Integrated nano-opto-electro-mechanical sensor for spectrometry and nanometrology

Abstract

Spectrometry is widely used for the characterization of materials, tissues, and gases, and the need for size and cost scaling is driving the development of mini and microspectrometers. While nanophotonic devices provide narrowband filtering that can be used for spectrometry, their practical application has been hampered by the difficulty of integrating tuning and read-out structures. Here, a nano-opto-electro-mechanical system is presented where the three functionalities of transduction, actuation, and detection are integrated, resulting in a high-resolution spectrometer with a micrometer-scale footprint. The system consists of an electromechanically tunable double-membrane photonic crystal cavity with an integrated quantum dot photodiode. Using this structure, we demonstrate a resonance modulation spectroscopy technique that provides subpicometer wavelength resolution. We show its application in the measurement of narrow gas absorption lines and in the interrogation of fiber Bragg gratings. We also explore its operation as displacement-to-photocurrent transducer, demonstrating optomechanical displacement sensing with integrated photocurrent read-out.

Multimode photonic molecules for advanced force sensing

“…The first regime is the force sensing regime, in which the S (AS) modes rigidly red (blue) shift, accordingly with the previous experimental results [19]. Here we can quantify the minimum detectable force (MDF) of the device, by evaluating the minimum detectable rigid shift of the modes, to be compared with a spectral resolution of the order of γ/1000 (where γ is the FWHM of a single peak with Q = 10 4 ) which can be detected by resonant detection methods [21]. Given the elastic constant (10 N/m) [18][19][20][21] of the membrane, we obtain a MDF of the order of 10 pN for a minimum displacement ∆d of the order of 1 pm.…”

“…Here we can quantify the minimum detectable force (MDF) of the device, by evaluating the minimum detectable rigid shift of the modes, to be compared with a spectral resolution of the order of γ/1000 (where γ is the FWHM of a single peak with Q = 10 4 ) which can be detected by resonant detection methods [21]. Given the elastic constant (10 N/m) [18][19][20][21] of the membrane, we obtain a MDF of the order of 10 pN for a minimum displacement ∆d of the order of 1 pm. For larger values of ∆d the system enters in the torque sensing regime, in which the eight DM modes experiment a non-rigid shift with respect to one another, accompanied by a consequent modification of the energy splittings between the modes with respect to the initial condition.…”

“…These actuation methods allow the control of the spectral properties of coupled cavities in an ultrawide spectral range, demonstrating a fine and reversible mode shift. Viceversa, by monitoring the variation of the coupling strength of the two PhCCs induced by the deformation of the upper membrane, forces can be measured with pico-Newton sensitivity [21].…”

Visible to long-wave infrared chip-scale spectrometers based on photodetectors with tailored responsivities and multispectral filters

“…The need for collecting visible and infrared spectroscopic measurements in the field, both for scientific experiments and consumer applications provides motivation for the development of mechanically robust spectrometers with minimized extent and weight. A microspectrometer chip should typically not have moving any components, with the notable exception of microelectromechanical system (MEMS)-based examples [20][21][22], and as such are not as vulnerable to misalignment or mechanical failure due to shocks or vibrations. The dimensions and mass of the chips are on the order of millimeters and grams respectively.…”

“…The FADA approach utilizes a planar optical element which consists of a set of spectral filters each with a unique transmission spectrum. Some of the nanophotonic spectral filters used in FADA microspectrometers include thin film (etalon) bandpass or linear variable filters with transmission bands in the visible [32][33][34][35][36], and infrared [37], plasmonic nanoantennas [38,39], plasmonic nanoapertures resonant in the mid-and long-wave infrared (M/LWIR) spectral bands [40,41], photonic crystal (PhC) slabs [20,42], on-chip waveguide coupled disordered scattering media [43,44] and colloidal quantum dot (QD) optical absorption based filters [45]. The transmission spectrum of each nanophotonic filter in the filter array is measured via a grating-based or an FTIRbased spectrometer in the lab and stored for later use.…”