Enhancing collection efficiency in large field of view multiphoton microscopy.

Many multiphoton imaging applications would benefit from a larger field of view; however, large field of views (>mm) require low magnification objectives which have low light collection efficiencies. We demonstrate a light collection system mounted on a low magnification objective that increases fluorescence collection by as much as 20-fold in scattering tissues. This peripheral detector results in an effective numerical aperture of collection >0.8 with a 3-4 mm field of view.

Analysis of compression of frequency chirped optical pulses by a strongly dispersive grating pair.

An optical pulse compression medium formed by two parallel gratings can be strongly dispersive if the diffracted beam emerges at grazing angle from the surface of the first grating. Strong dispersion makes possible temporal compression of broad incident pulses. However, sufficiently strong dispersion is accompanied by a nonlinear variation of group delay with carrier frequency, which will cause the envelope of the compressed pulse to be distorted and limit the minimum attainable pulse width. Strong dispersion as a limiting influence upon compression of linearly chirped pulses is examined for the grating pair at several laser wavelengths. Specific examples are discussed for the compression of CO(2) laser pulses at 10.6-microm wavelength.