Stark-tunable InGaAs laser diodes

Summary form only given. Cost-effective wavelength-tunable laser diodes (LDs) can become crucial components in optical telecommunications. There are currently several technologically interesting solutions to achieve tunability based on temperature, external cavity laser, or a multi-section DBR laser. In this work we explore an alternative approach, where the LD tuning mechanism is based on the quantum-confined Stark effect (QCSE). To achieve this, the LD active region is designed such that the injection current generates during lasing a space-charge field that tunes the lasing wavelength λ_L. We show a schematic band diagram of the LD active region we propose. It consists of three quantum wells (QWs) separated by two tunneling barriers. The central QW is the active QW (AQW), whose lowest transition is the ground state of the whole structure. The outer QWs are the collection QWs (CQWs), whose role is to collect the carriers that generate the space-charge field. To ensure efficient carrier injection in the AQW for lasing, it is essential to keep the barriers sufficiently thin to allow for carrier tunneling from the CQWs into the AQW. The active region is embedded in the intrinsic region of a p-i-n diode. During electrical injection, the CQWs accumulate a transient excess of electrons and holes on either side of the AQW. This results in a space-charge field, acting on the AQW through QCSE and tuning λ_L. With increasing injection current, the space-charge field increases and λ_L redshifts further. We have fabricated and processed in the InGaAs/AlGaAs system a number of LD structures, with varying key heterostructure parameters such as barrier and AQW widths.