A proposal of broad-bandwidth vertical-cavity laser amplifier

We propose a generic vertical-cavity amplifier (VCA) using a coupled-cavity design to broaden the bandwidth. Calculations are made for cavities with GaAs-AlAs and GaAs-Al_xO₂ distributed Bragg reflectors (DBR). We found that at reasonable pumping levels the VCA increased the bandwidth by 85% (GaAs-AlAs) to 500% (GaAs-Al_xO₂) as compared to a simple two-mirror structure similar to vertical-cavity surface-emitting lasers. In particular, the GaAs-AlAs VCA shows a bandwidth of 2 nm at 6-dB signal gain, while the GaAs-Al_xO₂ VCA demonstrates a 5-nm bandwidth at 6-dB signal gain with no ripple at required single-pass power gain of ~2-2.5%. Furthermore, as large as 30-nm bandwidth in a lossless bandpass filter can be obtained