Continuous wave microscopy based on solid immersion lens

We describe a basic approach of transmission terahertz microscopy based on solid immersion lenses. We use a Backward Wave Oscillator (BWO) as a radiation source, a hyper-hemispherical silicon lens as solid immersion lens and as adetector a low power pyroelectric. The experimental results show that with this approach we can improve the terahertz spot diameter size of the system compared with a simply aspherical lens. The spot diameter at the focus of the immersion lens is about 0.34 λ at 600 GHz. This approach is extended to an interferometric system to achieve a better sensitivity of the microscope.