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Abstract The generation of ultra-low-noise microwave and mmWave in miniaturized, chip-based platforms can transform communication, radar and sensing systems^1–3. Optical frequency division that leverages optical references and optical frequency combs has emerged as a powerful technique to generate microwaves with superior spectral purity than any other approaches^4–7. Here we demonstrate a miniaturized optical frequency division system that can potentially transfer the approach to a complementary metal-oxide-semiconductor-compatible integrated photonic platform. Phase stability is provided by a large mode volume, planar-waveguide-based optical reference coil cavity^8,9and is divided down from optical to mmWave frequency by using soliton microcombs generated in a waveguide-coupled microresonator^10–12. Besides achieving record-low phase noise for integrated photonic mmWave oscillators, these devices can be heterogeneously integrated with semiconductor lasers, amplifiers and photodiodes, holding the potential of large-volume, low-cost manufacturing for fundamental and mass-market applications¹³. 

The integration of stabilized lasers, sources that generate spectrally pure light, will provide compact, low-cost solutions for applications including quantum information sciences, precision navigation and timing, metrology, and high-capacity fiber communications. We report a significant advancement in this field, demonstrating stabilization of an integrated waveguide Brillouin laser to an integrated waveguide reference cavity, where both resonators are fabricated using the same CMOS-compatible integration platform. We demonstrate reduction of the free running Brillouin laser linewidth to a 292 Hz integral linewidth and carrier stabilization to a 4.9 × 10 −13 fractional frequency at 8 ms reaching the cavity-intrinsic thermorefractive noise limit for frequencies down to 80 Hz. We achieve this level of performance using a pair of 56.4 × 10 6 quality factor Si 3 N 4 waveguide ring-resonators that reduce the high-frequency noise by the nonlinear Brillouin process and the low-frequency noise by Pound–Drever–Hall locking to the ultra-low loss resonator. These results represent an important step toward integrated stabilized lasers with reduced sensitivity to environmental disturbances for atomic, molecular, and optical physics (AMO), quantum information processing and sensing, and other precision scientific, sensing, and communications applications. 

Abstract Narrow linewidth visible light lasers are critical for atomic, molecular and optical (AMO) physics including atomic clocks, quantum computing, atomic and molecular spectroscopy, and sensing. Stimulated Brillouin scattering (SBS) is a promising approach to realize highly coherent on-chip visible light laser emission. Here we report demonstration of a visible light photonic integrated Brillouin laser, with emission at 674 nm, a 14.7 mW optical threshold, corresponding to a threshold density of 4.92 mW μm −2 , and a 269 Hz linewidth. Significant advances in visible light silicon nitride/silica all-waveguide resonators are achieved to overcome barriers to SBS in the visible, including 1 dB/meter waveguide losses, 55.4 million quality factor (Q), and measurement of the 25.110 GHz Stokes frequency shift and 290 MHz gain bandwidth. This advancement in integrated ultra-narrow linewidth visible wavelength SBS lasers opens the door to compact quantum and atomic systems and implementation of increasingly complex AMO based physics and experiments. 

Near field communication (NFC), which emerged only a decade ago, has been rapidly adopted in business services including point-of-sale (POS) systems, payments, identification, ticketing, and various other types of services. NFC offers great and varied promise in providing secure and implicit paired communication capability in smartphones. As a short-range wireless communication technology, the level of "secure" is contributed by the short-range nature. Compared with other competitive technologies, NFC achieves physical-level security but sacrifices convenience. For example, NFC cannot achieve device-free or hands-free payment transactions like the service provided by PayPal called PayPal beacon which utilizes Bluetooth-low-energy (BLE) technology. In this paper, we propose a low-cost wearable device that can achieve better physical-level security than NFC provides. This system is compatible with existing NFC-based POS systems and can help users realize a convenient hands-free payment transaction. Specifically, a custom NFC wristband was designed to channel its magnetic field through the human arm. By confining the magnetic field in NFC to the area around the body, we could minimize energy radiation, reduce the possibility of communication sniffing and hijackings, and improve security. To evaluate this approach, we conducted various experiments via different configurations. The results showed that the communication range for the human body channel was greater than that of the air and water channels. In addition, through this study we demonstrated that the human body is a naturally secure channel, and hacking and nearby interference are minimized during such communication. Our system also defines a new way of communication, for example, people can share confidential information with a simple handshake without pulling out and touching, or tapping smartphones.