Capability Limitations for Slow Light Using Vertical-Cavity Surface-Emitting Laser Amplifier

An analytical expression for the delay-bandwidth product (DBP) of slow light in a vertical-cavity surface-emitting laser (VCSEL) is derived and experimentally confirmed. The expression and theoretical results show that the DBP has a maximum value, which is only dependent on the front facet reflectivity of the VCSEL. For a practical VCSEL with the front facet reflectivity exceeding 90%, the resulting maximum DBP is close to a fixed value of 0.64. The expression and the results are also verified by the measured DBP of a VCSEL with different bias currents.