Optical resonance imaging: An optical analog to MRI with sub-diffraction-limited capabilities
We propose here optical resonance imaging (ORI), a direct optical analog to magnetic resonance imaging (MRI). The proposed pulse sequence for ORI maps space to time and recovers an image from a heterodyne-detected third-order nonlinear photon echo measurement. As opposed to traditional photon echo measurements, the third pulse in the ORI pulse sequence has significant pulse-front tilt that acts as a temporal gradient. This gradient couples space to time by stimulating the emission of a photon echo signal from different lateral spatial locations of a sample at different times, providing a widefield ultrafast microscopy. We circumvent the diffraction limit of the optics by mapping the lateral spatial coordinate of the sample with the emission time of the signal, which can be measured to high precision using interferometric heterodyne detection. This technique is thus an optical analog of MRI, where magnetic-field gradients are used to localize the spin-echo emission to a point below the diffraction limit of the radio-frequency wave used. We calculate the expected ORI signal using 15 fs pulses and 87° of pulse-front tilt, collected using f/2 optics and find a two-point resolution 275 nm using 800 nm light that satisfies the Rayleigh criterion. We also derive a general equation for resolution in optical resonance imaging that indicates that there is a possibility of superresolution imaging using this technique. The photon echo sequence also enables spectroscopic determination of the input and output energy. The technique thus correlates the input energy with the final position and energy of the exciton.
© 2016 American Chemical Society. Received: September 12, 2016; Published: November 8, 2016. The authors thank Kirk Lancaster for reading a draft of the manuscript. This work was supported by the Department of Defense as part of the National Security Science and Engineering Faculty Fellowship (NSSEFF) (N00014-15-1-0048 and N00014-16-1-2513) the Air Force Office of Scientific Research (FA9550-14-1-0367), the Dreyfus foundation, and the Sloan foundation. Additional support was provided by the Chicago MRSEC, which is funded by NSF through grant DMR-1420709. MAA acknowledges support from a Yen Postdoctoral fellowship from the Institute for Biophysical Dynamics at the University of Chicago. PDD acknowledges support from an NIH training grant (T32-EB009412) and the NSF GRFP. The authors declare no competing financial interest.
Accepted Version - acsphotonics_2E6b00694.pdf
Accepted Version - nihms828827.pdf
Supplemental Material - ph6b00694_si_001.pdf