Technical Insight
Hole etching forms single mode device (research review)
Hole etching forms single mode devices There are currently several different methods being investigated for reducing the cost of data communication lasers. Among these is the etching of DBR lasers to form single mode devices, which is achieved without the need for expensive regrowth techniques. The approach taken by L Sargent and colleagues (Bristol University, UK) has been to etch a two-dimensional lattice of holes, around 50 m long, on either side of a laser waveguide towards the back facet. This relatively simple process improves wave-guiding and produces a mode-hop-free, single longitudinal mode device capable of room temperature operation at 10 Gbit/s. The holes are etched by post-processing with focused ion beams into a 1300 nm InGaAsP/InP ridge-waveguide laser. The pitch is tuned to the device wavelength and uses a diameter-to-pitch ratio of 0.33. No expensive regrowth is required. Typically, an SMSR greater than 25 dB is observed, and open eyes are obtained at 10 Gbit/s with an extinction ratio of 6.5 dB, making the device suitable as a high-speed communications source. The work was first described in Electronics Letters 2000, 36(24) on page 2014.
