SUBTUNE · Widely Tunable VCSEL using Sub Wavelength Gratings

Wavelength-tunable lasers are key components for future reconfigurable optical networks and for cost-effective and compact telecommunication infrastructures. Moreover, a broadband and continuously tunable laser with high purity emission spectrum is a versatile tool for many sensing applications, e.g. for greenhouse gases (laser absorption spectroscopy) or deformations of buildings (fiber Bragg grating sensors).A novel concept for widely and continuously wavelength-tunable single-mode laser diodes in the 750-2100 nm wavelength range will be developed. The underlying VCSEL structure is completed by a micro-machined moveable Bragg-mirror with a sub-wavelength grating (SWG). The single-mode property of the VCSEL structure is thus ideally combined with the polarization stability of the SWG and the wide and continuous tunability of the electro-thermally or electro-statically actuated mirror. For the fabrication of the nano-scale SWGs an electron-beam writing process will be developed.The curvature of the micro-mirror will be matched to the phase front of the fundamental mode to achieve its maximum support while suppressing undesired polarization modes by means of a SWG. This technology can select the single fundamental mode from relatively large apertures. The optical output power will be high and a very good sidemode suppression will be achieved during tuning. The project will develop both long wavelength InP-based VCSELs (1.3μm to 2.1μm) and short wavelength GaAs VCSELs (down to 800nm), and thus introduces widely tunable VCSELs in a broad range of the optical spectrum. Additionally, a technology for integrated tunable VCSELs with dielectric Bragg mirrors will be developed for efficient manufacturing of the laser modules.The devices will be optimized in close cooperation between the university and industrial partners. Devices for gas detection, fiber Bragg grating sensing and optical communications will be investigated.