Though single-color coherent Raman microscopy has been widely used for vibrational imaging of isolated Raman bands, it is still challenging to visualize molecules having overlapping Raman bands. We address this issue by developing a spectroscopic SRS microscope with a time-lens laser source synchronized to a femtosecond laser. The time-lens source provides 2-ps pulse at the wavelength of 1064 nm. A pulse shaper is installed for intra-pulse spectral scanning of the femtosecond laser output. By electronically modulating the time-lens source at MHz frequency, spectroscopic stimulated Raman loss (SRL) images were obtained on a laser-scanning microscope. Using this microscope, we have been able to detect 0.2% DMSO in aqueous solution. Spectroscopic SRL images of prostate cancer cells were obtained. Multivariate curve resolution analysis was further applied to decompose the SRL images into concentration maps of proteins and lipids. With high sensitivity and high spectral resolution, this method offers exciting potential in label-free imaging of live cells using fingerprint Raman bands.
Photoacoustic microscopy using vibrational overtone absorption as a contrast mechanism allows bond-selective imaging of deep tissues. Due to the spectral similarity of molecules in the region of overtone vibration, it is difficult to interrogate chemical components using photoacoustic signal at single excitation wavelength. Here we demonstrate that lipids and collagen, two critical markers for many kinds of diseases, can be distinguished by multispectral photoacoustic imaging of the first overtone of C-H bond. A phantom consisting of rat-tail tendon and fat was constructed to demonstrate this technique. Wavelengths between 1650 and 1850 nm were scanned to excite both the first overtone and combination bands of C-H bonds. B-scan multispectral photoacoustic images, in which each pixel contains a spectrum, were analyzed by a multivariate curve resolution-alternating least squares algorithm to recover the spatial distribution of collagen and lipids in the phantom.
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.