Study On Balancing Gain Spectrum And Refractive Index Change Spectrum Of Quantum Well

Active optical switches,wavelength converters and active microring resonators are the key devices to develop optical packet switching network characterized by high speed and flexibility.Refractive index change induced by carrier concentration change in active region is the operating mechanism of these devices,while optical gain is needed when these devices operate.When designing these devices,we should consider both gain and refractive index change in order to let these devices satisfy the performance request.For the first time,this paper studied on balancing gain spectrum and refractive index change spectrum,which has the function of theoretical guidance in developing key devices of all-optical network and is helpful for the theoretical analysis of physical properties of active material.In this paper,the band structure of semiconductor is analyzed and the calculation models of gain and refractive index change of quantum well are presented.Firstly,the effective mass theory is introduced and the effect of strain on band structure is analyzed.Then the critical thickness?band structure parameters and band offsets of strained quantum well are calculated.And the band structure is calculated,based on which the calculation model of optical gain is given.Changes in optical gain brings along with refractive index change which can be calculated by using Kramers-Kronig transformation.Furthermore,taking free carrier absorption effect into account,we can finally get the calculation model of refract index change of quantum well material.Based on the energy band structure and the calculation models of gain and refractive index change,the influences of width?strain and carrier concentration on gain and refract index change are analyzed by contrast,and the causes are dissected.Proposing taking the overlap region area of the two spectra in their 3dB spectrum width as a metric,the influences of the above factors on balancing amplitude and spectrum width of gain spectrum and refractive index change spectrum are further investigated.Research shows:The overlap region area of 3dB spectrum width of the two spectra has a maximum during its variation with well width;the compressive strain is propitious for the increase of overlap region area;an turning point exists during the monotone increasing of overlap region area with carrier concentration,before which the overlap region area increases rapidly,and after which the overlap region area slows down its increasing.Based on the laws given above,by picking suitable well width and compressive strain value,the In0.583Ga0.417As/In0.817Ga0.183As0.4P0.6 quantum well designed can appropriately balance gain spectrum and refractive index change spectrum within C wave-band when the injected carrier concentration is 3.0 × 1024m-3,the overlap region area of the two spectra in their 3dB spectrum width is 3.7×104 nm/cm.