A laser source driver in 0.18 <i>μ</i>m SiGe BiCMOS technology for high speed quantum key distribution

Quantum key distribution (QKD) has rapidly developed recently. The repetition frequency of the QKD system increases from tens or hundreds MHz to GHz. A laser diode (LD) operating in gain-switched mode is widely used as a weak coherent light source system. We present an LD driver circuit fabricated 0.18 μm SiGe heterojunction bipolar transistor complementary metal oxide semiconductor technology. can operate at frequencies up 2.5 GHz, satisfying requirements high-speed drives practical systems. output current reach 100 mA when driving whose input equivalent resistance ∼21 Ω. extinction ratio 1550-nm distributed feedback driven by our reaches 23 dB meeting This will be miniaturized