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

• US 5,907,427 A
• Filed: 10/24/1997
• Issued: 05/25/1999
• Est. Priority Date: 10/24/1997
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America), Time Domain Corporation (Humatics Corporation)
• Original Assignee: Time Domain Corporation (Humatics Corporation)
• Inventors: Tocci, Michael D., Scalora, Michael, Bloemer, Mark J.
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): Lester, Evelyn A.
• Application Number:
  US08/956,112
• Time in Patent Office: 578 Days
• Field of Search: 359/140, 359/248, 359/250, 359/259, 359/260, 359/264, 359/279, 359/331, 359/586-588
• US Class Current: 359/248
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 6/1225 comprising photonic band-gap structures or photonic lattices
• CPC Class Codes: G02B 6/2861 using fibre optic delay lines and optical elements associated with them, e.g. for use in signal processing, e.g. filtering delay lines in general H03H, H01P9/00; optical computing devices G06E

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.

Claims

1. A device for delaying a first photonic signal by a first predetermined delay, the first photonic signal having a first predetermined frequency and a first predetermined bandwidth, comprising:

a first region having periodically alternating refractive material layers which exhibit a photonic band gap structure, wherein said first region comprises

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, wherein said second region comprises

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 first periodicity defect region, interposed between said first and second regions of periodically alternating refractive material layers, whereby the first predetermined delay is imparted to the first photonic signal during passage through the device.

2. The device according to claim 1, wherein said first region of periodically alternating refractive material layers comprises:

a plurality of first refractive material layers having said first thickness and said first index of refraction; and

a plurality of second refractive material layers having said second thickness and said second index of refraction, wherein said first and second refractive material layers are arranged in an alternating manner.

3. The device according to claim 1, wherein said second region of periodically alternating refractive material layers comprises:

a plurality of third refractive material layers, wherein said third thickness equals said first thickness and said third index of refraction equals said first index of refraction; and

a plurality of second refractive material layers, wherein said fourth thickness equals said second thickness and said fourth index of refraction equals said second index of refraction, wherein said third and fourth refractive material layers are arranged in an alternating manner.

4. The device according to claim 1, wherein said first periodicity defect region has a thickness different than said first, second, third, or fourth thickness, an index of refraction approximately the same as either said first or second index of refraction, and a photonic transmission resonance.

5. The device according to claim 4, wherein said first periodicity defect region has a predetermined thickness such that said transmission resonance is centrally located in said corresponding photonic band gap of the device.

6. The device according to claim 4, wherein said alternating refractive material layers and said first periodicity defect region have predetermined thicknesses such that said transmission resonance corresponds to the first predetermined frequency of the first photonic signal.

7. The device according to claim 1, further comprising a tunable laser source;

wherein the first photonic signal is generated by said tunable laser source and the delay that is imparted to the first photonic signal during passage through the device varies as a function of first photonic signal frequency.

8. The device according to claim 4, further comprising:

electrical contacts located on said first periodicity defect region; and

a power supply source coupled to said electrical contacts, to impart a variable voltage across the device which varies said index of refraction of said first periodicity defect, and thereby varies the delay imparted to the first photonic signal passing therethrough.

9. The device according to claim 1, wherein said first thickness of said first refractive material layer and said second thickness of said second refractive material layer are each proportional to the wavelength of the incoming first photonic signal, and wherein said first and second thicknesses are chosen to control the delay of the first photonic signal.

10. The device according to claim 1, wherein said alternating refractive material layers comprise GaAs and AlAs semiconductor layers grown on a semiconductor substrate.

11. The device according to claim 1, wherein the device delays a second photonic signal by a second predetermined delay, the second photonic signal having a second predetermined frequency and a second predetermined bandwidth, further comprising:

a third region of periodically alternating refractive material layers, wherein said third region comprises

a fifth refractive material layer having a thickness equal to said first thickness and an index of refraction equal to said first index of refraction, and

a sixth refractive material layer having a thickness equal to said second thickness and an index of refraction equal to said second index of refraction; and

a second periodicity defect region, interposed between said second and third regions of periodically alternating refractive material layers, having a thickness different than said thicknesses of said first and second refractive material layers, an index of refraction approximately the same as either said first or second index of refraction, and a second photonic transmission resonance.

12. The device according to claim 11, wherein said third region of periodically alternating refractive material layers comprises:

a plurality of fifth refractive material layers; and

a plurality of sixth refractive material layers, wherein said fifth and sixth refractive material layers are arranged in an alternating manner.

13. The device according to claim 11, wherein said first and second photonic transmission resonances are located at different locations in said corresponding photonic band gap of the device.

14. The device according to claim 11, wherein said first transmission resonance corresponds to said first predetermined photonic signal frequency, and said second transmission resonance corresponds to said second predetermined photonic signal frequency, whereby said first and second predetermined delays are imparted to said first and second photonic signals respectively during passage through the device.

15. The device according to claim 11, further comprising:

electrical contacts located on said first and second periodicity defect regions; and

a power supply source coupled to said electrical contacts, to impart a variable voltage across the device which varies said indices of refraction of said first and second periodicity defect regions, and thereby varies the delay imparted to the first and second photonic signals passing therethrough.

16. The device according to claim 11, wherein the device delays a plurality of photonic signals having differing frequencies and bandwidths, comprising:

one or more additional regions of periodically alternating refractive material layers exhibiting a photonic band gap structure; and

one or more additional periodicity defect regions interposed throughout said regions of periodically alternating refractive material layers to impart varying delays to said photonic signals.

17. A method for 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:

(1) sending the photonic signal along an optical path;

(2) passing the photonic signal through a first region of periodically alternating refractive sections in said optical path of the photonic signal;

(3) passing the photonic signal through a periodicity defect region in said optical path; and

(4) passing the photonic signal through a second region of periodically alternating refractive sections in said optical path.

18. The method according to claim 17, wherein step (2) comprises the step of passing the photonic signal through said first region of periodically alternating refractive sections that includes at least one first refractive material layer having a first thickness and first index of refraction and at least one second refractive material layer having a second thickness and a second index of refraction, wherein said first and second layers are arranged to form a periodically alternating structure, and wherein said periodically alternating structure exhibits a photonic band gap.

19. The method according to claim 17, wherein step (4) comprises the step of passing the photonic signal through said second region of periodically alternating refractive sections that includes at least one third refractive material layer having said first thickness and said first index of refraction and at least one fourth refractive material layer having said second thickness, and said second index of refraction, wherein said third and fourth layers are arranged to form a periodically alternating structure, and wherein said periodically alternating structure exhibits a photonic band gap.

20. The method according to claim 17, wherein step (3) comprises the step of passing the photonic signal through said periodicity defect region having a third thickness and a third index of refraction, wherein a photonic transmission resonance peak is created in said photonic band gap.

21. The method according to claim 20, further comprising the step of:

(5) determining said third thickness and said third index of refraction such that said transmission resonance peak corresponds to the predetermined frequency of the photonic signal.

22. The method according to claim 17, wherein step (2) comprises the step of passing the photonic signal through said first region of periodically alternating refractive sections that includes at least one first section having a first thickness and first index of refraction and at least one second section having a second thickness and a second index of refraction, wherein said first and second sections are arranged to form a periodically alternating structure in a fiber grating structure, and wherein said periodically alternating structure exhibits a photonic band gap.

23. The method according to claim 22, wherein step (4) comprises the step of passing the photonic signal through said first region of periodically alternating refractive sections that includes at least one third section having said first thickness and first index of refraction and at least one fourth section having said second thickness and said second index of refraction, wherein said third and fourth sections are arranged to form a periodically alternating structure in said fiber grating structure, and wherein said periodically alternating structure exhibits a photonic band gap.

24. The method according to claim 22, wherein step (3) comprises the step of passing the photonic signal through said periodicity defect region in said fiber grating structure having a third thickness and a third index of refraction, wherein a photonic transmission resonance peak is created in said photonic band gap.

25. The method according to claim 20, wherein the temporal delay imparted to the photonic signal is variable, comprising the step of:

(6) varying said third index of refraction of said periodicity defect region by electrical means.

26. The method according to claim 24, wherein the temporal delay imparted to the photonic signal is variable, comprising the step of:

(7) varying an optical path length of said periodicity defect region by piezo-electric means.

27. The method according to claim 17, wherein the temporal delay imparted to the photonic signal is variable, further comprising the step of:

(8) tuning the optical source to alter the frequency of the photonic signal to thereby alter the temporal delay imparted to the photonic signal.

28. A method for imparting a first temporal delay to a first photonic signal of a first predetermined frequency and a first predetermined bandwidth by a first predetermined temporal duration and a second temporal delay to a second photonic signal of a second predetermined frequency and a second predetermined bandwidth by a second predetermined temporal duration, wherein the first and second photonic signals are generated by an optical source, comprising the steps of:

(1) sending the first and second photonic signals along an optical path;

(2) passing the first and second photonic signals through a first region of periodically alternating refractive sections in said optical path of the photonic signal;

(3) passing the first and second photonic signals through a first periodicity defect region in said optical path;

(4) passing the first and second photonic signals through a second region of periodically alternating refractive sections in said optical path;

(5) passing the first and second photonic signals through a second periodicity defect region in said optical path; and

(6) passing the first and second photonic signals through a third region of periodically alternating refractive sections in said optical path.

29. The method according to claim 28, wherein step (2) comprises the step of passing the first and second photonic signals through said first region of periodically alternating refractive sections that includes at least one first refractive material layer having a first thickness and first index of refraction and at least one second refractive material layer having a second thickness and a second index of refraction, wherein said first and second layers are arranged to form a periodically alternating structure, and wherein said periodically alternating structure exhibits a photonic band gap.

30. The method according to claim 28, wherein step (4) comprises the step of passing the first and second photonic signals through said second region of periodically alternating refractive sections that includes at least one third refractive material layer having said first thickness and said first index of refraction and at least one fourth refractive material layer having said second thickness and said second index of refraction, wherein said third and fourth layers are arranged to form a periodically alternating structure, and wherein said periodically alternating structure exhibits said photonic band gap.

31. The method according to claim 28, wherein step (6) comprises the step of passing the first and second photonic signals through said third region of periodically alternating refractive sections that includes at least one fifth refractive material layer having said first thickness and said first index of refraction and at least one sixth refractive material layer having said second thickness and said second index of refraction, wherein said fifth and sixth layers are arranged to form a periodically alternating structure, and wherein said periodically alternating structure exhibits said photonic band gap.

32. The method according to claim 28, wherein step (3) comprises the step of passing the first and second photonic signals through said first periodicity defect region having a third thickness and a third index of refraction, wherein a first photonic transmission resonance peak corresponding to the first predetermined frequency of the first photonic signal is created in said photonic band gap.

33. The method according to claim 28, wherein step (5) comprises the step of passing the first and second photonic signals through said second periodicity defect region having a fourth thickness and a fourth index of refraction, wherein a second photonic transmission resonance peak corresponding to the second predetermined frequency of the second photonic signal is created in said photonic band gap.