Deep and dynamic metabolic and structural imaging in living tissues.

Label-free imaging through two-photon autofluorescence of NAD(P)H allows for nondestructive, high-resolution visualization of cellular activities in living systems. However, its application to thick tissues has been restricted by its limited penetration depth within 300 μm, largely due to light scattering. Here, we demonstrate that the imaging depth for NAD(P)H can be extended to more than 700 μm in living engineered human multicellular microtissues by adopting multimode fiber-based, low repetition rate, high peak power, three-photon excitation of NAD(P)H at 1100 nm.

Balanced wavelength modulated Zeeman spectroscopy for oxygen detection.

In this paper, we present the development and testing of a balanced Zeeman spectroscopy method utilizing wavelength modulation for selective detection of paramagnetic molecules. We perform balanced detection via differential transmission measurement of right-handed circularly polarized and left-handed circularly polarized light and compare the performance of our system to the Faraday rotation spectroscopy technique. The method is tested using oxygen detection at 762 nm and can provide real-time oxygen or other paramagnetic species detection for a variety of applications.