Thick biological tissue presents many experimental difficulties for microscopy imaging applications; depth of penetration and scattering being the most prevalent. Two-photon (or, more generally, multi-photon) microscopy is one answer to these demands. With multi-photon excitation, fluorescence occurs as a result of the simultaneous absorption of two photons in an introduced marker or an intrinsic molecule within the sample. As a result, a signal is generated only within an extremely small focal region in the sample. Furthermore, the multi-photon absorption requirement means that the excitation wavelength is typically in the near-infrared range, which is ideal for enhanced penetration depth.

For imaging microscopy, the main advantages of multi-photon methods are localization and selectivity of the excitation, a significant reduction of background, and an increased penetration depth. Among the applications that have benefited greatly from multi-photon microscopy are in-vivo and in-vitro neurological imaging studies.

• H9305-03 compact photosensor module: contains 13 mm diameter side-on PMT and power supply circuit. Spectral response from 185 to 900 nm.
• H7422P-40 photosensor module: metal package PMT with cooler. Spectral response from 300 to 720 nm. High gain for photon counting. Modified protection circuit is required for this application.
• R6357 13 mm side-on PMT: spectral response from 185 to 900 nm.
• R3896 28 mm side-on PMT: includes high-sensitivity multialkali photocathode with spectral response from 185 to 900 nm.
• H7422-40 photosensor module: metal package PMT with cooler. Spectral response from 300 to 720 nm. Requires modified protection circuit for this application.
• ImagEM electron multiplier CCD camera (C9100-13): wide dynamic range, high-speed readout, and high signal-to-noise ratio. Provides two readout modes, EM-CCD readout and normal CCD readout.

Please contact us for information on other products which can be used for this application.