Wavelength trimming by external light irradiation-post-fabrication lasing wavelength adjustment for multiple-wavelength distributed-feedback laser arrays

Oscillation wavelength of distributed-feedback (DFB) lasers is easily affected by small variation in device parameters, and therefore, prescribing oscillation wavelength is very difficult. This insufficient wavelength reproducibility limits the device yield, specifically, in multiple-wavelength DFB laser arrays whose element needs to have lasing wavelength that matches pre-defined wavelength-division-multiplexed (WDM) channels. In this paper, we describe a novel concept to manage this problem, namely, “wavelength trimming.” Here, the oscillation wavelength error is corrected after the device fabrication without using external active control circuitry. In this particular demonstration, we have used Se-based chalcogenide glass film having photo-induced refractive index change as a part of the laser waveguide, and demonstrated the wavelength trimming of 0.14 nm at 1.55 μm in an index-coupled DFB laser by He-Ne laser irradiation