Abstract
Four-wave-mixing microscopy is widely researched in both biology and medicine. In this paper, we present a simplified near-degenerate four-wave-mixing microscopy (SNDFWM). An ultra-steep long-pass filter is utilized to produce an ultra-steep edge on the spectrum of a femtosecond pulse, and a super-sensitive four-wave-mixing (FWM) signal can be generated via an ultra-steep short-pass filter. Compared with the current state-of-the-art FWM microscopy, this SNDFWM microscopy has the advantages of simpler experimental apparatus, lower cost, and easier operation. We demonstrate that this SNDFWM microscopy has high sensitivity and high spatial resolution in both nanowires and biological tissues. We also show that the SNDFWM microscopy can achieve an ultra-sensitive detection based on the electron-resonance effect. This method might find an important application in tracking of nano drugs in vivo.
Highlights
The continuous progress of optical microscopy is of great significance to the development of biomedicine
FWM has been widely used in nonlinear optical microscopy for decades, such as coherent anti-Stokes Raman scattering (CARS) [4,5,6] and stimulated Raman scattering (SRS) [7,8,9]
The CARS microscope was optimized by Xie’s group at Harvard University. This microscope is composed of a laser-scanning microscope, which realizes the scanning of externally introduced laser and the collection of CARS signals through a simple modification of commercial confocal microscopy [11]
Summary
The continuous progress of optical microscopy is of great significance to the development of biomedicine. We present a simpler near-degenerate FWM microscopy by replacing the complex pulse shaper used in a previous study with a compact and low-cost long-pass filter, an ultra-steep long-pass filter (ULPF). This ULPF produces a sharp “edge” on the spectrum of the incoming femtosecond laser, achieving an infinitely close FWM signal on the spectrum to the incident laser, and generating a super-strong FWM signal. We call this method a simplified near-degenerate four-wave-mixing (SNDFWM) microscope system
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