Resonant Modulation of Single-Contact Lasers

Abstract

Chapters 9 and 10 describe in detail the concept and performances of narrow-band subcarrier modulation of a laser diode at mm-wave frequencies based on the concept of mode-locking, alternatively known as “resonantly-enhanced modulation” (or simply “resonant modulation” for short). This technique is useful in applications where optical fiber is used for the remote transport of millimeter wave ( > 30 GHz) signals for phased-array antenna systems [107] and wireless personal communication networks [101]. Because of the fact that efficient longitudinal mode-coupling requires inhomogeneous modulation of the laser cavity in the longitudinal spatial dimension, previous demonstrations of monolithic resonant modulation such as those described in Chap. 10 were performed using split(multi)-contact laser diodes. Although the fabrication of a multi-contact structure itself is neither difficult nor intricate, the increased complexity is undesirable – considering the fact that it does require a non-standard fabrication process; rendering them unsuitable for seamless integration into a standard telecom laser fabrication line. Recent measurements of millimeter-wave propagation along the contact stripe of a semiconductor laser showed a high attenuation ( ∼ 60 dB/mm at 40 GHz) of the signal along the laser stripe [108].