| Because of its unique spectral characteristics,1.7?m-band pulsed laser has been widely used in the fields of biological imaging,organic matter detection,and Polymer Welding,and has become one of the research hotspots of New Light sources at home and abroad in recent years.The 1.7?m band laser is between 1.5?m and 2?m in the commonly used band,and is at the edge of the gain spectrum of erbium-doped fiber,Therefore,it lacks in-depth research.In this paper,a 1.7?m band pulsed fiber lasers are designed and constructed based on the theory of 1.7?m laser generation,and the experimental research is carried out.In the experiments,gain switching,synchronous pumping,and soliton self-frequency shift were used to obtain microsecond,nanosecond,and femtosecond pulse outputs.Based on the generated pulsed laser source in the 1.7?m band,the alcohol concentration measurement and water fog transmission experiments were performed.The main research work is summarized as follows:In terms of theory,the related theory of generating a 1.7?m band gain spectrum based on Tm-doped fiber and nonlinear effects is first introduced;then three mechanisms of pulse generation in the 1.7?m band are explained.A theoretical model of 1.7?m band femtosecond soliton self-frequency shift is established,and the relationship between the peak power of pump light,pulse width,the fiber length and the frequency shift of solitons are further discussed,which provides a theoretical reference for experimental research.In the aspect of experiment,according to the theory of nonlinear effects,a 1.7?m band femtosecond fiber laser based on soliton self-frequency shifting technology was constructed and experimentally studied.In the structure,the femtosecond pulse in 1561.8nm band is amplified by chirped pulses and injected into a highly nonlinear fiber to achieve a 1.7?m Raman soliton output with a repetition frequency of 43 MHz;By adjusting the pump power,a tunable femtosecond soliton source in the 1.6?m to 1.8?m band with a tuning range of 200 nm was experimentally obtained.On this basis,the supercontinuum spectrum covering the band of 1.7?m was also obtained by replacing the high nonlinear fiber with the dispersive displacement fiber.Based on the theory of Tm-doped fiber gain spectrum,a 1.7?m band ring-cavity Tm-doped fiber laser was constructed and experimentally studied.A 1.7?m band continuous-wave fiber laser is fabricated using a ring cavity laser,a 1550 nm band laser as pump source,a thulium doped fiber as gain medium and a Fiber Bragg grating(FBG)as filter.The results show that the center wavelength of the output is 1727.92 nm,the laser line width is 0.18 nm,and the side mode suppression ratio(SMSR)of the laser is about 62 d B.On the basis of this,the gain switching and synchronous pumping experiments of Tm doped fiber pumped by pulse modulated 1550 nm band laser have been carried out.A 1.7?m band pulse is obtained at the wavelength of 1727.92 nm with the width from microsecond to nanosecond and the repetition rate is adjustable from k Hz to MHz.Applied research is studied based on 1.7?m pulsed laser.The experimental research content includes two parts: alcohol telemetry and water fog channel transmission.1)According to the spectral characteristics of alcohol at 1.7?m band,a set of 1.7?m band remote sensingof alcohol concentration experiment platform was designed and built based on the previous research of 1.7?m fiber laser as the measuring light source,the relationship between different alcohol concentration and laser spectrum power was studied experimentally,and the feasibility of alcohol measurement at 1.7?m band was also verified.2)According to the relatively high transmittance characteristics of water in the 1.7?m band,an experimental platform for the transmission characteristics of the 1.7?m band laser signal in water fog was designed and constructed.The transmission characteristics of 1.7?m wave band optical signal with 11 MHz sine wave in water fog channel are experimentally studied,Compared with the traditional optical signal experiments of the 1550 nm band,the signal strength of the 1.7?m band after transmission in the water fog channel is better than 1.5?m band about 4.5d B.The research in this paper has certain reference value for the generation and application of 1.7?m band laser signal. |
PDF Full Text Request