Tiny lasers acting together as one: Topological vertical cavity laser arrays

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fairly difficult
An international research team uses topological platform to demonstrate coherent array of vertical lasers.
Israeli and German researchers have developed a way to force an array of vertical cavity lasers to act together as a single laser -- a highly effective laser network the size of a grain of sand. The findings are presented in a new joint research paper published online by the journal Science on Friday, September 24.

Cell phones, car sensors or data transmission in fiber optic networks are all using so called Vertical-Cavity Surface-Emitting Lasers (VCSELs) -- semiconductor lasers that are firmly anchored in our everyday technology. Though widely used, the VCSEL device has miniscule size of only a few microns, which sets a stringent limit on the output power it can generate. For years, scientists have sought to enhance the power emitted by such devices through combining many tiny VCSELs and forcing them to act as a single coherent laser, but had limited success. The current breakthrough uses a different scheme: it employs a unique geometrical arrangement of VCSELs on the chip that forces the flight to flow in a specific path -- a photonic topological insulator platform.

From topological insulators to topological lasers

Topological insulators are revolutionary quantum materials that insulate on the inside but conduct electricity on their surface -- without loss. Several years ago, the Technion group led by Prof. Mordechai Segev has introduced these innovative ideas into photonics, and demonstrated the first Photonic Topological Insulator, where light travels around the edges of a two-dimensional array of waveguides without being affected by defects or disorder. This opened a new field, now known as "Topological Photonics," where hundreds of groups currently have active research. In 2018, the same group also found a way to use the properties of photonic topological insulators to force many micro-ring lasers to lock together and…
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