US Patent 7367653 Laser ink jet printer

An ink ejecting apparatus that rapidly heats a small volume of ink using radiative heating from pulsating laser light radiation (as opposed to surface conductive heating from a thin film electrical resistive heater). The laser light travels through a bubble that has been formed by a previous pulse and is absorbed by the ink (specifically designed to absorb the laser light) in the first few microns of the ink free surface. By radiatively heating the ink at a heating rate above its critical heating limit (for an example, for water at atmospheric pressure, that limit is about 0.25 MW/g), at least substantially, if not all, of the heated portion of the ink is brought to its superheat limit so as to boil instantaneously (i.e., explosively). This heating technique keeps the bubble from completely collapsing between excitations. The result is a bubble oscillating at high frequencies. This new type of bubble formation enables ink jet printers to run at resonance and at very high speeds. In addition, non-water based inks can be reliably used because the ink is no longer heated by conduction.