Scalable High Speed Laser Diode for Silicon Integration
Abstract
Very high-speed optical data requires high efficiency, small cavity semiconductor lasers that use directly modulated lasers. If a laser lacks high efficiency and has low thermal resistance, its differential gain and stimulated emission rates suffer due to excessive self-heating. Vertical-cavity surface-emitting lasers (VCSELs) are todayÕs highest speed laser diodes. These existing oxide devices are able to reach data speeds above 50 Gbps at room temperature, thus partly satisfy these requirements. New and emerging VCSEL designs that are scalable to small cavity size, have even higher efficiency, and low thermal resistance are even more promising. In our prior ARO work, we developed a breakthrough VCSEL technology that exceeds the best oxide VCSELs in key properties needed for high speed. These include size scaling, high efficiency, and low thermal resistance. This new VCSEL is based on an internal confinement scheme that eliminates the internal oxide, replacing it with an epitaxial confinement scheme that is lithographic. Because the confinement is lithographic the VCSELs achieve near perfect uniformity even for very small single mode sizes. In this project we propose to develop very high speed, directly modulated lasers based on temperature control and flip-chip mounting of the lithographic VCSELs. We have extensive experimental data on the VCSEL thermal properties and size scaling. Theoretical modeling indicates that the fundamental limits to high-speed laser modulation are due to self-heating and electrical parasitics. Modeling reveals that data rates well in excess of 100 Gbps are possible by scaling the lasers down to micron and sub-micron dimensions by maintaining high efficiency and design of electrical contacting. Very small, even sub-micron lithographic VCSELs have decided advantages for high speed over oxide VCSELs. Flip-chip mounting on silicon further increases the speed and is important for silicon chip integration. Developing the ability to integrate with driver electronics and data processing circuitry are also project goals. This project uses epitaxial crystal growth and fabrication technology to create novel vertical cavity structures to develop the high-speed laser sources. The laser sources will be created for high speed testing focusing on designs with low electrical parasitics. Initial research confirms that flip-chip mounting can reduce electrical parasitics while dramatically improving the thermal properties. In the proposed project, designs will be developed for waveguide integration with silicon and silicon on insulators to generate intrachip optical interconnects. These innovative designs will target data speeds for temperatures up to 85 C that reach 100 Gbps and greater. The new designs with their scaled small size laser diodes will target low bit energy. The laser designs proposed in this project promise technology surpassing existing laser technology/sources/devices.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 22, 2019
- Source ID
- W911NF1510579
Entities
People
- Dennis Deppe
Organizations
- Army Contracting Command
- United States Army
- University of Central Florida