Visible light communication using InGaN optical sources with AlInGaP nanomembrane down-converters

Abstract

Abstract:We report free space visible light communication using InGaN sources, namely micro-LEDs and a laser diode, down-converted by a redemitting AlInGaP multi-quantum-well nanomembrane. In the case of micro-LEDs, the AlInGaP nanomembrane is capillary-bonded between the sapphire window of a micro-LED array and a hemispherical sapphire lens to provide an integrated optical source. The sapphire lens improves the extraction efficiency of the color-converted light. For the case of the downconverted laser diode, one side of the nanomembrane is bonded to a sapphire lens and the other side optionally onto a dielectric mirror; this nanomembrane-lens structure is remotely excited by the laser diode. Data transmission up to 870 Mb/s using pulse amplitude modulation (PAM) with fractionally spaced decision feedback equalizer is demonstrated for the micro-LED-integrated nanomembrane. A data rate of 1.2 Gb/s is achieved using orthogonal frequency division multiplexing (ODFM) with the laser diode pumped sample.

Laser-excited 580nm AlGaInP nanomembrane for visible light communications

“…Owing to its higher cc efficiency, the highest data rate, 180 Mb/s, was obtained for the superlattice design at (37 Mb/s above the anti-symmetric design). These values are below the previously reported values of 1.2 Gb/s for the 650nm membranes [13] and are currently limited by the lower cc efficiency. However, they are still at least an order of magnitude above those of conventional phosphors.…”

“…Compared to a similar structure with red emission [13], the efficiency of the yellow membranes is one order of magnitude lower. This is to be expected, since these membranes emit at a wavelength closer to the direct/indirect bandgap transition of the AlGaInP alloy, and the carriers are less confined (electron confinement is ~ 90meV for yellow QWs and ~200meV for the red QWs in [13]). Furthermore, the wet etch process appears non-uniform, possibly over etching the active region, which is detrimental to the efficiency.…”

“…An additional AlAs layer on the buffer side acts as etch stop. To obtain sub-micron-thick color converting membranes, the substrate is removed by wet etching following a similar process to the one in [13]; however here the sides of the membrane were also protected by an acid resistant wax to avoid lateral etching. The samples were bonded onto a /10 smooth glass piece for handling and testing ( Figure 1).…”

“…An epitaxial quantum-well structure specifically designed for optical pumping with a GaN source is an attractive color converter candidate, as reported with II-VI [10] and III-V [11] material systems (emission at 545, 581 and 626 nm, and 535 nm, respectively) although these reports did not consider VLC at the time. More recently, our group has shown the integration of thin, 520nm-emitting ZnCdSe and 650nm-emitting AlGaInP membranes with optics and with LEDs and studied their VLC performance [12,13].…”

Theoretical and experimental optimization of DMT-based visible light communication under lighting constraints

“…A detailed study should be realized to determine the optimal modulated bandwidth suitable for each desired luminance level allowing the maximal transmission rate. Otherwise, we would like to report that very high data rates are mentioned in the literature using more complex types of lighting sources such as micro-LEDs [23][24][25] and special made LEDs including organic [26] semiconductor [27] and photonic crystal materials [28]. A maximum data rate of 8 Gbps is achieved in [25].…”