Very High Data Rate Optical Wireless Communication with Micro Organic LED

International audienceWe present a broadband free space light communication using high-speed micro organic light emitting diode (OLED) as transmitter. We report first the design and bandwidth measurements of innovative OLEDs whose size are in the range of tens of micrometres. For OLEDs with reduced active area such as 40 µm x 40 µm, a cut-off frequency up to 345 MHz is reached. Then a free-space optical wireless link is build based on these high-speed micro-OLED. Using Direct Current Optical-Orthogonal Frequency Division Multiplexing) with adaptive bit and energy loading, we achieve a data rate of 2.85 Gb/s

Sub-ns High-Speed Organic Light Emitting Diodes and Perspectives to Light Communication

The literature reports some experiments on light communication based on organic light emitting diode emitters with data rate up to 1.13GBit/s [1]. We present theoretical and experimental evidences indicating that high-speed OLEDs exhibit dynamical behavior in the sub-nanosecond time scale which opens perspectives for Light Communication not only in the GHz regime but tenfold larger. From the theoretical point of view, we will present an electrical dynamical model and an organic laser diode dynamical model based on rate equations that predict both spontaneous and stimulated emission dynamical behaviors in the sub-ns and picoseconds time scale following electrical pulsed excitation. These models also describe emission of Organic light emitting diodes (OLED). Simulations show that firstly, spontaneous emission with 800ps optical pulses and below are possible. Secondly, above threshold, dynamical optical responses of Alq3 based organic devices predict relaxation oscillations with frequencies from 4GHz to 14GHz [2]. In the experimental section we present both the fabrication aspect of the devices and the measured electrical and optical responses of high-speed OLEDs. Among the fabrication aspect, we describethe design and the fabrication of coplanar waveguide necessary to provide 50 Ohm characteristic impedance to the high-speed OLED electrodes [3]. We also present the fabrication of distributed feedback (DFB) nanostructures compatible with organic heterostructures as necessary cavity for the development of organic laser diodes. Different types of measurement are presented; firstly we report optical pulses of 1ns, 800ps and down to 400ps in duration emitted by specifically designed High-Speed OLEDs. We present also optical and electrical measurement of 100x100μm2 OLED to 20ns electrical pulses at medium (460A/cm2) and high (8.8kA/cm2) current density [4]. These measurements are fitted with simulations, thus validating the proposed dynamical model and givingcredibility that OLED can be as fast as, or even faster than III-V based LEDs.Finally, the combined conclusions from the models and the measurements are twofold. Firstly the fabrication and the demonstration of organic laser diode is at hand with cavities and current density large enough to reach the laser threshold. Secondly, we propose High-Speed-OLED based organic light-communication emitters: together with Direct-Current Optical Orthogonal Frequency DivisionMultiplexing (DCO-OFDM) and bit/power loading algorithms allowing spectral efficiency as high as 8bit/Hz/s, we project data transmission rates up to 10Gbit/s

2.85-Gb/s Organic Light Communication With a 459-MHz Micro-OLED

We present a broadband free space light communication system using high-speed organic light emitting diodes (OLEDs) as transmitters. Firstly, we report the design and bandwidth measurements of micro-OLEDs with active area of 40 × 40μm2. For this OLED, a cut-off frequency up to 459 MHz is observed. Secondly, by applying Direct Current Optical Orthogonal Frequency Division Multiplexing (DCO-OFDM) with adaptive bit and energy loading techniques, a data rate of 2.85 Gb/s is achieved. The increase of bandwidth and throughput reported in the current work are attributed to the improvements at the material, device and transmission levels. At the material level, a low work function Calcium cathode and ALD encapsulation of OLED is considered. At the device level, the active area is reduced in size and the OLEDs thickness is optimized. At the transmission level, parameters such as bias voltage, modulation amplitude and clipping have been fine-tuned to obtain high data rate

High-speed OLED bandwidth optimisation method based on Relative Intensity Noise measurements

International audienceIn the context of visible light communication, we present a heuristic approach to optimize the bandwidth of organic light-emitting diodes. Our approach utilizes a vector network analyzer and an optoelectronic loop to directly and rapidly visualize the effects of stack modifications on the optical bandwidth of high-speed OLEDs. This technique is applied for the first time to conduct systematic heuristic studies on OLED bandwidth and to identify relevant parameters such as OLED capacitance, serial resistance, emission layer thickness, and active area. More precisely, we utilize high-speed OLEDs based on coplanar wave guided electrodes, and demonstrate that reducing the active area of OLEDs from 500 x 500 μm² to 200 x 200 μm² and further to 100 x 100 μm² increases the bandwidth from 49 MHz to 91 MHz and above 200 MHz, respectively. Moreover, and counter intuitively, the bandwidth is increased when the hole blocking layer is removed from the organic heterostructure