It also uses n- type dopants for the filament. The shutter, suspended from the substrate by folded beams and driven with electrostatic combs, is similar to the resonators first created by Dr. William Tang. Calculations were performed prior to fabrication to assess the shuttered microlamp performance. The lower yield for the shutter is attributed to the fact that most of the failed shutters have lum features that were not strong enough to withstand prolonged rinsing. Visible output radiation, becoming more intense with increasing filament voltage, was clearly observable during microlamp testing, even under normal indoor illumination.
Filament lifetime is also strongly dependent on voltage.
The measured shutter resonant frequencies matched closely those obtained through simulations. The matches in resonant frequencies, combined with the mismatches in bandwidths and displacements, suggest that the damping effect modeled in simulation may have been overestimated. The polysilicon shutters were found to absorb most of the visible output radiation. However, an infrared-absorbing metal layer would be needed in order to modulate the lamp's infrared output.