External-cavity semiconductor laser with focusing grating mirror

A novel external-cavity semiconductor laser with a focusing grating mirror (FGM), which enables a single-mode oscillation at a specified wavelength, is proposed. The optical properties of the FGM, which is a computer-generated holographic grating with chirp and bend structure, are numerically analyzed. An optimally designed FGM for realizing laser oscillation at a specific wavelength of 1.30 mu m is fabricated by using a computer-controlled electron-beam writing system. The fabricated FGM with grating area of 1*1 mm/sup 2/ is combined as an external feedback mirror with an InGaAsP-InP semiconductor laser of 1.3 mu m wavelength range, and the lasing characteristics are experimentally measured. Stable and single-mode oscillations with spectral line width less than 10 MHz are observed.<
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