Investigation Of Light Manipulation Based On Photonic Crystal Dynamic Nanocavity

In the past decades,the information industry has caught on the express train of the electronics industry and entered an era of rapid development.Nowadays,the development of the electronic information industry is limited by the“electron bottleneck”,and it is urgent to find a new development direction.It is an ideal choice to turn to the direction of using photon as a new information carrier.In light applications such as optical signal processing or light-matter interaction,arbitrary control of photon flow is essential,including the capture,storage and delivery of signal photons to any desired locations,just like what we can do for particles using optical tweezers.In order to trap and store signal photons,an ultrahigh-Q nanocavity based on photonic crystal(PC)is a good candidate.But the problem is that ultrahigh-Q means that only light pulses with a time domain duration equal to or longer than the photon lifetime of the nanocavity can be effectively coupled into them,which makes the response speed of photonic devices based on ultrahigh-Q nanocavity usually quite slow and the operating bandwidth is ultranarrow,which is known as“delay-bandwidth product”limit.In order to break this limit,it is necessary to dynamically tune the coupling strength between the nanocavity and the waveguide.However,the proposed methods for this purpose have some drawbacks such as the modal volume of the resonator is large and there are many undesirable resonance modes,or rigorous dynamic-phase-matching conditions are required,or ultrahigh-speed periodic-refractive-index modulation is required.In addition,these methods cannot move the captured photons to a specified position,and thus cannot achieve the purpose of arbitrary control of the photons.In order to overcome the shortcomings of these existing methods,in this thesis,we start from a W1 waveguide structure based on a silicon photonic crystal slab,and investigate studied the influence on the band structure if we decrease the refractive index of the dielectric material in the waveguide region.Based on this,we then propose a new-type ultrahigh-Q“potential-barrier-like”cavity which is consisted of two local refractive index reduction regions on the waveguide.FDTD simulations are performed to verify the predictions of this theory.Based on the“potential-barrier-like”nanocavity,a new-type photonic manipulation method is realized through the method of dynamic refractive-index modulation.This photonic manipulation method has high flexibility.It can trap and store the travelling signal light at any time and at any position on the waveguide;it can transfer the trapped signal photons to any desired position on the waveguide to join light-matter interaction or for other purposes;it also can release the trapped photons on demand,and can make the released signal light output along a specified direction in the waveguide.Then,through investigate studied the influence on the band structure if we increase the refractive index of the dielectric material in the waveguide region,we have proposed another kind of photonic manipulation method that utilizes an ultrahigh Q“potential-well-like”dynamic microcavity.This kind of photonic manipulation method also has high flexibility:it can capture and store signal light with a long photon lifetime(more than 10ns,corresponding to a Q factor of more than 10~7),and it is also moveable.We also study the significant spectral bandwidth compression and dynamic wavelength conversion during the capture and storage process,and the underlying physical mechanism is revealed.Finally,a novel phenomenon of energy leakage in a moving cavity at high speed is discussed.