Electron energy probability functions (EEPFs) having a fine resolution of electron energy were measured in low-pressure inductively coupled plasma with laser Thomson scattering method (LTS) at various plasma conditions (rf powers and gas pressures) and compared with the EEPFs measured by a single Langmuir probe (SLP) at the same experimental conditions. The result of LTS showed that the measured electron density normally increases with the rf power and the gas pressure, and the electron temperature decreased with the rf power and the gas pressure. This result have a good agreement not only with the previous reports qualitatively but also with our SLP measurement result quantitatively [15]. The reasons for the discrepancy between two methods in absolute value might be expected to these facts as following: the probe perturbation effect from the probe holder volume, RF noise, and not sufficient signal level of laser Thomson scattering.
We experimentally demonstrated a widely tunable multi-wavelength Brillouin-erbium fiber laser by utilizing a double-pass pre-amplification Brillouin pump (BP) within a single-linear laser cavity. Owing to this pre-amplification technique, the laser can operate at low pump power and exhibit a low threshold operation of 35 mW pump power to create the first Stokes signal. By adjusting the polarization controller (PC), self-lasing cavity modes' oscillation can be tuned over 10 nm from 1562 nm to 1572 nm. We experimentally showed that the proposed novel fiber laser structure can achieve up to ~33 output channels with a constant wavelength spacing of 0.088 nm at 7.4 dBm of BP power and 250 mW of the 980 nm pump power by varying the wavelength of the BP and adjusting the PC. In addition, an average of 32 stable output channels could all be tuned over 12 nm with an average optical signal to noise ratio of 25 dB.
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