Berry’s Phase in Single Mode Optical Fiber PHY 243W Advanced Lab Chris McFarland Ryan Pettibone Emily Veit

Theory Berry’s Phase is a geometric phenomenon the can manifest itself in optics, quantum mechanics and even classical mechanics. It occurs when more than one physical parameter of the particle’s path are changed adiabatically. Although the parameters are returned to their original values the measured quantity (spin or polarization) does not. EXAMPLE: Two parameters characterizing an EM wave could be the polar and azimuthal angle of the wave’s propagation vector!

Manifestation of Theory As we all know {k,E,B} constitutes an orthogonal basis. The optical fiber parallel transports the basis. Linearly polarized light enters the optical fiber in one direction, exits in same direction, but plane of polarization is different! Ein Eout 

Experimental Setup He-Ne Laser Reflectors Polarizer Single-Mode Fiber Optic Cable Oscilloscope Tube Photo-Detector Polarizer

Experimental Setup The helix is uniform and has pitch angle  and N turns: The plane of polarization rotation angle is given theoretically by:  =360°N(1-cos  ) Ein Eout  Side View  N

Experimental Issues We felt that there were two main sources of error: The “Dandruff Effect:” Noise is created by air currents and tiny dust particles blocking the laser. –SOLUTION: Create a tunnel around the laser Slack in the Cable: Berry’s phase can occur in the optical fiber. –SOLUTION: Lay the fiber flat

Experimental Issues  not large enough to measure accurately –SOLUTION: Increase N to amplify  since  is proportional to N.

Results

Conclusion Qualitatively observing the effect of Berry’s phase by manipulation of the optical fiber was relatively easy. However, the next group working on this should be careful to eliminate aforementioned errors if they wish to obtain results approximating theoretical results. Our data matches the theoretical results closely, providing strong evidence for the Berry’s phase hypothesis.

ANY QUESTIONS??