Study On The Generation Of Optical Frequency Comb Based On Nonlinear Effect

The optical frequency comb is a kind of comb-like spectrum consisting of tens or even millions of combs with the characteristics of very small interval, stability amplitude, constant frequency and spacing.Because of its good stability, the optical frequency comb has been extensively used in different fields. The optical band comb within the communication wave-band is used in the field of communication to realize stable modulation and efficient transmission. The optical frequency comb of ultraviolet wave-band can be applied to the fields of physics, chemistry, and astronomy for high precision observation and measurement. In biology and medical fields, it can achieve infrared imaging and molecular detection. Optical frequency comb has also been widely used in other areas where high-precision measurement is needed.This paper focus on the method of generating optical frequency combs in the communication and mid-infrared wave-bands. By using the optical fiber, micro-ring and other structures, combined with the modulator system and AWG system, different frequency comb generation schemes are proposed. The main research contents and the achievements of the innovative research are summarized as follows1. The method of optical frequency comb generation based on nonlinear effects such as FWM, XPM. The micro-ring structure with high Q factor is adopted, and the Lugiato-Lefever equation (LLE) derived from the modified nonlinear Schrodinger equation is used. The system produced infrared wave-band optical frequency comb. The micro-ring structure used greatly improves the stability of the optical frequency comb, and the number of combs produced by the micro-ring is one order of. magnitude more than that generated by the modulator system, and the micro-ring structure can be integrated on-chip implementation.2. The technology of optical frequency comb generation based on nonlinear effects in highly nonlinear fiber is studied. The enhanced nonlinearity of highly nonlinear fiber is beneficial to produce the supercontinuum (SC), which can be used to generate the frequency comb structure. The injection light source uses short pulses of more than lps level and weak CW light, which increases the contribution of nonlinear effects such as modulation instability (MI) and crossphase modulation(XPM). Three methods are supported for the generation of optical frequency comb as following. Firstly, for the generated octave-spanning SC, the frequency comb structure with stable output and spacing is obtained by injecting the repetitive pulse sequence at the input end by using the Fourier transform characteristic. Secondly, the output SC from the highly nonlinear fiber is used as the input of the AWG system, and the arrayed waveguide gratings with up to 50 layers of 750 filter channels are connected to each other by means of parallel and cascade connection.Then the fixed pitch is less than 0.26 nm. within the range of 1800?3000 nm frequency comb structure. Thirdly, we propose a new way which combines of modulation system and highly nonlinear fiber to generate the optical frequency comb, and try to use the advantages of subsystems to obtain a stable optical frequency comb structure.3. The influence of the high-order nonlinear effects on the spectrum is studied. The nonlinear characteristics of the structure of the cone are studied by pulling the arsenic trioxide from the structure and material.The effect of the cone structure on the optical frequency comb is studied.It is proved that the cone-pull waveguide structure can effectively improve the efficiency of the optical frequency comb.Based on the nonlinear characteristics of SPM, FWM, XPM, SRS,MI, combined with the dispersion characteristics, through the use of micro-ring nonlinear characteristics of the complex process, finally the stable optical comb output is realized. By combining a laser pulse of a ps level and a weak CW light into the highly nonlinear fiber tapered, a better SC and a wide range of optical frequency combs are obtained. The study enriches the diversity of the method of optical frequency comb generation and provides a good theoretical support for further in-depth research.