Ridge-waveguide laser achieves a 22-nm tuning range

Researchers at the University of California (Santa Barbara, CA) achieved a 22-nm tuning range in a ridge-waveguide structure. The group`s ridge-waveguide, sample-grating distributed-Bragg-reflector (SGDBR) laser differs from other SGDBR designs in the use of offset quantum wells to form the gain section--these allow formation of active and passive sections without the need for butt-joint regrowth, thereby eliminating one metal-organic chemical-vapor-deposition growth step from the fabrication pr

Ridge-waveguide laser achieves a 22-nm tuning range

Researchers at the University of California (Santa Barbara, CA) achieved a 22-nm tuning range in a ridge-waveguide structure. The group`s ridge-waveguide, sample-grating distributed-Bragg-reflector (SGDBR) laser differs from other SGDBR designs in the use of offset quantum wells to form the gain section--these allow formation of active and passive sections without the need for butt-joint regrowth, thereby eliminating one metal-organic chemical-vapor-deposition growth step from the fabrication procedure. The four main elements of the 3-µm-wide ridge-waveguide laser were a 520-µm front mirror, a 450-µm gain section, a 150-µm phase-control section, and a 790-µm back mirror. Periodic sampling of front and back mirror gratings at intervals of 64 and 71 µm, respectively, produced a reflection spectrum with peak spacing at about 5 nm, and parallel tuning of the mirrors allowed fine-tuning of the system between spectral peaks.

Simultaneous control of mirror currents as well as gain and phase currents enabled the device to cover 27 wavelength-division-multiplexing channels from 1531.12 to 1551.72 nm, with precise 100-GH¥spacing between channels and more than 40 dB of sidelobe suppression. Design difficulties still to be overcome include prevention of electron leakage current in the tuning sections and increasing gain to compensate for reduced modal overlap.

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