Massachusetts Institute of Technology

Other

Reuel Bennett Swint

Steven Jay Spector

Paul William Juodawlkis

Boris G Kharas

Mark S Zediker

Milos A Popovic

Todd A Thorsen

Mark Alexander Hollis

Caroline Anne Ross

Donna-Ruth Webb Yost

Suraj Deepak Bramhavar

Joseph P Donnelly

James J Coleman

Cheryl Marie Sorace-Agaskar

Juan Montoya

Jason Plant

Gregory D Allen

Dominic Siriani

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

Electrical and electromechanical devices often require maintaining a specific temperature, or a narrow range or temperatures, during operation. An assembly regulates the temperature of a device by providing a variable thermal resistance between the device and a heatsink. The device can be mounted to a base having a high thermal resistance, the base thermally isolating the device from the heatsink. At low environmental temperatures, the base enables the device to rise to its operating temperature as a result of the device's waste heat, and with no or minimal use of a heater. As the environmental temperature increases, a working fluid, having a low thermal resistance, undergoes thermal expansion to fill a portion of a volume in the base between the device and the heat sink, lowering the thermal resistance between the device and the heatsink to maintain the device at the required operating temperature.

Variable thermal resistance

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

An optical structure for generating nonreciprocal loss is provided that includes a first substrate layer and a magneto-optical layer positioned on the first substrate layer. The magneto-optical layer achieves nonreciprocity with application of an external magnetic field so as to produce resonantly enhanced nonreciprocal loss.

On-chip miniature optical isolator

A solid state waveguide coupler is provided including a first coupler end disposed on a solid state material substrate for connection to a first solid state waveguide located on the substrate and a second coupler end disposed on the substrate for connection to a second waveguide located on the substrate. A coupling span, comprising a waveguide material layer on the substrate, is disposed between the first and second coupler ends and tapers between a height of the first waveguide and a height of the second waveguide, tapers between a width of the first waveguide and a width of the second waveguide, and includes curved sidewalls along at least a portion of the tapered coupling span. In a method for fabricating the waveguide coupler, material is isotropically removed from a waveguide material layer on the substrate to produce tapered surfaces between the first waveguide and the second waveguide.

Waveguide coupler having continuous three-dimensional tapering

A semiconductor quantum well laser having separate lateral confinement of injected carriers and the optical mode. A ridge waveguide is used to confine the optical mode. A buried heterostructure confines injected carriers. A preferred embodiment laser of the invention is a layered semiconductor structure including optical confinement layers. A buried heterojunction quantum well within the optical confinement layers is dimensioned and arranged to confine injected carriers during laser operation. A ridge waveguide outside the optical confinement layers is dimensioned and arranged with respect to the buried heterojunction to confine an optical mode during laser operation. An index step created by the buried heterojunction is substantially removed from the optical mode.

Separate lateral confinement quantum well laser

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Billerica, MA, United States of America

Reuel Bennett Swint