Methods and apparatus for storing and retrieving data using two-dimensional arrays. In the case of an ultra-dense wavelength division multiplexing device, a wavelength division multiplexing device is used for combining at least one plurality of monochromatic optical beams into a corresponding at least one single, multiplexed, polychromatic optical beam, wherein the wavelength division multiplexing device has an input element and an output element. The water-impermeable disk seals off the layer stack on the side facing the outside air. In either case, the polarity of the input or output clock signal is adjusted as the delay is adjusted so there are always an even number of inverters or inverting gates between an input terminal to which the input clock signal is applied and an output terminal from which the output clock signal is generated. The potential for cavitation at high fuel injection pressure is reduced by throttling the flow of fuel past the control valve seat when the control valve opens, thereby maintaining sufficient back pressure in the control valve chamber and upstream connecting passages.