A gobo holder for a gobo wheel has a base element, a gobo fastening element rotatably mounted to the base element, and a resilient latching member on the base element. An example method may include generating signal timing information, and determining times for a plurality of window periods for the signal of interest based on the signal timing information. The metal material is brought into contact with a solution of the diazonium salt in a solvent and negatively polarized relative to an anode that is also in contact with the solution. The wideband gain is subsequently reduced if the reduction limit of the narrowband gain has been achieved and the clipping persists. With electron affinity engineering, a minority carrier hole barrier may be inserted adjacent to the quantum wells to improve hole confinement at high current density and high temperature.