Renewed interest in vertical-cavity surface-emitting lasers (VCSELs) operating in the regions of 1300 and 1550 nm has come as a result of the desire for so-called ‘eye-safe’ lasers (>1400 nm) in consumer applications, for below-screen sensing in mobile devices (>1380 nm) and for light detection and ranging (LiDAR). Current VCSELs have a host of applications, including printing, bar code reading, data communications and facial recognition systems. Typical (In)GaAs quantum-well VCSEL active-regions are sub-optimal for reaching telecoms and ‘eye-safe’ wavelengths because of the large strain accompanying the increased In fraction required. Here, a case is made for the use of GaSb quantum rings (QRs) over other materials in VCSEL active regions for devices across the telecoms range. The design and fabrication of two prototype quantum ring VCSELs is discussed and provisional results are presented for continuous operation at room temperature and at 77 K. The origin of background emission is considered and a sub-milliamp threshold current achieved for emission at 1257 nm.
Advances in single-photon sources have proved pivotal to the progress of quantum information processing and secure communication systems. This study addresses the imperative need for developing commercially viable, electrically-driven single-photon sources capable of operating at or above room temperature with rapid response times and emission in the telecom wavelength range of 1260 to 1675 nm. We introduce an innovative single-photon light-emitting diode (SPLED) design employing GaAs quantum dots (QDs) and self-assembled GaSb quantum rings (QRs). The core of our design is an electron filter layer composed of GaAs QDs embedded in AlxGa1-xAs, engineered to inject (single) electrons into an ensemble of type-II GaSb QRs in GaAs, where they recombine with strongly confined holes producing (single) photons at a wavelength governed by an optical cavity created using distributed Bragg reflectors (DBRs). This concept removes the need to select individual QD emitters, rendering the device highly suitable for scalable production. Our research demonstrates a comprehensive theoretical and experimental analysis using nextnano++ simulations and fabricated prototype device characteristics. Quite remarkably, we find that the emission properties of the SPLED devices actually improves as operational temperature is increased from 20 °C to 80 °C, making them attractive as practical devices.
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