Abstract: The output beam from a laser may be modulated using a coupled waveguide modulator that may be endfire coupled to the laser, or integrally formed on a common substrate with the laser, thereby providing a monolithic laser/modulator system that may manufactured using a high-volume semiconductor manufacturing process. The coupled waveguide modulator includes a substrate having a coupler region and an output region. A first waveguide on the substrate is parallel to an optical axis. A second waveguide is formed proximate the first waveguide, is parallel to the optical axis, and is separated from the first waveguide by a coupling distance in at least the coupler region. The second waveguide is nonparallel to the optical axis and separated from the first waveguide by at least the coupling distance in at least part of the output region.

Abstract: A tunable waveguide filter, formed from two waveguides, has an improved selectivity. The filter is tuned by passing a current through the filter. One of the waveguides is a semi-active waveguide. The increased absorption of charge carriers that occurs when current is injected into the semi-active waveguide is compensated by gain enhancement in the waveguide, because the material used for the semi-active waveguide is selected to provide an appropriate amount of gain. Therefore, the gain compensates for the losses that arise from free carrier absorption when the tuning current is applied to the filter.

Abstract: An electro-absorption modulator is tunable along with the laser. Tuning the electro-absorption modulator permits optimum detuning to be maintained, even though the laser is tuned over several tens of nm. One approach to tuning the electro-absorption modulator is to heat the electro-absorption modulator. A semiconductor laser device includes a semiconductor laser positioned on a substrate. The semiconductor laser produces output light that is tunable over a tuning range between a first wavelength and a second wavelength. An electro-absorption modulator is disposed to modulate the light produced by the semiconductor laser. The operating temperature of the electro-absorption modulator is tunable so as to maintain constant detuning over at least a portion of the tuning range.

Abstract: A method of wavelength locking and mode monitoring a tuneable laser that includes two or more tuneable sections in which injected current can be varied, including at least one reflector section and one phase section. Laser operation points are determined as different current combinations through the different laser sections, and the laser operates at a predetermined operation point. The wavelength of light emitted by the laser is detected by a wavelength selective filter. The laser is controlled in an iterative process in which alternated currents through the reflector section and, when applicable, its coupler section, and the current through the phase section are adjusted. The currents through the reflector section and the coupler section are adjusted to obtain a minimum ratio between power rearwards and power forwards. The current through the phase section is adjusted to hold the wavelength constant, the wavelength being measured against a wavelength reference.

Abstract: A method of evaluating a tuneable laser and determining suitable hysteresis-free laser operation points. The laser includes two or more tuneable sections in which injected current can be varied, the tuneable sections including at least one reflector section and one phase section. The current injected through the reflector section is varied at different constant currents injected through respective remaining tuneable sections. The laser power output is measured at the front or the rear mirror of the laser while sweeping the reflector current in one direction and then in the opposite direction back to its starting value. The power difference with one and the same reflector current is calculated in the different sweep directions, and those combinations that give rise to a power difference that falls below a predetermined level are detected and stored as hysteresis-free current combinations.

Abstract: A method of evaluating a tuneable laser and determining suitable laser operation points, wherein the laser includes one or more tuneable sections in which injected current can be varied. A portion of the laser light output is divided into parallel paths, one part of which passes through a periodic filter, a second part of which is unfiltered, and a third part of which passes through a monotonic filter. The light power outputs from the respective paths are compared as sweep currents are injected into the tuning sections of the laser. When the ratios of the power outputs are within a predetermined range the tuning current combinations for those operating points are stored.

Abstract: In an apparatus and method for locking the wavelength of a laser, a fringe-producing optical element is disposed directly in the in the output beam from the laser. The fringe-producing optical element produces a fringe pattern in a second light beam derived from the output beam. The fringe pattern is detected by a detector unit. Signals generated by the detector unit are used to generate a laser tuning control signal that tunes the laser to a desired operating wavelength.

Abstract: A method for locking the wavelength of a laser uses a non-planar etalon, for example a non-parallel etalon, to produce a periodic spatial interference pattern, typically in the light reflected from the non-planar etalon. At least three different portions of the interference pattern are detected to generate at least three respective detection signals. A feedback signal is generated using the detection signals, and the operating wavelength of the laser is adjusted in response to the feedback signal.

Abstract: An apparatus for locking the wavelength of a laser uses a non-planar etalon, for example a non-parallel etalon, to produce a periodic spatial interference pattern, typically in the light reflected from the etalon. The apparatus also uses a detector to detect the spatial interference pattern having at least three separate detector elements, commonly referred to as pixels. The etalon and the detector are matched to each other so that adjacent pixels detect a specific portion of the phase of the periodic interference pattern.

Abstract: The output beam from a laser may be modulated using a coupled waveguide modulator that may be endfire coupled to the laser, or integrally formed on a common substrate with the laser, thereby providing a monolithic laser/modulator system that may manufactured using a high-volume semiconductor manufacturing process. The coupled waveguide modulator includes a substrate having a coupler region and an output region. A first waveguide on the substrate is parallel to an optical axis. A second waveguide is formed proximate the first waveguide, is parallel to the optical axis, and is separated from the first waveguide by a coupling distance in at least the coupler region. The second waveguide is nonparallel to the optical axis and separated from the first waveguide by at least the coupling distance in at least part of the output region.

Abstract: An electro-absorption modulator is tunable along with the laser. Tuning the electro-absorption modulator permits optimum detuning to be maintained, even though the laser is tuned over several tens of nm. One approach to tuning the electro-absorption modulator is to heat the electro-absorption modulator. A semiconductor laser device includes a semiconductor laser positioned on a substrate. The semiconductor laser produces output light that is tunable over a tuning range between a first wavelength and a second wavelength. An electro-absorption modulator is disposed to modulate the light produced by the semiconductor laser. The operating temperature of the electro-absorption modulator is tunable so as to maintain constant detuning over at least a portion of the tuning range.

Abstract: A wide band reflector, for example a wideband grating reflector is provided as the output coupler of a semiconductor laser. This permits the semiconductor laser to be integrated with other components on a single semiconductor substrate, if desired, without requiring that the laser beam be emitted from the tuning element. Thus, the laser can be tuned over a wide bandwidth with efficient power extraction and high wavelength selectivity.

Abstract: A method of optimizing the operation point of a laser, including characterizing the laser and controlling the different laser sections by varying the currents injected into the respective laser sections. The method includes sensing discontinuities that occur at mode jumps in a signal by utilizing a detection device that is firmly connected to the laser. Control of the different laser sections is effected by means of a control unit. Different control current combinations and the signal delivered by the detection device are provided to the control unit, which causes the control unit to detect the mode plane of the laser. At least a part of a mode plane, or several mode planes, are stored in a memory connected with the control unit, and the control unit controls the different laser sections so that the laser will operate at the desired operation point.

Abstract: The present invention relates to an approach to locking the output wavelength of a laser that uses an etalon having non-parallel surfaces. Under this approach, the non-parallel etalon is formed from a readily available, low cost optical component, and may include an etalon with a wedged shape or with at least one curved surface. This approach offers significant advantages over the use of a planar etalon. It provides two degrees of freedom in alignment of the device, and so both the absolute wavelength and the spacing between the interference fringes can be independently adjusted. It also reduces the cost and difficulty of assembly, since it utilizes standard optical parts with wide tolerances. The invention may be used within a standard laser package. The invention also permits the laser to be tuned to a precise operating wavelength by setting various tuning signals according to values stored in memory.

Abstract: A tunable waveguide filter, formed from two waveguides, has an improved selectivity. The filter is tuned by passing a current through the filter. One of the waveguides is a semi-active waveguide. The increased absorption of charge carriers that occurs when current is injected into the semi-active waveguide is compensated by gain enhancement in the waveguide, because the material used for the semi-active waveguide is selected to provide an appropriate amount of gain. Therefore, the gain compensates for the losses that arise from free carrier absorption when the tuning current is applied to the filter.

Abstract: An approach for compensating for losses in a tunable laser filter comprising includes providing a tunable waveguide material and an amplifying material that have different compositions. The tuning material and the amplifying material are placed parallel to one another. The amplifying material is disposed so that it covers the tuning material at discrete locations. Carriers are injected simultaneously into both materials. The tuning material is spaced from the amplifying material at an average distance that is greater than the charge carrier diffusion length, so as to reduce avoid diffusion of charge carriers from the tuning material into the amplifying material. This prevents the amplifying material draining the charge carriers out of the tuning material, thus enabling the refractive index of the tuning material to be tuned for a desired wavelength effect.