Emerging Photonic Hardware Platforms

Photonic integrated circuit technology could revolutionize optical information processing, beyond conventional binary-logic approaches, granting the capacity of ultrafastcategorization and decision-making. We will discuss the progress and requirements of scalable and reconfigurable emerging photonic hardware platforms. © 2016 Optical Society of America OCIS codes: (200.0200) Optics in computing; (200.3050) Information processing; (200.4650) Optical interconnects; (250.0250) Optoelectronics; (250.5300) Photonic integrated circuits; (250.5960) Semiconductor lasers. Photonics has revolutionized information communication, while electronics, in parallel, has dominated information processing. Recently, there has been a determined exploration of the unifying boundaries between photonics and electronics on the same substrate, driven in part as Moore’s Law approaches its long-anticipated end [1, 2]. For example, the computational efficiency (multiply-accumulate (MAC) operations per joule) for digital processing has leveled-off around 100 pJ per MAC [2]. As a result, there has been a widening gap between computational efficiency and the next generation needs, such as Big Data applications which require advanced pattern matching and analysis on increasingly dense, voluminous data in real-time. This in turn, has led to expeditious advances in: (1) emerging devices that are called beyond-CMOS or More-than-Moore, (2) novel processing or unconventional computing architectures called beyond-von Neumann, that are bio-inspired i.e. neuromorphic, and (3) CMOS-compatible photonic interconnect technologies. Collectively, these research endeavors have opened opportunities for emerging photonic hardware platforms that are reconfigurable i.e. programmable optical integrated circuits (POIC) such as photonic spike processors [3–8]. Such chips in the near future could combine ultrafast operation, moderate complexity, and full programmability, extending the bounds of computing for applications such as navigation control on hypersonic aircrafts, and real-time sensing and analysis of the radio frequency (RF) spectrum. We will discuss the current progress and requirements of such a platform. In a photonic spike processor, information is encoded as events in the temporal and spatial domain of spikes (or optical pulses). This hybrid coding scheme is digital in amplitude but analog in time and benefits from the bandwidth efficiency of analog processing and the robustness to noise of digital communication. Optical pulses are received, processed, and generated by certain class of semiconductor devices that exhibit excitability—a nonlinear dynamical mechanism underlying all-or-none responses to small perturbations [9]. Optoelectronic devices operating in the excitable regime are dynamically analogous with the spiking dynamics observed in neuron biophysics but roughly eight orders of magnitude faster. Example of excitable photonic devices include two-section gain and saturable absorber (SA) lasers [3, 6, 10], semiconductor ring [11–13] and microdisk lasers [14, 15], two-dimensional photonic crystal nanocavities [16, 17], resonant tunneling diode photodetector and laser diode [7], semiconductor lasers based on optical injection [18–20] and optical feedback [21–24], and polarization switching in VCSELs [8]. Using a gain and SA excitable laser, we recently demonstrated [3] the first unified, experimental demonstration of low-level spike processing functions in an optical platform. Excitatory input pulses to this laser increase the carrier concentration within the gain region by an amount proportional to its energy through gain enhancement. Beyond some excitation energy, the absorber is saturated, resulting in the release of a pulse. This is followed by a relative refractory period during which the arrival of a second excitatory pulse is unable to cause the laser to fire as the gain recovers. We showed that this platform can simultaneously exhibit logic-level restoration, cascadability and input-output isolation— fundamental challenges in optical information processing [25–27]. We also implemented the classic spike processing tasks of temporal pattern detection and stable recurrent memory—while simple, these fundamental behaviors underly higher level processing. We will review the recent surge of interest in the information processing abilities of such excitable optoelectronic devices. The field is now reaching a critical juncture where there is shift from studying single excitable (spiking) devices to studying an interconnected network of such devices to build a photonic spike processor. We recently proposed [4] IW1B.1.pdf Advanced Photonics Congress 2016 (IPR, NOMA, Sensors, Networks, SPPCom, SOF) © OSA 2016 Microring Resonators (MRR) Bank