METHOD OF VARYING OPTICAL PROPERTIES OF PHOTONIC CRYSTALS ON FAST TIME SCALES USING ENERGY PULSES

摘要

The present invention provides a method for fast switching of opticalproperties inphotonic crystals using pulsed/modulated free-carrier injection. The resultsdisclosedherein indicate that several types of photonic crystal devices can be designedin whichfree carriers are used to vary dispersion curves, stop gaps in materials withphotonicbandgaps to vary the bandgaps, reflection, transmission, absorption, gain, orphase. Theuse of pulsed free carrier injection to control the properties of photoniccrystals on fasttimescales forms the basis for all-optical switching using photonic crystals.Ultrafastswitching of the band edge of a two-dimensional silicon photonic crystal isdemonstratednear a wavelength of 1.9 µm. Changes in the refractive index are opticallyinduced byinjecting free carriers with 800 nm, 300 fs pulses. Band-edge shifts have beeninduced insilicon photonic crystals of up to 29 nm that occurs on the time-scale of thepump pulse.The present invention also provides a method of producing a virtual ortemporary photoniccrystal using free carrier injection into pure semiconductors, bulk or thinfilm, in which thecarriers are generated in patterns which create a patterned refractive indexcontrast usedto steer light beams in the semiconductor while it is being pulsed.