Abstract: A high power laser source comprises a bar of laser diodes having a first coefficient of thermal expansion CTEbar on a submount having a second coefficient CTEsub and a cooler having a third coefficient CTEcool. The submount/cooler assembly shows an effective fourth coefficient CTEeff differing from CTEbar. This difference leads to a deformation of the crystal lattice of the lasers' active regions by mechanical stress. CTEeff is selected to be either lower than both CTEbar and CTEcool or is selected to be between CTEbar and CTEcool. The submount may either comprise layers of materials having different CTEs, e.g., a Cu layer of 10-40 ?m thickness and a Mo layer of 100-400 ?m thickness, or a single material with a varying CTEsub. Both result in a CTEsub varying across the submount's thickness.

Abstract: There is described an optoelectronic device having a housing and a chip housed by the housing. At least a portion of the chip protrudes through an aperture in a wall of the housing. There is further provided an optoelectronic module comprising such an optoelectronic device and electronic control circuitry adapted to control the operation of the optoelectronic device.

Abstract: A multi-port wavelength selective switch includes a one dimensional array of input and output ports. The multi-port wavelength selective switch further includes a wavelength dispersive element configured to receive input optical signals from the input ports, and to disperse wavelength components thereof. Additionally, the multi-port wavelength selective switch includes an array of beam steering devices. Each beam steering device is controllable to a position at which the beam steering device directs a wavelength component of an input optical signal received through a first input port to an output port and directs the same wavelength component of an input optical signal received through a second input port away from all of the output ports.

Abstract: There is described an optical modulation system for transmitting modulated optical light. The system comprises an electro-optic modulator having at least two arms through which light is transmitted and an imbalance electrode located on at least one arm. A current source is configured to inject current into the imbalance electrode for modifying the phase of light passing through the arm. A dither generator is configured to modulate the injected current, or bias voltage applied to at least one of the arms, with a dither signal. A phase sensitive detector is configured to detect an error in the phase of light emitted by the modulator. An operating point controller is configured to monitor the detected phase error and adjust the current injected into the imbalance arm so as to compensate for the detected error and thereby control an operating point of the modulator.

Abstract: A vertical cavity surface emitting laser (VCSEL) (100) has a substrate (104), on which are disposed first and second distributed Bragg reflectors (DBRs) (106, 112), each DBR comprising a stack of layers of alternating refractive index, an active layer (108) disposed between the DBRs, and an aperture layer (110) disposed either between the DBRs or within one of the DBRs. The aperture layer (110) has a border (116) having an internal boundary with a plurality of indented portions defining one or more apertures. Such a VCSEL is easily manufacturable and provides a narrow bandwidth output, as well as mitigating at least some of the problems of prior art VCSELs. Mesa (102) may be etched to be non-circular and subsequent selective oxidation of aperture layer (110) results in a non-circular current confinement aperture (114) promoting higher-order lateral modes (LP21).

Abstract: A high power laser source comprises a bar of laser diodes having a first coefficient of thermal expansion CTEbar on a submount having a second coefficient CTEsub and a cooler having a third coefficient CTEcool. The submount/cooler assembly shows an effective fourth coefficient CTEeff differing from CTEbar. This difference leads to a deformation of the crystal lattice of the lasers' active regions by mechanical stress. CTEeff is selected to be either lower than both CTEbar and CTEcool or is selected to be between CTEbar and CTEcool. The submount may either comprise layers of materials having different CTEs, e.g., a Cu layer of 10-40 ?m thickness and a Mo layer of 100-400 ?m thickness, or a single material with a varying CTEsub. Both result in a CTEsub varying across the submount's thickness.

Abstract: A metallization on a semiconductor substrate is disclosed in the form of a laminate comprising a plurality of layers of a “conducting” metallization for providing electrical conductivity, interspersed with a plurality of layers of another metallization. By providing many layers the thickness of each individual layer can be reduced. Reduction in thickness of each layer leads to a reduction in grain size and a consequent reduction in creep over the lifetime of a device.

Abstract: The present invention provides a method and apparatus for phase aligning two optical signals within an optical transmitter to each other (and, in some embodiments, to a pulse carved optical signal) using integrated complimentary taps and a dither signal. The phase of a first signal may be intentionally offset relative to the phase of a second signal. Based on the offset, a correction factor may be calculated. The correction factor may be used to shift the phase of the first signal and/or the second signal in order to generally align the signals. This procedure may be automatically performed in a feedback loop to cause the signals to come into alignment and maintain the alignment of the signals during operation of the transmitter.

Abstract: The present invention concerns tunable distributed Bragg reflector (DBR) semiconductor lasers, in particular a DBR laser with a branched optical waveguide 5 within which a plurality of differently shaped lasing cavities may be formed, and a method of operation of such a laser. The laser may comprise a phase control section (418), gain section (420, 422), a sampled grating DBR (412) giving a comb-line spectrum and two tunable, chirped DBRs (414, 416) for broadband frequency training and a coupling section (410).

Abstract: Described are Gain Flattening Filters (GFFs) implemented using mechanical translating assemblies to move selected thin film Gain Attenuating Filters (GAFs), and combinations of selected GAFs, into or out of the output path from an optical amplifier. The GAFs may be used singly, or in combinations that synthesize many target filter characteristics. The GFF is primarily adapted for WDM systems operating with a wavelength range of approximately 1520 nm to 1620 nm. Several embodiments are shown for effectively combining different GAFs to provide multiple GFF curves.

Abstract: A delay line interferometer is configured with a liquid-crystal (LC) tuning element as a phase modulator for demodulating a phase-modulated input signal. The LC tuning element allows for quickly tuning the phase difference between two optical signals separated from the phase-modulated input signal, so that the two optical signals can be coherently recombined to interfere with each other and produce one or more intensity-modulated optical signals. In some embodiments, the LC tuning element is configured to reduce polarization-dependent frequency shift without the use of additional high-precision optical elements and/or coatings.

Abstract: A method of adjusting a power density in a laser device including a VCSEL array providing an increased power density at a high wall-plug efficiency in that the lateral design parameters are appropriately selected on the basis of a relationship that has been established for a specified vertical design, a corresponding process technology and specified operating conditions. Thus, the total output power, the power density, and the efficiency may be optimized independently from other design criteria and application requirements by tuning only the lateral size of the individual VCSEL elements and the pitch of nearest neighbors of the elements within the array. Hence, for a lateral size of less than 30 ?m and a pitch of less than 80 ?m, a highly efficient VCSEL array can be provided with a high power density, thereby optimizing manufacturing costs for the output power per chip area.

Abstract: A method of transmitting a plurality n data streams comprises modulating an optical carrier using differential M-ary phase shift key (DMPSK) signalling in which M=2n. Advantageously the method comprises using differential quaternary phase shift keying in which n=2. A particular advantage of the method of the present invention is that since the data is differentially encoded in the form of phase changes rather than absolute phase values this enables the modulated optical carrier to be demodulated using direct detection without requiring a phase-locked local optical oscillator. The invention is particularly applicable to WDM communication systems.

Abstract: A method of transmitting a plurality n data streams comprises modulating an optical carrier using differential M-ary phase shift key (DMPSK) signaling in which M=2n. Advantageously the method comprises using differential quaternary phase shift keying in which n=2. A particular advantage of the method of the present invention is that since the data is differentially encoded in the form of phase changes rather than absolute phase values this enables the modulated optical carrier to be demodulated using direct detection without requiring a phase-locked local optical oscillator. The invention is particularly applicable to WDM communication systems.

Abstract: A laser light source comprises a semiconductor laser adapted for pulsed operation, a partially transmitting wavelength selective light reflector. The semiconductor laser comprises a front facet and a back facet. The front facet and the back facet define an internal laser cavity. The internal laser cavity comprises a laser active medium. The partially transmitting wavelength selective light reflector has a peak reflectivity within a gain bandwidth of said laser active medium. The wavelength selective light reflector and the back facet define an external laser cavity. A roundtrip time of light in the external laser cavity is about 20 nanoseconds or less. A full width half maximum bandwidth of the wavelength selective light reflector is adapted to accommodate at least 12 longitudinal modes of the internal laser cavity and at least 250 longitudinal modes of the external laser cavity.

Abstract: A Bragg reflector grating comprises a plurality of chirped grating sections (65-72), in which at least a first chirped grating section and a second chirped grating section have differing ranges of grating pitches. The combined range of grating pitches provided by the first and second chirped grating sections includes at least one discontinuity, such that the first and second chirped grating sections have one or more grating pitches in common and/or there are one or more ranges of grating pitches within the combined range of grating pitches that are absent.

Abstract: Semiconductor laser diodes, particularly broad area single emitter (BASE) laser diodes of high light output power, are commonly used in opto-electronics. Light output power and stability of such laser diodes are of crucial interest and any degradation during normal use is a significant disadvantage. The present invention concerns an improved design of such laser diodes, the improvement in particular significantly minimizing or avoiding degradation of such laser diodes at very high light output powers by controlling the current flow in the laser diode in a defined way. The minimization or avoidance of (front) end section degradation of such laser diodes significantly increases long-term stability compared to prior art designs. This is achieved by controlling the carrier injection into the laser diode in the vicinity of its facets in such a way that abrupt injection current peaks are avoided.

Abstract: The invention provides an optoelectronic device combining a vertical cavity surface emitting laser (VCSEL) and a photodetector for monitoring the output power of the vertical cavity surface emitting laser. To improve the signal-to-noise ratio of the photodetector, a light deflector is interposed between the photodetector and the VCSEL.

Abstract: A vertical cavity surface emitting laser (VCSEL) (100) has a substrate (104), on which are disposed first and second distributed Bragg reflectors (DBRs) (106, 112), each DBR comprising a stack of layers of alternating refractive index, an active layer (108) disposed between the DBRs, and an aperture layer (110) disposed either between the DBRs or within one of the DBRs. The aperture layer (110) has a border (116) having an internal boundary with a plurality of indented portions defining one or more apertures. Such a VCSEL is easily manufacturable and provides a narrow bandwidth output, as well as mitigating at least some of the problems of prior art VCSELs. Mesa (102) may be etched to be non-circular and subsequent selective oxidation of aperture layer (110) results in a non-circular current confinement aperture (114) promoting higher-order lateral modes (LP21).

Abstract: A modulator arrangement for modulating an optical signal using a differential quadrature phase shift key for use in an optical wavelength division multiplex (WDM) optical communications system comprising a laser for producing an optical signal of a selected wavelength, which signal is split by a splitter (4), each part of said split signal being applied to a respective phase modulator (6, 8). The phase modulators (6, 8) are adapted to modulate the phase of the signal in dependence on a respective drive voltage and the phase of the output of at least one modulator is shiftable. The split signals are recombined by an optical recombiner (12) to form an optical phase shift key output. The arrangement further comprises a phase modulator (20) adapted to chirp the optical phase shift key output.