Research On Temporal Profile Characterization Of Femtosecond Laser Pulses

Ultrashort femtosecond laser pulses have now widely been used as important tools in many scientific research fields such as ultra-intense laser physics,ultrafast spectroscopy,and nonlinear optical microscopy.The progress of optical metrology of ultrashort femtosecond laser pulses is always tightly-coupled with the development of femtosecond laser sources and the extending of different applications,which make it always an important topic in ultrashort laser technology research field.A technique with a simple and alignment-free setup,a wide spectral application range,single-shot and few-cycle full amplitude and phase measurement ability is required as the advanced laser pulses and extended application.The main work of this paper is shown as follows:1.The development of ultrashort lasers and the significance of temporal profile characterization of femtosecond laser pulses are described.The principles and properties of several typical techniques are summarized,which including:autocorrelation method,FROG,and SPIDER.The FTSI algorithm process and the principle of SRSI(self-referenced spectral interferometry)are summarized,several SRSI methods based on XPW,SD or TG effects are described.2.We proposed an all-reflective SRSI technique based on transient grating(TG)effect and built up a simple and almost alignment-free device with the size of about an A4 paper.Except for a thin third-order nonlinear medium(hundreds microns thick)which is used to generate the TG signal,no other transmitted optics are used in the proposed device,then few-cycle pulses in a broad spectral range from DUV to Mid-IR can be characterized in a single shot.With the homemade device,an 800 nm/5.0 fs pulse and a 1800 nm/14.3 fs pulse were characterized successfully.3.We proposed an all reflective combining technique for few-cycle pulses measurement at different situations,where the TG-FROG and TG-SRSI can be switched easily.A home-made device based on this technique was built up with a size of 340×240×80 mm~3.An 8.9 fs laser pulse at 800 nm,and a 16.5 fs pulse at 1800 nm were successfully measured,which proves the ability of the device.4.The limitation of SRSI method due to the necessary of high spectral resolution was analyzed,and a new method SEA-SRSI by combining spatial interference and SRSI method was proposed to solve the problem.This method has a simple optical path.Furthermore,a simple method was proposed to roughly measure the pulse duration in a single shot.It only needs a CCD for real-time measurement.The most striking is its simple configuration and low cost.A 35 fs pulses at 800nm was successfully characterized.