All-optical spatial light modulators
A spatial light modulator (SLM) comprised of a 2D array of optically-controlled semiconductor nanocavities can have a fast modulation rate, small pixel pitch, low pixel tuning energy, and millions of pixels. Incoherent pump light from a control projector tunes each PhC cavity via the free-carrier dispersion effect, thereby modulating the coherent probe field emitted from the cavity array. The use of high-Q/V semiconductor cavities enables energy-efficient all-optical control and eliminates the need for individual tuning elements, which degrade the performance and limit the size of the optical surface. Using this technique, an SLM with 10 6 pixels, micron-order pixel pitch, and GHz-order refresh rates could be realized with less than 1 W of pump power.
1. A spatial light modulator comprising:
a layer patterned with a two-dimensional array of semiconductor cavities, the two-dimensional array of semiconductor cavities each scattering signal light at a resonant wavelength;
a two-dimensional array of light-emitting diodes (LEDs), in optical communication with the two-dimensional array of semiconductor cavities, to tune the resonant wavelength of at least one semiconductor cavity in the two-dimensional array of semiconductor cavities via optical free carrier injection;
a control layer, operably coupled to the two-dimensional array of LEDs, to modulate LEDs in the two-dimensional array of LEDs at a rate of at least 1 GHz; and
a waveguide layer, in optical communication with the two-dimensional array of LEDs and the two-dimensional array of semiconductor cavities, to image pump signals emitted by the two-dimensional array of LEDs onto the two-dimensional array of semiconductor cavities.
2. The spatial light modulator of claim 1 , wherein the semiconductor layer comprises silicon.
3. The spatial light modulator of claim 1 , wherein each semiconductor cavity in the two-dimensional array of semiconductor cavities has a quality factor Q of at least 1000.
4. The spatial light modulator of claim 1 , wherein the two-dimensional array of semiconductor cavities is comprised of H1 photonic crystal cavities.
5. The spatial light modulator of claim 1 , wherein the two-dimensional array of semiconductor cavities is comprised of L4/3 photonic crystal cavities.
6. The spatial light modulator of claim 1 , wherein the two-dimensional array of semiconductor cavities is comprised of micropillar cavities.
7. The spatial light modulator of claim 1 , wherein the two-dimensional array of semiconductor cavities has a pitch of about half the resonant wavelength to about the resonant wavelength.
8. The spatial light modulator of claim 1 , wherein the pump signals emitted by the two-dimensional array of LEDs are at a wavelength of less than 500 nm and the signal light is at a wavelength of more than 500 nm.
9. The spatial light modulator of claim 1 , further comprising:
a signal light waveguide layer, in optical communication with the semiconductor layer, to guide the signal light to the at least one semiconductor cavity.
10. The spatial light modulator of claim 9 , further comprising:
a signal light source, in optical communication with the signal waveguide layer, to launch the signal light into the signal waveguide layer.
11. The spatial light modulator of claim 1 , wherein the two-dimensional array of semiconductor cavities comprises a surface defined by a photonic crystal slab guided mode resonator.
12. The spatial light modulator of claim 1 , wherein the two-dimensional array of semiconductor cavities includes a wavelength-scale patterned semiconductor slab.
13. The spatial light modulator of claim 12 , wherein the two-dimensional array of semiconductor cavities supports a spatially distributed resonant mode.
14. The spatial light modulator of claim 1 , wherein a free carrier lifetime of the two-dimensional array of semiconductor cavities is about 100 ps or less.
15. The spatial light modulator of claim 1 , wherein a free carrier lifetime of the two-dimensional array of semiconductor cavities is about 1 ns or more.