Precision Control Of Light Field In Inverse Compton Scattering Source

Inverse Compton Scattering(ICS)refers to the process in which low-energy photons interact with relativistic electrons,transferring energy from the electrons to the photons and resulting in the scattering of higher-energy photons.ICS sources have characteristics such as high brightness,tunability,high coherence,high energy,and narrow spectral linewidth,making them important in fields such as life sciences,medical imaging,astronomy,and semiconductor lithography.Due to its excellent coherence,a Free-electron laser(FEL)is an excellent electron source.Additionally,square pulses are well suited for high-power applications due to their characteristic of having a flat power top.Therefore,by utilizing FEL and megawatt-level square pulses as the electron source and laser field,respectively,in an ICS system,the interaction between them can generate high-coherence,high-repetition-rate,kilowatt-level Extreme Ultraviolet(EUV)light sources.This has significant application value in achieving higher chip image resolution and improved lithography efficiency in the semiconductor lithography field.However,this approach imposes stringent requirements on the frequency stability and average power of the laser field,and generating square pulses remains a challenge.Addressing the difficulties and challenges faced by the laser field in the ICS system,this paper conducts the following three studies: Firstly,based on the high requirements for laser frequency stability in the FEL system,the influence of modulation frequency on the demodulation signal is analyzed,and an electro-optic modulator(EOM)for the stabilization system of the Modulation Transfer Spectrum(MTS)is developed,with a central frequency of 5.45 MHz and a quality factor Q of 80.Secondly,by modulating and shaping continuous light using a dual-modulation model,coherent square pulses with specific spectral structures are obtained,and the influence of the delay time between the two modulation processes on the shape of square pulses is discussed.Finally,to enhance the power of square pulses,a physical model of pulse amplification is constructed based on the basic principles of intracavity multi-beam interference and mode locking.Through simulations of pulse amplification of traditional nanosecond pulses in resonant cavities of different lengths,the conditions for pulse amplification are summarized from the perspectives of time domain and frequency domain,and corresponding resonant cavity designs are performed,achieving nearly 350 times amplification of nanosecond square pulses in a high-Q resonant cavity with a cavity length of 120 m.This paper focuses on precise control of the optical field in the ICS system using laser modulation technology.The innovation of this paper lies in the generation and enhancement design of square pulses.By generating fully coherent square pulses and using them as seed light to enhance them in a resonant cavity,high-quality square pulses are ultimately obtained.The use of megawatt square pulses in the ICS process with FELs enables highrepetition-rate and high-coherence ICS light sources,which have profound significance in improving resolution,reducing feature size,increasing lithography area,and improving operational efficiency in semiconductor chip manufacturing.