Researchers at Rice University (USA) have developed a micron-scale spatial light modulator (SLM) similar to those currently used in sensing and imaging devices, but with the potential to run several orders of magnitude faster. Their ‘antenna on a chip’ operates in 3D ‘free space’ instead of the two-dimensional space of conventional semiconductor devices.
In current optical computing devices, light is confined to two-dimensional circuitry and travels in waveguides from point to point. According to the researchers, 2D systems ignore the massive multiplexing capability of optical systems arising from the fact that multiple light beams can propagate in the same space without affecting each other.
The new SLM devices essentially consist of nanoscale ribs of crystalline silicon forming a cavity between p- and n-doped silicon slabs connected to metallic electrodes. The rib positions can be ‘warped’ at the microscale level to tune the resonant cavity for coupling with incident light, which ‘pulls’ incident light into the cavity. Although silicon is transparent to infrared light, after the light has been captured by the SLM it can be modulated by manipulating it as it passes through the chip.