Opto-Electronic Non-Volatile Memory Cell

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A single Opto-Electronic, Non-Volatile Memory Cell (OENVM) capable of storing 16-Bits of data in a small (n scale) could result in fast, compact, memory storage for future computers.

Being able to modulate light’s properties (e.g. frequency, intensity, polarization, phase, etc.) allows for very fast optical telecommunication devices that are less massive and require less power than conventional copper/aluminum coaxial cable and trace routings in integrated circuits. In this regard, the OENVMC described here would record 16-bits of data using the addition of two phase shifted, linearly polarized pulses of light and the adjustment of the pulse energy of a Read/Write Vertical External Cavity Surface Emitting Laser (VECSEL) using Aluminum (very similar to conventional DVD/CD RW mediums). The difficulty with compacting 16-Bits of data into a single cell is being able to detect/decode the 16-bits of data using a single “read” operation and restoring the recording medium to an initial state .

Writing would include the encoding a 16-Bit word using the least significant 12-bits for Pulse Width Modulation of the VECSEL output energy. Each bit of the first 12 bits would define a certain pulse width or output energy. A polarizing material epitaxially grown at the output of the VECSEL would polarize the originating wave of light. The most significant four bits of the 16 would be used with an integrated Pockels cell and parallel waveguide (interferometric modulator {IM}) to adjust the amplitude of the wave of laser light that will hit the aluminum. Two paths, one for the pockels cell and one for the original output, would meet providing interference of the light waves. An integrated convergent lens at the output of the waveguide would also be used to focus the output beam. The resulting data would be encoded on the aluminum as a “pit” of certain depth/energy and length.

Reading the data would include fabricating a second waveguide in close proximity to the output portion of the IM. The reflected energy of the wave from the aluminum would be coupled to this waveguide and sent to a very sensitive photodiode. The current developed would be inversely related to the amount of energy that the laser used to create the pit. Amplitude measurement would be vital to reconstruct the original 4-MSB while depth of pit would be used to constitute the 12-LSB amount of energy developed during the write process.

Conductive vias/traces could be used to write a Reset to the memory cell aluminum to place it in its original non pitted state.

Future developments could include using two orthogonal waves in the IM so as to create a variety of polarization patterns for the light, increasing the possibility of bit density within the cell. Detection of the polarization, amplitude, and energy (depth) could provide additional read detection problems.

Various images of circuits/cross sections of fabricated devices included in this summary can be found at the following URL’s: http://www.photonics.com/Article.aspx?AID=29078;


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  • Name:
    Jason Dietrich
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