  We present a new model of high-energy lightcurves from rotation powered
pulsars. The key ingredient of the model is the gap region (i.e. the region
where particle acceleration is taking place and high-energy photons originate)
which satisfies the following assumptions: i) the gap region extends from each
polar cap to the light cylinder; ii) the gap is thin and confined to the
surface of last open magnetic-field lines; iii) photon emissivity is uniform
within the gap region. The model lightcurves are dominated by strong peaks
(either double or single) of caustic origin. Unlike in other pulsar models with
caustic effects, the double peaks arise due to crossing two caustics, each of
which is associated with a different magnetic pole. The generic features of the
lightcurves are consistent with the observed characteristics of pulsar
lightcurves: 1) the most natural (in terms of probability) shape consists of
two peaks (separated by 0.4 to 0.5 in phase for large viewing angles); 2) the
peaks posess well developed wings; 3) there is a bridge (inter-peak) emission
component; 4) there is a non-vanishing off-pulse emission level; 5) the radio
pulse occurs before the leading high-energy peak. The model is well suited for
four gamma-ray pulsars - Crab, Vela, Geminga and B1951+32 - with double-peak
lightcurves exhibiting the peak separation of 0.4 to 0.5 in phase. Hereby, we
apply the model to the Vela pulsar. Moreover, we indicate the limitation of the
model in accurate reproducing of the lightcurves with single pulses and
narrowly separated (about 0.2 in phase) pulse peaks. We also discuss the
optical polarization properties for the Crab pulsar in the context of the
two-pole caustic model.
