Stimulated Raman scattering (SRS) microscopy has shown superior chemical resolution due to the much narrower vibrational spectral bandwidth than its fluorescence counterpart. However, breaking the diffraction-limited spatial resolution of SRS imaging is much more challenging because of the intrinsically weak scattering cross section and inert/stable nature of molecular bond vibrations. We report superresolution SRS (SR-SRS) nanoscopy based on reversible-switchable vibrational photochromic probes integrated with point spread function engineering strategy. By introducing a Gaussian-shaped ultraviolet excitation beam and a donut-shaped visible depletion beam in addition to the pump and Stokes beams, SR-SRS could reach sub-100 nm resolution on photoswitchable nanoparticles (NPs). Furthermore, NP-treated live cell imaging was demonstrated with resolution improvement by a factor of ∼4. Our proof-of-principle work provides the potential for SR vibrational imaging to assist research on complex biological systems.
Coherent anti-Stokes Raman scattering (CARS) can be used to excite vibrational bonds with chemical selectivity, high spatial and spectral resolution, and high sensitivity, which has many applications in biomedical research. The common way to realize CARS imaging is illuminating sample with two synchronized ultra-short pulses. Recent development of various fiber laser schemes based on nonlinear optical effect provides compact laser source for CARS imaging. However, the nonlinear conversion in optical fiber may inevitably introduce temporal or spectral noise to the newly generated pulses. In this paper, we have proposed a polarization-maintaining (PM) passive-synchronized picosecond fiber laser system that generates dual-color picosecond pulses for CARS. An Er-doped fiber laser and a Yb-doped fiber laser were passively synchronized by cross phase modulation based on master-slave injection scheme. In the experiment, the wavelength of one branch was fixed at 791 nm, which was generated by second harmonic generation of Er-doped fiber laser. The wavelength of the other branch can be continuously tuned from 1017-1047 nm, which was obtained by adding an active spectral broadening module and an optical bandpass filter after Yb-doped fiber laser. As a result, the laser source allows to probe vibrational bonds with frequencies difference between 2809 cm-1 and 3091 cm-1 . Finally, the achieved tunable synchronized pulses enabled us to microscopically image mouse ear samples. The compact optical fiber laser proposed with PM fiber design, stable synchronization and large wavelength tunability would become a promising laser source for CARS imaging in clinical use.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.