The Experiment

 

In order to show that we had produced a material that had a negative index of refraction, we cut our sample into a prism shape and measured the refraction. We found that for certain frequencies, the incident microwave beam was refracted into a negative angle as defined by Snell's Law and shown below. To measure the refraction, we directed microwave rays from the material side of the refraction interface at a fixed angle, θ_m, and measured the transmitted power as a function of angle, θ_a. Since the index of refraction of air is known to be 1 and only one angle is negative, the index of refraction of our material must be negative in order to satisfy Snell's Law. When the left-handed material sample is replaced with a similar shaped prism of normal right-handed material (we used teflon in our experiment), the transmitted rays are refracted to the opposite side of the interface normal from what was observed with the left-handed sample.

 

 

Snell's law is: n_asin(θ_a)=n_msin(θ_m)

 

This image below is photograph of the experimental setup, there is an additional round aluminum plate that is placed on top the apparatus shown that confines the microwaves to two dimensions. The the prism shaped sample is between the plates and the distance between the plates is about 1/2 inch. We introduce the microwaves from the waveguide shown in the bottom of the photo. The microwaves then propagate through the prism and are refracted at the second material interface (or the refraction interface). A left-handed material will refract the microwaves into the left quadrant as illustrated by the red line, and a right-handed material will refract into the right quadrant as is shown by the blue line. The brown material around the sample is microwave absorber that is in place to prevent stray reflections from interfering with the measurement.