Single-transverse-mode InGaAsP-InP edge-emitting bipolar cascade laser

In order to improve the radio frequency (RF) link gain of opto-RF links, we have designed, fabricated, and characterized a bipolar cascade laser (BCL). It includes two active regions and one highly doped backward-biased tunnel junction. In order to study the intrinsic properties, we have etched a 18-mu m-wide deep-ridge. Comparing the result with a similar structure that does not recycle the carriers, we found an increase by a factor of two of the internal quantum efficiency. The same structure was etched into a 2.5-mu m-wide shallow ridge laser. We demonstrate a single- transverse-mode edge-emitter 1.55-mu m BCL with enhanced external efficiency, paving the way to short term opto-RF system characteristics improvement.