Photonic band gap device and method using a periodicity defect region doped with a gain medium to increase photonic signal delay

Abstract

A photonic band gap structure device and method for delaying photonic signals of a predetermined frequency and a predetermined bandwidth by a predetermined delay is provided. A Fabry-Perot delay line device has several regions of periodically alternating refractive material layers which exhibit a series of photonic band gaps and a periodicity defect region, interposed between the regions of periodically alternating refractive material layers. The Fabry-Perot delay line device imparts a predetermined delay to photonic signals that pass therethrough. The introduction of the periodicity defect region into this photonic band gap structure creates a sharp transmission resonance within the corresponding photonic band gap of the structure and causes at least an order of magnitude improvement in photonic signal delay for a band-edge delay line device of similar size. Variable photonic delays to multiple photonic signals are also generated by this Fabry-Perot delay line device. In addition, a photonic signal delay device based on an optical fiber grating structure is provided. A defect layer doped with a gain medium increases the density of modes thereby increasing the density of photons at a particular frequency. The introduction of gain automatically causes an increase in the photon density, and therefore, a narrowing of the density of modes. This allows tuning of the group velocity, just as if periods were being added. This also enables larger delays.

What is claimed is:  
     
         1 . A device for delaying a photonic signal by a predetermined delay, the photonic signal having a predetermined frequency and a predetermined bandwidth, comprising: 
 a first region having periodically alternating refractive material layers which exhibit a photonic band gap structure, said first region comprising a first refractive material layer having a first thickness and a first index of refraction, and a second refractive material layer having a second thickness and a second index of refraction;    a second region having periodically alternating refractive material layers which exhibit a photonic band gap structure, said second region comprising a third refractive material layer having a third thickness and a third index of refraction, and a fourth refractive material layer having a fourth thickness and a fourth index of refraction; and    a periodicity defect region, interposed between said first and second regions of periodically alternating refractive material layers, wherein said periodicity defect region is doped with a gain medium;    wherein the first predetermined delay is imparted to the photonic signal during passage through the device when said periodicity defect region is excited by an energy source.    
     
     
         2 . The device of  claim 1 , wherein said energy source is an electrical current.  
     
     
         3 . The device of  claim 1 , wherein said energy source is an optical signal having the predetermined frequency.  
     
     
         4 . A method of imparting a delay to a photonic signal of a predetermined frequency and a predetermined bandwidth by a predetermined temporal duration, wherein the photonic signal is generated by an optical source, comprising the steps of: 
 sending the photonic signal along an optical path;    passing the photonic signal through a first region of periodically alternating refractive sections in said optical path of the photonic signal;    passing the photonic signal through a periodicity defect region in said optical path, wherein the periodicity defect region is doped with a gain medium and excited by an energy source; and    passing the photonic signal through a second region of periodically alternating refractive sections in said optical path.    
     
     
         5 . The method of  claim 4 , wherein the energy source is an electrical current; and further comprising the step of setting the electrical current to impart the desired delay.  
     
     
         6 . The method of  claim 4 , wherein the energy source is an optical signal having the predetermined frequency; and further comprising the step of setting the optical signal to impart the desired delay.