Doreen A. Weinberger

Observation of polarization instabilities and modulational gain in a low-birefringence optical fiber

Intense linearly polarized light has been used to observe polarization instabilities due to the optical Kerr effect in a low-birefringence optical fiber. Near the onset of instability small intensity modulations are amplified and a sixfold increase in modulation depth is observed. The transmission through a crossed polarizer is markedly different for intense beams aligned near the fast and slow axes. The critical power of 250 W is in agreement with theoretical predictions.

Spatially resolved Raman study of self-organized χ (2) gratings in optical fibers

A spatially resolved Raman study of self-organized χ(2) gratings in optical fibers shows a periodic modulation in the strength of the low-frequency (ν ≤ 600 cm−1) Raman spectrum. In a fused-silica fiber the measured period ranges from 27 to 50 μm, and the modulation amplitude is ±3% of the average Raman signal.

Optical NOR gate using diode laser sources.

Two diode lasers are employed as probe and pump light sources for an optical NOR gate consisting of a GaAs/AlGaAs multiple-quantum-well etalon. The frequency spectrum of the probe diode laser was found to be influenced by pump-laser injection into the probe laser as well as feedback of the probe laser itself, which can cause erroneous gate operation or a noisy output signal. Both the pump and feedback effects on the probe-laser frequency were eliminated using a Faraday isolator.

Additive pulse mode-locking using a birefringent optical fiber

Abstract A powerful and increasingly common method to mode-lock a variety of lasers is additive pulse mode-locking (APM). In this technique, a nonlinear medium is placed in an external cavity which is coupled to the main laser cavity. As a result of interference at the common mirror between the pulses returning from each cavity, significant pulse shortening may be obtained. Optical fiber is often used as the nonlinear medium, and polarization effects and fiber birefringence are generally neglected. A computer model has been developed in order to simulate the effect of using a birefringent fiber. The simulations indicate that although the birefringence often has little qualitative effect on the system, in certain cases the birefringence may be exploited for enhanced mode-locking.

Dynamics of self-organized χ(2) gratings in optical fibers

In this paper we report experiments on the dynamic of self-organized (chi)(2) gratings. An important observation is that the initial growth rate of (chi)(2) gratings is always linear in time. A fast transient and slow fluctuations are also observed in certain cases. The initial growth rate of the grating amplitude as a function of the irradiances of the seeding fundamental ((omega)) and second harmonic (2(omega)) beams was measured and was determined to have a power dependence on I(2(omega)) of exponent 1.48 +/- 0.2, and on I((omega)) of 0.9 +/- 0.2. A model based on selective ionization of dipolar defects due to an interference between two-photon and three-photon processes has been explored in the context of these results.