We report measurements of the dispersion in the linear optical properties (linear absorption coefficient and refractive index) of polydiacetylene
para-toluene sulfonate (PDA–PTS) single crystal ...waveguide films prepared by thermal polymerization of the monomer free floating in solution and subsequent attachment of the film to the substrate. A maximum absorption coefficient >10
5
cm
−1
at a wavelength of 620 nm is measured for polarization parallel to the polymer chains, in agreement with previous measurements. The refractive index parallel to the polymer axis is significantly lower in these thin films as compared to bulk PDA–PTS crystals, whereas the index perpendicular to the chains is comparable to that of bulk crystals. Sellmeier parameters describing the dispersion of the refractive index in the near-infrared spectral range are given.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The performance of fiber Bragg grating (FBG) stabilized pump-laser modules is strongly influenced by changes of the state of polarization (SOP) arising from intrinsic and/or induced birefringence of ...the fiber. Birefringence changes the SOP as the light propagates back and forth between laser and FBG, which are separated by a distance of 1 to 2 m. As a result, the effective wavelength-selective feedback provided by the FBG varies accordingly. Based on the steady-state solution of a set of multimode rate equations we present a new model allowing us to calculate the output characteristics of a grating-stabilized pump-laser module as function of effective feedback. An effective-reflector approach is applied to describe the external cavity between the front mirror and the FBG on the module's front side. The polarization- and wavelength-dependent effective feedback from the grating is taken into account by a feedback parameter in the equations for the effective reflector. We present an extended traveling-wave amplifier model for calculating the TE- and TM-polarized contributions to the power from all output ports of the module. Our model is verified by comparison of simulation results with experimental data for a typical FBG-stabilized pump-laser module. The output characteristics are analyzed as function of effective feedback for both the principal TE-polarization as well as the residual TM-polarization modes.
Light versus current (L-I) characteristics, of fiber Bragg grating stabilized 980-nm pump lasers, is experimentally studied and theoretically modeled. It is shown that a conventional design of such ...laser modules can result in sudden transitions between a coherence-collapse multimode emission, and a coherent single-mode state of operation.
We review the development of wavelength stabilized 980nm pump laser modules without active temperature stabilization for applications in erbium-doped fiber amplifiers. Operation over a wide ...temperature range with an output power exceeding 400mW at an ambient temperature of 70°C is demonstrated. The overall reliability of uncooled modules is estimated to be well below 500 FIT at all operating conditions. Such devices are made possible by continuous development and steady improvement of the pump laser chip, the optimization of the fiber Bragg grating stabilization scheme, careful design of the module package, and extended reliability analysis on the basis of stress tests as well as field data.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Effects of polarization change in the feedback provided by fiber Bragg gratings that stabilize 980-nm pump lasers are investigated. The effective feedback in the proper transverse-electric ...polarization is calculated from an easily measured parameter, describing the polarization at the fiber grating. This provides a useful experimental tool to investigate the effect of feedback loss due to polarization change that can occur in nonpolarization maintaining fibers. On the basis of our calculations, we give guidelines for optimum fiber layout to minimize polarization change.
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