Massachusetts Institute of Technology

Jie Sun

Michael Robert Watts

Ehsan Shah Hosseini

Matteo Cherchi

Ami Yaacobi

Purnawirman Purnawirman

Erman Timurdogan

Jonathan B Bradley

Brad Cordova

Christopher Vincent Poulton

Zhan Su

Manan Raval

Jerry Zhou

Jonathan D B Bradley

Examples of the present invention include integrated erbium-doped waveguide lasers designed for silicon photonic systems. In some examples, these lasers include laser cavities defined by distributed Bragg reflectors (DBRs) formed in silicon nitride-based waveguides. These DBRs may include grating features defined by wafer-scale immersion lithography, with an upper layer of erbium-doped aluminum oxide deposited as the final step in the fabrication process. The resulting inverted ridge-waveguide yields high optical intensity overlap with the active medium for both the 980 nm pump (89%) and 1.5 &#x3bc;m laser (87%) wavelengths with a pump-laser intensity overlap of over 93%. The output powers can be 5 mW or higher and show lasing at widely-spaced wavelengths within both the C- and L-bands of the erbium gain spectrum (1536, 1561 and 1596 nm).

Photonic devices and methods of using and making photonic devices

A display for augmented reality (AR) includes an array of optical phased arrays (OPAs) integrated into a transparent substrate. The array of OPAs emit light encoded with four dimensional (4D) light field including 2D spatial coordinates and 2D directional coordinates to create an image of a virtual object on a retina of a viewer. By adjusting the emission directions of light beam emitted by individual OPAs in the display, the depth perception can be adjusted accordingly. The array of OPAs can also be encoded with holographic information, including intensity and phase distribution, of a virtual object to create the image of the virtual object on the retina. The AR display can further incorporate liquid crystal (LC) into the OPAs for modulating the amplitudes and relative phases of light emitted by the OPAs.

Display apparatus comprising first and second optical phased arrays and method for augmented reality

A photodetector includes a germanium layer evanescently coupled to a ring resonator. The ring resonator increases the interaction length between light guided by the ring resonator and the germanium layer without increasing the size of the photodetector, thereby keeping the photodetector's dark current at a low level. The germanium layer absorbs the guided light and converts the absorbed light into electrical signals for detection. The increased interaction length in the resonator allows efficient transfer of light from the resonator to the germanium layer via evanescently coupling. In addition, the internal and external quality factors (Q) of the ring resonator can be matched to achieve (nearly) full absorption of light in the germanium with high quantum efficiency.

Apparatus, systems, and methods for waveguide-coupled resonant photon detection

An optical phased array formed of a large number of nanophotonic antenna elements can be used to project complex images into the far field. These nanophotonic phased arrays, including the nanophotonic antenna elements and waveguides, can be formed on a single chip of silicon using complementary metal-oxide-semiconductor (CMOS) processes. Directional couplers evanescently couple light from the waveguides to the nanophotonic antenna elements, which emit the light as beams with phases and amplitudes selected so that the emitted beams interfere in the far field to produce the desired pattern. In some cases, each antenna in the phased array may be optically coupled to a corresponding variable delay line, such as a thermo-optically tuned waveguide or a liquid-filled cell, which can be used to vary the phase of the antenna's output (and the resulting far-field interference pattern).

Optical phased arrays with evanescently-coupled antennas

A frequency-chirped nano-antenna provides efficient sub-wavelength vertical emission from a dielectric waveguide. In one example, this nano-antenna includes a set of plasmonic dipoles on the opposite side of a SiYVwaveguide from a ground plane. The resulting structure, which is less than half a wavelength long, emits a broadband beam (e.g., &#x3e;300 nm) that can be coupled into an optical fiber. In some embodiments, a diffractive optical element with unevenly shaped regions of high- and low-index dielectric material collimates the broadband beam for higher coupling efficiency. In some cases, a negative lens element between the nano-antenna and the diffractive optical element accelerates the emitted beam's divergence (and improves coupling efficiency), allowing for more compact packaging. Like the diffractive optical element, the negative lens element includes unevenly shaped regions of high- and low-index dielectric material that can be designed to compensate for aberrations in the beam emitted by the nano-antenna.

Methods and apparatus for vertical coupling from dielectric waveguides

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Cambridge, MA, United States of America

Jie Sun