Single-stripe GaAsAlGaAs semiconductor optical amplifiers which simultaneously generates from four to more than twenty tunable WDM channels. The apparatus includes a memory configured to store an original pump parameter and a current pump parameter. The magnetic recording layer is in advance magnetized for concentrically or spirally around the center of the disk in such a manner that magnetized regions are disposed such that adjacent regions are magnetized in different directions and alternately arranged in the radial direction of the disk. An electrical received signal is received from the acoustic device. Each stacking shell is configured to be received in the object opening of one of the preformed flower pot covers. In various embodiments, the inductor is electrically connected to a resistor and a capacitor to provide a tunable RLC circuit.