Proposal of wavelength trimming of 1.55 μm GC-DFB laser using photoabsorption-induced disordering of superlattices

Wavelength-division multiplexing (WDM) systems require their light sources to have an oscillation wavelength that matches predefined wavelength channels and are stable over a long period of time. One remaining issue of the multiple-wavelength DFB laser array is the poor wavelength reproducibility of individual lasers. In order to manage this problem, the concept of "wavelength trimming" was proposed. Wavelength trimming techniques include using chalcogenide glass having photo-induced refractive index change or relying on the photoabsorption-induced disordering (PAID) process. However, the problem with these wavelength trimming techniques is that they cause the lasing characteristics to change. In order to manage this problem, we propose a new wavelength trimming technique using photoabsorption-induced disordering of superlattices. We propose the new structure of GC-DFB laser with this technique that the superlattices was grown above quantum wells. Using this new GC-DFB laser structure, the superlattices can absorb laser photons before quantum wells and intermixing is induced at the superlattices instead of at the quantum wells. As a result, the lasing characteristics of laser, except for oscillation wavelengths, can be kept after wavelength trimming. We have demonstrated 0.32 nm wavelength trimming.