Single-Mode VCSELs

Abstract

The only active transverse mode in a truly single-mode VCSEL is the fundamental mode with a near Gaussian field distribution. A single-mode VCSEL produces a light beam of higher spectral purity, higher degree of coherence and lower divergence than a multimode VCSEL and the beam can be more precisely shaped and focused to a smaller spot. Such beam properties are required in many applications. In this chapter, after discussing applications of single-mode VCSELs, we introduce the basics of fields and modes in VCSELs and review designs implemented for singlemode emission from VCSELs in different materials and at different wavelengths. This includes VCSELs that are inherently single-mode as well as inherently multimode VCSELs where higher-order modes are suppressed by mode selective gain or loss. In each case we present the current state-of-the-art and discuss pros and cons. At the end, a specific example with experimental results is provided and, as a summary, the most promising designs based on current technologies are identified. IntroductionThe vertical-cavity surface-emitting laser (VCSEL) is an attractive light source for an expanding range of applications. Due to low cost manufacturing, low power consumption, simplified packaging, attractive beam properties (circular and low divergence beam) and excellent high-speed modulation characteristics at low currents, it has replaced the edge-emitting laser in short-reach optical communication links

Vertical-cavity surface-emitting laser technology applications with focus on sensors and three-dimensional imaging

“…Prominent applications include fingertip navigation, industrial displacement sensing, and laser computer mice, 7) where the latter significantly advanced early mass production of VCSELs. The sensors often require single-mode 20,21) and single-polarization emission. 22,23) More recently, the global market for VCSELs is rising at a compound annual growth rate (CAGR) of more than 20%.…”

Localization of Laterally Confined Modes in a 2D Semiconductor Microcavity

“…11 Generally, the optical confinement in a planar microcavity (i.e., 1D photonic crystal) is formed along the longitudinal direction, but the transverse electromagnetic field is poorly confined, which leads to a limited spontaneous-emission coupling factor of β; for example, it is less than 0.1 in a GaAs quantum-well microcavity. 12 To enhance β 13 and develop single-mode emission sources, 14,15 control of transverse modes is highly demanded in planar microcavities. Transverse modes in microcavities may present complex field patterns and involve multiple factors such as lateral size, shape, and boundary conditions.…”

“…Technically, transverse modes in resonant cavities can be managed by different confinement approaches, such as introduction of a waveguiding effect, modification of local structures, and incorporation with photonic crystal structures . By transferring TMDs onto 2D-photonic-crystal and 1D-nanobeam cavities or inserting them into microdisks, confined electromagnetic fields were realized in designed mode locations. − Interestingly, theoretical calculations predicted that monolayer material was able to support guided optical modes and the in-plane waveguiding effect was recently observed in a suspended monolayer photonic crystal structure .…”