Whispering gallery mode resonator based on cylindrical cavity in optical fiber and fabrication method thereof

A fabrication method for a whispering gallery mode resonator based on a cylindrical cavity in an optical fiber, comprising:

• step A:
• performing a femtosecond laser micromachining process, comprising:
• placing an optical fiber body on a three-dimensional micro-displacement platform controlled by computer software, monitoring the micromachining process through a Charge Coupled Device (CCD) camera;
• after a focusing adjustment between the optical fiber body and a femtosecond laser device is completed, etching, by a femtosecond laser pulse, a ring structure with a required diameter on a surface of the optical fiber;
• after the etching the ring structure is completed, moving a femtosecond laser beam in steps at an interval of 2 μm upwards an inside of the optical fiber body to continuously etch a same ring structure, and sequentially moving the optical fiber body step by step for etching until a cylindrical structure with a required depth is etched;
• step B:
• performing a corrosion process by using hydrofluoric acid solution, comprising:
• connecting one end of the optical fiber body to a red laser pointer, and finding out a waveguide position in the optical fiber body through red light display, that is, the position of the cylindrical structure, and then immersing a portion of the optical fiber body where the cylindrical structure is located in the hydrofluoric acid solution for corrosion for a period of time;
• and
• step C:
• putting the cylindrical cavity subjected to the corrosion in the step B into an ultrasonic cleaning machine for cleaning for a certain period of time, thus smoothing an inner wall of the cylindrical cavity to facilitate forming of a whispering gallery mode;
• wherein the whispering gallery mode resonator comprises:
• the optical fiber body, wherein the cylindrical cavity is provided in the optical fiber body, a central axis of the cylindrical cavity is perpendicular to a central axis of the optical fiber body, a top end of the cylindrical cavity is open, a bottom end of the cylindrical cavity is located inside the optical fiber body, part or all of the cylindrical cavity blocks part of transmitted light beam of the optical fiber body, so that the part of transmitted light beam of the optical fiber body is coupled to the inner wall of the cylindrical cavity in a tangential direction, and then periodically propagates on the inner wall of the cylindrical cavity to form the whispering gallery mode.