[CST] Gain value is more then Directivity..WHy is that?

Hello Everyone
I am simulating an antenna at 193.5 THz frequency range (150-250 THz). The design is a simple Dielectric Resonator fed by a microstrip line. I am facing two problems:
1) I am getting the value of Gain to be more than Directivity, i.e. My directivity = 12.47 and Gain =13.18 as shown in Figures below. Which means that my radiation efficiency = 1.17% which is very low..Why is that? Normally the gain should be 1dB less than Directivity.
2) My antenna is producing end-fire radiation pattern although DR antennas of different shapes produce broadside radiation pattern..
I would really appreciate the Help guyz.
Regards

So when you say ~200THz, you are basically working in the Infra-red region ? Wavelength of around 1.5 nanometer ?

Yes U r right..So any idea whats the problem?