Theoretical analysis on optical frequency response of tunnel-junction transistor lasers operated in different configurations

The optical frequency responses of tunnel junction transistor lasers (TJTLs) in the presence of the intra-cavity photon-assisted tunneling (ICPAT) effect in different small-signal configurations are demonstrated. With the Franz-Keldysh (F-K) absorption, TLs can be modulated with the voltage across the base-collector junction in the reverse-bias regime. We simulate both the responses through current and voltage modulations of TJTLs based on the modified rate equations and small-signal model incorporating the F-K and ICPAT effects. The input electrical signal is transferred to both the base-collector junction voltage and base current through the equivalent circuit, leading to simultaneous modulations of voltage and current. It is shown that the resistance and capacitance of the base-collector tunnel-junction play essential roles in electrical transfer functions and modulation bandwidth. With the small-signal optical responses, the eye diagrams of TJTLs under current and voltage modulations are also calculated. The device can be potentially modulated at a speed over 20 Gb/s with clear eye-opening.