Mirror with photonic band structure

• US 5,365,541 A
• Filed: 01/27/1993
• Issued: 11/15/1994
• Est. Priority Date: 01/29/1992
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Bullock, Donald L.
• Primary Examiner(s): Bovernick, Rodney B.
• Assistant Examiner(s): Sanghavi, Hemang
• Application Number:
  US08/001,231
• Time in Patent Office: 657 Days
• Field of Search: 372/99, 372/18, 372/19, 372/102, 372/107, 372/50, 372/97
• US Class Current: 372/99
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 6/00 Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
• CPC Class Codes: G02B 6/1225 comprising photonic band-gap structures or photonic lattices
• CPC Class Codes: H01S 5/11 Comprising a photonic bandgap structure
• CPC Class Codes: H01S 5/14 External cavity lasers H01S5/18 takes precedence; mode locking H01S5/065
• CPC Class Codes: H01S 5/4062 with an external cavity or using internal filters, e.g. Talbot filters

Abstract

An apparatus for achieving in-phase mode operation of a diode laser. A photonic band gap mirror (photonic crystal) having a periodic lattice structure is placed in front of light emitted from one side of the laser diode array. Because of an incomplete photonic band gap in the photonic crystal, light normal to the crystal will be primarily reflected while light at an angle will be primarily transmitted through the mirror. Since in-phase emission is primarily normal and out-of-phase emission primarily off axis, the reflected light which is directed back into the laser cavity will be the predominant lasing mode. The out-of-phase mode primarily transmitted will have significantly larger losses. The resulting laser diode apparatus will therefore operate in-phase and produce a single lobe far-field distribution.

Claims

1. An apparatus including a laser for generating in-phase light from the laser, said apparatus comprising:

a laser producing a light beam at a predetermined wave length;

a periodic lattice structure of regular geometric shapes disposed to receive light from said laser, said structure having a first index of refraction;

an interstitial medium existing between said geometric shapes, said interstitial medium having a second index of refraction which is different from said first index of refraction; and

said periodic lattice structure adapted to receive the light beam, said lattice structure having a spatial period between said geometric shapes which is chosen such that the light of symmetric uniphase mode from said laser is selectively reflected with a substantially enhanced reflectivity relative to other modes by said periodic lattice structure as a result of the photonic band structure of said periodic lattice.

2. The apparatus of claim 1 wherein said laser is an array of lasers.

3. The apparatus of claim 1 wherein said laser is a broad area laser.

4. The apparatus of claim 1 wherein said periodic lattice Structure is a three-dimensional structure.

5. The apparatus of claim 1 wherein the regular geometric forms in said periodic lattice structure comprise Bravais lattices.

6. The apparatus of claim 1 wherein the regular geometric shapes are composed of gallium arsenide and the interstitial medium is composed of gallium aluminum arsenide.

7. The apparatus of claim 1 wherein said first index of refraction is greater than said second index of refraction.

8. The apparatus of claim 7 wherein the ratio of said first index of refraction to said second index of refraction is less than 2.0.

9. The apparatus of claim 1 wherein said spatial period is such that light of said wave length is substantially reflected by said periodic lattice structure when incident from said laser on said periodic lattice at angles between ±

10 degrees.

10. The apparatus of claim 1 wherein said periodic lattice structure is a photonic crystal.

11. The apparatus of claim 1 wherein said spatial period is chosen such that the distance between said geometric shapes divided by the wavelength of the light in said laser is between 0.1 and 10.

12. An apparatus including a laser for generating light from the laser, said apparatus comprising:

a laser array producing a light beam at a predetermined wavelength;

a periodic lattice structure comprising a grid creating interstitial spaces between said grid, said lattice disposed to receive light from said laser, said spaces having regular geometric shapes, said grid having a first index of refraction;

an interstitial medium existing between said grid and having a second index of refraction which is different from said first index of refraction; and

said periodic lattice structure adapted to receive the laser beam the lattice structure having a spatial period between said geometric shapes which is chosen such that light from said laser of symmetric uniphase mode is selectively reflected with substantially enhanced reflectivity relative to other modes by said periodic lattice structure as a result of the photonic band structure of said periodic lattice.

13. The apparatus of claim 12 wherein said spatial period is such that light of said wave length is substantially reflected by said periodic lattice structure when incident from said laser on said periodic lattice at angles between ±

10 degrees.

14. The apparatus of claim 12 wherein said periodic lattice structure is a three-dimensional structure.

15. The apparatus of claim 12 wherein said regular geometric forms in said periodic lattice structure comprise Bravais lattices.

16. The apparatus of claim 12 wherein said regular geometric shapes are composed of gallium arsenide and the interstitial medium is composed of gallium aluminum arsenide.

17. The apparatus of claim 12 wherein said first index of refraction is greater than said second index of refraction.

18. The apparatus of claim 12 wherein the ratio of said first index of refraction to said second index of refraction is less than 2.0.

19. Diode laser array apparatus, including a laser array having a plurality of semiconductor diode lasers spaced at regular intervals, each diode laser having partially transmitting and reflecting facets at each end, and producing light beams at a predetermined wavelength, said apparatus further comprising:

a periodic lattice structure of regular geometric shapes, said structure having a first index of refraction;

an interstitial medium existing between said geometric shapes, said interstitial medium having a second index of refraction which is different from said first index of refraction; and

said periodic lattice structure having a spatial period between said geometric shapes which is chosen such that light of said wavelength from said laser array of symmetric uniphase mode is substantially reflected by said periodic lattice structure as a result of the photonic band structure of said periodic lattice.

20. A photonic band gap mirror for selectively reflecting electromagnetic radiation of a predetermined wave length comprising:

a source of electromagnetic radiation;

a periodic lattice structure of regular geometric shapes disposed to receive electromagnetic radiation from said source of electromagnetic radiation, said structure having a first index of refraction;

an interstitial medium existing between said geometric shapes, said interstitial medium having a second index of refraction which is different from said first index of refraction; and

said periodic lattice structure having a spatial period between said geometric shapes which is chosen such that said electromagnetic radiation from said source in a predetermined angle about the normal to the periodic lattice structure is reflected with a substantially enhanced reflectivity as a result of the photonic band structure of said periodic lattice structure.

21. The apparatus of claim 20 wherein the regular geometric forms in the periodic lattice structure comprise a two dimensional Bravais lattice.

22. The apparatus of claim 20 wherein said the regular geometric forms within said periodic lattice structure comprise a three dimensional Bravais lattice.

23. The apparatus of claim 20 wherein said first index of refraction is greater than said second index of refraction.

24. The apparatus of claim 23 wherein the ratio of said first index of refraction to said second index of refraction is less than 2.0.

25. The apparatus of claim 20 wherein said spatial period is such that electromagnetic radiation of said wave length is substantially reflected by said periodic lattice structure when incident from said laser on said periodic lattice at angles between ±

10 degrees.

26. The apparatus of claim 20 wherein said periodic lattice structure is a photonic crystal.

27. The apparatus of claim 20 wherein said spatial period is chosen such that the distance between said geometric shapes divided by the wavelength of the light in said laser is between 0.1 and 10.

28. A photonic band gap mirror for selectively reflecting electromagnetic radiation of a predetermined wave length comprising:

a periodic lattice structure of regular geometric shapes disposed to receive said electromagnetic radiation, said structure having a first index of refraction;

an interstitial medium existing between said geometric shapes, said interstitial medium having a second index of refraction which is different from said first index of refraction; and

said interstitial medium having linear interfaces which are aligned substantially parallel to the direction of said electromagnetic radiation, the periodic lattice structure also having a spatial period between said geometric shapes which is chosen such that said electromagnetic radiation in a predetermined angle about the normal to the periodic lattice structure is reflected with a substantially enhanced reflectivity as a result of the photonic band structure of said periodic lattice structure.

29. A photonic band gap mirror for selectively reflecting electromagnetic radiation of a predetermined wave length comprising:

a periodic lattice structure of regular geometric shapes disposed to receive electromagnetic radiation, said structure having a first index of refraction;

an interstitial medium existing between said geometric shapes, said interstitial medium having a second index of refraction which is different from said first index of refraction; and

said periodic lattice structure having a spatial period between said geometric shapes which determines the variation in reflectivity of said electromagnetic radiation as a function of the angle of incidence to the periodic lattice structure, the varying reflectivity being a result of the photonic band structure of said periodic lattice structure.