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Studies On Fabrication And Saturable Absorption Properties Of 2D/0D Materials

Posted on:2020-01-27Degree:MasterType:Thesis
Country:ChinaCandidate:Y QiuFull Text:PDF
GTID:2381330590495347Subject:Optical Engineering
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The rapid development of ultra-short pulse has a major impact on related scientific research,enabling human to observe faster phenomenon in nature.In optical fiber communications,sensing,laser micromachining,precision measurement,data storage,bioimaging,military defense and other fields,it has important applications.Mode-locked fiber laser is an effective way to generate ultra-short pulse,and saturable absorption technology is one of the key means to achieve mode-locked pulse output.In this thesis,based on PbS quantum dots and graphene,a saturable absorber with high damage threshold,ultra-fast relaxation time,large modulation depth and wide band is prepared to realize high performance ultra-short pulse fiber laser.The main research contents are as follows:?1?Preparation and characterization of PbS quantum dots saturable absorbers and application of ultra-fast laserA saturable absorber based on PbS quantum dots was developed to achieve a mode-locked pulse output in the 1550 nm band.The PbS quantum dots solution was prepared by hot injection method,and the PbS quantum dot saturable absorber was prepared by dropping directly onto the optical fiber-ends by drop coating.The morphology,size,linear and nonlinear optical properties of PbS quantum dots were characterized.It was found that PbS quantum dots were uniformly distributed on the optical fiber-ends with an average diameter of 5.7±0.5 nm.PbS quantum dots have strong absorption at 1550nm.The peak has a modulation depth of up to44.5%.A traditional soliton output with a center wavelength of 1563 nm,a pulse width of 559 fs and a signal-to-noise ratio which was greater than 65dB is realized in a fiber laser based on PbS quantum dots mode-locking.The thermal damage characteristics of PbS quantum dots were further studied.When the maximum pump power was 1.1W,the shape and center wavelength of the output spectrum remain unchanged.Therefore,the damage threshold is greater than 30 mJ/cm2.?2?Preparation,characterization of graphene saturable absorber and application of ultra-fast laserGraphene was directly grown on the single-mode optical fiber-ends by plasma enhanced chemical vapor deposition?PECVD?.Graphene prepared by PECVD could be made into a full-fiber saturable absorber without complicated transfer operation.By controlling the growth time,the number of layers of graphene could be effectively regulated.The morphology,linear and nonlinear optical properties of graphene were measured.The results showed that when the number of graphene layers was 22,the modulation depth was28.3%and the damage threshold was bigger than 42mJ/cm2.Based on the graphene saturable absorber,in a Er3+doped fiber laser,mode-locked pulse with a center wavelength of 1561 nm,a pulse width of 561 fs,a spectral width of 4.86 nm,a repetition rate of 13.5 MHz and a signal-to-noise ratio greater than 60 dB was obtained and output.
Keywords/Search Tags:PbS quantum dots, graphene, saturable absorber, ultra-short pulse, fiber laser
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