1858results about "Laser output parameters control" patented technology

A method for making a laser driver circuit for burst mode is described. The method includes the following steps: First, a continuous mode laser driver circuit is selected, the chip having a temperature compensation output, a bias current setting input, and a reference current setting input. Next, the temperature compensation signal is converted to a reference current setting signal via a first bias adjustment circuit, and the reference current setting signal is input to the reference current setting input. Then, the bias current setting input is connected to ground via a second bias adjustment circuit. The reference current setting signal automatically adjusts the high level and the low level of the eye diagram of the laser according to the environmental temperature, so that the high level and the low level are kept stable to reduce the bit error rate in transmission.

Optical gain of a nonpolar or semipolar Group-III nitride diode laser is controlled by orienting an axis of light propagation in relation to an optical polarization direction or crystallographic orientation of the diode laser. The axis of light propagation is substantially perpendicular to the mirror facets of the diode laser, and the optical polarization direction is determined by the crystallographic orientation of the diode laser. To maximize optical gain, the axis of light propagation is oriented substantially perpendicular to the optical polarization direction or crystallographic orientation.

An external cavity laser has a mirror-based resonant tunable filter, such as a Fabry Perot tunable filter or Gires-Tournois interferometer tuning element, with the tunable filter being preferably used as a laser cavity mirror. A mirror-based resonant tunable filter is selected in which the spectral response in reflection has an angular dependence. A tilt scheme is used whereby by selecting an appropriate angle between the filter's nominal optical axis and the cavity optical axis, a narrowband peak spectral reflection is provided to the laser cavity. This tunable narrowband spectral reflection from the filter is used to lock and tune the laser output wavelength.

Apparatus and methods for altering one or more spectral, spatial, or temporal characteristics of a light-emitting device are disclosed. Generally, such apparatus may include a volume Bragg grating (VBG) element that receives input light generated by a light-emitting device, conditions one or more characteristics of the input light, and causes the light-emitting device to generate light having the one or more characteristics of the conditioned light.

The present invention discloses a low-cost light source for optical transmission systems and optical networks based on wavelength-division multiplexing (WDM) technology. A light source in accordance with the present invention is implemented by externally injecting a narrow-band incoherent light into a Fabry-Perot laser diode (F-P LD). After injection of narrow-band incoherent light, the output of F-P LD becomes wavelength-selective rather than multi-mode and the output wavelength of F-P LD coincide with the peak wavelength of the injected incoherent light. Multi-channel WDM light sources according to the present invention can be implemented using a single broadband incoherent light source and plurality of F-P LDs. An optical transmission system for upstream signal transmission in an passive optical network using the light source according the present invention is also disclosed.

The present invention provides a continuously tunable external cavity laser (ECL) with a compact form factor and precise tuning to a selected center wavelength of a selected wavelength grid. The ECL may thus be utilized in telecom applications to generate the center wavelengths for any channel on the ITU or other optical grid. The ECL does not require a closed loop feedback. A novel tuning mechanism is disclosed which provides for electrical or mechanical tuning to a known position or electrical parameter, e.g., voltage, current or capacitance, with the required precision in the selected center wavelength arising as a result of a novel arrangement of a grid generator and a channel selector. The grid generator exhibits first pass bands which correspond to the spacing between individual channels of the selected wavelength grid and a finesse which suppresses side band modes of the laser. The channel selector exhibits second pass bands that are wider than the first pass bands. In an embodiment of the invention the second pass bands have a periodicity substantially corresponding with the separation between the shortest wavelength channel and the longest wavelength channel of the selected wavelength grid and a finesse which suppresses channels adjacent to the selected channel. The broad second pass bands of the channel selector reduce the sensitivity of the ECL to tuning variations about the selected channel, thus avoiding the requirement of a closed loop feedback system to control the channel selector.

The present invention provides a continuously-tunable external cavity laser (ECL) with a compact form factor and precise tuning. A novel interference filter which may be used to tune the ECL provides an absence of mode-hopping and reduced feedback from both spurious interference and reflections in the external cavity. A novel tuning mechanism is disclosed which provides for mechanical FM tuning of a wide range ECL tuning elements such as: an interference filter, a diffraction element, and a retroreflector. A novel feedback circuit is disclosed which provides closed loop feedback for selecting output wavelength in a laser.

A novel class of optoelectronic devices incorporate an interference filter. The filter includes at least two optical cavities. Each of the cavities localizes al least one optical mode. The optical modes localized at two cavities are at resonance only at one or at a few discrete selective wavelengths. At resonance, the optical eigenmodes contain one mode having a zero intensity at a node position between the two cavities, where this position shifts as a function of the wavelength. A non-transparent element, which is preferably an absorbing element, a scatterer, or a reflector, is placed between two cavities. At a discrete selective wavelength, when the node of the optical mode matches with the non-transparent element, the filter is transparent for light. At other wavelengths, the filter is not transparent for light. This allows for the construction of various optoelectronic devices showing a strongly wavelength-selective operation.

A wavelength discretely tunable semiconductor laser that addresses wide wavelength tuning range, is mode hopping free, has high output power, has fast wavelength switching time, is wavelength locking free and is relatively simple. Four exemplary embodiments disclosed herein utilize a wavelength discretely tunable semiconductor laser that comprises a discretely tunable filter and laser amplifier. In the first embodiment, the tuning element comprises a pair of cascade Fabry-Perot filters, each having a plurality of characteristic narrow transmission passbands that pass only the cavity mode under the passband. The spacing between the narrow transmission passbands are slightly different in one filter from the other filter so that only one passband from each filter can be overlapped in any given condition over the entire active element gain spectral range, thereby permitting lasing only at a single cavity mode passed by the cascade double filters. One of the two etalon filters can be made with a plurality of transmission passbands predetermined by industry, application and international standards, making this element an intra-cavity wavelength reference and eliminating further wavelength locking needs for the tunable laser. In a second embodiment, one of the two etalons is replaced by a wedge filter. The filter optical path change and thus the transmission passband shift are achieved by translating the wedge filter in a direction perpendicular to the optical axis. In a third embodiment, one of the two etalon filters is replaced by a polarization interference filter. The polarization interference filter consists of an electro-optically-tunable birefringent waveplate, a fixed birefringent waveplate, the laser cavity and T.E. polarization light emitted from the laser diode. In a fourth embodiment, the laser and wavelength tuning structure are integrated on a semiconductor substrate by epitaxy processes.

A tunable laser for providing a laser beam with a selectable wavelength. In one example, the tunable laser includes a gain medium for generating the laser beam; a waveguide for processing the laser beam, the waveguide having liquid crystal material or other electro-optic material disposed therein; an optical path length control element disposed within said waveguide for controlling an effective optical path length of the laser cavity; and a wavelength selective element for controlling the wavelength of the laser beam. The tunable laser may be designed without any moving mechanical parts if desired.

An external cavity laser has a mirror-based resonant tunable filter, such as a Fabry Perot tunable filter or Gires-Tournois interferometer tuning element, with the tunable filter being preferably used as a laser cavity mirror. A mirror-based resonant tunable filter is selected in which the spectral response in reflection has an angular dependence. A tilt scheme is used whereby by selecting an appropriate angle between the filter's nominal optical axis and the cavity optical axis, a narrowband peak spectral reflection is provided to the laser cavity. This tunable narrowband spectral reflection from the filter is used to lock and tune the laser output wavelength.

A swept wavelength light source is provided, the light source includes a semiconductor gain device operable to provide amplification, an optical retarding device, the retarding device having a block of material, a beam path with a well-defined beam path length being defined for light within the block of material produced by the gain device, a wavelength selector, and the gain device, the retarding device and wavelength selector being mutually arranged on the base so that a resonator is established for light portions emitted by the gain device and selected by wavelength selector; this does not exclude the presence of further elements contributing to the resonator, such as additional mirrors (including resonator end mirrors), lenses, polarization selective elements, other passive optical components, etc.; wherein the beam path in the retarding device is a part of a beam path of the resonator.

A controller (320) for controlling various operational parameters of the Laser Module (303). The modulation drive signal (300) causes the circuits in the driver (301) to send a signal to the output (302) so that the laser can send an optical power output (304) proportional to the drive signal (300). The control methods in Laser Controller IC (320) consist of control algorithms embedded in firmware. The Laser Controller IC (320) includes support circuits for control of a laser. Some of the distinguishing features in the present invention are 1) feedback information from the sensors is obtained in a synchronous manner as a snapshot of the laser performance, and 2) algorithms handle the entire set of controls in firmware. The algorithm feature allows for advanced servo controls, which precisely stabilize the laser, can accommodate adaptive controls, and can be leveraged from one laser transmitter design to another.

The invention relates to an optically pumped multilayered modulator having surface-normal geometry. The multilayer structure comprises an absorber section through which an optical signal (401) to be modulated is coupled from an input (401) to an output (400). The multilayer structure further comprises control means for supplying a control signal for controlling the transmission characteristics of the absorber section. The control signal is generated by an in-plane waveguide-type laser integrated monolithically with the saturable absorption region. The in-plane control laser includes waveguide regions (405) and multiple-quantum-well layers (409) used as a gain medium. The laser beam is adapted to travel through the absorber section in order to modulate the transmission characteristics of the absorber section.

An apparatus and method for modifying the spread of a laser beam. The apparatus comprises a laser source operable to generate a laser beam having a flux that exceeds a predetermined value and an optical train operable to modify the beam such that the flux of the beam through a predetermined aperture does not exceed the predetermined value. The optical train may include a focusing lens, a diffractive focusing vortex lens, a beam splitting device, or a two-dimensional diffraction grating.

A monolithic apparatus has a laser optical cavity. The laser optical cavity has a multi-layer structure that includes a first active semiconductor multi-layer and a second semiconductor multi-layer. The second semiconductor multi-layer is located laterally adjacent to the first active semiconductor multi-layer. The first active semiconductor multi-layer includes a sequence of quantum well structures that produce light of a lasing frequency in response to being electrically pumped. The second semiconductor multi-layer includes a sequence of quantum well structures and is configured to both absorb light of the lasing frequency and produce one of parametric light and harmonic light in response to absorbing light of the lasing frequency.

An optical semiconductor device has a structure in which a semiconductor active layer is sandwiched by a p-type semiconductor cladding layer and an n-type semiconductor cladding layer and a p-type contact layer is formed on the p-type semiconductor cladding layer side and an n-type contact layer is formed on the n-type semiconductor cladding layer side, wherein two ferromagnetic layers are formed on the n-type contact layer and two ferromagnetic layers are formed on the p-type contact layer. Magnetization directions of a pair of ferromagnetic layers vertically opposed to each other are set to be parallel to each other, and the magnetization directions of adjacent ferromagnetic layers are inverted to each other.

A method and system for adaptively controlling a laser-based material processing process are provided. The system includes sensing equipment to measure a process variable or condition of at least one of a laser-based material processing system and a workpiece processed by the material processing system and to provide a corresponding measurement signal. The control system also includes a signal processor for processing the measurement signal to obtain a processed signal which initiates, at least semi-automatically, an action associated with at least one of the material processing system and the workpiece. A method and system for at least semi-automatically qualifying a laser-based material processing system which delivers laser energy to locations on or adjacent a plurality of microstructures formed on a workpiece to at least partially process the microstructures are also provided.

A tunable optical system with hybrid integrated semiconductor laser is provided. The optical system includes a silicon-on-insulator (SOI) substrate; a first optical waveguide tunable comb filter formed at the first side of the SOI substrate; a second optical waveguide tunable comb filter with detuned filter response formed at the first side of the SOI substrate; an etched laser pit at the first side of the SOI substrate; a plurality of spacers formed on the bottom surface of the laser pit near the plane of the first side of the SOI substrate; a plurality of bumping pads formed on the bottom surface of the laser pit near the plane of the first side of the SOI substrate; and a laser chip flip-chip bonded at the first side of the SOI substrate supported by the spacers. Heating sections may be provided on the filters to tune the filters.

An active gain region sandwiched between a 100% reflective bottom Bragg mirror and an intermediate partially reflecting Bragg mirror is formed on a lower surface of a supporting substrate, to thereby provide the first (“active”) resonator cavity of a high power coupled cavity surface emitting laser device. The bottom mirror is preferably in direct thermal contact with an external heat sink for maximum heat removal effectiveness. The reflectivity of the intermediate mirror is kept low enough so that laser oscillation within the active gain region will not occur. The substrate is entirely outside the active cavity but is contained within a second (“passive”) resonator cavity defined by the intermediate mirror and a partially reflecting output mirror, where it is subjected to only a fraction of the light intensity that is circulating in the gain region. The active gain region is preferably electrically excited, with a circular bottom electrode formed by an oxide current aperture between the bottom mirror and the heat sink, and with an annular top electrode formed on an upper surface of the substrate.

In a laser source, a first optical waveguide includes a gain medium, and a second optical waveguide includes a phase tuner which adjusts a phase value of the phase tuner to specify the wavelength of the laser source. Furthermore, the laser source includes a first ring resonator and a second ring resonator, which, respectively, are optically coupled to the first optical waveguide and the second optical waveguide at opposite ends of the laser source. In particular, coupling wavelengths of the first and second ring resonators may match a wavelength of the optical signal, thereby defining an optical resonance cavity in the laser source and selecting a laser mode of the laser source which is associated with the wavelength. Additionally, the laser source includes an optical amplifier that receives and amplifies the optical signal output from the optical resonance cavity.

The present invention discloses a low-cost light source for optical transmission systems and optical networks based on wavelength-division multiplexing (WDM) technology. A light source in accordance with the present invention is implemented by externally injecting a narrow-band incoherent light into a Fabry-Perot laser diode (F-P LD). After injection of narrow-band incoherent light, the output of F-P LD becomes wavelength-selective rather than multi-mode and the output wavelength of F-P LD coincide with the peak wavelength of the injected incoherent light.Multi-channel WDM light sources according to the present invention can be implemented using a single broadband incoherent light source and plurality of F-P LDs. An optical transmission system for upstream signal transmission in an passive optical network using the light source according the present invention is also disclosed.

Monolithic integrated vertical-cavity surface-emitting laser devices are disclosed including an edge-emitting semiconductor pump laser (PL), an optically-pumped vertical-cavity surface-emitting laser (VCSEL), and a means for deflecting and shaping the output beam of the pump laser to optically excite the VCSEL. The optically-pumped VCSEL structure may be adapted to include a resonant cavity with multiple fixed wavelengths, or a resonance cavity whose wavelength is continuously tunable. Wafer level manufacturing techniques are also disclosed.

A variable wavelength laser light source to improve the resolution of the outgoing light and output only pure laser light without the natural emitted light has an optical amplification element (laser) 11, a first optical reflector 12 at one end surface 11a of the optical amplification element 11, and a wavelength selection element (diffraction grating) 13 at the other end surface 11b of the optical amplification element 11 which selects and outputs the desired wavelength light emitted by the optical amplification element 11. A second optical reflector 14 receives the outgoing light from the wavelength selection element 13 to form the optical resonator with the first optical reflector 12. A first rotating mechanism 15 rotates the second optical reflector 14 around its axis, and a second rotating mechanism 16 connected to the first rotating mechanism 15 rotates the second optical reflector 14 around a second axis 16a remote from the second optical reflector 14 by rotating the first rotating mechanism.

An optical lasing device, comprising (i) a lasing medium disposed in a lasing cavity, (ii) an etalon disposed within the lasing cavity, and (iii) an electrically tuned filter device, such as a grating waveguide structure device. The lasing device also comprises a detector for determining the lasing power of the lasing device, and a controllable phase shift capability, and the device is preferably locked to a maximum of the lasing power by adjusting the phase, thereby achieving locking to a wavelength predetermined by the etalon, aligned to an ITU grid wavelength. Adjusting the phase shift to achieve the maximum of the lasing power is preferably performed using a closed loop system. Furthermore, adjusting of the phase shift to achieve a maximum of the lasing power is preferably also operative to wave lock the lasing device to a peak wavelength of the etalon.

In practical WDM systems, the maximum SMSR for each channel does not necessarily occur where dPout / dItune=0. In fact, for most channels the maximum SMSR occurs at values of tuning current where this first derivative in not zero. In accordance with one aspect of the invention, a wavelength stabilized optical transmitter includes a DBR laser and a feedback loop for controlling the center wavelength of the laser, characterized in that the transmitter also includes a memory in which are stored the non-zero values of dPout / dItune where the SMSR is a maximum for each of a multiplicity of different channel wavelengths and further includes a controller responsive to the stored values for delivering to the laser a level of tuning current that maximizes the SMSR for a particular channel wavelength.

A surface emitting laser (SEL) with an integrated absorber. A lower mirror and an output coupler define a laser cavity of the SEL. A monolithic gain structure positioned in the laser cavity includes a gain region and an absorber, wherein a saturation fluence of the absorber is less than a saturation fluence of the gain region.

A dual-port broadband light source with independently controllable output powers includes a broadband light source having a first gain medium pumped by an input pump light in order to output a first amplified spontaneous emission through both ends thereof. A second gain medium pumped by another input pump light in order to output a second amplified spontaneous emission through both ends thereof. A reflector disposed between the opposite ends of the first and second gain mediums to reflect the input first and second amplified spontaneous emissions. The first and second amplified spontaneous emissions output from the first and second gain mediums are then output to the outside through first and second output terminals.

An apparatus comprising a laser transmitter having a first side and a second side, a filter coupled to the first side, a detector coupled to the second side, and a temperature controller coupled to the laser transmitter and the detector. Also disclosed is an apparatus comprising at least one processor configured to implement a method comprising receiving a photocurrent of a backward light from a laser, determining a wavelength shift offset between a wavelength of the output light and a filter transmission peak, and adjusting a temperature of the laser to substantially reduce the wavelength shift and align the wavelength of the output light with the filter transmission peak.