Patent ID: 6771682
Filing Date: 2004-08-03
Classification: B82Y,H01S

Abstract:
A photonic integrated circuit (PIC) comprising:a semiconductor laser and an electro-optic semiconductor modulator integrated on a substrate where said laser and modulator are aligned in and serially along an optical waveguide path, also formed on said substrate, aid optical waveguide path substantially parallel with a planar extent of said substrate; an electrical isolation region formed into said semiconductor bulk between said laser and said modulator; said electrical isolation region formed by a pair of spaced current blocking regions extending into said semiconductor bulk from an exposed surface of said electrical isolation region to a depth of a parasitic current, I2, established in a semiconductor bulk between said laser and said modulator, said spaced current blocking regions establishing an electrical path therebetween and providing electrical coupling between said parasitic current, I2, at one end of said electrical path and an electrode formed at the other end of said electrical path at said exposed surface of said electrical isolation region; and wherein: said laser having a first applied bias current, I1, applied thereto as steady state condition, said modulator having a second applied bias current, I3, different from said first applied bias current, I1, and applied thereto as modulated variations in accordance with an electrical modulated signal applied to said modulator, the first and second applied bias currents creating said parasitic current, I2, in said semiconductor bulk region where said parasitic current, I2, is substantially aligned in parallel relative to said optical waveguide path, said second applied bias current, I3, causing modulated variations of said parasitic current, I2, which, in turn, causes undesirable modulated variations of said firs applied bias current, I1, through said laser so that said laser is no longer operating in said steady state condition; and a bias applied to said electrode to divert said parasitic current, I2, through said electrical path to said applied bias such that there results divided parasitic currents, I2A and I2B, established, respectively, between said laser and said applied bias and between said applied bias and said modulator so that the undesired modulated variations affecting said first applied bias current, I1, to said laser are substantially eliminated.