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1. Advantages of concave quantum barriers in AlGaN deep ultraviolet light-emitting diodes

   https://doi.org/10.1117/12.2650411  

   Jain, Barsha T.; Muthu, Manobalasankar; Velpula, Ravi Teja; Nguyen, Ngoc T.; Nguyen, Hieu Pham (March 2023, Gallium Nitride Materials and Devices XVIII)

   Morkoç, Hadis; Fujioka, Hiroshi; Schwarz, Ulrich T. (Ed.)

   Although AlGaN-based deep ultraviolet (UV) light-emitting diodes (LEDs) have been studied extensively, their quantum efficiency and optical output power still remain extremely low compared to the InGaN-based visible color LEDs. Electron leakage has been identified as one of the most possible reasons for the low internal quantum efficiency (IQE) in AlGaN based UV LEDs. The integration of a p-doped AlGaN electron blocking layer (EBL) or/and increasing the conduction band barrier heights with prompt utilization of higher Al composition quantum barriers (QBs) in the LED could mitigate the electron leakage problem to an extent, but not completely. In this context, we introduce a promising approach to alleviate the electron overflow without using EBL by utilizing graded concave QBs instead of conventional QBs in AlGaN UV LEDs. Overall, the carrier transportation, confinement capability and radiative recombination are significantly improved. As a result, the IQE, and output power of the proposed concave QB LED were enhanced by ~25.4% and ~25.6% compared to the conventional LED for emission at ~254 nm, under 60 mA injection current. 

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2. An Empirical Study of Deep Learning Models for LED Signal Demodulation in Optical Camera Communication

   https://doi.org/10.3390/network1030016  

   Ahmed, AbdulHaseeb; Trichy Viswanathan, Sethuraman; Rahman, MD Rashed; Ashok, Ashwin (December 2021, Network)

   Optical camera communication is an emerging technology that enables communication using light beams, where information is modulated through optical transmissions from light-emitting diodes (LEDs). This work conducts empirical studies to identify the feasibility and effectiveness of using deep learning models to improve signal reception in camera communication. The key contributions of this work include the investigation of transfer learning and customization of existing models to demodulate the signals transmitted using a single LED by applying the classification models on the camera frames at the receiver. In addition to investigating deep learning methods for demodulating a single VLC transmission, this work evaluates two real-world use-cases for the integration of deep learning in visual multiple-input multiple-output (MIMO), where transmissions from a LED array are decoded on a camera receiver. This paper presents the empirical evaluation of state-of-the-art deep neural network (DNN) architectures that are traditionally used for computer vision applications for camera communication. 

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3. Harvesting Planck radiation for free-space optical communications in the long-wave infrared band

   https://doi.org/10.1364/OL.476394  

   Weinstein, Haley_A; Cai, Zhi; Cronin, Stephen_B; Habif, Jonathan_L (November 2022, Optics Letters)

   We demonstrate a free-space optical communication link with an optical transmitter that harvests naturally occurring Planck radiation from a warm body and modulates the emitted intensity. The transmitter exploits an electro-thermo-optic effect in a multilayer graphene device that electrically controls the surface emissivity of the device resulting in control of the intensity of the emitted Planck radiation. We design an amplitude-modulated optical communication scheme and provide a link budget for communications data rate and range based on our experimental electro-optic characterization of the transmitter. Finally, we present an experimental demonstration achieving error-free communications at 100 bits per second over laboratory scales. 

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4. Optimized communication strategies with binary coherent states over phase noise channels

   https://doi.org/10.1038/s41534-019-0177-4  

   DiMario, M. T.; Kunz, L.; Banaszek, K.; Becerra, F. E. (July 2019, npj Quantum Information)

   Abstract The achievable rate of information transfer in optical communications is determined by the physical properties of the communication channel, such as the intrinsic channel noise. Bosonic phase noise channels, a class of non-Gaussian channels, have emerged as a relevant noise model in quantum information and optical communication. However, while the fundamental limits for communication over Gaussian channels have been extensively studied, the properties of communication over Bosonic phase noise channels are not well understood. Here we propose and demonstrate experimentally the concept of optimized communication strategies for communication over phase noise channels to enhance information transfer beyond what is possible with conventional methods of modulation and detection. Two key ingredients are generalized constellations of coherent states that interpolate between standard on-off keying and binary phase-shift keying formats, and non-Gaussian measurements based on photon number resolving detection of the coherently displaced signal. For a given power constraint and channel noise strength, these novel strategies rely on joint optimization of the input alphabet and the measurement to provide enhanced communication capability over a non-Gaussian channel characterized in terms of the error rate as well as mutual information. 

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5. Wireless Communication Testbed and Tools for Authentic STEM Learning

   Marojevic, Vuk; Goff, Richard; Dietrich, Carl B.; Yang, Taeyoung; Hearn, Christian W.; Polys, Nicholas F.; Buehrer, Michael R. (July 2015, ASEE Annual Conference proceedings)

   We propose a novel educational gamification approach that employs and reinforces otherwise abstract concepts currently taught in graduate-level courses to become a standard part of undergraduate communications courses in the future. In particular, we develop software tools that visually demonstrate relevant wireless communications parameters and processes, including those already taught in undergraduate communications courses (e.g., power, modulation type, data rate and bandwidth, coding rate) to students in an interactive way. We exploit our Internet-accessible wireless communication testbed X to enable students to experience wireless communication challenges and learn different solutions in realistic environments via an ordinary web browser. This paper presents our approach to authentic STEM learning and compares it with other past and ongoing initiatives. We conclude that there is a gap of practical teaching tools and methods for educating students as well as radio engineers and researchers about new trends in wireless communications with a focus on spectrum sharing. 

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