Abstract: The thermo-optic behavior of an optical path over a range of temperatures &Dgr;T is controlled by determining a figure-of-merit (FOM) for the optical path and including in the path a body of crystalline material that enables the conditions specified by the FOM to be satisfied. The crystalline material is highly transparent at a wavelength &lgr; of radiation propagating in the path, and it has a coefficient of thermal expansion (CTE) and a refractive index n such that the CTE and dn/dT are mutually adapted to satisfy the FOM over the range &Dgr;T. In one embodiment, the CTE and dn/dT of an etalon compensate one another so as to perform frequency discrimination that is essentially temperature insensitive over the range &Dgr;T. In a preferred embodiment of the optical etalon the crystalline material comprises LiCaAlF6.

Abstract: The invention is a method and apparatus for controlling the wavelength of a first optical component such as a laser. The light from the laser is coupled to a second optical component, such as a modulator, which produces an output which is function of the wavelength of the light and also a function of voltage applied to the second component. The light from the second component is converted to an electrical signal, and the derivative of the amplitude of the signal with respect to voltage is determined. The derivative is used as a basis for an error signal which controls the wavelength of the first component.

Abstract: A multi-wavelength etalon suitable for tuning and maintaining the operating frequency of a laser used in an optical communication system is disclosed. The communication system has a representative channel wavelength and a channel spacing. The etalon has a plurality of steps on one of the sides with a step size that is a fraction of the channel spacing. The nominal thickness of the etalon is chosen so that a transmission peak occurs at a wavelength substantially equal to the representative channel wavelength and a next peak occurs at the wavelength of an adjacent channel. The step size is a fraction of the channel separation and is substantially optimized so that a peak or trough in the transmission curve in the region of one step overlaps a steep portion of the transmission curve for one or more other steps.

Abstract: The invention in one aspect is an optical modulator which includes a waveguide region of semiconductor material. In order to achieve a gradual, essentially linear transfer function, the bandgap of the waveguide region is graded along the direction of light propogation or perpendicular thereto. In accordance with another aspect, the invention is an electroabsorption modulated laser where the portion of the waveguide region defining the modulator has a graded bandgap. In accordance with a method aspect, the waveguide region of the modulator is grown using a mask having a varying width to achieve the graded bandgap.

Abstract: A raised photodetector constructed to define an open channel extending between opposite edges of the photodetector and dimensioned for permitting light from laser to pass therethrough. The photodetector has a light-collecting region disposed in an outward facing wall recessed within the channel for collecting light from the laser.

Abstract: The invention is a laser assembly for reducing distortion ripple. The assembly includes a spherical lens which has a portion of its surface made optically asymmetric to prevent multiple reflections of scattered light within the lens.

Abstract: The invention is a laser assembly with reduced distortion ripple. The assembly includes a spherical lens for collimating light emitted from the laser. The lens is made of a material which attenuates scattered light which is the source of ripple without appreciably affecting the main beam.

Abstract: The invention is a laser with improved turn-on time for digital applications. The low bias capacitance effect of the laser is reduced by use of a buffer region formed between the substrate and the active region, the buffer region having a lower dopant concentration than the substrate.