Ultraviolet Unblocked ((exclusive)) | TRUSTED |

A hemispherical fused silica concentrator with a narrow field-of-view (3°) that can be steered electronically. 4. Experimental Validation We constructed a UV² testbed in a suburban environment (humidity 65%, visibility 10 km). The transmitter and receiver were placed behind separate concrete barriers with no LOS.

The author declares no competing interests. End of generated paper. ultraviolet unblocked

OOK (On-Off Keying) with pulse-position modulation at 500 MHz. Range: 1.2 km. Data Rate: 9.8 Gbps (measured, with BER < ( 10^{-9} )). A hemispherical fused silica concentrator with a narrow

Please note that while this paper follows rigorous academic structure and plausible science, it is a generated synthesis for illustrative purposes. Author: J. A. Sinclair Affiliation: Institute for Photonic Advancements Journal: Journal of Next-Generation Communications (Vol. 14, Issue 2) Date: April 14, 2026 Abstract The conventional electromagnetic spectrum is congested. Radio frequencies (RF) are contested, while visible and infrared (IR) channels suffer from high background noise and atmospheric scattering. The ultraviolet (UV) band, specifically the 200–280 nm "solar-blind" region, has historically been dismissed as "blocked" by stratospheric ozone. This paper re-evaluates that assumption. We demonstrate that rather than a limitation, atmospheric absorption presents a unique opportunity for non-line-of-sight (NLOS), low-interception, all-weather communication. By utilizing resonant Raman scattering and novel aluminum gallium nitride (AlGaN) deep-UV LEDs, we show that data rates exceeding 10 Gbps are achievable over kilometer-scale NLOS paths. We term this paradigm "Ultraviolet Unblocked" (UV²), arguing that the very opacity of the atmosphere to solar UV creates a pristine, noise-free quantum channel for secure, next-generation photonic networks. 1. Introduction For decades, the ultraviolet C (UVC, 100–280 nm) spectrum was considered an impediment to optical communications. Unlike visible light, which propagates easily, or radio waves, which diffract around obstacles, UVC is strongly absorbed by ozone, oxygen, and water vapor. This absorption, however, is not a blockade but a filter. The same atmosphere that blocks solar UV (creating the "solar-blind" window) also blocks man-made UV signals after a single scattering event. The transmitter and receiver were placed behind separate

This work was supported by the DARPA UV² program (Contract No. HR0011-25-2-004).