image courtesy: Dr. Hand Fried, DZNE Bonn, Germany


Femtosecond fiber lasers for 2-photon microscopy and 2-photon optogenetics in Neuroscience

2-photon microscopy in Neuroscience
2-photon fluorescence microscopy has become a key technology in biological imaging enabling three-dimensional, noninvasive studies of biological tissue on the submicron scale. The contrast mechanism in 2-photon microscopy is based on the excitation of fluorophores by two photons, typically in the infrared spectral range. Upon excitation the fluorophores relax back by emitting a photon in the visible which is detected.
High peak power of the laser is key to drive this nonlinear process. Therefore femtosecond lasers with clean temporal pulse shape and average output powers of >1W are essential for such applications. In addition integrated power control and dispersion precompensation are a must to enable maximum image brightness in the experiment. To get a better idea of the requirements on two-photon microscopy we recommend the following white paper and webinar:

In contrast to conventional linear fluorescence microscopy, the nonlinear character and the longer excitation wavelength in multi-photon microscopy offer several advantages: (i) larger probing depth (ii) lower phototoxicity and reduced photodamage.
Both advantages make 2p-fluorescence microscopy an ideal choice for the direct spatiotemporal visualization of neurons and neuronal activity in living animals. The key fluorescent proteins for such experiments are green and red fluorescent proteins that can be excited by 2-photon absorption at 920nm and 1050nm, respectively. The clear requirements in terms of wavelength, pulse duration, and output power make TOPTICA's easy-to-use and fully integrated fiber lasers FemtoFiber ultra 920 at 920nm and FemtoFiber ultra 1050 at 1050nm the perfect choice for 2-photon experiments in neuroscience.

To understand the potential and latest trends in 2-photon fluorescence microscopy in neuroscience please watch the webinar with Dr. Weijian Zong from the Moser lab in Trondheim, pioneering the field of miniaturized 2-photon microscopy:

2-photon Optogenetics in Neuroscience
All-optical interrogation is a novel approach to understand how active patterns in neuronal activity drive behavior. In such experiments the visualization of neuronal activity by 2-photon imaging is combined with 2-photon optogenetics to stimulate individual neurons by photoactivation of channelrhodopsins within the cell.
With the need of exciting many neurons in parallel, the laser requirements and microscopy technology for 2-photon optogenetics are fundamentally different from 2-photon imaging. Typically, high-power multi-Watt lasers at 1030-1040nm with repetition rates in the 100kHz - 1MHz range are used in combination with a spatial light modulator (SLM) to excite 10s to 100s of neurons simultaneously. Such lasers ideally offer integrated power control and dispersion precompensation to optimize 2-photon excitation efficiency.
TOPTICAs FemtoFiber vario 1030 HP has been fully optimized to perfectly match these requirements and, together with the FemtoFiber ultra 920, complements TOPTICA's product offering for all-optical interrogation experiments in neuroscience.