Influence Of Pulse Parameters On Optical Coherence Tomography Light Source Properties In Medical Photonic Crystal Fiber

Objective The longitudinal resolution and imaging quality of optical coherence tomography are improved by optimizing the parameters of pump pulse source.Methods The generation of supercontinuum of pump pulse in photonic crystal fiber(PCF)is simulated by split step Fourier method and fourth-order Runge Kutta method.The effects of central wavelength,peak power,width and shape,modulation depth,modulation frequency and initial chirp on the supercontinuum characteristics are studied.The results of spectral quality of optical coherence tomography using initial parameters are discussed.Results For the medical photonic crystal fibers with the central wavelengths of 1.06?m,1.31?m and 1.55?m,under the same parameters,the pump pulse of 1.55?m produces a wider bandwidth,and the longitudinal resolution of 1.31?m is smaller.For a medical photonic crystal fiber of1.55?m,the peak power of the selected hyperbolic secant pump is 20.5 W,and the longitudinal resolution is 5.0?m when the pulse width is 2 ps.When the pulse width is 0.5ps and the peak power is 18 W,the longitudinal resolution is 3.7?m.Compared with Gaussian,hyperbolic secant and chirped Gaussian pumping pulses,the super Gaussian pumping pulses are easier to obtain wider and flatter supercontinuum source.When the modulation depth is 0.2,the supercontinuum spectrum with R value of 143.55 and K value of 0.9998 is obtained.When the modulation frequency is 16 THz and the modulation depth is 0.2,the high coherent and high SNR supercontinuum spectrum with K value of 0.9999,R value of 205.48 and extreme SNR of 459.10 can be obtained.When the modulated pulse parametersd₀=0.2 andf₀=4 THz,the initial chirp C=4 can obtain a stable supercontinuum with a higher SNR and high coherence with an extreme SNR of 368.14 and an R value of134.53.Conclusion Choosing pulses with appropriate pump parameters as the light source of the OCT system can improve its longitudinal resolution and imaging quality,reaching or even lower than that obtained by directly using a femtosecond laser as the light source of the OCT system.At the same time,choosing appropriate parameters can effectively optimize the quality of the supercontinuum light source.