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Separating higher-order nonlinearities in transient absorption microscopy

Publication ,  Conference
Wilson, JW; Anderson, M; Park, JK; Fischer, MC; Warren, WS
Published in: Proceedings of SPIE - The International Society for Optical Engineering
January 1, 2015

The transient absorption response of melanin is a promising optically-accessible biomarker for distinguishing malignant melanoma from benign pigmented lesions, as demonstrated by earlier experiments on thin sections from biopsied tissue. The technique has also been demonstrated in vivo, but the higher optical intensity required for detecting these signals from backscattered light introduces higher-order nonlinearities in the transient response of melanin. These components that are higher than linear with respect to the pump or the probe introduce intensity-dependent changes to the overall response that complicate data analysis. However, our data also suggest these nonlinearities might be advantageous to in vivo imaging, in that different types of melanins have different nonlinear responses. Therefore, methods to separate linear from nonlinear components in transient absorption measurements might provide additional information to aid in the diagnosis of melanoma. We will discuss numerical methods for analyzing the various nonlinear contributions to pump-probe signals, with the ultimate objective of real time analysis using digital signal processing techniques. To that end, we have replaced the lock in amplifier in our pump-probe microscope with a high-speed data acquisition board, and reprogrammed the coprocessor field-programmable gate array (FPGA) to perform lock-in detection. The FPGA lock-in offers better performance than the commercial instrument, in terms of both signal to noise ratio and speed. In addition, the flexibility of the digital signal processing approach enables demodulation of more complicated waveforms, such as spread-spectrum sequences, which has the potential to accelerate microscopy methods that rely on slow relaxation phenomena, such as photothermal and phosphorescence lifetime imaging.

Duke Scholars

Published In

Proceedings of SPIE - The International Society for Optical Engineering

DOI

EISSN

1996-756X

ISSN

0277-786X

ISBN

9781628417500

Publication Date

January 1, 2015

Volume

9584

Related Subject Headings

  • 5102 Atomic, molecular and optical physics
  • 4009 Electronics, sensors and digital hardware
  • 4006 Communications engineering
 

Citation

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Wilson, J. W., Anderson, M., Park, J. K., Fischer, M. C., & Warren, W. S. (2015). Separating higher-order nonlinearities in transient absorption microscopy. In Proceedings of SPIE - The International Society for Optical Engineering (Vol. 9584). https://doi.org/10.1117/12.2187133
Wilson, J. W., M. Anderson, J. K. Park, M. C. Fischer, and W. S. Warren. “Separating higher-order nonlinearities in transient absorption microscopy.” In Proceedings of SPIE - The International Society for Optical Engineering, Vol. 9584, 2015. https://doi.org/10.1117/12.2187133.
Wilson JW, Anderson M, Park JK, Fischer MC, Warren WS. Separating higher-order nonlinearities in transient absorption microscopy. In: Proceedings of SPIE - The International Society for Optical Engineering. 2015.
Wilson, J. W., et al. “Separating higher-order nonlinearities in transient absorption microscopy.” Proceedings of SPIE - The International Society for Optical Engineering, vol. 9584, 2015. Scopus, doi:10.1117/12.2187133.
Wilson JW, Anderson M, Park JK, Fischer MC, Warren WS. Separating higher-order nonlinearities in transient absorption microscopy. Proceedings of SPIE - The International Society for Optical Engineering. 2015.
Journal cover image

Published In

Proceedings of SPIE - The International Society for Optical Engineering

DOI

EISSN

1996-756X

ISSN

0277-786X

ISBN

9781628417500

Publication Date

January 1, 2015

Volume

9584

Related Subject Headings

  • 5102 Atomic, molecular and optical physics
  • 4009 Electronics, sensors and digital hardware
  • 4006 Communications engineering