Daniel Lopez

Direct observation of coherent energy transfer in nonlinear micromechanical oscillators

Energy dissipation is an unavoidable phenomenon of physical systems that are directly coupled to an external environmental bath. In an oscillatory system, it leads to the decay of the oscillation amplitude. In situations where stable oscillations are required, the energy dissipated by the vibrations is usually compensated by replenishment from external energy sources. Consequently, if the external energy supply is removed, the amplitude of oscillations start to decay immediately, since there is no means to restitute the energy dissipated. Here, we demonstrate a novel dissipation engineering strategy that can support stable oscillations without supplying external energy to compensate losses. The fundamental intrinsic mechanism of resonant mode coupling is used to redistribute and store mechanical energy among vibrational modes and coherently transfer it back to the principal mode when the external excitation is off. To experimentally demonstrate this phenomenon, we exploit the nonlinear dynamic response of microelectromechanical oscillators to couple two different vibrational modes through an internal resonance.

New optical technology for low mass intelligent trigger and readout

New optical devices offer the potential for reductions in mass, power, and cost of data paths for on-board trigger and readout of tracking detectors. We give examples of optical modulators, MEMS beam steering devices, and optical coupling. We also present results on radiation hardness of materials as well as different approaches to using optics in triggering.

Dynamic Correlation in Driven Vortex Phases

We describe transport experiments where the spatial gradient of the driving Lorentz force is controlled. The velocity profiles induced by the Lorentz force gradient in the driven liquid and lattice vortex phases are characteristic of hydrodynamic, plastic, and elastic motion.

Dynamic metasurface lens based on MEMS technology

In the recent years, metasurfaces, being flat and lightweight, have been designed to replace bulky optical components with various functions. We demonstrate a monolithic Micro-Electro-Mechanical System (MEMS) integrated with a metasurface-based flat lens that focuses light in the mid-infrared spectrum. A two-dimensional scanning MEMS platform controls the angle of the lens along two orthogonal axes by ±9°, thus enabling dynamic beam steering. The device could be used to compensate for off-axis incident light and thus correct for aberrations such as coma. We show that for low angular displacements, the integrated lens-on-MEMS system does not affect the mechanical performance of the MEMS actuators and preserves the focused beam profile as well as the measured full width at half maximum. We envision a new class of flat optical devices with active control provided by the combination of metasurfaces and MEMS for a wide range of applications, such as miniaturized MEMS-based microscope systems, LIDAR scanners, a...

Temporal modulation of x-rays using MEMS micromirrors

Investigations into temporal development of far-from-equilibrium processes can tremendously benefit from ultra-fast x-ray pulses with picosecond time resolution and high pulse repetition rates. Current x-ray modulation techniques fall short of providing solutions for generating such ultra-fast x-rays. However, x-ray modulators based on MEMS micromirrors are promising candidates for this challenge. Design, fabrication and characterization of such a micromirror are presented in this paper. Testing of this micromirror in an x-ray beamline demonstrates its feasibility for generating ultra-fast x-rays.

Enhanced synchronization range from non-linear micromechanical oscillators

In this paper, we report that the synchronization range of micro-oscillators increases with increasing drive force when operating the oscillators in the non-linear regime. This enhancement is contrary to the same observation for oscillators operating in the linear regime where the synchronization range decreases with increasing drive force. This creates the ability to synchronize multiple oscillators operating in the non-linear regime across a greater frequency range to accommodate larger frequency deviations between devices caused by fabrication variances. We have observed the increased synchronization range in both mechanical hardening and electrostatic softening non-linear micro-oscillators.

Diffraction limited focusing and routing of gap plasmons by a metal-dielectric-metal lens

Passive optical elements can play key roles in photonic applications such as plasmonic integrated circuits. Here we experimentally demonstrate passive gap-plasmon focusing and routing in two-dimensions. This is accomplished using a high numerical-aperture metal-dielectric-metal lens incorporated into a planar-waveguide device. Fabrication via metal sputtering, oxide deposition, electron- and focused-ion- beam lithography, and argon ion-milling is reported on in detail. Diffraction-limited focusing is optically characterized by sampling out-coupled light with a microscope. The measured focal distance and full-width-half-maximum spot size agree well with the calculated lens performance. The surface plasmon polariton propagation length is measured by sampling light from multiple out-coupler slits.

2-D MEMS scanner for handheld multispectral confocal microscopes

We describe a 2-D MEMS scanner for a handheld multispectral confocal microscope for early detection of cervical cancer. The MEMS scanner has an inner gimbal design with torsional springs separated from the reflectors to reduce light loss while maintaining chip size to 3.25 × 3.25 mm2. The devices are large-scale batch fabricated using a double layer SOI process. The scanner has electrostatic optical deflection angles of 3.25° for the inner axis at 75 V and ±1.6° for the outer axis at 60 V. The device has resonance frequencies of 2.84 kHz and 452 Hz for the inner and outer axis torsional modes respectively.

Handheld multispectral confocal microscope for cervical cancer diagnosis

We demonstrated a handheld multispectral fluorescence confocal microscope for cervical cancer diagnostic using dual-axis confocal microscope architecture and a microelectromechanical systems scanner. The real time images are acquired with frame rate up to 15 Hz.

Self-sustained oscillation of MEMS torsional micromirrors

Several applications of optical micromirrors need synchronization of its mechanical oscillation with an external control signal. Self-sustained oscillation of micromirrors is a prerequisite for achieving such synchronization. To suppress its mechanical deformation these micromirrors are operated under atmospheric or controlled pressure environment. Operation under this environment leads to increase in driving voltages to achieve required deflections. However, significant parasitic crosstalk due to these high driving voltages presents a challenge for achieving their self-sustained oscillations. In this paper, stable self-sustained oscillation of a 13.5kHz micromirror is achieved at atmospheric pressure by actively suppressing its crosstalk. Frequency stability of 7.2ppm is obtained for this micromirrors self-sustained oscillation at atmospheric pressure.