Typically, our fiber-optic cannulas with diffuser layer spread the light output to over 300° apex angle (solid angle > 3.7pi [sr]). This is over 74 times larger in terms of solid angle, than the light output angle of the standard fiber-optic cannula with NA=0.22 where the solid angle is 0.05pi [sr]). The maximum light intensity is along the fiber axis and falls-off gradually as the angle increases.

Consequently, for the same amount of input light power, the diffusive cannula will illuminate larger area albeit with reduced illumination intensity. The illumination intensity drops as 1/r² where r is the distance from the fiber tip. Additionally, the diffuser layer absorbs about 25% of the input power. Therefore, the diffusive tip enlarge the illumination area and necessitate to adjust the illumination power in consequence.

Read the application note

November 2011 Optogenetics catalog

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