An automatically power-stabilized (with power fluctuation < 0.155 dB), narrow-linewidth (0.0171 nm), wavelength-tunable (10.69 nm) erbium-doped fiber laser has been proposed by cascading two fiber Mach-Zehnder interferometers (MZI) without using any temperature controlling device. One of the MZIs (here called the 1st MZI) is composed of two 3 dB couplers to form interference patterns while the other MZI (here termed the 2nd MZI) is constructed with a tapered seven-core fiber (SCF) and based on the principle of supermode interference. For the two MZIs, the free spectral range (FSR), the passband bandwidth and the extinction ratio (ER) at 1560 nm are 0.37 nm, 0.19 nm, 16.6 dB and 13.93 nm, 7.93 nm, 10.1 dB, respectively. Due to the major difference between the two FSR values, the 1st MZI and the 2nd MZI respectively play a role in controlling the laser linewidth and suppressing the homogeneous broadening effect to reach to a satisfactory level of power stability. The 2nd MZI is also used to fine tune the laser wavelength by applying strain to the tapered SCF (TSCF) over the spectral range of 1570.22 - 1559.33 nm, with an incremental step of 0.37 nm being used. The side-mode suppression ratio (SMSR) of the tunable fiber laser can be up to 45 dB. By appropriately adjusting the polarization controller, dual wavelength lasing can also be achieved. For single wavelength lasing, the 3 dB laser linewidth is 0.0171 nm. The power fluctuation, without a temperature controlling device being used and operating at room temperature, is found to be less than 0.155 dB over 1 hour while the central wavelength drift is less than 0.19 nm.

Based on the coupled Ginzburg-Landau equations and Jones matrices of the waveplates considered, a numerical model of an all-normal-dispersion fiber laser mode-locked by nonlinear polarization rotation has been proposed. The operating characteristics of the fiber laser discussed were studied numerically. It has been found that the proposed all-normal-dispersion mode-locked fiber laser (AND-MLFL) could deliver dissipative solitons (DSs) with a M-shaped and U-shaped spectrum, the splitting pulse with a divided spectrum and the amplifier similaritons. The evolution of the intra-cavity pulse and spectrum has been calculated under different regimes and the effects of group velocity dispersion (GVD) and nonlinearity are analyzed. When the fiber laser delivers DSs or causes pulse splitting, nonlinear effects dominate the pulse evolution. With the increase of the accumulated nonlinear phase shift, the operation states change from DS with a M-shaped spectrum to a U-shaped spectrum, and then to the splitting pulse. In the case of amplifier similaritons, both the GVD and nonlinearity play important roles in pulse evolution. The effect of nonlinear polarization rotation and filtering on the pulse reshaping has been analyzed. When the fiber laser delivers DSs with a M-shaped spectrum, the filter has a very weak effect on the pulse and on spectral reshaping. However, when the fiber laser operates in the amplifier similariton state, the filter plays a key role in pulse and spectral reshaping, whereas the nonlinear polarization rotation become less dominant. The dependence of the operational states on the filter bandwidth, fiber length, small signal gain coefficient and orientation of waveplates has also been calculated. A Yb-doped doubled-cladding fiber laser, mode-locked by nonlinear polarization rotation, has also been demonstrated and all of the four pulse regimes are obtained experimentally.

We demonstrate a real-time microanalysis approach to the evaporation rate of a (sub)picoliter liquid drop, measured over a 7.85-0.38 picoliter volume, using an off-axis fiber interferometer and achieving the best displacement resolution of 24 nm.