Abstract: A wavelength filter is disposed between a laser diode and a photodiode that receives the rear-facet output light of the laser diode. Either a part on one side of an input or an output surface of the wavelength filter is bounded to a protrusion provided in a metal holder for holding the wavelength filter. As a result, a support structure is obtained that does not bring a damage on the wavelength filter caused by degradation of optical characteristics or temperature variation of the wavelength filter when support-fixing a wavelength filter having a complex refractive index crystal.

Abstract: A laser oscillation apparatus includes a wavelength change unit for driving a wavelength selection element in a band-narrowing module and changing the oscillation wavelength of a laser beam to a target value, and an oscillation history memory for storing the oscillation state of the laser beam as an oscillation history. The wavelength change unit drives the wavelength selection element on the basis of the oscillation history and changes the oscillation wavelength of the laser beam to the target value.

Abstract: A grating is provided in an optical fiber for adjusting the wavelength of an output light from the optical resonator which consists mainly of a semiconductor light emitting device and the optical fiber to be slightly shorter than a wavelength range of an input light where the wavelength range of an input light can be converted by a wavelength conversion device. As the grating is adjustably expanded with a knob control being turned, the wavelength of the output light from the optical resonator is modified to be matched with the wavelength range of the input light where the wavelength of the input light can be converted by the wavelength conversion device.

Abstract: A laser transmitter device includes a laser light source, first and second optical elements, and first and second detection elements. The first optical element has a first optical characteristic with wavelength dependency, whose light transmissivity or reflectivity shows a monotone increase or decrease within a wavelength range over channels. The second optical element has a second optical characteristic with wavelength dependency, whose transmissivity or reflectivity changes in a cycle corresponding to intervals of the channels or two times the intervals. The first detection element detects an intensity of light emitted from the laser light source and coming via the first optical element, and generates a first electric signal reflecting the first optical characteristic. The second detection element detects an intensity of light emitted from the laser light source and coming via the second optical element, and generates a second electric signal reflecting the second optical characteristic.

Abstract: Provided is a wavelength tunable light source that can electrically tune wavelengths by monolithically integrating an optical amplifier, a beam steering unit, and a concave diffraction grating on a single substrate. A beam is deflected by the beam steering unit when an electrical signal is applied to two electrodes installed in the beam steering unit to be incident on the diffraction grating, and then diffracted by the diffraction grating according to the incidence angle such that part of the beam with a specific wavelength is reflected, thereby achieving wavelength tuning. Since the wavelength tuning is achieved electrically, the wavelength tunable light source is structurally stable and has a rapid wavelength tuning rate.

Abstract: There is provided a phase control portion for controlling phase of a laser beam resonated in a resonator based on detected results by two optical detectors. The phase control portion adjusts the longitudinal mode positions by a feedback control so that a ratio of intensities detected by the two optical detectors comes to a predetermined reference value. To one of the optical detectors, part of a laser beam outputted from the resonator is irradiated as it is, whereas, to the other one of the optical detectors, part of the laser beam outputted from the resonator is irradiated after passing through an etalon. An FSR of the etalon is a double of that of another etalon in the resonator.

Abstract: An open-path optical communication system has either optical or laser sources and communicates between the source and a detector. In a first embodiment, the laser source includes a gas cell in the laser cavity to regulate laser wavelengths based on the minimum absorption between spectral lines of the gas in the cell. The laser is tuned close to a minimum absorption wavelength and the minimum absorption line locks the laser wavelength to the minimum position. In a second embodiment, the strong absorption lines of a gas in a gas cell positioned at a receiver site are used to provide channel isolation of the receiver. In a third embodiment, an atmospheric gas provides the channel isolation. In the fourth embodiment, individual wavelength channels are positioned between the absorption lines of atmospheric or non-atmospheric gases to prevent cross-talk between adjacent channels.

Abstract: 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.

Abstract: This invention provides an optical transmitter in which reduced power consumption is achieved by, when a signal generator needs data transmission, driving a laser emitting device to perform emission. An optical transmitter includes a receiver, a laser driving circuit, a light emitting unit constituted by a plurality of laser emitting devices, and an EDID memory. The receiver and the laser driving circuit are supplied with power from a dedicated external power supply through a power-supply line, and the power-supply line is provided with a switch. The contact of the switch is controlled to open and close based on a power-supply voltage supplied from the DDC controller to the EDID memory.

Abstract: An optical module according to the present invention includes: a light-emitting device that outputs laser light; a temperature adjustment unit that adjusts a wavelength of the laser light outputted from the light-emitting device so as to be locked at a predetermined wavelength; a wavelength monitor unit that receives laser light outputted from the light-emitting device by allowing the laser light to pass through an optical filter provided above the temperature adjustment unit and monitors the wavelength thereof; a package for sealing the light-emitting device, the temperature adjustment unit, and the wavelength monitor unit into the inside thereof; and a package temperature detection unit for detecting a temperature of the package, in which the temperature adjustment unit adjusts an oscillation wavelength of the laser light outputted from the light-emitting device to the predetermined lock wavelength based on a signal outputted from the wavelength monitor unit, and a signal from the package temperature detect

Abstract: A compact single frequency, single-mode 2 ?m fiber laser with narrow linewidth, <100 kHz and preferably <100 kHz, is formed with a low phonon energy glass doped with triply ionized rare-earth thulium and/or holmium oxide and fiber gratings formed in sections of passive silica fiber and fused thereto. Formation of the gratings in passive silica fiber both facilitates splicing to other optical components and reduces noise thus improving linewidth. An increased doping concentration of 0.5 to 15 wt. % for thulium, holmium or mixtures thereof produces adequate gain, hence output power levels for fiber lengths less than 5 cm and preferably less than 3 cm to enable single-frequency operation.

Abstract: An optical module comprises a splitting element that splits light outputted from a light source; a first monitoring means that detects the intensity of light split by the splitting element; a polarization control means that switches the polarization state of light outputted from the splitting element based on a control signal; a filter means that accepts light outputted by the polarization control means as input, and whereof the characteristic changes depending on the polarization state of the input light; and a second monitoring means that detects the intensity of the light transmitted through the filter means.

Abstract: The influences on transmission quality caused by chirp and self-phase modulation are at least largely corrected by way of an optimally set operating point of the modulator (2). Suitable criteria are obtained in control loops in order to maintain the optimal setting.

Abstract: A high-speed optical transmitter having an optical modulator and a driver circuit while maintaining optical modulator performance. The high-speed optical transmitter comprises the optical modulator which modulates and outputs an input light in accordance with an applied voltage, and a driver circuit which outputs the applied voltage into the optical modulator and has an emitter follower circuit at an output stage thereof.

Abstract: An optical transmitter includes an external cavity laser array formed in a PLC, a trench-based detector array and an AWG. The external cavity laser is formed using an array of substantially similar laser gain blocks and an array of gratings formed in waveguides connected to the gain blocks. Each grating defines the output wavelength for its corresponding external cavity laser. Each detector of the detector array includes a coupler to cause a portion of a corresponding laser output signal of the laser array to propagate through a first sidewall of a trench and reflect off a second sidewall of the trench to a photodetector. In one embodiment, the photodetector outputs a signal indicative of the power level of the reflected signal, which a controller uses to control the laser array to equalize the power of the laser output signals.

Abstract: A wavelength-tunable laser apparatus includes a semiconductor substrate, a Fabry-Perot (FP) laser, and a planar lightwave circuit. The FP laser is formed on the semiconductor substrate at one side thereof, and has a plurality of longitudinal modes. The planar lightwave circuit is formed on the semiconductor substrate at the other side thereof, and includes a waveguide and a clad surrounding the waveguide with a grating carved into a portion of the waveguide. Light outputted from the FP laser is coupled to the waveguide, the grating reflects a plurality of light beams of different wavelengths, and the FP laser is wavelength-locked by one of the light beams reflected from the grating.

Abstract: An optical monitoring circuit includes a photoelectric device such as a photo-detector that produces a signal in response to incident light thereon corresponding to a characteristic of the incident light such as intensity, or wavelength. A light source is disposed within the circuit for emitting a beam of light, a portion of which is to be incident upon the photoelectric device. The photoelectric device when reversed biased provides an output electrical signal from which the intensity of light from the light source impinging thereon can be determined. The photoelectric device when forward biased provides an output signal from which the temperature of the photoelectric device can be determined. A method and circuit are disclosed for calibrating out the unwanted effect of light from the light source affecting accuracy of the determined temperature derived from the output signal when the photoelectric device is forward biased.

Abstract: A method of operating an array of integrated laser sources formed as an integrated array on a single substrate in a photonic integrated circuit (PIC) where the laser sources are designed for operation at different targeted emission wavelengths which, in toto, at least approximate a grid of spatial emission wavelengths. A first wavelength tuning element is associated with each laser source and is adjusted over time so that each laser source maintains its targeted emission wavelength. As an alternative, the drive current to each laser source may be initially set so that each laser source operates at its targeted emission wavelength. Thereafter, adjustments to retune the laser sources to their targeted emission wavelengths are accomplished by the first wavelength tuning elements. The outputs of the laser sources may be combined via an optical combiner to produce a single combined output from the PIC.

Abstract: A method and apparatus for measuring a wavelength-related characteristic of a radiation source is provided. Two beams travel through substantially identical filters at different angles, which produces two different output signals that behave similarly with respect to power and/or temperature variations. In various embodiments, the two beams are filtered through two portions of a single filter. A diffraction grating may be mounted to the filter to split incident radiation into first and second beams. The beams thus travel through the filter at different angles, to produce two output signals that can be combined to compensate for common-mode errors as well as power variations. Extremely small size and high-resolution may be achieved. Single or multiple detectors may also be used.

Abstract: A method of operating an array of laser sources integrated as an array in a single monolithic chip where the steps include designing the laser sources to have different target emission wavelengths so that together they form a spectral emission wavelength grid, coupling outputs from the laser sources to an array of gain/loss elements also integrated on the single monolithic chip, one each receiving the output from a respective laser source; and adjusting the outputs with the gain/loss elements so that the power levels across the laser source array are substantially uniform.

Abstract: A method and apparatus operates an array of laser sources as an integrated array on a single substrate or as integrated in an optical transmitter photonic integrated circuit (TxPIC) maintaining the emission wavelengths of such integrated laser sources at their targeted emission wavelengths or at least to more approximate their desired respective emission wavelengths. Wavelength changing elements may accompany the laser sources to bring about the change in their operational or emission wavelength to be corrected to or toward the desired or target emission wavelength. The wavelength changing elements may be comprise of temperature changing elements, current and voltage changing elements or bandgap changing elements.

Abstract: Method and apparatus for stabilizing an optical carrier frequency of a generated carrier signal with respect to a target carrier frequency. The apparatus includes a multi-channel optical filter for filtering the generated carrier signal, thereby to provide a first filtered optical signal and a second filtered optical signal, each filtered optical signal including the portion of the generated carrier signal contained in a pass band surrounding a respective channel center frequency. The apparatus also includes a detection unit for determining an indication of a characteristic of the target carrier frequency in the first and second filtered optical signals, as well as a control unit for adjusting the optical carrier frequency of the generated carrier signal as a function of the difference in the indication of the characteristic of the target carrier frequency in the first and second filtered optical signals.

Abstract: A monolithic transmitter photonic integrated circuit (TxPIC) chip comprises an array of modulated sources formed on the PIC chip and having different operating wavelengths according to a standardized wavelength grid and providing signal outputs of different wavelengths. Pluralities of wavelength tuning elements are integrated on the chip, one associated with each of the modulated sources. An optical combiner is formed on the PIC chip and the signal outputs of the modulated sources are optically coupled to one or more inputs of the optical combiner and provided as a combined channel signal output from the combiner. The wavelength tuning elements provide for tuning the operating wavelength of the respective modulated sources to be approximate or to be chirped to the standardized wavelength grid. The wavelength tuning elements are temperature changing elements, current and voltage changing elements or bandgap changing elements.

Abstract: A method of tuning optical components integrated on a monolithic chip, such as an optical transmitter photonic integrated circuit (TxPIC), is disclosed where a group of first optical components are each fabricated to have an operating wavelength approximating a wavelength on a standardized or predetermined wavelength grid and are each included with a local wavelength tuning component also integrated in the chip. Each of the first optical components is wavelength tuned through their local wavelength tuning component to achieve a closer wavelength response that approximates their wavelength on the wavelength grid.

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 and method of controlling an optical signal includes superimposing at least one optical reference signal and the optical signal to obtain at least one interference signal having an actual beat frequency, and pre-selecting one or more of the at least one interference signals using a predetermined bandwidth and a filter characteristic that is asymmetric with respect to an actual frequency of the optical signal, to determine a position of the optical signal relative to the at least one optical reference signal.

Abstract: A wavelength locker comprising a semiconductor or air gap etalon is used to monitor and maintain the output wavelength of a coherent radiation source. Said etalon may be fabricated from a commercially available silicon wafer, with individual regions of the wafer, each functioning as a separate etalon, etched or otherwise processed to produce different thicknesses. Illumination by the coherent radiation source generated transmitted signal intensities that are detected and processed to determine the output wavelength of the coherent radiation source. A wavelength tuner is then used to maintain or vary the output wavelength based on continuous measurements of etalon signal intensity.

Abstract: Systems, apparatuses, and methods for driving an optical source with a current source. The optical source driver has a primary control loop having a DC—DC converter and an operational amplifier, wherein the DC—DC converter has a power input, a power output connected to the input of the optical source, and a control input, and wherein the operational amplifier has a first input connected between the optical source and the current source, a second input, and an output connected to the control input of the DC—DC converter, for controlling the output of the DC—DC converter in response to a control signal at the second input.

Abstract: A quartz etalon having light reflecting film layers on the Z-cut surfaces and electrode layers on the X-cut surfaces are axially supported in the X-cut surface electrode layers. A dither signal is applied to this axially supported portion to resonate the etalon. In this state, laser-beam is transmitted through the Z-cut surfaces of the etalon. The transmitted light is photo-electrically converted and subjected to synchronous detection by a dither signal. On the basis of an error signal obtained by the detection output, the oscillation wavelength of the semiconductor laser is controlled. Since the etalon resonates as its axially supported central portion functions as a node, the mechanical loss is small, and the Q value upon mechanical resonance is extremely large. This makes the synchronous detection output about 100 times as large as the conventional value. This increases the signal-to-noise ratio of the photoelectric conversion signal, and increases the wavelength accuracy.

Abstract: A partially mirrored beam tap for use in wavelength and power monitoring, wherein the partially mirrored beam tap splits off at least two beams from an elliptical Gaussian output beam, wherein a first split-off beam is transmitted to an etalon and one or more first photo-detectors for wavelength monitoring, while a second split-off beam is transmitted to one or more second photo-detectors as a reference and for power monitoring. The partially mirrored beam tap splits off the first and second split-off beams from upper and lower tails of the output beam, wherein upper and lower portions of the partially mirrored beam tap comprise mirrored surfaces that reflect tails of the output beam and a center portion of the partially mirrored beam tap comprises a clear rectangular aperture that passes the output beam.

Abstract: A C- and/or L-band booster optical amplifier is utilized in an optical communication system at the output of one or more semiconductor transmitter photonic integrated circuit (TxPIC) chips or the optical combined outputs of multiple semiconductor transmitter photonic integrated circuit (TxPIC) chips employed in an optical communication module, the deployment of integrated semiconductor optical amplifiers (SOAs) on the TxPIC chips can be eliminated. This would reduce both the complexity in designing and fabricating these chips as well as reducing the power consumption of the TxPIC chips. The deployment of such a Tx booster optical amplifier would also take into consideration the nonlinear effects of difficult high loss single mode fiber (SMF) or other fiber type links by allowing a higher power per channel to be achieved compared to the case where channel amplification is attempted solely on the TxPIC chip.

Abstract: An excited state atomic line filter. The present invention solves the problem of lack of ground state resonant lines in at wavelengths substantially longer than those of visible light. Atomic line filters of the Faraday or Voigt crossed polarizer type are provided in which alkali metal atomic vapor in a vapor cell is excited with a pump beam to an intermediate excited state where a resonant absorption line, at a desired wavelength, is available. A magnetic field is applied to the cell producing a polarization rotation for polarized light at wavelengths near the resonant absorption lines. Thus all light is blocked by the cross polarizers except light near one of the spaced apart resonant lines. However, the polarization of light at certain wavelengths near the resonant is rotated in the cell and therefore passes through the output polarizer.

Abstract: A method for compensating for wavelength drift in a fiber-optic laser transmitter includes 1) controlling a temperature within the optoelectronic assembly at a defined level; 2) driving the optoelectronic assembly to emit light, wherein the emitted light has a wavelength that is within a channel of operation, the channel of operation including a range of wavelengths centered around a channel center wavelength; 3) accessing from memory within the optoelectronic assembly a control value associated with the temperature of the optoelectronic assembly at defined points within an operational lifetime of the optoelectronic assembly; and 4) recalculating the defined level by reference to the control value, whereby a wavelength of the optoelectronic assembly is maintained within the channel of operation despite an expected drift of wavelength.

Abstract: A relatively constant average optical power is provided over a user-defined range of temperatures by detecting the temperature, and adjusting the bias currents input to the laser diodes in an array of laser diodes based on the temperature and the channel loss of the channel connected to each diode.

Abstract: Bright and dark field imaging operations in an optical inspection system occur along substantially the same optical path using the same light source by producing either a circular or an annular laser beam. Multiple beam splitting is achieved through the use of a diffractive optical element having uniform diffraction efficiency. A confocal arrangement for bright field and dark field imaging can be applied with multiple beam scanning for suppressing the signal from under-layers. A scan direction not perpendicular to the direction of movement of a target provides for improved die-to-die comparisons.

Abstract: A method and system for dispersion control of electromagnetic signals in communication networks by narrowing the widths of electromagnetic pulses such as modulated laser signals. Generally, in the preferred embodiment, the present invention utilizes a feedback loop based on dither frequency modulation which dynamically adjusts the alignment of the laser center frequency with the filter passband. In this way, there is an acceptable tradeoff between optical power and pulse width, so a higher power laser can be used to generate a narrower optical pulse. The narrower pulses then travel farther in the fiber link before reaching their dispersion limit. It is believed that, by using this invention, existing link distance could be doubled, while re-using existing installed singlemode fiber. The systems employing the feedback loop may be information carrying or control systems.

Abstract: In a stabilized laser system, a an output signal is to be generated having a desired central wavelength. At least one laser, which, while emitting light and having a preselected portion thereof fed back thereto, causes the output signal of the laser to be shifted in wavelength in a first direction which is spaced apart from the center wavelength of the fed back signal. A feedback generating arrangement processes a first portion of the output signal from each laser and generates a feedback signal having a spectral response peaking at a wavelength shifted in an opposite direction to the first direction generated by each laser. The feedback signal each laser to provide an output signal at the output of the stabilized laser system having a spectral response that peaks essentially at the desired wavelength.

Abstract: The method and system operate to maintain a widely tunable laser (WTL) at a selected transmission wavelength. To lock the WTL to an ITU grid line, a portion of the output beam from the WTL is routed through the etalon to split the beam into a transmission line for detection by an etalon fringe detector. Another portion of the beam is routed directly to a laser wavelength detector to determine the power of the beam. A wavelength-locking controller compares signals from the two detectors and adjusts the temperature of the etalon to align the wavelength of one of the transmission lines of the etalon with the wavelength of the output beam, then controls the WTL in a feedback loop to lock the laser to the etalon line. The wavelength-locking controller thereafter monitors the temperature of the etalon and keeps the temperature constant to prevent any wavelength drift attributable to the etalon.

Abstract: The present invention provides a multimode semiconductor laser module. The module comprises a multimode laser element 34, an optical filter 54, a light-receiving element 52 and a temperature regulator 24. Multimode light from the laser element 34 is transmitted through the filter 54 and then detected by the light-receiving element 52. The output of the light-receiving element 52 changes according to the degree of overlap between the oscillation wavelength spectrum of the laser element 34 and the transmission wavelength region of the filter 54. The temperature regulator 24 modifies the oscillation wavelength region toward the desired region in response to the output of the light-receiving element 52. As a result, the oscillation wavelength region is stabilized.

Abstract: Optical wavelength control method and apparatus which are capable of controlling an optical wavelength of a light source with a central wavelength which is uncertain and unstable at nanometer order is disclosed. In the optical wavelength control apparatus, the control target light entered from the variable wavelength light source is scanned at a prescribed period and optical pulses having a phase corresponding to the optical wavelength of the control target light are obtained. Then, a phase difference between a phase of the optical pulses and a phase corresponding to a reference optical wavelength is detected, and the variable wavelength light source is controlled by feeding back the phase difference to the variable wavelength light source such that the optical wavelength of the control target light is controlled by an optical frequency pulling with respect to the reference optical wavelength according to the phase difference.

Abstract: The thermo-optic behavior of an optical path over a range of temperatures is controlled by determining a figure of merit (FoM) for the optical path and including in the path a body of NaBi(Mo1-xWxO4)2 crystalline material that enables the conditions specified by the FOM to be satisfied. The NaBi(Mo1-xWxO4)2 crystalline material is highly transparent at a wavelength of radiation propagating in the path, and has a coefficient of thermal expansion (CTE) and a refractive index n such that the CTE and dn/dT of the etalon compensate one another so as to perform frequency discrimination that is essentially temperature insensitive over the range ?T. The NaBi(Mo1-xWxO4)2 crystalline material exhibits temperature independent transmission characteristics at about room temperature and at a wavelength of about 1550 nm.

Abstract: Laser wavelength stabilization is achieved by locating a low selectivity reference filter in a reference path of a laser beam. The low selectivity reference filter, with a periodicity greater than the control filter, is used together with a lookup table for the reference filter to resolve the uncertainty associated with the multivalued control filter. After the wavelength uncertainty for the control filter is resolved, the laser beam is stabilized based on the response of the control filter, as if the reference filter was not present.

Abstract: A wavelength stabilization module having a light-receiving element array and a method of manufacturing the same are disclosed.

Abstract: A method of deploying a passive optical combiner that is a broad bandwidth spectral wavelength combiner for combining the outputs from multiples transmitter photonic integrated circuit (TxPIC) chips and, thereafter, the amplification of the combined channel signals with a booster optical amplifier couple between the passive optical combiner and the fiber transmission link. The booster optical amplifier may be a rear earth fiber amplifier, such as an erbium doped fiber amplifier (EDFA), or one or more semiconductor optical amplifiers (SOAs) on one or more semiconductor chips.

Abstract: A tunable laser system includes a gain medium and an optical resonator for generating a laser beam, and a spectral narrowing and tuning unit within the resonator. A detection and control unit controls a relative wavelength of the laser system. A wavelength calibration module calibrates the detection and control unit. The module contains more than one species each having an optical transition line within the tuning spectrum of the laser. A beam portion of the narrowed emission from the laser is directed through the wavelength calibration module and a beam portion is directed through the detection and control unit when the laser beam is scanned through the optical transition line of each of the species within the module. The detection and control unit is monitored and calibrated during the scanning.

Abstract: A system and method for stabilizing the frequency of the optical output signal of a laser wherein the laser output signal is interfered with at least one time delayed version of said signal to produce an optical interference signal having a frequency shift proportional to the rate of optical frequency change of the laser. The interference signal is processed to produce a frequency correction signal representing the frequency drift of the laser output signal. The laser output signal is combined with the frequency correction signal to stabilize the frequency of the laser output signal.

Abstract: A photonic-crystal distributed-feedback laser includes a laser cavity with a waveguide structure that has a cavity length Lc and is bounded by two mirrors; an active region for producing optical gain upon receiving optical pumping or an input voltage; at least one layer having a periodic two-dimensional grating with modulation of a modal refractive index, the grating being defined on a rectangular lattice with a first period along a first axis of the grating and a second period along a second perpendicular axis of the grating, and wherein the grating produces three diffraction processes having coupling coefficients ?1?, ?2?, ?3?; and a lateral gain area contained within a second area patterned with the grating that has substantially a shape of a gain stripe with a width W, with the gain stripe tilted at a first tilt angle relative to the two mirrors.

Abstract: A CPT detector and a method for detecting CPT are disclosed. The CPT detector includes a quantum absorber, a polarization analyzer, and a detector. The quantum absorber includes a material having first and second low energy states coupled to a common high energy state. Transitions between the first low energy state and the common high energy state and between the second low energy state and the common high energy state are induced by electromagnetic radiation having a predetermined polarization state. The polarization analyzer blocks electromagnetic radiation of the predetermined polarization while passing electromagnetic radiation having a polarization state that is orthogonal to the predetermined polarization. The polarization analyzer is irradiated with a portion of the generated electromagnetic radiation that has passed through the quantum absorber. The detector generates a signal related to the intensity of electromagnetic radiation that leaves the polarization analyzer.

Abstract: Optical filters having at least two coupled whispering-gallery-mode (WGM) optical resonators to produce a second order or higher order filter function with a desired spectral profile. At least one of the coupled WGM optical resonators may be tunable by a control signal to adjust the filtering function.

Abstract: A laser diode module includes a laser diode device, a first photo detector part for receiving, first divided light that is a first portion of light when at least one of light emissions of the laser diode device is divided into two portions of light each traveling a different optical path, a second photo detector part for receiving second divided light that is a second portion of light thus divided via at least a wavelength selective member, and a controller which controls the lasing wavelength of the laser diode device on the basis of outputs of the first and second photo detector parts. A beam splitter provided between the laser diode and the wavelength selective member divides light emitted from the laser diode into the first and second divided light and a quarter-wave plate is provided in an optical path between the beam splitter and the wavelength selective member.