Quantum interference effects Quantum interference effects can result in spontaneous emission reduction and cancellation. Electromagnetically induced transparency, and many other interesting phenomenon, such as low light velocity (17m/s). In usual nonlinear optics, strong coherent light is required for the pumping. By using the quantum interference, we could greatly decrease the intensity requirement. All these are current research frontiers.
Noise reduction Noise is always bad, but inevitable. The reduction of noise in radiation field has been a continuously pursuing topic since the invention of lasers. Different methods will be considered to reach the goal of noise reduction, such as correlated spontaneous emission, quantum interference.
Interaction between materials and radiation The interaction between materials (such as atoms, molecule and crystals) and the radiation field is a fundamental problem in physics, which can be used to check the theory of quantum mechanics. In dealing with this problem, the field can be treated classically or quantum mechanically. This study can also result in opto-electronics devices.
Meta-materials The optical properties of solid state materials are of great interest. Recently, a new type of materials called photonic crystals attracts a lot of attention of physicists in quantum optics and condensed matter physics. A photonic crystal is a three-dimensional periodic structure of different refractive index, which can be used to block the propagation of light with certain frequency, to slow down the group velocity of light. The propagation of light in photonic crystals is the main research frontier, which could leave to the design of new opto-switch, light-delay lines and etc.
