ABSTRACT
We present a thorough theoretical analysis and experimental study of the shot and electronic noise spectra of a balanced optical detector based on an operational amplifier connected in a transimpedance scheme. We identify and quantify the primary parameters responsible for the limitations of the circuit, in particular, the bandwidth and shot-to-electronic noise clearance. We find that the shot noise spectrum can be made consistent with the second-order Butterworth filter, while the electronic noise grows linearly with the second power of the frequency. Good agreement between the theory and experiment is observed; however, the capacitances of the operational amplifier input and the photodiodes appear significantly higher than those specified in manufacturers' datasheets. This observation is confirmed by independent tests.
ABSTRACT
A new technique to measure the frequency-resolved temporal image of a single ultrashort light pulse is presented. This technique is based on a single-shot self-diffraction autocorrelator in which the pulse duration is related to the spatial width of a diffracted beam, the pulse spectrum is related to its divergence, and the pulse chirp appears as a curvature of the diffracted-beam wave front. An analysis of wave-front curvature by means of a slit diaphragm and a cylindrical lens results in a time-frequency image of the initial pulse when a spectrometer is not used. This image gives a simple intuitive picture of the chirp and the phase modulation of a pulse.
