the angle of incidence of this second laser beam on the hologram plane is 10 degrees fig5 b shows the top view of this package the submounts 502 and 505 are silicon photodetectors detector elements 508 and 507 serve as the power monitors for lasers 501 and 504 respectively the laser chips and the power monitors are connected to the leads of the package by bond wires in this particular embodiment the distance of the second laser chip to the hologram plane is about 5 mm the distance between the second laser chip and the optical axis of the hologram is about 1 mm based on this configuration the hologram function needed to correct for the spherical aberration caused by the change in substrate from 0 6 mm to 1 2 mm is given by u03c6 x y 2 u03c0 u03bb a sub 1 x a sub 2 x sup 2 a sub 3 y sup 2 a sub 4 x sup 3 a sub 5 xy sup 2 a sub 6 x sup 4 a sub 7 x sup 2 y sup 2 a sub 8 y sup 4 where a 1 0 197 a 2 0 0788 a.