Massachusetts Institute of Technology

Paul William Juodawlkis

Suraj Deepak Bramhavar

Cheryl Marie Sorace-Agaskar

Marin Soljacic

Dirk Robert Englund

Simon Verghese

Jeffrey Scott Herd

Scott A Skirlo

Mihika Prabhu

Yi Yang

Reuel Bennett Swint

Siva Yegnanarayanan

William Loh

Rajeev J Ram

Mark Alexander Hollis

Joseph P Donnelly

Boris G Kharas

Jason Plant

Dominic Siriani

The accelerometers disclosed herein provide excellent sensitivity, long-term stability, and low SWaP-C through a combination of photonic integrated circuit technology with standard micro-electromechanical systems (MEMS) technology. Examples of these accelerometers use optical transduction to improve the scale factor of traditional MEMS resonant accelerometers by accurately measuring the resonant frequencies of very small (e.g., about 1 &#x3bc;m) tethers attached to a large (e.g., about 1 mm) proof mass. Some examples use ring resonators to measure the tether frequencies and some other examples use linear resonators to measure the tether frequencies. Potential commercial applications span a wide range from seismic measurement systems to automotive stability controls to inertial guidance to any other application where chip-scale accelerometers are currently deployed.

Apparatus and methods for photonic integrated resonant accelerometers

Photonic integrated circuits (PICs) enable manipulation of light on a chip for telecommunications and information processing. They can be made with silicon and silicon-compatible materials using complementary metal-oxide-semiconductor (CMOS) fabrication techniques developed for making electronics. Unfortunately, most light sources are made with III-V and II-VI materials, which are not compatible with silicon CMOS fabrication techniques. As a result, the light source for a PIC is either off-chip or integrated onto the PIC after CMOS fabrication is over. Hybrid integration can be improved by forming a recess in the PIC to receive a III-V or II-VI photonic chip. Mechanical stops formed in or next to the recess during fabrication align the photonic chip vertically to the PIC. Fiducials on the PIC and the photonic chip enable sub-micron lateral alignment. As a result, the photonic chip can be flip-chip bonded to the PIC with sub-micron vertical and lateral alignment precision.

Hybrid integration for photonic integrated circuits

An integrated optical beam steering device includes a planar dielectric lens that collimates beams from different inputs in different directions within the lens plane. It also includes an output coupler, such as a grating or photonic crystal, that guides the collimated beams in different directions out of the lens plane. A switch matrix controls which input port is illuminated and hence the in-plane propagation direction of the collimated beam. And a tunable light source changes the wavelength to control the angle at which the collimated beam leaves the plane of the substrate. The device is very efficient, in part because the input port (and thus in-plane propagation direction) can be changed by actuating only logN of the N switches in the switch matrix. It can also be much simpler, smaller, and cheaper because it needs fewer control lines than a conventional optical phased array with the same resolution.

Methods and systems for optical beam steering

In an ultrastable laser, using a large mode-volume optical resonator, which suppresses the resonator's fast thermal fluctuations, together with the stimulated Brillouin scattering (SBS) optical nonlinearity presents a powerful combination that enables the ability to lase with an ultra-narrow linewidth of 20 Hz. The laser's long-term temperature drift is compensated by using the narrow Brillouin line to sense minute changes in the resonator's temperature (e.g., changes of 85 nK). The precision of this temperature measurement enables the stabilization of resonators against environmental perturbations.

Narrow-linewidth microcavity brillouin laser with suppressed temperature fluctuations

An accelerometer may comprise a proof mass, a first tether mechanically coupled to the side of the proof mass and to an anchor, and a ring resonator integrated with the tether to form a sensing tether. The ring resonator and the tether may be configured such that a strain sustained by the sensing tether causes a change of a resonance condition of the ring resonator. The accelerometer may comprise a wavelength locking loop configured to adaptively maintain a center frequency of the light energy at a resonant frequency of the sensing element, and a scale factor calibrator configured to stabilize a scale factor associated with the accelerometer. The accelerometer may further include a detection processor configured to receive the detection signal and produce an acceleration signal therefrom. The acceleration signal may correspond to an amount of change of the resonance condition with respect to a reference resonance condition.

Integrated resonant accelerometer using optical strain sensor

An optoelectronic filter having at least one input and an output includes a modulator circuit having at least first and second inputs with a first one of the modulator circuit inputs adapted to couple to a respective one of the at least one input of the optoelectronic filter. The modulator circuit receives at least a first radio frequency (RF) signal having a first power level and a second RF signal having a second, different power level at the first one of the modulator circuit inputs and in response thereto generates a modulated signal at an output thereof. The first RF signal is suppressed relative to the second RF signal in the modulated signal. The optoelectronic filter additionally includes a light source adapted to couple to a second one of the modulator circuit inputs. A corresponding method is also provided.

Optoelectronic filter and method for signal suppression

Apparatus and methods for photonic integrated resonant accelerometer

An electro-optic modulator imparts the information contained in an electrical signal traveling along a transmission line onto an optical carrier by using signal-related variations in the electrical signal's voltage to modulate the refractive index or absorption in an electro-optic material through which the optical carrier propagates. For optimal bandwidth and modulation efficiency, the microwave and optical waves should be matched in velocity. However, conventional microwave transmission lines have a microwave velocity that is somewhat higher than the optical group velocity in typical optical waveguides. Tuning a microwave transmission line's capacitance reduces the microwave velocity, but also reduces the impedance below the 50&#x3a9; impedance of most microwave components. Conversely, tuning the microwave transmission line's inductance makes it possible to match the microwave velocity to the optical group velocity over bandwidths of 100 GHz or greater while maintaining a microwave impedance of 50&#x3a9;.

Inductance-tuned electro-optic modulators

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Arlington, MA, United States of America

Paul William Juodawlkis