Continuous wavelength-swept MEMS-VCSEL

In this talk, we review recent progress of monolithic, wavelength-swept vertical-cavity surface-emitting lasers (VCSELs) and their applications. A typical electrically-pumped VCSEL consists of two oppositely doped distributed Bragg reflectors (DBRs) with a cavity layer in between. In the center of the cavity layer resides an active region, consisting of multiple quantum wells. Due to the short cavity length which results in a very large longitudinal mode spacing, there is only one longitudinal mode that lases. Lasing wavelength can be continuously swept with continuously varied cavity length. The first generation of sweptable tunable VCSELs were demonstrated with part or entire top DBR be held by a micro-electro-mechanical structure (MEMS) and the lasing wavelength is varied by moving the MEMS with an electric bias. Electrically-pumped, tunable VCSELs emitting at 850-nm, 940-nm, 1060-nm, 1300-nm and 1550-nm were all demonstrated. These VCSELs are demonstrated with high modulation rate and coherent lengths, well poised for optical communications applications in datacenters, fiber-to-the-home and metropolitan area networks. Recently, optically pumped tunable VCSEL has been demonstrated with an ultrawide tuning range. In addition, new applications in optical coherence tomography and LIDAR are particular interesting for continuously tunable VCSEL. Finally, replacing the movable top DBR mirror by an ultra-thin high-contrast grating (HCG), the sweep rate of the tunable VCSEL was reported to drastically increased to 1~10 MHz, which can enable many real-time 3D imaging applications. We will discuss the design criteria, characteristics, challenges, advances and prospects of wavelength-swept MEMS-VCSEs.