Quantification of broadband chromatic drifts in Fabry–Pérot resonators for exoplanet science
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Periodically poled aluminum scandium nitride bulk acoustic wave resonators and filters for communications in the 6G era
Bulk Acoustic Wave (BAW) filters find applications in radio frequency (RF) communication systems for Wi-Fi, 3G, 4G, and 5G networks. In the beyond-5G (potential 6G) era, high-frequency bands (>8 GHz) are expected to require resonators with high-quality factor (Q) and electromechanical coupling (({k}_{t}^{2})) to form filters with low insertion loss and high selectivity. However, both the Q and ({k}_{t}^{2}) of resonator devices formed in traditional uniform polarization piezoelectric films of aluminum nitride (AlN) and aluminum scandium nitride (AlScN) decrease when scaled beyond 8 GHz. In this work, we utilized 4-layer AlScN periodically poled piezoelectric films (P3F) to construct high-frequency (~17–18 GHz) resonators and filters. The resonator performance is studied over a range of device geometries, with the best resonator achieving a ({k}_{t}^{2}) of 11.8% and a ({Q}_{{rm {p}}}) of 236.6 at the parallel resonance frequency (({f}_{{rm {p}}})) of 17.9 GHz. These resulting figures-of-merit are (({{{rm {FoM}}}}_{1}={{k}_{t}^{2}Q}_{{rm {p}}}) and ({{{rm {FoM}}}}_{2}={f}_{{rm {p}}}{{{rm {FoM}}}}_{1}{times }{10}^{-9})) 27.9 and 500, respectively. These and the ({k}_{t}^{2}) are significantly higher than previously reported AlN/AlScN-based resonators operating at similar frequencies. Fabricated 3-element and 6-element filters formed from these resonators demonstrated low insertion losses (IL) of 1.86 and 3.25 dB, and −3 dB bandwidths (BW) of 680 MHz (fractional BW of 3.9%) and 590 MHz (fractional BW of 3.3%) at a ~17.4 GHz center frequency. The 3-element and 6-element filters achieved excellent linearity with in-band input third-order intercept point (IIP3) values of +36 and +40 dBm, respectively, which are significantly higher than previously reported acoustic filters operating at similar frequencies.
High-performance magnetostatic wave resonators based on deep anisotropic etching of gadolinium gallium garnet substrates
Magnetostatic wave resonators based on yttrium iron garnet (YIG) are a promising technology platform for future communication filters. Such devices have demonstrated better quality factors than acoustic resonators in the 7 GHz range and above. However, the coupling coefficients of these resonators have been limited to less than 3%, primarily due to the restricted design space that is a result of microfabrication challenges related to the patterning of gadolinium gallium garnet (GGG), the substrate material used for growing single-crystal YIG. Here we report magnetostatic wave resonators created through the anisotropic etching of GGG substrates. Our approach, which is based on the YIG-on-GGG platform, uses a transducer with a hairclip-like structure. It is created by developing a microfabrication methodology that involves thinning and deep etching (up to 100 μm) of the GGG substrate. The resulting magnetostatic wave resonators exhibit a coupling of more than 8% in the 6–20 GHz frequency range.
Digital infrastructure construction and corporate innovation efficiency: evidence from Broadband China Strategy
Adopting the Broadband China Strategy as a quasi-natural experiment, we construct a multi-period Difference-in-Differences (DID) model to examine the impact of digital infrastructure construction on corporate innovation efficiency with panel data from Chinese listed companies between 2010 to 2022. Our findings indicate that the development of digital infrastructure significantly boosts corporate innovation efficiency. Mechanistic analysis reveals that financing constraints negatively moderates this innovation impact, while human capital positively moderates it. The effects of the Broadband China Strategy are particularly pronounced in non-state-owned enterprises, non-high-tech enterprises, and firms located in the non-eastern region of China. Our research provides important insights for enterprises seeking to enhance their innovation efficiency, while also offering strong empirical evidence on the role of digital infrastructure in fostering corporate innovation. Our study contributes to the literature on digital economy and innovation, with practical implications for policymakers and firms aiming to leverage digital infrastructure for sustained competitive advantage.
Comparative analysis of nanomechanical resonators: sensitivity, response time, and practical considerations in photothermal sensing
Nanomechanical photothermal sensing has significantly advanced single-molecule/particle microscopy and spectroscopy, and infrared detection. In this approach, the nanomechanical resonator detects shifts in resonant frequency due to photothermal heating. However, the relationship between photothermal sensitivity, response time, and resonator design has not been fully explored. This paper compares three resonator types – strings, drumheads, and trampolines – to explore this relationship. Through theoretical modeling, experimental validation, and finite element method simulations, we find that strings offer the highest sensitivity (with a noise equivalent power of 280 fW/Hz1/2 for strings made of silicon nitride), while drumheads exhibit the fastest thermal response. The study reveals that photothermal sensitivity correlates with the average temperature rise and not the peak temperature. Finally, the impact of photothermal back-action is discussed, which can be a major source of frequency instability. This work clarifies the performance differences and limits among resonator designs and guides the development of advanced nanomechanical photothermal sensors, benefiting a wide range of applications.
Collective quantum enhancement in critical quantum sensing
Critical systems represent a valuable resource in quantum sensing and metrology. Critical quantum sensing (CQS) protocols can be realized using finite-component phase transitions, where criticality arises from the rescaling of system parameters rather than the thermodynamic limit. Here, we show that a collective quantum advantage can be achieved in a multipartite CQS protocol using a chain of parametrically coupled critical resonators in the weak-nonlinearity limit. We derive analytical solutions for the low-energy spectrum of this unconventional quantum many-body system, which is composed of locally critical elements. We then assess the scaling of the quantum Fisher information with respect to fundamental resources. We demonstrate that the coupled chain outperforms an equivalent ensemble of independent critical sensors, achieving quadratic scaling in the number of resonators. Finally, we show that even with finite Kerr nonlinearity or Markovian dissipation, the critical chain retains its advantage, making it relevant for implementing quantum sensors with current microwave superconducting technologies.
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