About WGM

About WGM

Whisperring Gallery Mode resonators is an important topic in physics.  Recent publications about this topic globally: http://www.nature.com/subjects/microresonators 

Whispering-gallery modes (WGM) are waves that can travel around a concave surface. The mode trajectory can be imagined like a poligon bound inside the microresoanator by the surface due to the total internal reflection. Any changes to radius ΔR or refraction index Δn, lead to significant shift of the wavelength Δλ.

 

 

Microsphere resoantors are the simplest 3D WGM resonators. These resonators are easy to fabricate. The principle is based on melting the tip of an optical waveguide fiber and allowing the surface tension of liquid glass to do all the work to reform the material into a sphere.

To use mocroresonators an effective way to couple the light inside is needed. One way to couple light is to use a prism with a high refractive index. Light beam enters the prism and due to total internal reflection is reflected from the surface. However, light electromagnetic field slightly extrudes outside of the prism and may overlap with the field outside of the the resonator to form WGM.

The picture on the left shows how the prism couples light inside a sphere with a diameter of 6 cm. Brilliant green bar in the middle is the WGM. Image on the right is merely repeating the experiment with a significantly smaller size a sphere having a diameter of only about millimeter.

2014 Kerry Vahala lecture (Youtube) about microresonators. K.Vahala is an important leader in the microresonator field. K.Vahara scientific group (web), Caltech, USA. 

2014 Tobias J. Kippenberg lecture (Youtube) about microresonators. T.Kippenberg is an important leader in the microresonator field.

2013 Takasumi Tunabe lecture (Youtube) about microresonators.