This content will become publicly available on May 5, 2025
- Award ID(s):
- 2244365
- PAR ID:
- 10537387
- Publisher / Repository:
- Optica Publishing Group
- Date Published:
- ISBN:
- 978-1-957171-39-5
- Page Range / eLocation ID:
- STh3Q.5
- Format(s):
- Medium: X
- Location:
- Charlotte, North Carolina, United States
- Sponsoring Org:
- National Science Foundation
More Like this
-
null (Ed.)We present a hybrid optical-electrical analog deep learning (DL) accelerator, the first work to use incoherent optical signals for DL workloads. Incoherent optical designs are more attractive than coherent ones as the former can be more easily realized in practice. However, a significant challenge in analog DL accelerators, where multiply-accumulate operations are dominant, is that there is no known solution to perform accumulation using incoherent optical signals. We overcome this challenge by devising a hybrid approach: accumulation is done in the electrical domain, while multiplication is performed in the optical domain. The key technology enabler of our design is the transistor laser, which performs electrical-to-optical and optical-to-electrical conversions efficiently to tightly integrate electrical and optical devices into compact circuits. As such, our design fully realizes the ultra high-speed and high-energy-efficiency advantages of analog and optical computing. Our evaluation results using the MNIST benchmark show that our design achieves 2214× and 65× improvements in latency and energy, respectively, compared to a state-of-the-art memristor-based analog design.more » « less
-
Abstract The advancement in high power lasers has urged the requisite of efficient optical limiting materials for both eye and sensor protection. The discovery of atomically thin 2D transition metal dichacogenides with distinctive properties has paved the way for a variety of applications including optical limiting. Until recently, the optical limiting effect exhibited by 2D materials is inferior to the benchmark materials fullerene (C60) and graphene. This article reports the optical limiting activity of the 2D transition metal dichalcogenide, titanium disulfide (TiS2) nanosheets, using optical and photoacoustic z‐scan techniques. The 77% nonlinear optical limiting exhibited by the TiS2sheets with 73% linear‐transmittance is superior to that of any other existing 2D dichalcogenide sheets, graphene, and the benchmark optical limiting material, C60. The enhanced nonlinear response is attributed to the concerted effect of 2‐photon and the induced excited state absorptions. By using photoacoustic z‐scan, a unique tool developed to determine the nonlinear optical limiting mechanism in materials, it is found that the optical limiting exhibited by TiS22D sheets and graphene are mainly due to nonlinear absorption rather than scattering effects. These results have opened the door for 2D‐dichalcogenide‐materials‐based highly efficient optical limiters, especially at low fluences.
-
Acousto-optic modulation in piezoelectric materials offers the efficient method to bridge electrical and optical signals. It is widely used to control optical frequencies and intensities in modern optical systems including
Q -switch lasers, ion traps, and optical tweezers. It is also critical for emerging applications such as quantum photonics and non-reciprocal optics. Acousto-optic devices have recently been demonstrated with promising performance on integrated platforms. However, the conversion efficiency of optical signals remains low in these integrated devices. This is attributed to the significant challenge in realizing large mode overlap, long interaction length, and high power robustness at the same time. Here, we develop acousto-optic devices with gallium nitride on a sapphire substrate. The unique capability to confine both optical and acoustic fields in sub-wavelength scales without suspended structures allows efficient acousto-optic interactions over long distances under high driving power. This leads to the complete optical conversion with integrated acousto-optic modulators. With the unidirectional phase matching, we also demonstrate the non-reciprocal propagation of optical fields with isolation ratios above 10 dB. This work provides a robust and efficient acousto-optic platform, opening new opportunities for optical signal processing, quantum transduction, and non-magnetic optical isolation. -
null (Ed.)ABSTRACT The bright quasar PG1302-102 has been identified as a candidate supermassive black hole binary from its near-sinusoidal optical variability. While the significance of its optical periodicity has been debated due to the stochastic variability of quasars, its multiwavelength variability in the ultraviolet (UV) and optical bands is consistent with relativistic Doppler boost caused by the orbital motion in a binary. However, this conclusion was based previously on sparse UV data that were not taken simultaneously with the optical data. Here, we report simultaneous follow-up observations of PG1302-102 with the Ultraviolet Optical Telescope on the Neil Gehrels Swift Observatory in six optical + UV bands. The additional nine Swift observations produce light curves roughly consistent with the trend under the Doppler boost hypothesis, which predicts that UV variability should track the optical, but with a ∼2.2 times higher amplitude. We perform a statistical analysis to quantitatively test this hypothesis. We find that the data are consistent with the Doppler boost hypothesis when we compare the the amplitudes in optical B-band and UV light curves. However, the ratio of UV to V-band variability is larger than expected and is consistent with the Doppler model, only if either the UV/optical spectral slopes vary, the stochastic variability makes a large contribution in the UV, or the sparse new optical data underestimate the true optical variability. We have evidence for the latter from comparison with the optical light curve from All-Sky Automated Survey for Supernovae. Additionally, the simultaneous analysis of all four bands strongly disfavours the Doppler boost model whenever Swift V band is involved. Additional, simultaneous optical + UV observations tracing out another cycle of the 5.2-yr proposed periodicity should lead to a definitive conclusion.more » « less
-
Abstract Titanium nitride nanoparticles have become a research interest due to their distinguished optical and photothermal properties. Furthermore, the search for nanoparticle solutions with tunable nonlinear optical properties for laser‐based applications is critical. More specifically, third order optical nonlinearities such as reverse saturable absorption, optical liming, and self‐focusing are important in the biomedical and electronics fields. The optical nonlinearities of titanium nitride plasmonic nanoparticles are investigated as a function of material concentration in water solutions. Furthermore, the effect of nanoparticle clustering on optical nonlinearities is investigated by fabricating micrometer‐sized clusters of ≈50 nm titanium nitride particles. These studies demonstrate that the nonlinear absorption coefficient increases linearly with concentration. However, clusters require higher concentrations compared to the freestanding nanoparticles to exhibit similar nonlinear absorption coefficient and optical density. Similarly, the optical limiting threshold for titanium nitride nanoparticles appears to be lower compared to the cluster solutions, which is impacted by the collective scattering of nanoparticles and high reverse saturable absorption. In addition, self‐focusing is observed in the continuous resonant regime. This study provides an in‐depth analysis of the nonlinear optical properties of titanium nitride, with relevant consequences for applications such as sensor protection and photothermal therapy.