Thermal wavelength stability of ultraviolet-B vertical-cavity surface-emitting lasers enabled by short cavity length and dielectric mirrors

For wavelength-sensitive applications, the lasing wavelength shift with temperature should be negligible. In vertical-cavity surface-emitting lasers (VCSELs), this wavelength shift is set by the resonance shift with temperature. We here propose and demonstrate an approach to drastically reduce this temperature dependence by compensating the inherent redshift by the semiconductor cavity with a blueshift induced by the dielectric distributed Bragg reflectors (DBRs) in short-cavity lasers. This was implemented in optically pumped VCSELs emitting at 310 nm, which resulted in lasers with a measured blueshift of less than 0.1 nm over 80°C with a maximum slope of 3.4 pm/K, to be compared with the redshift of about 1-1.5 nm over the same temperature range reported for III-nitride blue-emitting VCSELs. This concept to achieve a more temperature-stable lasing wavelength is generic and could be applied to any VCSELs.