Precise control and generation of self-phase-modulation-enabled spectral broadening for biomedical imaging

Shih-Hsuan Chia^1*

¹Institute of Biophotonics, National Yang Ming Chiao Tung University, Taipei, Taiwan

* Presenter:Shih-Hsuan Chia, email:shchia@nycu.edu.tw

Advanced laser technology usually plays as a game-changer in many photonic-related research/industries applications. We tried to contribute more to the advancements of ultrafast laser technology and look forward to providing new horizons for femtosecond applications. We have successfully demonstrated a compact and versatile fiber source, capable of independent tuning both the spectral peak and bandwidth, through detailed investigations on a fundamental nonlinear process, self-phase modulation. We also studied the interplay between different dispersion characteristics and other accompanying nonlinear interactions, such as self-steepening and Raman scattering, over a broad spectral range. Our investigation opens the door to precisely control the spectral location and bandwidth of a light source only by varying the input conditions, with relieved constraints on the engineering of the interacting materials and corresponding geometry. In our demonstration, the spectral peak can be tuned with an unprecedented spectral coverage between 740-1250 nm from a Yb-based femtosecond fiber laser, and the maximum bandwidth is close to three times larger than the minimum bandwidth at a fixed center wavelength. Both the spectral peak and bandwidth are continuously tunable, and the resulting pulse is easily compressible down to a few-optical-cycle pulse duration. The dual tunability of both the spectral peak and bandwidth will contribute to better optimization of all kinds of nonlinear light-matter interactions. Furthermore, the compactness of the fiber-source leads to the demonstration of portable nonlinear microscopy aiming for performing virtual optical biopsy with a pathohistological resolution, and the advancement may also pave a way to realize video-rate deep-tissue microscopic imaging using the three-photon contrast of widely-used green-fluorescence protein.

Keywords: Ultrafast optics, Nonlinear fiber optics, Nonlinear microscopy