Vertical-cavity surface-emitting laser diodes for short distance optical fiber networks

We have fabricated wavelength tunable vertical-cavity laser diodes in 2D arrays by molecular beam epitaxy, proton implantation, and wet chemical etching. Record low threshold currents of 650 /spl mu/A for continuous wave and 600 /spl mu/A for pulsed operation are obtained for devices with 8 /spl mu/m active diameter. Output power is up to 170 /spl mu/W CW and 400 /spl mu/W pulsed. The emission is single longitudinal and transversal mode at about 970 nm wavelength. Three terminals for each laser diode supply two separate currents for the independent control of output power and emission wavelength of individual elements in a 2D laser array. A record wide continuous wavelength tuning range of 8.2 nm is achieved in a slightly larger device with tuning currents of just 2.5 mA. Highly efficient and alignment tolerant coupling to single-mode optical fibers is demonstrated with quasi-planar vertical-cavity laser diodes which provide a two-sided light output. Direct contact butt coupling to flat cut single-mode optical fibers of 4.5 /spl mu/m diameter core results in coupling efficiencies over 90%. The lateral alignment tolerances defined by a -3 dB coupling efficiency decrease are as large as 5.6 /spl mu/m. Maximum power coupled into a 9 /spl mu/m diameter core fiber is 0.75 mW for a non-heat sinked laser diode.<
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