Noise characteristics of GaInNAsSb 1300-nm-range VCSEL with optical feedback for isolator-free module

The behavior of relative intensity noise of GaInNAsSb 1300-nm-range vertical-cavity surface-emitting lasers (VCSELs) is presented for the first time. The relative intensity noise drastically increases beyond a critical optical feedback. It was theoretically and experimentally found that the increase of relaxation oscillation frequencies was effective for the sensitivity of the optical feedback in the single-mode long-wavelength VCSELs. In our experiment, the critical feedback levels were -32 and -29 dB when frequencies were 4.0 and 5.8 GHz. This result is in good agreement with a theory.