Metrology experiments can be limited by the noise produced by the laser involved via small fluctuations in the laser’s power or frequency. Typically, active power stabilization schemes consisting of an in-loop sensor and a feedback control loop are employed. Those schemes are fundamentally limited by shot noise coupling at the in-loop sensor. In this Letter, we propose to use the optical spring effect to passively stabilize the classical power fluctuations of a laser beam. In a proof of principle experiment, we show that the relative power noise of the laser is stabilized from approximately 2 × 10−5Hz−1/2to a minimum value of 1.6 × 10−7Hz−1/2, corresponding to the power noise reduction by a factor of 125. The bandwidth at which stabilization occurs ranges from 400 Hz to 100 kHz. The work reported in this Letter further paves the way for high power laser stability techniques which could be implemented in optomechanical experiments and in gravitational wave detectors.
A surface-coupled optical trap with 1-bp precision via active stabilization
Optical traps can measure bead motions with Å-scale precision. However, using this level of precision to infer 1-bp motion of molecular motors along DNA is difficult, since a variety of noise sources degrade instrumental stability. In this chapter, we detail how to improve instrumental stability by (1) minimizing laser pointing, mode, polarization, and intensity noise using an acousto-optical-modulator mediated feedback loop and (2) minimizing sample motion relative to the optical trap using a three-axis piezo-electric-stage mediated feedback loop. These active techniques play a critical role in achieving a surface stability of 1 Å in 3D over tens of seconds and a 1-bp stability and precision in a surface-coupled optical trap over a broad bandwidth (Δf = 0.03–2 Hz) at low force (6 pN). These active stabilization techniques can also aid other biophysical assays that would benefit from improved laser stability and/or Å-scale sample stability, such as atomic force microscopy and super-resolution imaging.
more »
« less
- Award ID(s):
- 1734006
- NSF-PAR ID:
- 10057232
- Date Published:
- Journal Name:
- Methods in molecular biology
- Volume:
- 1486
- ISSN:
- 1064-3745
- Page Range / eLocation ID:
- 77-107
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
-
The center-of-mass motion of optically trapped dielectric nanoparticles in a vacuum is extremely well decoupled from its environment, making a powerful tool for measurements of feeble subattonewton forces. We demonstrate a method to trap and maneuver nanoparticles in an optical standing wave potential formed by retroreflecting a laser beam from a metallic mirror surface. We can reliably position a ∼ 170 n m diameter silica nanoparticle at distances of a few hundred nanometers to tens of micrometers from the surface of a gold-coated silicon mirror by transferring it from a single-beam tweezer trap into the standing wave potential. We can further measure forces experienced by the particle while scanning the two-dimensional space parallel to the mirror surface, and we find no significant excess force noise in the vicinity of the surface. This method may enable three-dimensional scanning force sensing near surfaces using optically trapped nanoparticles, promising for high-sensitivity scanning force microscopy, tests of the Casimir effect, and tests of the gravitational inverse square law at micrometer scales.more » « less
-
Abstract. A closed-path quantum-cascade tunable infrared laserdirect absorption spectrometer (QC-TILDAS) was outfitted with an inertialinlet for filter-less separation of particles and several custom-designedcomponents including an aircraft inlet, a vibration isolation mountingplate, and a system for optionally adding active continuous passivation forgas-phase measurements of ammonia (NH3) from a research aircraft. Theinstrument was then deployed on the NSF/NCAR C-130 aircraft during researchflights and test flights associated with the Western wildfire Experiment forCloud chemistry, Aerosol absorption and Nitrogen (WE-CAN) field campaign.The instrument was configured to measure large, rapid gradients in gas-phaseNH3, over a range of altitudes, in smoke (e.g., ash and particles), inthe boundary layer (e.g., during turbulence and turns), in clouds, and in ahot aircraft cabin (e.g., average aircraft cabin temperatures expected toexceed 30 ∘C during summer deployments). Important designgoals were to minimize motion sensitivity, maintain a reasonable detectionlimit, and minimize NH3 “stickiness” on sampling surfaces to maintainfast time response in flight. The observations indicate that adding ahigh-frequency vibration to the laser objective in the QC-TILDAS andmounting the QC-TILDAS on a custom-designed vibration isolation plate weresuccessful in minimizing motion sensitivity of the instrument during flight.Allan variance analyses indicate that the in-flight precision of theinstrument is 60 ppt at 1 Hz corresponding to a 3σ detection limitof 180 ppt. Zero signals span ±200, or 400 pptv total, withcabin pressure and temperature and altitude in flight. The option for activecontinuous passivation of the sample flow path with1H,1H-perfluorooctylamine, a strong perfluorinated base, preventedadsorption of both water and basic species to instrument sampling surfaces.Characterization of the time response in flight and on the ground showedthat adding passivant to a “clean” instrument system had little impact onthe time response. In contrast, passivant addition greatly improved the timeresponse when sampling surfaces became contaminated prior to a test flight.The observations further show that passivant addition can be used tomaintain a rapid response for in situ NH3 measurements over the duration of anairborne field campaign (e.g., ∼2 months) since passivantaddition also helps to prevent future buildup of water and basic species oninstrument sampling surfaces. Therefore, we recommend the use of activecontinuous passivation with closed-path NH3 instruments when rapid(>1 Hz) collection of NH3 is important for the scientificobjective of a field campaign (e.g., sampling from aircraft or anothermobile research platform). Passivant addition can be useful for maintainingoptimum operation and data collection in NH3-rich and humid environments orwhen contamination of sampling surfaces is likely, yet frequent cleaning isnot possible. Passivant addition may not be necessary for fast operation,even in polluted environments, if sampling surfaces can be cleaned when thetime response has degraded.more » « less
-
more » « less
Abstract Modern navigation systems integrate the global positioning system (GPS) with an inertial navigation system (INS), which complement each other for correct attitude and velocity determination. The core of the INS integrates accelerometers and gyroscopes used to measure forces and angular rate in the vehicular inertial reference frame. With the help of gyroscopes and by integrating the acceleration to compute velocity and distance, precision and compact accelerometers with sufficient accuracy can provide small‐error location determination. Solid‐state implementations, through coherent readout, can provide a platform for high performance acceleration detection. In contrast to prior accelerometers using piezoelectric or capacitive readout techniques, optical readout provides narrow‐linewidth high‐sensitivity laser detection along with low‐noise resonant optomechanical transduction near the thermodynamical limits. Here an optomechanical inertial sensor with an 8.2 µg Hz−1/2velocity random walk (VRW) at an acquisition rate of 100 Hz and 50.9 µg bias instability is demonstrated, suitable for applications, such as, inertial navigation, inclination sensing, platform stabilization, and/or wearable device motion detection. Driven into optomechanical sustained‐oscillation, the slot photonic crystal cavity provides radio‐frequency readout of the optically‐driven transduction with an enhanced 625 µg Hz−1sensitivity. Measuring the optomechanically‐stiffened oscillation shift, instead of the optical transmission shift, provides a 220× VRW enhancement over pre‐oscillation mode detection.
-
Copper oxide nanostructures are widely used for various applications due to their unique optical and electrical properties. In this work, we demonstrate an atmospheric laser-induced oxidation technique for the fabrication of highly electrochemically active copper oxide hierarchical micro/nano structures on copper surfaces to achieve highly sensitive non-enzymatic glucose sensing performance. The effect of laser processing power on the composition, crystallinity, microstructure, wettability, and color of the laser-induced oxide on copper (LIO-Cu) surface was systematically studied using scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GI-XRD), Raman spectroscopy, energy dispersive X-ray spectroscopy (EDX), EDX-mapping, water contact angle measurements, and optical microscopy. Results of these investigations showed a remarkable increase in copper oxide composition by increasing the laser processing power. The pore size distribution and surface area of the pristine and LIO-Cu sample estimated by N 2 adsorption–desorption data showed a developed mesoporous LIO-Cu structure. The size of the generated nano-oxides, crystallinity, and electroactivity of the LIO-Cu were observed to be adjustable by the laser processing power. The electrocatalytic activity of LIO-Cu surfaces was studied by means of cyclic voltammetry (CV) within a potential window of −0.8 to +0.8 V and chronoamperometry in an applied optimized potential of +0.6 V, in 0.1 M NaOH solution and phosphate buffer solution (PBS), respectively. LIO-Cu surfaces with optimized laser processing powers exhibited a sensitivity of 6950 μA mM −1 cm −2 within a wide linear range from 0.01 to 5 mM, with exceptional specificity and response time (<3 seconds). The sensors also showed excellent response stability over a course of 50 days that was originated from the binder-free robust electroactive film fabricated directly onto the copper surface. The demonstrated one-step LIO processing onto commercial metal films, can potentially be applied for tuneable and scalable roll-to-roll fabrication of a wide range of high surface area metal oxide micro/nano structures for non-enzymatic biosensing and electrochemical applications.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/978-1-4939-6421-5
