Mechanical resonances are used in a wide variety of devices, from smartphone accelerometers to computer clocks and from wireless filters to atomic force microscopes. Frequency stability, a critical performance metric, is generally assumed to be tantamount to resonance quality factor (the inverse of the linewidth and of the damping). We show that the frequency stability of resonant nanomechanical sensors can be improved by lowering the quality factor. At high bandwidths, quality-factor reduction is completely mitigated by increases in signal-to-noise ratio. At low bandwidths, notably, increased damping leads to better stability and sensor resolution, with improvement proportional to damping. We confirm the findings by demonstrating temperature resolution of 60 microkelvin at 300-hertz bandwidth. These results open the door to high-performance ultrasensitive resonators in gaseous or liquid environments, single-cell nanocalorimetry, nanoscale gas chromatography, atmospheric-pressure nanoscale mass spectrometry, and new approaches in crystal oscillator stability.

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Harnessing the full complexity of optical fields requires complete control of all degrees-of-freedom within a region of space and time -an open goal for present-day spatial light modulators (SLMs), active metasurfaces, and optical phased arrays. Here, we solve this challenge with a programmable photonic crystal cavity array enabled by four key advances: (i) near-unity vertical coupling to high-finesse microcavities through inverse design, (ii) scalable fabrication by optimized, 300 mm full-wafer processing, (iii) picometer-precision resonance alignment using automated, closed-loop "holographic trimming", and (iv) out-of-plane cavity control via a high-speed µLED array. Combining each, we demonstrate near-complete spatiotemporal control of a 64-resonator, two-dimensional SLM with nanosecond-and femtojoule-order switching. Simultaneously operating wavelength-scale modes near the space-and time-bandwidth limits, this work opens a new regime of programmability at the fundamental limits of multimode optical control.

On-chip nano-optomechanical systems (NOMS) have demonstrated a zeptogram-level mass sensitivity and are promising candidates for low-cost implementations in areas such as metabolite quantitation and chemical analysis. High responsivity and sensitivity call for substantial optomechanical coupling and cavity finesse, resulting in detuning-dependent stiffness and mechanical damping via optomechanical back-action. Since mass loading (or temperature or force change) can alter both mechanical and cavity properties, mechanical frequency shifts induced by loading can encompass both effects. Precision sensing requires understanding and quantifying the source of the frequency tuning. Here, we show the deconvolution of direct loading and optomechanical stiffness change on the mechanical eigenfrequency as a function of detuning for a nano-optomechanical sensor in gaseous sensing experiments. Responses were generally dominated by shifts in optical stiffness and resulted in a mass loading signal amplification by as much as a factor of 2.5. This establishes an alternative possible route toward better mass sensitivity in NOMS while confirming the importance of incorporating optical stiffness effects for precision mass sensing.

Subwavelength grating (SWG) metamaterial waveguides and ring resonators on a silicon nitride platform are proposed and demonstrated. The SWG waveguide is engineered such that a large overlap of 53% of the Bloch mode with the top cladding material is achieved, demonstrating excellent potential for applications in evanescent field sensing and light amplification. The devices, which have critical dimensions greater than 100 nm, are fabricated using a commercial rapid turn-around silicon nitride prototyping foundry process using electron beam lithography. Experimental characterization of the fabricated device reveals excellent ring resonator internal quality factor (2.11 × 10 5 ) and low propagation loss (≈1.5 dB cm −1 ) in the C-band, a significant improvement of both parameters compared to silicon-based SWG ring resonators. These results demonstrate the promising prospects of SWG metamaterial structures for silicon nitride based photonic integrated circuits. IntroductionSilicon photonics (SiP) has become a leading integrated photonics technology by leveraging existing microelectronics manufacturing processes and infrastructure to produce compact, scalable,

We demonstrate the actuation and detection of even flexural vibrational modes of a doubly clamped nanomechanical resonator using an integrated photonics transduction scheme. The doubly clamped beam is formed by releasing a straight section of an optical racetrack resonator from the underlying silicon dioxide layer, and a step is fabricated in the substrate beneath the beam. The step causes uneven force and responsivity distribution along the device length, permitting excitation and detection of even modes of vibration. This is achieved while retaining transduction capability for odd modes. The devices are actuated via optical force applied with a pump laser. The displacement sensitivities of the first through third modes, as obtained from the thermomechanical noise floor, are 228 fm Hz−1/2, 153 fm Hz−1/2, and 112 fm Hz−1/2, respectively. The excitation efficiency for these modes is compared and modeled based on integration of the uneven forces over the mode shapes. While the excitation efficiency for the first three modes is approximately the same when the step occurs at about 38% of the beam length, the ability to tune the modal efficiency of transduction by choosing the step position is discussed. The overall optical force on each mode is approximately 0.4 pN μm−1 mW−1, for an applied optical power of 0.07 mW. We show a potential application that uses the resonant frequencies of the first two vibrational modes of a buckled beam to measure the stress in the silicon device layer, estimated to be 106 MPa. We anticipate that the observation of the second mode of vibration using our integrated photonics approach will be useful in future mass sensing experiments.

We have developed a porous silicon nanocantilever for a nano-optomechanical system (NOMS) with a universal sensing surface for enhanced sensitivity. Using electron beam lithography, we selectively applied a V 2 O 5 /HF stain etch to the mechanical elements while protecting the silicon-on-insulator photonic ring resonators. This simple, rapid, and electrodeless approach generates tunable device porosity simultaneously with the mechanical release step. By controlling the porous etchant concentration and etch time, the porous etch depth, resonant frequency, and the adsorption surface area could be precisely manipulated. Using this control, cantilever sensors ranging from nonporous to fully porous were fabricated and tested as gas-phase mass sensors of volatile organic compounds coming from a gas chromatography stream. The fully porous cantilever produced a dramatic 10-fold increase in sensing signal and a 6-fold improvement in limit of detection (LOD) compared to an otherwise identical nonporous cantilever. This signal improvement could be separated into mass responsivity increase and adsorption increase components. Allan deviation measurements indicate that a further 4-fold improvement in LOD could be expected upon speeding up characteristic peak response time from 1 s to 50 ms. These results show promise for performance enhancement in nanomechanical sensors for applications in gas sensing, gas chromatography, and mass spectrometry.

To reduce the complexity in a nano-optomechanical system a pump and probe scheme using only a single input laser is used to both coherently pump and probe the nanomechanical device. The system operates similarly to the traditional two laser system, but instead of using a constant power to probe the device and a separate, modulated laser to drive it with an optical gradient force, a single laser is utilized for both functions. A model of the measurement scheme’s response is developed which matches the experimental data obtained in the optomechanical Doppler regime and low cavity power limit. As such, the unconventional response still yields useful device information such as the resonant frequency of the device and its mechanical quality factor. The device is driven with low noise and its frequency is tracked using a phase-locked loop. This demonstrates its potential use for dynamic frequency measurements such as nanomechanical inertial mass loading. In such a system, the estimated mass resolution of the device is 6 zg and consistent with other detection methods.