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Through light and shadow: How does an optical ring resonator concentrate light like magic?
In today's era of rapid advances in optical technology, optical ring resonators have become a very attractive topic in optoelectronics. Imagine a device that magically concentrates light and acts as an efficient filter in optical communications. The optical ring resonant cavity is such an innovative technology, and its working principle is derived from total internal reflection and interference effects.
The magic of focusing light: the basic principle of ring resonant cavity
The optical ring resonant cavity consists of a set of waveguides, at least one of which forms a closed loop and is connected to the input and output of light. The device exploits several important optical principles such as total internal reflection, interference and optical coupling.
Total internal reflection is an optical phenomenon. When light reaches a critical angle at an interface, the light will not be able to penetrate the interface, but will be completely reflected back.
The secret of total internal reflection
Light remains unchanged within the waveguide in the ring resonator due to total internal reflection. The key to this phenomenon is that the incident angle of the light must be greater than a certain critical angle, and the light passes from a medium with a higher refractive index into a medium with a lower refractive index. For the operation of a ring resonator, it is crucial to maintain good total internal reflection conditions to ensure that light is not lost.
The role of interference phenomena
Tectonic interference occurs when light completes multiple cycles and interferes within a ring resonant cavity. As long as there are no losses in the optical system, the light intensity output from the ring resonator will be equal to the input light intensity. However, only certain wavelengths will reach resonance, and the surrounding environment will filter out unwanted light based on the wavelength of the light waves.
The key to optical coupling
For a ring resonator to work effectively, the coupling between the waveguide and the ring waveguide must be understood. If the distance between the waveguide and the ring resonant cavity is moderate, some light will be coupled into the ring resonant cavity. This phenomenon is related to the excitation field of the waveguide, whose energy will attenuate as the distance increases, which makes the appropriate distance, coupling length and refractive index important coupling conditions.
Under optimal coupling conditions, all light will be coupled into the ring resonant cavity and avoid direct transmission out of the input waveguide.
Application of ring resonant cavity
The properties of optical ring resonators allow them to act as critical filters in many fields. By connecting multiple ring resonators in series, high-order optical filter design can be achieved. Additionally, these systems can also serve as mechanical sensors. When the optical fiber is affected by stress, it will change the size of the optical fiber, thereby changing the resonant wavelength of the light, providing an effective measurement tool.
The future of nested resonators
Researchers have also begun to explore the application of nested ring resonators. This design can significantly improve the quality factor and extend the interaction length between light and matter. This not only improves the multiple circulation effect of light, but also shows potential applications in exploring quantum information and biosensing.
The nonlinear optical properties of the ring resonant cavity enable it to generate pairs of parasitic photons, which can be used in the exploration of quantum information.
Conclusion
As a device with highly controlled optical wave characteristics, the optical ring resonant cavity not only provides efficient filtering performance in optical communications, but also has innovative application potential in fields such as mechanical sensing and biological detection. As technology develops, can we expect further breakthroughs that will usher in a new era of optics?
