The method of the spectral phase interferometry for direct electric-field reconstruction(SPIDER) is based on a self-referencing interferometric technique for measuring the amplitude and the phase of ultrashort optical pulses. It measures the interference between a pair of spectrally sheared replicas of an input pulse, and then a fast noniterative algorithm yields the electric field of the input pulse without ambiguity. This system does not use any moving components, and the interferogram is resolved with a spectrometer and recorded with a slow detector. It makes SPIDER a reliable technique to measure ultrashort pulses.
SPIDER was fabricated and used to characterize pulses with nanojoule energy from a Ti:Sapphire oscillator. In the SPIDER apparatus two replicas of the input pulse were generated with a time delay 200 fs. These two replicas were upconverted by use of sum-frequency generation with a strongly chirped pulse generated by 80-mm-long SF10 glass block at the 30-㎛-thick type II BBO(β-$BaB_2O_4$) crystal, and the resulting interferogram was recorded with an UV-enhanced CCD array in the spectrometer. A fast noniterative algorithm using one-dimensional Fourier transforms extracts the phase of the oscillatory term of the interferogram. After calibration, the spectral phase was obtained from the concatenation method. Finally, the time-dependent intensity and phase were calculated from the reconstructed spectral phase and separately recorded laser spectrum. The spectral phase was retrieved, and the corresponding temporal intensity profile was reconstructed with a duration of 19 fs. As an independent check of the accuracy of the method, we compared the interferometric autocorrelation (IAC) signal calculated from the SPIDER data with a separately measured IAC, which showed a good agreement. The conventional, but unjustified, method of fitting a $sech^2$ pulse to the autocorrelation deceivingly yielded a pulse duration of 15 fs. This systematic underestimation of the pulse duration affirms the need for complete characterization method. From the consideration in this thesis, we concluded that the SPIDER could provide an accurate characterization of femtosecond pulses.
주파수 위상 간섭계를 이용한 전기장 재구성 방법(spectral phase interferometry for direct electric-field reconstuction ; SPIDER)으로 커렌즈 모드록킹된 티타늄 사파이어 레이저 공진기에서 생성된 펨토초 영역의 극초단 펄스의 펄스폭과 위상을 측정하였다. SPIDER 장치를 구성하였으며, 8cm길이의 SF10 매질과 마이켈슨형의 시간지연 암(arm)을 사용하여 주파수 층밀림(shearing)을 구현하였고, 제 2종 BBO결정으로 합주파수 발생을 시켰다. 얻어진 층밀림 주파수 간섭 신호로부터 SPIDER알고리즘을 이용하여 펄스의 전기장을 복원하였다. SPIDER의 정확도를 확인하기 위해 SPIDER에서 얻은 펄스로 재구성한 간섭형 자체상관신호를 직접 측정한 간섭형 자체상관 신호와 비교하였다.
