| Silicon-based avalanche photodiodes(Si-APD)are widely used as semiconductor devices with excellent performance and mature technology.However,due to the limitation of the forbidden band width,the working wavelength is limited to the visible light band,which limits its development in the field of infrared photon detection.Now,as novel non-linear optical effects are observed and applied,Si-APD has gradually expanded its operating wavelength range and detection efficiency through non-linear optical effects.Among them,the two-photon absorption(TPA)effect refers to the process in which a carrier in a medium absorbs two photons at the same time and then transitions to a higher energy level,which is different from the frequency conversion mechanism.It does not require a special nonlinear crystal and a complicated optical system,and does not require harsh phase matching conditions and working environments.Two-photon absorption can be applied in a wide operating wavelength range.Si-APD can provide a broad working wavelength range when infrared light detection is achieved through two-photon absorption.Therefore,the two-photon absorption system has great research prospects in the realization of weak infrared light detection by Si-APD.In the TPA detection process,due to the action of the strong light field,two photons are absorbed almost simultaneously,and the sum of the energy of the two photons must be equal to or greater than the forbidden band width of the medium,so that the carriers in the medium can pass through the "virtual state".To achieve the transition from the valence band to the conduction band smoothly.The study of the two-photon absorption effect in Si-APD also provides new ideas for broadband infrared photon detection in different applications such as optical sampling,optical comb laser ranging,and infrared biological imagesIn this dissertation,the two-photon absorption characteristics in Si-APD are studied to realize broadband infrared light incidence.The main work is as follows(1)The specific contribution of degenerate and non-degenerate two-photon absorption(D-TPA and ND-TPA to the infrared detection of Si-APD was determined experimentally.By adjusting the delay to change whether the two light beams are separated intime,and then adjusting the intensity of the two light beams so that the sum of the photon counts of the two light beams remains fixed,and then the average photon number of the two light beams is recorded.Finally,after analyzing the data,the quantum detection efficiency of D-TPAat 1800 nm and 1550 nm is about 3.3×10-16 counts·pulse/photon2,4.3×10-15 counts·pulse/photon2,respectively.The average quantum detection efficiency of ND-TPA at 1550 nm and 1800 nm is 7.91×10-16 counts·pulse/photon2.This research further deepens the understanding of the infrared response of silicon-based photon counting detector devices,and provides new solutions for the development of photonic devices such as infrared quantum detectors and infrared autocorrelation measuring devices(2)The effect of ND-TPA on the detection effect of Si-APD for infrared photon detection was further investigated.The signal light energy at 1700-1850 nm is lower than the energy band gap of silicon material,but the high intensity pump laser field at 1550 nm can supplement this energy difference.When the pump laser power is 12.42 ?W,the Si-APD exhibits a linear response to the incident signal photons,indicating that ND-TPA dominates the Si-APD infrared photon detection in this case In addition,when the number of incident signal photons is 0.14×106 photons/pulse,the enhancement factor of Si-APD for signal photon detection is 20.This experiment provides a method for sensitive detection of infrared photons.This also provides new ideas for broadband infrared photon detection in different applications such as optical sampling and all-optical switching. |
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