Laterally-coupled dual-wavelength distributed feedback lasers

摘要

A novel laterally-coupled dual-wavelength distributed feedback (DFB) laser having two different grating periods, one on each sidewall, has been successfully realised. Single-mode DFB and distributed Bragg reflector (DBR) lasers have also been fabricated alongside in order to compare the lasing operation characteristics of the dual-wavelength DFB laser. The lasers were fabricated on InP/InAlGaAs epitaxial heterostructure material emitting at 1.35 μm. Measurements show stable dual-mode emission, with threshold currents around 50 mA and good extinction ratio of about 30 dB. At low current levels, two longitudinal modes having different transversal spatial distribution oscillate inside the laser cavity. The emission wavelengths of the two modes are selected by the grating periods defined on the sidewalls of the waveguide. At higher current levels, a strong single transversal mode appears at longer wavelengths. To gain a wider understanding on the different transversal and longitudinal modes, the dual-wavelength laser behaviour was assessed under external optical injection locking. Linewidth measurements of both the single modes and the mode beating are also reported.