Method for an on-chip decoupling capacitor. Since direct control by the digital signal of the base-band I channel and Q channel at the intermediate frequency can be performed and the analog-to-digital converter simultaneously performs the QPSK demodulation and the analog-to-digital conversion, the circuit design can be simplified and the characteristics reducing the noise can be obtained. The components of the SPM system include microstructured calibration structures. This type of laser gives a good SM-yield, an advantageous power asymmetry and a possibility to select good lasers using the threshold current as selection parameter. Further, a reactant delivery passage extends to an outlet at the recess for delivering reactant to the substance on the substrate to form the reaction product.