Abstract: A method for reducing the inherent polarization shift caused by birefringence between the TE and TM modes of an optical signal propagating in an optical grating which has a plurality of waveguides includes the step of: irradiating the waveguides of the optical grating for different periods of time to induce a compensating polarization shift that substantially reduces the inherent polarization shift. If desired, a compensating polarization shift may be induced which not only reduces but also substantially eliminates the inherent polarization shift.

Abstract: A method of making a silicate optical waveguide structure for transforming an optical beam of a first modal spot size to a beam of a second modal spot size includes the step of selecting an irradiation energy which is at least partially absorbed by the cladding of the structure. A variable dosage of radiation is then provided along the length of the structure. The radiation has an energy equal to the selected irradiation energy so that a refractive index change of the cladding is greater than a refractive index change of the core.

Abstract: A method for reducing birefringence in a silicate waveguide structure having a waveguide core and cladding includes the step of selecting an irradiation energy that induces compaction in the cladding. The waveguide structure is then irradiated with radiation having an energy equal to the irradiation energy to induce a reduction in birefringence.

Abstract: An optical system is disclosed which includes at least a first source of electromagnetic radiation (signal beam radiation), a device for processing the signal beam radiation, and a detector for detecting the processed signal beam radiation. The processing device functions, for example, as an amplitude modulator, a demultiplexer, or a switch, and includes a material region exhibiting a nonlinear optical response at one or more resonant wavelengths of electromagnetic radiation, as well as at least a second source of electromagnetic radiation (control beam radiation) for selectively inducing the nonlinear optical response. Significantly, the wavelength, duration and intensity of the control beam radiation are chosen to induce a resonant, nonlinear optical response, essentially free of any relatively slow component, in said material region at repetition rates higher than about 1.25.times.10.sup.4 Hz, or higher than about 3.3.times.10.sup.10 Hz, or even as high, or higher, than about 2.5.times.10.sup.11 Hz.

Abstract: An optical system is disclosed which includes at least a first source of electromagnetic radiation (signal beam radiation), a device for processing the signal beam radiation, and a detector for detecting the processed signal beam radiation. The processing device functions, for example, as an amplitude modulator, a demultiplexer, or a switch, and includes a material region exhibiting a nonlinear optical response at one or more resonant wavelengths of electromagnetic radiation, as well as at least a second source of electromagnetic radiation (control beam radiation) for selectively inducing the nonlinear optical response. Significantly, the wavelength, duration and intensity of the control beam radiation are chosen to induce a resonant, nonlinear optical response, essentially free of any relatively slow component, in said material region at repetition rates higher than about 1.25.times.10.sup.4 Hz, or higher than about 3.3.times.10.sup.10 Hz, or even as high, or higher, than about 2.5.times.10.sup.11 Hz.

Abstract: A ring cavity laser is disclosed wherein a Rhodamine 6G dye stream is used as the gain medium, and a saturable absorber stream is positioned in the ring cavity at a point such that the time difference between pulses arriving at the gain stream is not small compared to the recovery time of the gain medium. The saturable absorber is DODCI dissolved in ethylene glycol passed through a specially constructed nozzle that creates a dye stream having a thickness of about 10 microns in the optical cavity. As a result of this thin saturable absorber, the two counterpropagating pulses that collide in the saturable absorber are caused to interact in a way that results in a decrease of the pulse duration and an equalization of the pulse intensities.