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The development of silica planar lightwave circuits (PLCs) employing multiple phase-shifting elements to achieve optical signal processing is presented. Thermo-optic switching in Mach Zehnder interferometer (MZI) structures has been demonstrated with typical switching powers of 250-300 mW. 6-loop lattice-form MZI devices designed with specific filter responses have been fabricated, packaged, and tested. 10 GHz to 40 GHz pulse repetition rate multiplication has been achieved, and the tunability of the 6 phase control elements allows the generation of arbitrary 4-bit binary code patterns. Further improvements in complexity, power consumption, loss, and polarization sensitivity in these devices are discussed.

Modeling of a hybrid semiconductor external-cavity laser with an intra-cavity saturable absorber is presented. In this paper the simulations are based on a modified transmission line laser model for an external fiber grating laser. The designed model of a DFECL takes into account time-domain evolution of the dynamic grating due to the standing wave in the external cavity and high-power bleaching of the doped-fiber absorption. In contrast to the previous models of such a hybrid laser, here the properties of the dynamic grating strongly depend on the internal power inside the cavity, which causes the absorption bleaching. Modeling results of lasers at 980 nm and 1490 nm are presented.

We report on the first experiments of optical microwave generation by heterodyne beating of two doped-fiber semiconductor external-cavity lasers (DFECL). Our measurements show that minor side-mode beating in DFECL affect the optical heterodyne beat signal. Using the RF methods we study the side-mode suppression in the DFECL.

A numerical transmission line model for semiconductor lasers with long external fibre cavities and fibre grating reflectors is reported. The model is applied to high-power 980 nm lasers and shows good agreement with experiments in the coherence collapse regime (CCR). The numerical approach has been used to model the saturable absorber in the external cavity of the semiconductor laser with the external fibre grating in the "coherence enhanced regime" (CER). Our simulations show for the first time how line-narrowing evolves in CER lasers.

The effect of carrier-carrier relaxation on threshold and power-current characteristics of InAs and GaAs quantum well (QW) lasers is studied. Dependence of carrier relaxation time on temperature and carrier density is considered. It is shown that in this case the gain coefficient becomes a more pronounced function of temperature and carrier density, and threshold current density increases drastically.

A new method of additional transverse mode selection in high- power broad-waveguide separate confinement heterostructure quantum-well lasers by means of facet inclination is proposed. Theoretical investigation of mode selection and numerical calculations for GaAs-AlGaAs BW-SCH-QW laser with inclined facet with wavelength 860 nm and wide range of waveguide width has been carried out. The possibility of reducing power density on the mirror keeping single-mode generation and thus increasing fundamental mode output power 1.2 times is shown.