Broad-band tunable two-section laser diode with external grating feedback

A tunable laser light source consisting of a two-section laser diode and an external grating is discussed. A wide tunable range of 154 nm was realized by improving the antireflection (AR) coating and the coupling efficiency. At both edges of the tunable range, however, the tuning characteristics were strongly influenced by the internal mode, in spite of the high-quality AR coating. The effects of the internal mode were avoided by using a phase-control section of the laser. Consequently, single-mode oscillation can be obtained at any desirable wavelength within the above tunable range by controlling the current injected into the phase-control section.<
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