Abstract: Far-field optical microscopy has seen significant development in the last 20 years in its ability
to resolve specimen information beyond the diffraction limit. However, nearly all of these
super-resolution techniques are predicated on the use of fluorescence as the contrast mechanism
in the sample. While the variety of fluorophores available for labeling a sample are
a widely-utilized tool, in many instances non-fluorescent contrast mechanisms also provide
valuable information. Multiphoton microscopy is one route to probing non-fluorescent contrast
mechanisms. It has the benefit of sampling multiple contrast mechanisms at once, including
second- and third-harmonic generation and Raman vibrational characteristics, as well
as autofluorescence and labeled fluorescence. However, development of super-resolving techniques
for coherent scattering processes like harmonic generation or coherent Raman excitation
has lagged behind that of incoherent scattering processes like fluorescence.
In this work I present the first technique to simultaneously enhance resolution in both
real-state (e.g., fluorescence) and virtual-state (e.g. harmonic generation) molecular excitation
mechanisms, known as multiphoton spatial-frequency modulated imaging (MP-SPIFI).
SPIFI works by projecting spatial cosine patterns onto the sample and gathering object
spatial frequency information. Multiphoton SPIFI generates harmonics of these cosine patterns
and therein gathers information beyond the frequency passband of the microscope.

Adviser: Randy Bartels
Co-Adviser: N/A
Non-ECE Member: Thomas Borch, Soil and Crop Sciences
Member 3: Jesse Wilson, Electrical and Computer Engineering
Addional Members: Jeff Squier, Electrical and Computer Engineering

Publications:
Keith A. Wernsing, Jeffrey J. Field, Scott R. Domingue, Alyssa M. Allende-Motz, Keith F.
DeLuca, Dean H. Levi, Jennifer G. DeLuca, Michael D. Young, Jeff A. Squier, and Randy A.
Bartels. Point spread function engineering with multiphoton SPIFI. In Thomas G. Brown,
Carol J. Cogswell, and Tony Wilson, editors, Three-Dimensional and Multidimensional
Microscopy: Image Acquisition and Processing XXIII, volume 9713, pages 17 – 26. International
Society for Optics and Photonics, SPIE, 2016.

Jeffrey J. Field*, Keith A. Wernsing*, Scott R. Domingue, Alyssa M. Allende Motz, Keith F.
DeLuca, Dean H. Levi, Jennifer G. DeLuca,Michael D. Young, Jeff A. Squier, and Randy A.
Bartels. Superresolved multiphoton microscopy with spatial frequency-modulated imaging.
Proceedings of the National Academy of Sciences, 113(24):6605–6610, 2016.
* = co-first authors

Jeffrey J. Field, Keith A. Wernsing, Jeff A. Squier, and Randy A. Bartels. Three-dimensional
single-pixel imaging of incoherent light with spatiotemporally modulated illumination.
J. Opt. Soc. Am. A, 35(8):1438–1449, Aug 2018.

Chenfei Hu, Jeffrey J. Field, Varun Kelkar, Benny Chiang, Keith Wernsing, Kimani C. Toussaint,
Randy A. Bartels, and Gabriel Popescu. Harmonic optical tomography of nonlinear
structures. Nature Photonics, 14(9):564–569, Sep 2020.

Program of Study:
ECE 512
ECE 581A9
ECE 581B7
ECE 604
ECE 652
ECE 799
MATH 676
N/A