On-chip broadband nonreciprocal light storage

Breaking the symmetry between forward- and backward-propagating optical modes is of fundamental scientific interest and enables crucial functionalities, such as isolators, circulators, and duplex communication systems. Although there has been progress in achieving optical isolation on-chip, integrated broadband nonreciprocal signal processing functionalities that enable transmitting and receiving via the same low-loss planar waveguide, without altering the frequency or mode of the signal, remain elusive. Here, we demonstrate a nonreciprocal delay scheme based on the unidirectional transfer of optical data pulses to acoustic waves in a chip-based integration platform. We experimentally demonstrate that this scheme is not impacted by simultaneously counterpropagating optical signals. Furthermore, we achieve a bandwidth more than an order of magnitude broader than the intrinsic optoacoustic linewidth, linear operation for a wide range of signal powers, and importantly, show that this scheme is wavelength preserving and avoids complicated multimode structures

The bifurcation periods in low-mass X-ray binaries: the effect of magnetic braking and mass loss

The bifurcation period in low-mass X-ray binaries is the initial orbital pe- riod which separates the formation of converging systems (which evolve with decreasing orbital periods until the donor becomes degenerate) from the diverging systems (which evolve with increasing orbital periods until the donor star loses its envelope and a wide detached binary is formed). We calculate systematically the bifurcation periods of binary systems with a 1.4M_\sun neutron star and a 0.5-2M_\sun donor star, taking into account different kinds of magnetic braking and mass loss mechanisms. Our results show that the saturated magnetic braking can considerably decrease the values of bifurcation period compared to the traditional magnetic braking, while the influence of mass loss mechanisms on bifurcation periods is quite weak. We also develop a semi-analytical method to compute the bifurcation period, the result of which agrees well with the numerical method in the leading order.Comment: 18 pages, 4 figures, 1 table. Accepted to be published in Ap

Coherently refreshed acoustic phonons for extended light storage

Acoustic waves can serve as memory for optical information, however, acoustic phonons in the GHz regime decay on the nanosecond timescale. Usually this is dominated by intrinsic acoustic loss due to inelastic scattering of the acoustic waves and thermal phonons. Here we show a way to counteract the intrinsic acoustic decay of the phonons in a waveguide by resonantly reinforcing the acoustic wave via synchronized optical pulses. This scheme overcomes the previous constraints of phonon-based optical signal processing for light storage and memory. We experimentally demonstrate on-chip storage up to 40 ns, four times the intrinsic acoustic lifetime in the waveguide. We confirm the coherence of the scheme by detecting the phase of the delayed optical signal after 40 ns using homodyne detection. Through theoretical considerations we anticipate that this concept allows for storage times up to microseconds within realistic experimental limitations while maintaining a GHz bandwidth of the optical signal. The refreshed phonon-based light storage removes the usual bandwidth-delay product limitations of e.g. slow-light schemes

Formation of ultra-compact X-ray binaries through circum-binary disk-driven mass transfer

The formation of ultra-compact X-ray binaries (UCXBs) has not been well understood. Previous works show that ultra-short orbital periods ($<1$ hr) may be reached through mass transfer driven by magnetic braking in normal low/intermediate-mass X-ray binaries (L/IMXBs) only for an extremely small range of initial binary parameters, which makes it difficult to account for the rather large population of UCXBs. In this paper we report the calculated results on mass transfer processes in L/IMXBs with a circum-binary disk. We show that when the orbital angular momentum loss due to a circum-binary disk is included, ultra-short orbital periods could be reached for a relatively wide range of initial binary parameters. The results of our binary models suggest an alternative formation channel for UCXBs.Comment: 25 pages, 8 figures, accepted for publication in Ap

Highly sensitive, broadband microwave frequency identification using a chip-based Brillouin optoelectronic oscillator

Detection and frequency estimation of radio frequency (RF) signals are critical in modern RF systems, including wireless communication and radar. Photonic techniques have made huge progress in solving the problem imposed by the fundamental trade-off between detection range and accuracy. However, neither fiber-based nor integrated photonic RF signal detection and frequency estimation systems have achieved wide range and low error with high sensitivity simultaneously in a single system. In this paper, we demonstrate the first Brillouin opto-electronic oscillator (B-OEO) based on on-chip stimulated Brillouin scattering (SBS) to achieve RF signal detection. The broad tunability and narrowband amplification of on-chip SBS allow for the wide-range and high-accuracy detection. Feeding the unknown RF signal into the B-OEO cavity amplifies the signal which is matched with the oscillation mode to detect low-power RF signals. We are able to detect RF signals from 1.5 to 40 GHz with power levels as low as −67 dBm and a frequency accuracy of ± 3.4 MHz. This result paves the way to compact, fully integrated RF detection and channelization.Australian Research Council (ARC) Linkage grant (LP170100112) with Harris Corporation. U.S. Air Force (USAF) through AFOSR/AOARD (FA2386-16-1-4036); U.S. Office of Naval Research Global (ONRG) (N62909-18-1-2013)

On-chip multi-stage optical delay based on cascaded Brillouin light storage

Storing and delaying optical signals plays a crucial role in data centers, phased array antennas, communication, and future computing architectures. Here, we show a delay scheme based on cascaded Brillouin light storage that achieves multi-stage delay at arbitrary positions within a photonic integrated circuit. Importantly these multiple resonant transfers between the optical and acoustic domain are controlled solely via external optical control pulses, allowing cascading of the delay without the need of aligning multiple structural resonances along the optical circuit

High-density WGM Probes Generated by a ChG Ring Resonator for High-density 3D Imaging and Applications

In this paper, the ultra‐wideband source for light fidelity (LiFi) and high‐density 3D imaging applications is proposed. The system consists of an add‐drop multiplexer. The center ring is formed by the Chalcogenide glass (ChG), which is coupled with two GaAsInP/P side rings. The nonlinear effect within the side rings (phase modulators) is induced in the central ring. The superposition of light signals from side rings generates wider wavelength band, which makes the original input. The output is the set of squeezed light pulses known as whispering gallery mode (WGM) which is generated at the center of the system. Three different input sources are investigated, where the simulated results are comparatively plotted and discussed. The results show that the wavelength of 1.30 μm is the best input source. The output wavelengths band is ranged from 0.7‐3.1 μm, which is suitable for LiFi source and high‐density 3D imaging applications