Impact of Pump-Probe Time Delay on the Four Wave Mixing Conversion Efficiency in Semiconductor Optical Amplifiers

Abstract

Four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) have attracted much attention especially for applications involving fast wavelength conversion and optical demultiplexing (Mecozzi et al., 1995; Mecozzi & Mφrk, 1997; Das et al., 2000). The optimisation of the time delay between the input pump and probe pulses is crucial for maximising the FWM conversion efficiency and reducing the timing jitter (Inoue & Kawaguchi, 1998b; Das et al., 2005). The FWM conversion efficiency is mainly limited by the gain saturation of the SOA, which is strongly dependent on the pulse duration, repetition rate of the input pulses, and time delay between pump and probe pulses. Therefore, it is important to analyse theoretically and investigate experimentally the dependence of the FWM conversion efficiency on the time delay between the input pump and probe pulses in SOAs. The impact of the time-delay between sub-picosecond optical pump and probe pulses on the FWM conversion efficiency in SOAs was experimentally observed for the first time and reported by Inoue and Kawaguchi (Inoue & Kawaguchi, 1998b). A preliminary theoretical analysis for evaluating the FWM conversion efficiency of SOAs was reported by Das et al. (Das et al., 2005). The optimization of the time delay between the optical pump and probe pulses is very important in order to achieve a high FWM conversion efficiency and minimize the timing jitter (Inoue & Kawaguchi, 1998b; Das et al., 2005). Shtaif et al., (Shtaif & Eisenstein, 1995; Shtaif et al., 1995) have investigated analytically and experimentally the dependence of the FWM conversion efficiency for short optical pulses in SOA. They measured the FWM conversion efficiency for short optical pulses in the order of 10 ps and suggested that the high FWM conversion efficiency can be obtained when short optical pulses are used. The FWM characteristics for subpicosecond time-delays between the input optical pulses in SOAs have been reported. However, no theoretical analysis (Inoue & Kawaguchi, 1998b) was reported. Therefore, it is very important to analyze theoretically and measure