The Application Of Optical Frequency Comb In Photon Analog Signal Processing

Optical frequency comb (OFC) is a spectrum that consists of a set of evenly spaced frequency components with a coherent and stable phase relationship. In frequency domain, it consists of multi coherent frequency components and covers a wide bandwidth, which can be used as the light source of dense wavelength division multiplexing (DWDM) system. In time domain, OFC refers to an ultra-short pulse train, which can act as the input signal of optical time division multiplexing (OTDM) system. With the maturing of laser technology and the development of optical communication technology, OFC has attracted significant attentions due to its extensive applications in many arears. Moreover, OFC has become another considerable breakthrough in the field of laser technology, after the advent of ultrashort pulse laser.By direct operation of amplitude and phase in spectrum, certain basic functionalities of photonic analog signal can be realized, showing advantages of huge bandwidth, overcoming bandwidth bottlenecks incurred in conventional electronics, and improving of real-time performance. Thus, photonic analog signal processing plays a significant role in all-optical network. Meanwhile, silicon-based photonic integrated circuit is one of the most promising candidates for photonic analogy signal processing due to its intrinsic advantages of compact footprint, low consumption, well integration capability, and compatibility with complementary metal-oxide semiconductor (CMOS) technology. Additionally, photonic integrated circuits for photonic analog signal processing open up the possibility for the realization of ultra-high speed and ultra-wideband signal processing.The subject of this dissertation is to generate OFC with high-performance, and to explore the applications in photonic analog signal processing by combining with silicon-based photonic devices. The contents of this dissertation are listed as follows:(1) The characteristics and properties of OFC were introduced in detail. Firstly, we discussed the investigation background and significance of OFC generation, and summarized its investigation status. Then, we gave a briefly analysis of some presentative schemes of OFC generation. Additionally, we briefly introduced the significance of investigation on photonic analog signal processing and the methods to realize photonic analog signal processing. Moreover, we summarized the progress in photonic analog signal processing at home and abroad.(2) OFC generation using highly nonlinear fiber (HNLF) was studied experimentally. we proposed schemes for OFC generation based on cascaded four-wave mixing effect in HNLF, OFC generation based on self-phase modulation effect in HNLF, and OFC generation based on both cascaded four wave mixing effect and self-phase modulation effect in HNLF. We comparatively analyzed the impact of cascaded four-wave mixing and self-phase modulation on the performance of the OFC generation. Experimental results showed that both cascaded four wave mixing effect and self-phase modulation effect in HNLF could be used to generate wideband OFC, and with central wavelength and frequency spacing tunable. Under the same pump power, the scheme based on cascaded four-wave mixing effect generated more spectral lines, while the scheme based on self-phase modulation effect generated OFC with better flatness. Meanwhile, in time domain, these schemes refered to ultra short pulse generation with pulse width tunable.(3) An OFC generation scheme based on cascaded time lenses was proposed and experimentally demonstrated. First, based on space-time duality and time-frequency duality, the concept of time lens and spectral Talbot effect were introduced in detail. Then, we used two time lenses to realize frequency-time mapping and spectral Talbot effect. In frequency-time mapping part, multi frequency components were generated. Furtherly, we divided the frequency spacing and redistributed the energy of the original frequency components to generate more spectral lines through spectral Talbot effect. The experimental results showed that multi frequency components could be generated from a single tone using cascaded time lenses, and the number of comb lines and frequency spacing were tunable.(5) The application in photonic analog signal processing of OFC was studied using silicon-based photonic devices. And a series of photonic analog signal processing have been demonstrated, such as, optical differentiation, optical Hilbert transformation, fractional order differentiator, and simple optical arbitrary waveform generation. Among them, based on a single microdisk resonator, both the first-order optical differentiation and the first-order optical Hilbert transformation were realized. And for the first time, we experimentally analyzed the relationship between them. The experimental result showed that, for large pulse width input, the microdisk resonator could be used as optical differentiator, while for small pulse width input, the microdisk resonator could be used as optical Hilbert transformer.(6) A new scheme for temporal cloaking based on OFC and electrically tuned microring resonator was proposed for the first time. We used an OFC together with an electrically tuned microring resonator to implement time lens processing. And then, we analyzed the feasibility for temporal cloaking in simulation. Furtherly, we experimentally realized the cloak of clock signal and data signal.