Optical Frequency Comb (OFC) refers to a spectrum composed of a series of uniformly spaced frequency components with coherent and stable phase relationships on the spectrum. It is usually generated by a mode-locked laser, where each comb represents a single frequency vibration of the laser longitudinal mode. These comb teeth overlap and synchronize in phase with each other in space, resulting in the so-called "beat frequency" phenomenon.
In principle, an optical frequency comb appears as an optical frequency sequence with equal frequency intervals in the frequency domain, and as an electromagnetic field oscillation envelope with femtosecond level time width in the time domain. This distribution characteristic in both time and frequency domains resembles the comb commonly used in daily life, hence it is called the frequency comb of the optical band, abbreviated as "optical comb".
2、 Technical features and advantages
High precision: Optical frequency combs have extremely high measurement accuracy and can achieve precise measurement of optical frequencies.
Wide spectral range: The spectral range of the comb is extremely wide, covering multiple bands from visible light to near-infrared.
Coherent stability: The various comb teeth of the optical comb have a coherent and stable phase relationship, which enables it to maintain high stability and accuracy in various applications.
3、 Application Fields
Optical atomic clock: Optical atomic clock measures time based on the natural vibration of atoms, and its principle is similar to the swing of a traditional pendulum. The optical frequency comb provides a high-precision frequency standard for optical atomic clocks, making their accuracy far superior to traditional microwave atomic clocks. This high-precision clock plays an important role in fields such as space navigation, satellite communication, and ultra high precision verification of basic physics problems.
Chemical detector: By utilizing the ultra sensitive properties of optical frequency combs, high-sensitivity chemical detectors can be developed. This detector can quickly identify harmful substances such as explosives and dangerous pathogens, and has broad application prospects in security checks, environmental protection, and other fields.
Lidar: Lidar uses lasers to determine the position, velocity, and properties of distant targets. Optical frequency comb can generate laser with specific waveforms, which is expected to increase the sensitivity and detection range of laser radar by several orders of magnitude.
Optical communication: In the field of optical communication, optical frequency combs can be used to increase the capacity and transmission rate of fiber optic communication. By precisely controlling the various comb teeth of the optical comb, precise modulation and demodulation of optical signals can be achieved, thereby improving the performance and stability of communication systems.
4、 Technological Development and Prospects
With the continuous development of laser physics and optoelectronic technology, the technology of optical frequency comb is also constantly advancing. At present, various types of optical frequency combs have emerged, such as those produced by fiber lasers and solid-state lasers. These new optical combs have superior performance and a wider range of applications.
In the future, with further technological breakthroughs and cost reductions, optical frequency combs are expected to be applied and promoted in more fields. For example, in cutting-edge technological fields such as quantum computing and quantum communication, optical frequency combs are expected to play an important role. Meanwhile, with the continuous development of miniaturization and integration technology, optical frequency combs are also expected to achieve more convenient and efficient application methods.
In summary, laser frequency comb, as a new type of optical measurement technology, has significant advantages such as high accuracy, wide spectral range, and coherent stability. It has broad application prospects in fields such as optical atomic clocks, chemical detectors, laser radar, and optical communication. With the continuous advancement of technology and the reduction of costs, optical frequency combs are expected to be promoted and applied in more fields.