in relevant environments.

We have recently demonstrated:

  • Metallic photonic crystal structures for stable operation over wide temperature ranges
  • Tunable coupling of plasmonic-photonic Fano resonances based on nanograting geometry
  • Microfluidic alignment of gold nanorods for scalable/large-area plasmonic nanogratings
  • Sequence specific DNA detection using printed gold nanorods


T. Palinski, A. Tadimety, G. Hunter, X.J. Zhang, “Metallic photonic crystal-based sensor for cryogenic environments”, Optics Express., 27, 11, 2019

H. T. Chorsi, Y. Lee, A. Alu, X.J. Zhang, “Tunable plasmonic substrates with ultrahigh Q-factor resonances”, Scientific Reports, 7, 15985, 2017.

H. T. Chorsi, Y. Zhu, X.J. Zhang, “Patterned Plasmonic Surfaces on MEMS—Theory, Fabrication and Applications in Biosensing”, IEEE/ASME Journal of Microelectromechanical Systems, 26, 718-739, 2017.

H. T. Chorsi, X.J. Zhang, “Apertureless near-field scanning probes based on Graphene plasmonics”, IEEE Photonics, 9(1): 1-7, 2017.

H. T. Chorsi, M. T. Chorsi, X.J. Zhang, “Using graphene plasmonics to boost biosensor sensitivity”, SPIE Biomedical Optics & Medical Imaging, 2016, DOI: 10.1117/2.1201610.006712.

X. Li, X.J. Zhang, “Design of Terahertz metal-dielectric-metal waveguide with microfluidic sensing stub. Optics Communications, 361: 130–137, 2016.

X. Li, J. Song, X.J. Zhang, “Terahertz surface plasmon resonance on polyvinylidence fluoride layer for the profiling of liquid reflection spectrum”, Plasmonics, 12: 1–8, 2015.

G. Bhave, Y. Lee, X.J. Zhang, “Enhanced Light Emission from Quantum Dots with Thin Plasmonic Grating Electrodes”, Nanotechnology, 26(36): 5301, 2015.

S. M. Kazmi, E. Faraji, M. Davis Y.Y. Huang, X.J. Zhang, A. Dunn, “Flux or speed: Examining Speckle Contrast Imaging of vascular flows”, Journal of Biomedical Optics (JBO), 6(7): 2588–2608, 2015.

G. Bhave, E. Ng, Y. Lee, X.J. Zhang, “Micro patterned quantum dots excitation for cellular microarray imaging”, Proceeding of SPIE, 9342: 93410F-1 (invited paper), 2015.

G. Bhave, Y. Lee, K. Hoshino, X.J. Zhang, “Colloidal Quantum Dot Based Light Emitting Diodes with Solution Processed Electron Transporting Layer, IEEE Sensors Journal, 15(1): 234–239, 2015.

K. Hoshino, G. Behave, E. Ng, X.J. Zhang, “Micro Patterned Quantum Dots Excitation and Imaging for Cellular Microarray Screening”, Sensors and Actuators A, 216: 301–307, 2014.

Y. Wang, N. Triesault, D.Y. Gokdel, L. Wang, Y.Y. Huang, and X.J. Zhang, “Magnetic actuated stainless steel scanner for two photon imaging based circulating tumor cell screening”, Journal of Micro-Electro-Mechanical Systems, DOI 10.1109, 2014.

K. Hoshino, P. Joshi, G. Bhave, K. Sokolov, and X.J. Zhang, “Use of colloidal quantum dots as a digitally switched swept light source for gold nanoparticle based hyperspectral microscopy,” Biomedical Optics Express, 5(5): 1610–1615, 2014.

L. Wang, Y. Wang, and X.J. Zhang, “Embedded metallic focus grating and photonic crystal based lambda/4 nano-slot for subwavelength near-field light confinement”, IEEE Journal of Selected Topics in Quantum Electronics, 20: 3, 2014.

S. Bish, M. Sharma, Y. Wang, N. Triesault, J. Reichenberg, X.J. Zhang, J.W. Tunnell, “Handheld diffuse reflection spectral imaging (DRSi) for in-vivo characterization of skin”, Biomedical Optics Express, 5(2): 573–586, 2014.

Y. Lee, K. Hoshino, A. Alu and X.J. Zhang, “Tunable directive radiation using surface-plasmon diffraction gratings,” Optics Express, 21(3): 2748–2756, 2013.

L. Wang, Y. Wang, X.J. Zhang, “Embedded metal focus grating for silicon nitride waveguide with enhanced coupling and directive radiation”, Optical Express, 20(16): 17509–17521, 2012.

Y. Wang, S. Bish, J. Tunnell,  X.J. Zhang “MEMS scanner based handheld fluorescent hyperspectral imaging system”, Sensors and Actuators: A Physical, 188: 450–455, 2012.

K. Hoshino, A. Gopal, M. S. Glaz, D. A. Vanden Bout, and X.J. Zhang, “Nanoscale fluorescence imaging with quantum dot near-field electroluminescence”, Applied Physics Letters, 101: 043118, 2012.

Y. Lee, K. Hoshino, A. Alu, X.J. Zhang, “Efficient directional beaming from small apertures using surface-plasmon diffraction gratings”, Applied Physics Letters, 101: 041102, 2012.

Y. Lee, X.J. Zhang, “Designs of apertureless probe with nano-slits for near-field light localization and concentration”, Optics Communications, 285(16): 3373–3377, 2012.

Y. Wang, M. Raj, G. Bhave, B. Yang, S. McGuff, T. Shen and X.J. Zhang, “Portable oral cancer detection using miniature confocal imaging probe with large field of view”, Journal of Micromechanics and Microengineering, 22: 065001, 2012. (Highlighted by Science Daily and selected for inclusion in IOP Select.)

Y. Wang, K. Kumar, L. Wang, X.J. Zhang, “Monolithic integration of binary-phase fresnel zone plate objectives on 2-axis scanning micromirrors for compact microscopes”, Optical Express, 20(6): 6657–6668, 2012. [Selected by the editors for publication in the most recent issue of the Virtual Journal for Biomedical Optics (VJBO). http://vjbo.osa.org/virtual_issue.cfm]

Y. Lee, A. Alu,  X.J. Zhang “Efficient Apertureless Scanning Probes Using Patterned Plasmonic Surfaces”, Optical Express, 19(27): 25990–25999, 2011. [Also selected for publication in the Virtual Journal for Biomedical Optics (VJBO), http://vjbo.osa.org/virtual_issue.cfm]

R. Zaman, A. Gopal, K. Starr, X.J. Zhang, S. Thomsen, J. Tunnell, A.J. Welch, G. Rylander, “Micro-patterned Drug Delivery Device for Light-Activated Drug Release”, Laser in Surgery and Medicine, DOI 10.1002/lsm.21149, 2011.

L. Wang, K. Hoshino, X.J. Zhang, “Near field sub-wavelength light focusing via slotted Fabry-Pérot photonic crystal with low in-plane index contrast”, Optics Letters, 36(10): 1917–1919, 2011.

Y. Wang, S. Bish, J. Tunnell, X.J. Zhang, “MEMS Scanner Enabled Real-Time Depth Sensitive Hyperspectral Imaging of Biological Tissue”, Optical Express, 18(23): 24101–24108, 2010.

N. Rajaram, A. Gopal, X.J. Zhang and J.W. Tunnell, “Experimental validation of the effects of microvasculature pigment packaging on in vivo diffuse reflectance spectroscopy”, Lasers in Surgery and Medicine, 42: 680–688, 2010.

Y. Wang, Y. Y. Huang, X.J. Zhang, “Plasmonic nanograting tip design for high power throughput near-field scanning aperture probe” Optical Express, 18(13): 14004–14011, 2010. [Selected by the editor-in-chief for publication in the Virtual Journal for Biomedical Optics (VJBO). http://vjbo.osa.org/virtual_issue.cfm.]

A. Gopal, K. Hoshino and X.J. Zhang, “Photolithographic patterning of sub-wavelength colloidal quantum dot based inorganic light emitting diodes on silicon”, Applied Physics Letters, 96(13): 131109–131113, 2010.

K. Karthik, R. Avritscher, D.C. Madoff, T. K. Yu, and X.J. Zhang, “Handheld Histology-Equivalent Sectioning Laser-Scanning Confocal Optical Microscope for Interventional Imaging”, Biomedical Microdevices, 12: 223–233, 2010.

A. Gopal, K. Hoshino, S. Kim and X.J. Zhang, “Multi-color colloidal quantum dot based light emitting diodes micropatterned on silicon hole transporting layers”, Nanotechnology, 20: 235201, 2009. [Among 10% of most-downloaded IOP articles in the second quarter of 2009 and IOP highlight publishing on Science, Application, Industry, “Nano LEDs printed on silicon”) in 2009 http://nanotechweb.org/cws/article/lab/39721.]

K. Hoshino, A. Gopal, X.J. Zhang, “Near-field scanning nanophotonic microscopy – breaking the diffraction limit using integrated nano light emitting probe tip”, IEEE Journal of Selected Topics in Quantum Electronics (JSTQE), 15: 393–399, 2009.

K. Hoshino, T. Turner, S. Kim, A. Gopal and X.J. Zhang, “Single molecular stamping of sub-10-nm colloidal quantum dot array”, Langmuir, 24: 13804 –13808, 2008.

K. Kumar, K. Hoshino, and X.J. Zhang, “Handheld subcellular-resolution single-fiber confocal microscope using high-reflectivity two-axis vertical combdrive silicon microscanner”, Biomedical Microdevices 10: 653–660, 2008.

A. Gopal, Z. Luo, J.Y. Lee, K. Kumar, K. Hoshino, B. Li, C. E. Schmidt, P. S. Ho and X.J. Zhang, “Nano-Opto-Mechanical Characterization of Neuron Membrane Mechanics under Cellular Growth and Differentiation”, Biomedical Microdevices, 10: 611–622, 2008. (Highlighted in the theme on “mechanics in neuronal development” on iMechanica in 2008.)

K. Kumar, J.C. Condit, A. McElroy, N.J. Kemp, K. Hoshino, T.E. Milner, X.J. Zhang, “Fast 3D in vivo swept-source optical coherence tomography using two-axis MEMS scanning micromirror”, Journal of Optics A: Pure and Applied Optics, 10: 044013, 2008. [Highlighted in: (1) Laser Focus World, August Issue, 2008; (2) “MEMS scanners enable in vivo 3-D optical coherence tomography,” BioOptics World, 1(5): 31–34, 2008; (3) “Biomedical Imaging: MEMS scanners enable in vivo 3-D OCT”, Laser Focus World, 44(8), 2008; and (4) the 2008 Journal of Optics annual highlights collection.]

K. Hoshino, L. Rozanski, D. A. Vanden Bout and X.J. Zhang, “Near-field scanning optical microscopy with monolithic silicon light emitting diode on probe tip”, Applied Physics Letters, 92: 131106, 2008. (Highlighted in Photonics Spectra, “For a Real Close-up, a Little Light,” June Issue, 104, 2008; and the IEEE EDS Distinguished Lecture, by Dr. Usha Vashney, NSF EECS Division Director, Irvine, April 10, 2008)

K. Hoshino, L. Rozanski, D. A. Vanden Bout and X.J. Zhang, “Direct fabrication of nano-scale light emitting diode on silicon probe for scanning microscopy”, IEEE/ASME Journal of Microelectromechnical Systems (JMEMS), 17: 4–10, 2008.

A. B. Parthasarathy, A. Gopal,  X.J. Zhang and A. K. Dunn, “Robust flow measurement with multi-exposure speckle imaging”, Optics Express, 16(3): 1975–1989, 2008.

X.J. Zhang, M. P. Scott, C.F. Quate and O. Solgaard, “Micro-optical Characterization of Piezoelectric Vibratory Microinjections on Drosophila Embryos for Genome-wide RNAi Screen”, Journal of Microelectromechanical Systems, 15(2): 1–11, 2006.

X.J. Zhang, C.C. Chen, R.W. Bernstein, S. Zappe, M.P. Scott and O. Solgaard, “Micro-optical Characterization and Modeling of Positioning Forces on Drosophila Embryos Self-Assembled in Two-Dimensional Arrays”, Journal of Microelectromechanical Systems, 14(5): 1187–1197, 2005.

X.J. Zhang, C.C. Chen, M.P. Scott and O. Solgaard, “Micro-optical Characterization of Fluidic Self-assembly of Drosophila Embryos through surface tension: principle, simulation and experiments”, Optical Review, 12(4): 1–6, 2005.

X.J. Zhang, “Silicon Micro-Surgery Force Sensor Based on Diffractive Optical MEMS Encoders”, Sensor Review, 24(1): 37–41, 2004.

X.J. Zhang, S. Zappe, R.W. Bernstein, C.C. Chen, O. Sahin, M. Fish, M.P. Scott and O. Solgaard, “Micromachined Silicon Force Sensor Based on Diffractive Optical Encoders for Characterization of Microinjection”, Sensors and Actuators: A Physical, 114(2–3): 197–203, 2004.