Mid-infrared Several Nonlinear Effect In The Silicon Ring Resonator And Its Application Research

Mid-infrared wavelengths, usually between2and20microns, are very importantbecause the vibration and rotation of many important molecules in biology or organicchemistry have their spectral fingerprints in this wavelength range. Besides, thiswavelength range contains two transparent windows in atmosphere:3-5μm and8-13μm. Due to the advantages mentioned above, mid-infrared is a critical wavebandin many research areas, such as ultrafine spectrum analysis, remote sensing, andpollution detecting.On the other hand, silicon is a promising material thanks to its uniquecharacteristics: relatively high refractive index, large nonlinear coefficient, CMOScompatible, and the mature fabrication technology. Tremendous researches have beenfocused on silicon photonics for tens of years, especially on integrated photonics incommunication waveband around1.55μm. Unfortunately, the application of silicon innear infrared is strongly quenched by two photon absorption effect. However, thisdisadvantage can be overcome in mid-infrared because the photon energy is lowerthan half of the silicon bandgap. As a result, silicon will be the first choice forinformation processing in mid-infrared.According to the discussion above, this thesis tightly surrounds mid-infrared andsilicon photonics. We propose and simulate several important photonics devices insilicon based ring resonator, including cascade Raman laser, all optical diode andfrequency comb generator following the general introduction of ring resonator inChapter2.In mid-infrared, the first question is to build up a reliable laser source. In thisthesis, we have numerically investigated the generation of a fourth order stimulatedRaman scattering (SRS) signal in a silicon ring cavity. Output power saturation of thesilicon Raman laser has been observed. The influences of effective free carrier lifetime, length of ring cavity and coupling ratio on the signal generation are discussedbased on our simulation. Finally, we put forward a double-ring cavity scheme toimprove the output characteristics of the Raman laser. Nonreciprocal transmission device is one of the fundamental elements inmid-infrared signal processing. An all optical diode based on self-phase modulation(SPM) effect is numerically demonstrated in Chapter4. The diode consists of a linearwaveguide and a pair of silicon ring resonators. The waveguide and the rings are allbased on suspended waveguide with an optimized effective cross section area. Thenonreciprocal transmission ratio can be more than20dB in the power range between0.5mW and20mW, while the transmission loss in forward direction is less than10dB. Moreover, the impacts of linear absorption coefficient of ring resonators and thebi-stability effect on the performance of the diode are discussed.Frequency comb is studied in Chapter5. Optical frequency comb, a light sourcewhose spectrum consists of a series of discrete, equidistant elements, is an importanttool for optical metrology and spectroscopy. John L. Hall and Theodor W. H nschwon Nobel Prize in2005for their great job in developing frequency comb. Here wesimulate an on-chip mid-IR frequency comb generator based on the four-wave mixingeffect in a silicon micro-ring resonator. The resonator is based on a suspended ridgewaveguide which is designed to have low group-velocity dispersion. The threshold,waveband, energy transmission efficiency, and the impact of coupling coefficients arenumerically analyzed in our research. Finally we propose a comb generator based oncoupled ring resonators. This scheme can overcome the drawback that pump powercannot be coupled into the cavity efficiently in a single ring resonator, which is themain issue in our previous model. A lower threshold, wider waveband and higherenergy efficiency are expected in our improved structure.