Supercontinuum Generation by Nonlinear Optics - Optical Signal Processing by Silicon Photonics - page 74

spectral range of 11 nm with average power of 7 W [ 22 ]. Ultra short high pulse SC
is generated by using a sub-picoseconds erbium fiber laser source that operates at
wavelength of 1.557 μ m and give peak power more than 1 MW [ 23 ]. SC is gener-
ated in [ 24 ] by using Er-doped fiber chirped laser at 1.55 μ m. This generates the
pulses with duration of 1 ps and 2 μ J pulse energy at repetition rate of 200 kHz.
As the pulse energy is so high it results in generating a smooth SC at wavelength
region of 1.3 μ m shown in Fig. 6.2 using 1 ps pulses and dispersion-shifted fibers.
6.6 SC Using Continuous Wave Pumping
Picoseconds pulses are not required for generating spectral broadening as ns-
pulses gave result of SC generation at high power levels. Even CW pumping lasers
led to spectral broadening at high power levels [ 20 ]. In Travers et al. [ 25 ] the first
CW source is investigated that generates SC in visible spectral region 400 W CW
pump source with average power of 50 W is used to led spectral power densities
of 50 mW/nm and spectral broadening over 1,300 nm. CW Raman fiber laser cen-
tered at the wavelength of 1455.3 nm generates SC over more than 200 nm band-
width [ 12 ]. SC is reported in the wide spectral range of 1,200-1,780 nm [ 26 ]. This
is achieved by using the continuous waves in highly nonlinear fibers (Fig. 6.4 ).
6.7 SC Generation with Femtosecond Pulses
The use of femtosecond pulses gained practical importance with the advent
of highly nonlinear fibers. SC using femtosecond pulses is generated with the
power conversion efficiency of 55 % in optical fibers. The spectral characteris-
tic of this SC depends upon power radiation and pulse wavelength of pump. High
spectral densities of 300 mW/nm and average power densities of approximately
Fig. 6.4 Ultra wideband SC
generation using 1 ps pulses
and dispersion shifted fibers
[ 24 ]