Vertical Cavity Light Emitters for Plastic Optical Fibers

Abstract

Plastic optical fibres, which have a local attenuation minimum at 650 nm, have attracted much interest for low-cost short-haul communication systems. Red vertical-cavity surface-emitting lasers (VCSELs) and resonant cavity light emitting diodes (RCLEDs) provide a potential solution as light sources for these systems. The operation principle of vertical cavity emitters is based on a Fabry-Perot microcavity, which is formed by placing an optically active region inside of two parallel mirrors. The RCLEDs with emission windows of 84 μm in diameter, suitable for standard POFs, exhibit bandwidths up to 200 MHz and light power of 3 mW (cw). The maximum external quantum efficiency is 9.5%. Larger devices, ø500 μm in size, launch light power up to 15 mW. Record high transmission rates, 622 Mbit/s, with bit-error-rate <1 × 10-11 have been demonstrated for a 1-m-long step-index POF. Neither sudden unexpected failure, nor gradual power degradation has been observed after operation under accelerated ageing conditions for about 100 000 device-hours. The alignment tolerance of the coupling efficiency is found to be very large, ±0.5 mm in all directions x-y-z, suggesting that the fibre pigtail packaging is inexpensive. First MBE-grown visible AlGaInP vertical-cavity surface-emitting lasers have been demonstrated. A laser with a 10-μm emitting window has external quantum efficiency of 6.65% under continuous wave operation and it is still lasing at 45°C. Furthermore, a threshold current less than 1.0 mA is obtained for a device, which has an 8-μm emitting window.