Mode-locked resonator and ultrashort pulse laser comprising the same

1 . A mode-locked resonator 10 , comprising:

a resonator 11 including a shape of a sphere; and

a saturable absorber 12 coated on a surface of the resonator 11 ,

wherein the resonator 11 is coupled with some photons traveling in a tapered optical fiber 21 disposed near the resonator 11 and interacts with the saturable absorber 12 based on a Whispering Gallery Mode (WGM),

wherein the mode-locked resonator 10 determines a pulse repetition rate of an ultrashort pulse laser beam output from the mode-locked resonator 10 based on a diameter of the sphere, wherein the shape of the sphere includes a shape of a microsphere produced by an electric arc, wherein a diameter of the microsphere is determined based on a diameter of a raw optical fiber to which the electric arc is applied, and

wherein the tapered optical fiber 21 injects pump light to compensate for a change in an effective refractive index of the mode-locked resonator caused by a photothermal effect of the saturable absorber 12 .

2 . The mode-locked resonator 10 according to claim 1 , wherein the resonator 11 is disposed near the tapered optical fiber 21 without contact with the tapered optical fiber 21 .

3 . The mode-locked resonator 10 according to claim 1 , wherein the saturable absorber 12 is formed by synthesizing and coating non-linear nanomaterials including graphene.

4 . The mode-locked resonator 10 according to claim 3 , wherein the saturable absorber 12 is formed by growing and coating the non-linear nanomaterials on the surface of the resonator 11 based on Atomic Carbon Spray (ACS).

5 . The mode-locked resonator 10 according to claim 1 , wherein the mode-locked resonator 10 filters some of wavelengths in a spectrum of light traveling in the tapered optical fiber 21 based on the whispering gallery mode.

6 . The mode-locked resonator 10 according to claim 1 , wherein the mode-locked resonator 10 outputs an ultrashort pulse laser beam by outputting light of a first intensity by constructive interference of phase matched modes in some photons coupled with the resonator 11 and outputting light of a second intensity by destructive interference of phase mismatched modes.

7 . An ultrashort pulse laser 100 , comprising:

the mode-locked resonator 10 according to claim 1 ;

a light source 30 to supply light;

an optical multiplexer 40 (a wavelength division multiplexer) to perform wavelength division multiplexing of the light;

an amplifier 50 to amplify the light;

a polarization controller 70 to control a polarization state of the light;

an optical isolator 60 to adjust a direction of the light; and

an optical fiber 20 connecting the tapered optical fiber 21 , the light source 30 , the optical multiplexer 40 , the amplifier 50 , the polarization controller 70 and the optical isolator 60 .

8 . The ultrashort pulse laser 100 according to claim 7 , wherein the resonator 11 is disposed near the tapered optical fiber 21 without contact with the tapered optical fiber 21 .

9 . The ultrashort pulse laser 100 according to claim 7 , wherein the saturable absorber 12 is formed by synthesizing and coating non-linear nanomaterials including graphene.

10 . The ultrashort pulse laser 100 according to claim 9 , wherein the saturable absorber 12 is formed by growing and coating the non-linear nanomaterials on the surface of the resonator 11 based on Atomic Carbon Spray (ACS).

11 . The ultrashort pulse laser 100 according to claim 7 , wherein the mode-locked resonator 10 filters some of wavelengths in a spectrum of light traveling in the tapered optical fiber 21 based on the whispering gallery mode.

12 . The ultrashort pulse laser 100 according to claim 7 , wherein the mode-locked resonator 10 outputs the ultrashort pulse laser beam by outputting light of a first intensity by constructive interference of phase matched modes in some photons coupled with the resonator 11 and outputting light of a second intensity by destructive interference of phase mismatched modes.