GaSb quantum-rings for vertical-cavity surface-emitting lasers emitting at telecommunications and mobile sensing wavelengths

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.