Optical Pulse Compression Based On Microwave Magneto-optical Effect

With the development of optical fiber communication, the information transmission rate is greatly increased by using short optical pulses with high repetition. The optical signal pulses will suffer from a larger spread with the increase of transmission distance due to the existence of fiber dispersion, which may lead to the overlap of pulses or inter-symbol interference. Some optical pulse compression technologies, which are for example based on the high order soliton effect, the nonlinear optical loop mirror and the adiabatic compression in step-decreasing-dispersion fiber, et al, can help to reduce the bit error rate (BER) or extend the optical relay distance. From the view of microwave-optoelectronics, the other optical pulse compression method based on magneto-optic (MO) Bragg diffraction is studied in this paper and the compression of incident linearly chirped Gaussian optical pulses is achieved by utilizing continuous magnetostatic waves (MSWs), which provides us with a new idea for the development of MO signal processing devices. In comparison with acousto-optic Bragg devices, the MSW-based MO cells are capable of providing faster modulation speeds and larger bandwidths with potential applications to optical communication and signal processing and laser radar.The main works and innovations are listed as follows:1. The coupling equations for optical pulses with magnetostatic surface waves (MSSWs) and magnetostatic forward volume waves (MSFVWs) are obtained respectively, which can be used to analyze MSW-based optical pulse signal processing. According to the analytical and numerical solutions of the MO coupling equations, the frequency spectrum of diffracted optical pulse resulting in optical pulse compression is dependent on the chirp parameter and the frequency distribution of phase mismatching factors (in terms of phase mismatching slope). It is shown that, the performance of pulse compression can be further improved with the rise of phase mismatching slopes by increasing the GOW mode-order and the chirp parameter or by optimizing the normalized MO film thickness (the ratio of the film thickness to the light wavelength).2. The MSSW- and MSFVW-based optical pulse compression at 1310nm and 1550nm wavelengths is analyzed in detail. Calculation results show that, for the same MSW frequency and wavenumber, the MSSW-based MO collinear interaction may have larger compression efficiency and a narrower diffracted pulse at 1550nm can be obtained.3. The influence of magnetic loss on output pulse intensity and pulse-width is investigated in detail. The magnetic loss mainly affects the peak intensity of diffracted optical pulse, but hardly changes the pulse compression efficiency for the general MO films used in practice.