In-phase Coupling Research Articles

In-phase locking in diffraction-coupled phased-array diode lasers

Design criteria are presented for strong in-phase coupling of diffraction-coupled phased-array diode lasers. Theoretical predictions are confirmed by our experimental observations of double-lobe and single-lobe far-field patterns.

Coupled-cavity semiconductor lasers under current modulation: Small-signal analysis

The modulation characteristics such as the power response and the chirp (dynamic line broadening) of single-frequency coupled-cavity semiconductor lasers are analyzed theoretically. The model is based on the small-signal analysis of a set of generalized rate equations and neglects the lateral variations of the optical field and the carrier density in the two cavity sections. When the controller section is biased below threshold in a three-terminal device the modulation response is not significantly affected by the intercavity coupling. By contrast, new features arise when both sections are biased above threshold. It is found that the chirp can be significantly reduced by a proper combination of the bias levels and the modulation splitting between the two sections. The chirp reduction also depends on the strength of the intercavity coupling and its phase, and the best performance is achieved for the case of in-phase coupling. The calculated results are in qualitative agreement with the reported experimental data and are useful as a guide to optimize the performance of a coupled-cavity device.

Internal feedback caused by variation of the plasma potential in a bounded plasma

The mechanism of in-phase coupling in the ion-ion and electron-ion instabilities is found experimentally. The coupling is through perturbation of the plasma potential due to electron collection by a grid.

Sodium+potassium-activated ATPase of mammalian brain regulation of phosphatase activity

1. 1. The K +-nitrophenylphosphatase activity associated with mammalian brain (Na ++K +)-ATPase displays K + activation curves that have intermediary plateaus and maxima in the presence of less than saturating concentrations of Na +. Zero Na + and saturating Na + produce sigmoid K +-activation curves with low and high K + affinities respectively. 2. 2. ATP inhibits K +-activated nitrophenylphosphatase through both competitive and non-competitive mechanisms. ATP is synergistic with Na + in the mechanism which converts the enzyme from low to high K + affinity. 3. 3.|The Na + and K + interactions can be accounted for by aquations which describe a model with separate regulatory sites for Na + and K + and with a K +-requiring catalytic site which is only accessible in one of the two principal conformational states of the enzyme. 4. 4. The effects of ATP can be accounted for by the same model through interactions at a single nucleotide binding site. Inhibition which is competitive with K + and non-competitive with substrate arises from stabilization of the inactive enzyme conformation. Inhibition which is non-competitive with K + and competitive with substrate results from interactions with the active enzyme conformation. The synergism between Na + and ATP appears to arise as a consequence of the formation of phosphoryl enzyme. 5. 5. A model for (Na ++K +)-ATPase is discussed with involves in-phase coupling of subunit interactions as suggested by these studies.

Effect of Redirectors, Refocusers, and Mode Filters on Light Transmission Through Aberrated and Misaligned Lenses

The field distortion of a beam propagating through a sequence of identical, misaligned and slightly aberrated lenses is calculated as a perturbation of the Gaussian beam that would propagate in the absence of aberration. It is found that most of the converted power goes to the first and second modes. They produce deflection and spot-size change of the ideal beam, respectively. The power coupled to modes higher than the second deform the Gaussian profile. In general, the mode conversion per unit length of guide can be reduced by making the spot size small and by avoiding in-phase coupling at every lens. This last condition is achieved by choosing the period of oscillation of the beam different from an integer number of lens spacings. Before the beam becomes too distorted, the converted modes must be eliminated. Power in the first and second modes can be reconverted loss-lessly to the fundamental Gaussian beam by means of servoloops that redirect and refocus the beam. If refocusers are not used, the power in the second mode, as well as the power in the higher-order modes must be absorbed in mode filters such as irises. For lenses with fourth-order aberration such that at a beam half-width distance from the center the focal length departs δ percent from ideal, the following typical results are obtained: In a guide in which the distance between the beam and guide axes is a constant plus a sinusoid, the converted power is proportional to δ2, to the fourth power of the amplitude of the sinusoid and to the square of the number of lenses, but is roughly independent of the curvature of the guide axis. On the other hand, in a guide in which the distance between the beam and guide axes is a constant plus a random quantity the converted power is proportional to δ2, to the square of the guide curvature, to the mean square of the random deviation, and to the number of lenses. Fof &delta =1 percent, a 1 power conversion to the second mode occurs is typical examples, after a few of lenses, and the order of magnitude of mode conversion is 0.001 dB/lens. Most of that power is in the second mode and can be recovered with refocusers.

Surface damage in machined beryllium : S. W. Porembka and H. D. Hanes, DMIC Memorandum 198, Battelle Memorial Institute, Defense Metals Information Center, January 4, 1965, 9 pp. (OTS $ 1.00)

The oscillation of loads in high-pressure zones (hpzs) formed in ice compressive failure is shown, under the right conditions, to constitute a regular self-sustained oscillation. This occurs in a system comprising the moving ice field, which supplies an internal source of energy, and a compliant structure with which the ice interacts. The supplied energy is dissipated within a layer of microstructurally modified ice by means of viscoelastic deformation enhanced by damage processes, as well as by spalling fracture. An important question arises with regard to vibrations found in large structures such as the Molikpaq. Given that high-pressure zones in field situations are on the order of 1 m in size, how do large structures respond and participate in ice-induced vibrations? The concept of ‘entrainment’ or synchronization of hpzs via elastic and inertial structural feedback is introduced. In this, failure of one high-pressure zone leads to failure of another through structurally-coupled feedback, whereby the first failure increases the load on another as a result of elastic rebound of the structure. This constitutes in-phase coupling and synchronization, but anti-phase coupling whereby failure of one high-pressure zone leads to a decrease in load on another, is also considered. These hypotheses were confirmed in an experimental programme, in which a series of tests with a compliant beam applying load to ice specimens through a pair of indentors was carried out. The test results confirm the hypotheses, with both in- and anti-phase synchronization being observed. Relevance to real structural systems is discussed in the context of the Molikpaq structure and the JZ-20-2-1 jacket platform.