We report on far-infrared absorption in directly and modulation doped self-organized InAs quantum dots. Photoluminescence spectra demonstrate a blue shift in peak intensity for increasing doping in the quantum dots. Band to band transitions from InAs wetting layer, and InAs ground and excited states are observed from photovoltage spectroscopy. Far infrared absorption measurements using a Fourier transform infrared spectrometer show absorption in the range of 6-18 mu m for InAs quantum dots using a waveguide (45 degrees) geometry and under normal incidence.