Nonvolatile Rewritable Frequency Tuning of a Nanoelectromechanical Resonator Using Photoinduced Doping

Abstract

Tuning the frequency of a resonant element is of vital importance in both the macroscopic world, such as when tuning a musical instrument, as well as at the nanoscale. In particular, precisely controlling the resonance frequency of isolated nanoelectromechanical resonators (NEMS) has enabled innovations such as tunable mechanical filtering and mixing 1 as well as commercial technologies such as robust timing oscillators 2 . Much like their electronic device counterparts, the potential of NEMS grows when they are built up into large-scale arrays. Such arrays have enabled neutral-particle mass spectroscopy 3 and have been proposed for ultralowpower alternatives to traditional analog electronics 4 as well as nanomechanical information technologies like memory 5,6 , logic 7 , and computing [8][9][10][11] . A fundamental challenge to these applications is to precisely tune the vibrational frequency and coupling of all resonators in the array, since traditional tuning methods, like patterned electrostatic gating 12,13 or dielectric tuning 14 , become intractable when devices are densely packed. Here, we demonstrate a persistent, rewritable, scalable, and high-speed frequency tuning method for graphene-based NEMS [15][16][17][18] . Our method uses a focused laser and two shared electrical contacts to photodope [19][20][21][22] individual resonators by simultaneously applying optical and electrostatic fields. After the

Rewritable Photonic Integrated Circuit Canvas Based on Low-Loss Phase Change Material and Nanosecond Pulsed Lasers

“…Here, we experimentally demonstrate a low-loss and rewritable PIC platform using laser-written Sb 2 S 3 . A dielectric-assisted waveguide structure 8,26 is used to lower the optical propagation loss while enhancing the endurance and reliability of PCMs. We first demonstrate arbitrary patterning on the PCM canvas with a fine resolution of 600 nm line pitch, to demonstrate the rewritable capability of our platform, then write laser-written waveguides between pairs of predefined grating couplers.…”

“…The propagation loss was then measured via a cutback measurement as 0.01722 dB/μm, comparable to the 0.010 dB/μm loss in simulation. 8 While this loss is ∼1000 times larger than current commercial silicon photonic waveguides, 27 this loss is acceptable to create waveguides of submm length. Our rewritable and low-cost platform shows a promising path to democratizing PIC prototyping for designers without access to a nanofabrication facility, which will enhance PIC education and accelerate rapid PIC prototyping.…”

“…The PIC canvas was fabricated by depositing multiple materials on a silicon substrate in the order of 3.5 μm SiO 2 , 15 nm Sb 2 S 3 , 20 nm Al 2 O 3 and 400 nm Si 3 N 4 (see Supplementary Section S2 for fabrication process steps), as shown in the inset of Figure 1a. This multilayer design enables the low-loss dielectric-assisted waveguide mode (see Supplementary Figure S2) 8 and is key to low-loss waveguiding. We started with a c-Sb 2 S 3 PIC canvas by annealing the chip at 325 °C on a hot plate.…”

“…A linearly fitted trendline had a slope of 17.2 dB/mm, which matched well with the theoretical value of 10 dB/mm. 8 This variation could be attributed to several factors, such as (1) the anisotropy of c-Sb 2 S 3 crystals, (2) mode leakage during propagation, (3) variation in the grating couplers, (4) misalignment between the axis of the writing laser and the chip, and (5) variation in the waveguide widths and cladding thicknesses. Among the etched Si 3 N 4 waveguides, there was a standard deviation from the mean of 3.5 dB, implying variation in the material and gratings.…”

Kirigami Engineering of Suspended Graphene Transducers

“…For example, a small-size membrane operating at low frequencies with reasonable bandwidth and displacement amplitude has implications for ultrasonic and audio transduction. Previous studies have shown that electric field gating and photodoping can tune the resonant frequency of a graphene mechanical transducer, but these methods are more effective in upshifting, rather than downshifting, the resonant frequency. Furthermore, the bandwidth of a graphene transducer normally shrinks (quality factor, Q , increases) when the resonant frequency is decreased because of reduced energy dissipation, and the displacement amplitude ( d ) of the vibrating membrane also decreases with the reduced membrane radius ( r ) as , …”