Electronic Military & Defense Annual Resource

5th Edition

Electronic Military & Defense magazine was developed for engineers, program managers, project managers, and those involved in the design and development of electronic and electro-optic systems for military, defense, and aerospace applications.

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Technology Electronic Military & Defense Annual Resource, 5th Edition 19 the beam width only scales with N, as the other dimension can be addressed by changing grating length. This decreases control electronics complexity by one to two orders of mag- nitude for the designs discussed here. A recent realization of such a fully integrated beam steering chip by Hulme et al. is shown in Figure 7. Opportunities For Military Applications Photonic and photonic-electronic integration offer compact and high-speed beam steering solutions. The main strength of such chips is their potential for integration with co- packaged or on-chip electronics, as well as on-chip control elements. This includes on-chip optical calibration elements, allowing for the elimination of temperature and other envi- ronmental effects, which is essential for field operation of such systems ii,iii . Although intrinsically safe, due to the narrow beam angle (hence, low probability of interception), free-space optical communication systems based on this technology also can use well-known advanced optical encryption techniques, such as chaotic encryption and quantum encryption. The latter option is especially attractive in environments with low attenuation, like space-based communications, where the light travels through a vacuum. Transmitter and receiver photonic components, such as modulators and photodetec- tors, can be integrated on the same chip for a full monolithic solution. Along the same lines, Lidar systems based on optical beam steering technology can benefit by integrating optical signal generation and processing on the same chip. For example, Aflatouni et al. have presented an optical phased array chip that includes coherent detection iv . Based on a frequency- modulated continuous-wave ranging scheme, as known from radar technology, they achieved three-dimensional imaging. This is a significant achievement for portable imaging and targeting systems. In closing, it warrants mention that silicon photonics, and silicon-compatible materials like silicon oxide and silicon nitride, can be used to make optical chips for wavelengths ranging from the ultraviolet to the mid-infrared. This means that a large part of the electromagnetic spectrum can be lever- aged for electronic warfare. Separate laser diodes can be co- packaged and coupled to the optical chip. This also can be achieved on a single chip using heterogeneous integration. Wavelength sources in the range of 1.0 µm to 2.0 µm already have been successfully integrated with optical chips based on silicon substrates. Using a non-silicon substrate — indium phosphide, for example — the full beam steering chip can be integrated monolithically, as shown by Guo et al. v Outlook Photonic integration technology offers, in principle, low-cost and low-SWaP solutions for beam shaping and steering. Important military applications include secure free-space communications, compact Lidar systems, and precision tar- geting and countermeasures in electronic warfare. In R&D; labs, it has been shown experimentally that such systems are feasible. Still, the question remains whether this technology can soon move out of the lab and into the field. Optical chip technology often has been cost-prohibitive for applications outside telecom. However, with a maturing technology, which can now be accessed through established foundries, this bottleneck is opening up. Already, silicon photon- ics technology can be accessed for prototyping through Europractice and A*STAR, and indium phosphide technol- ogy is available through the JePPIX platform. The recently announced $200 million national manufacturing initiative in photonics in the United States will only increase the pos- sibilities, especially for the U.S. defense industry. This set of circumstances has created a clear path out of the lab, which is key for applying optical beam steering chips to the next generation of portable and unmanned military systems. References i J. Sun, E. Timurdogan, A. Yaacobi, E. S. Hosseini, and M. R. Watts, "Large-scale nanopho- tonic phased array," Nature 493, 7431, 195-199 (2013). ii H. Abediasl, and H. Hashemi, "Monolithic optical phased-array transceiver in a standard SOI CMOS process," Optics Express 23, 5, 6509-6519 (2015). iii J. C. Hulme, J. K. Doylend, M. J. R. Heck, J. D. Peters, M. L. Davenport, J. T. Bovington, L. A. Coldren, and J. E. Bowers, "Fully integrated hybrid silicon two dimensional beam scanner," Optics Express 23, 5, 5861-5874 (2015). iv F. Aflatouni, B. Abiri, A. Rekhi, and A. Hajimiri, "Nanophotonic coherent imager," Optics Express 23, 4, 5117-5125 (2015). v W. Guo, P. R. A. Binetti, C. Althouse, M. Masanovic, H. P. M. M. Ambrosius, L. Johansson, and L. Coldren, "Two-dimensional optical beam steering with InP-based photonic integrated circuits," IEEE Journal of Selected Topics in Quantum Electronics 19, 4, 6100212 (2013). Martijn Heck is an associate professor in the department of engineering at Aarhus University, Denmark, where he works on photonic integration technology. He received his Ph.D. from Eindhoven University of Technology, Netherlands. Previously, he worked at the University of California Santa Barbara and the Vrije Universiteit, Amsterdam. Figure 7: Hybrid silicon beam steering chip, integrating a tunable laser, optical amplifiers, photodiodes, phase tuners, grating emitters, and calibration elements. A total of 164 photonic components are integrated. Reprinted with permission of The Optical Society iii .

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