1 Gbps free-space deep ultraviolet communications based on III-nitride micro-LEDs emitting at 262 nm

The low modulation bandwidth of deep-ultraviolet (UV) light sources is considered as the main reason limiting the data transmission rate of deep-UV communications. Here, we present high-bandwidth III-nitride microlight- emitting diodes (µLEDs) emitting in the UV-C region and their applications in deep-UV communication systems. The fabricated UV-C µLEDs with 566 µm2 emission area produce an optical power of 196 µW at the 3400 A/cm ² current density. The measured 3 dB modulation bandwidth of these µLEDs initially increases linearly with the driving current density and then saturates as 438 MHz at a current density of 71 A/cm ², which is limited by the cutoff frequency of the commercial avalanche photodiode used for the measurement. A deep-UV communication system is further demonstrated. By using the UV-C µLED, up to 800 Mbps and 1.1 Gbps data transmission rates at bit error ratio of 3.8 × 10-3 are achieved assuming on-off keying and orthogonal frequency-division multiplexing modulation schemes, respectively.