A stimulated emission (SE) based optical coherence tomography (OCT) setup has been established for feasibility study. The setup conducts coherent gating for depth resolution using fluorescence based stimulated emission, an unprecedented scheme. The resulting depth resolution of this interferometric OCT setup is approximately 66 μm, determined by the coherence of the stimulation light source. Additionally, the SE signal can be used to obtain fluorescence lifetime.
Fluorescence lifetime imaging microscopy (FLIM) can reveal important biological information and recently stimulated emission (SE) has been applied in FLIM to improve the spatial resolution of micrographs and detect fluorophore over a long working distance. An issue with SE is that the SE signal is much weaker than the probe laser beam that is used to generate the SE, therefore the signal to background ratio is low. Here we demonstrate using interferometric setup to decrease this background laser intensity, thus achieving higher S/N ratio and dye concentration detection sensitivity in SE microscopy.
Focused Ion Beam (FIB) lithography not only can produce features on photoresist, it can also be used to manufacture
mold for Nanoimprint. FIB provides fast results with a well focused minimum 7 nm diameter Ga+ ion beam, and making
mold for Nanoimprint with FIB immunes oneself from photoresist issues involved in sub-45 nm large area patterning.
However, due to surface charge accumulation, large area patterning often results in displaced and overlapped patterns,
similar to e-beam lithography. This displacement occurs in area as small as 5 µm2, and is a function of beam dwell time
and ion current dose. A small dwell time can lessen this displacement to certain degree if the pattern is small, but fails
when the area to be pattern is large. In this paper we present a correct scheme in which the ion beam is check
periodically against a pre-drilled mark for beam displacement, and made adjustment in beam control correspondently. In
this manner, a large area (10 µm2) pattern of 50 nm squares is successfully demonstrated on a Si wafer.