Antenna feedback scheme for achieving narrow beam emission from plasmonic lasers
A distributed antenna-coupling feedback scheme and specially designed distributed feedback (DFB) metallic cavity and grating for laser application and in particular to plasmonic lasers ensuring a predesigned phase condition such that a mode traveling inside a waveguide is coupled/phase-locked to a mode traveling on the top metal improving the beam quality of the laser.
1. A plasmonic laser comprising:
an optical cavity enclosed in a surrounding medium;
a metallic cladding surrounding the optical cavity;
an optical gain medium enclosed in the cavity; and
a periodic structure implemented in at least one of the cladding and the optical cavity, wherein the periodic structure is determined from a phase match condition, such that upon pumping of the gain medium a coupling is established between a first guided electromagnetic wave in the optical cavity and a second guided electromagnetic wave in the surrounding medium.
2. The plasmonic laser according to claim 1 , wherein the first and second guided waves are surface-plasmon-polaritons (“SPPs”).
3. The plasmonic laser according to claim 1 , wherein the coupling between the first and second guided waves establishes a phase lock between the waves.
4. The plasmonic laser according to claim 3 , wherein the periodic structure comprises a grating in the cavity, which facilitates the coupling.
5. The plasmonic laser according to claim 4 , wherein the grating diffracts the first guided wave due to generate the second guided wave.
6. The plasmonic laser according to claim 5 , wherein the grating has a period determined by the phase match condition between the first guided wave and the second guided wave.
7. The plasmonic laser according to claim 1 , wherein the phase match condition is
k
i
=
p
2
π
Λ
+
k
d
wherein K 1 is a wave number of an incident wave, k d is a wave number of a diffracted wave, p is an integer specifying a diffraction order (p=+/−1, +/−2, +/−3 . . . ) and Λ is the period of the grating.
8. The plasmonic laser according to claim 1 , wherein the cavity is a Fabry-Pérot cavity.
9. The plasmonic laser according to claim 1 , wherein the second guided wave is generated by Bragg diffraction.
10. The plasmonic laser according to claim 1 , wherein the second guided wave further comprises a propagating quasi-cylindrical wave.
11. A method for generating a narrow beam in a plasmonic laser comprising:
introducing a periodic structure determined from a phase match condition in a boundary separating an optical cavity and a surrounding medium; and
pumping the optical cavity, wherein a phase coupling is established between a first guided electromagnetic wave generated in the optical cavity and a second guided electromagnetic wave generated in the surrounding medium.
12. The method according to claim 11 , wherein the first and second guided waves are surface-plasmon-polaritons (“SPPs”).
13. The method according to claim 11 , wherein the periodic structure comprises a grating further comprising a plurality of apertures.
14. The method according to claim 13 , wherein the grating diffracts a first guided wave due to the periodic perturbation to generate the second guided wave.
15. The method according to claim 11 , wherein the phase match condition is
k
i
=
p
2
π
Λ
+
k
d
k
i
=
p
2
π
Λ
+
k
d
wherein k i is a wave number of an incident wave, k d is a wave number of a diffracted wave, p is an integer specifying a diffraction order (p=+/−1, +/−2, +/−3 . . . ) and Λ is a period of the grating.