Contents I. Introduction
The luminescence of quantum emitters is an important branch of nano-optics and has wide applications in fields such as quantum information processing and single-molecule spectroscopy. The key issue in nano-optics is how to modify the emission properties of a single quantum emitter. Prior to Purcell's analysis in 1946, spontaneous emission was interpreted as an intrinsic radiative property of atoms or molecules [1] – [4]. Purcell's work suggested that the spontaneous transition rate of a nuclear magnetic moment coupled to a resonant electronic device can be greatly enhanced compared with the free-space value. Thus, assumptions can be made that the environment around an atom can modify the radiative properties of the atom. Since then, the modification of the spontaneous decay rate of an atom or molecule has been investigated in various environments, including photonic crystals and optical antennas [5] – [10]. The research on the modification of the spontaneous emission spectrum mainly focuses on placing the source in the photonic crystals or optical antennas to enhance or suppress the spontaneous emission spectra [11] – [17]. However, it is expected to achieve customized emission spectra, for there is a need to customize the shape of spontaneous spectra in different scenarios. For a laser, a spectrum with a large quality factor is suitable, while a flat spectrum is preferred for the light-emitting diode (LED).
