Pulsed lidar systems typically use either 905 nm or 1550 nm lasers for optical emission. Above 1400 nm, various elements of the eye absorb the light, impeding it from reaching and damaging the retina. As laser power is increased, not all of it is absorbed, and at some point, retinal damage may occur. Since 905 nm light does not get absorbed, it does reach the retina, so care must be used to limit the energy density to prevent damage.
If the decision is to use 1550 nm light, efficiency differences in the semiconductor laser make it necessary to use higher current for the same optical power emitted compared with 905 nm light. Additionally, the same characteristics that allow the light to be absorbed by the eye before getting to the retina cause it to be absorbed by the atmosphere. This phenomenon is amplified as humidity increases to fog, rain, or snow. The drive power required for a 1550 nm laser may be up to 10 times higher than for a 905 nm laser based system. Fortunately, there is a solution to deliver the power necessary to drive 1550 nm lasers while maintaining the edge speed and pulse required for high resolution in pulsed lidar applications.