Abstract: A laser apparatus for generating optical pulses is disclosed, said laser apparatus has a reflecting gain element preferably including a fiber gain medium. The reflecting gain element is coupled to a controllable reflecting/transmitting module having a reflecting state and a transmitting state, wherein the controllable reflecting/transmitting means are operable to switch from the transmitting state to the reflecting state to initiate a build-up of an optical pulse, and to switch back to the transmitting state for outputting the optical pulse before it reaches the reflecting/transmitting means after a cavity roundtrip. In a preferred embodiment, the controllable reflecting/transmitting module includes an acousto-optic switch at an output end of a laser operable to output the optical pulse in zeroth diffraction order.

Abstract: A laser apparatus for nonlinear conversion of light is disclosed utilizing a laser diode having a reflective back facet and a front facet having a reflectance of less than about 1% for emitting a multifrequency optical beam, and a nonlinear optical element for receiving the multifrequency optical beam and for generating a frequency-converted radiation. An external frequency-selective reflector is provided for power and spectral stabilization of the multifrequency optical beam, and for confining its optical spectrum within a bandwidth of efficient nonlinear conversion in the nonlinear optical element. The laser diode reflective back facet and the external frequency-selective reflector form an extended laser cavity. In operation, the multifrequency optical beam contains a plurality of longitudinal modes of the extended laser cavity which are confined within the frequency conversion bandwidth of the nonlinear element.

Abstract: A laser apparatus is disclosed utilizing a laser diode having a reflective back facet and a front facet having a reflectance of less than about 1% for emitting an optical beam at a fundamental frequency along an optical path. A collimating lens is provided for collimating the optical beam into a collimated beam. A transmission grating is optically coupled to receive the collimated beam and returns a portion of the collimated beam back into the laser diode by means of diffraction through lens and the laser diode front facet. The laser diode reflective back facet and the transmission grating form an extended laser cavity. In operation, a substantial portion of the collimated beam is transmitted through the transmission grating for producing the laser output beam propagating along the optical path.

Abstract: A laser apparatus for nonlinear conversion of light is disclosed utilizing a laser diode having a reflective back facet and a front facet having a reflectance of less than about 1% for emitting a multifrequency optical beam, and a nonlinear optical element for receiving the multifrequency optical beam and for generating a frequency-converted radiation. An external frequency-selective reflector is provided for power and spectral stabilization of the multifrequency optical beam, and for confining its optical spectrum within a bandwidth of efficient nonlinear conversion in the nonlinear optical element. The laser diode reflective back facet and the external frequency-selective reflector form an extended laser cavity. In operation, the multifrequency optical beam contains a plurality of longitudinal modes of the extended laser cavity which are confined within the frequency conversion bandwidth of the nonlinear element.

Abstract: The invention relates to the monitoring of polarization mode dispersion (PMD) using heterodyne detection for providing PMD compensation in optical networks, and an apparatus for monitoring PMD. In the present invention, a broadband PMD monitor is disclosed based on heterodyne detection with a tunable laser source which can be fed to a compensator such as an add/drop or other wavelength switch and polarization dependent attenuation means. A signal from a local oscillator is combined with an optical signal and the beat frequency amplitude and phase is analyzed for two orthogonal polarization states simultaneously to obtain a state of polarization. By averaging a plurality of polarization states within a channel, PMD can be estimated for compensation.

Abstract: A lossless optical link in an optical transmission system comprises an optical fiber that is configured to produce Raman gain and provide for Raman distributed gain, via one or more pump sources, along the fiber so that, as an end result, the gain experienced by one or more propagating signals in the fiber link is made fairly uniform along the link or at least a portion of the optical link, such as not vary, for example, no more than five dB along the length of the optical fiber. The several embodiments disclosed provide for different optical pump/component architectures to achieve this end result.

Abstract: An optical fiber gain medium has a core region in which a signal propagates, and a cladding region surrounding the core into which a pump signal is coupled. The gain medium also includes a plurality of doped regions each of which has a different effect on the gain profile of the gain medium. In a first embodiment, two doped regions are located in the cladding region at different radial distances from the core. Each of the two doped regions has a different absorption characteristic such that it absorbs signal energy in a different wavelength region of the gain band. The relative contributions may be controlled by controlling a number of different factors, including type of dopant, density of dopant, radial width of the doped regions, and relative separation between the doped regions, and their positioning relative to evanescent portions of different wavelength bands.

Abstract: Apparatus for coupling light into a fiber, such as a double clad fiber (DCF) having a core having a refractive index n1, surrounded by an inner cladding having refractive index n2 which is surrounded by an outer cladding having a refractive index n3, where n1>n2>n3. An optical coupler medium, referred to as a Fiber Space Division Multiplexor or FSDM, is formed on an exposed portion of the fiber inner cladding at a position along the length of the fiber without interfering with the continuity of its core and provides at, at least one position, the imaging of light external of the fiber into the inner cladding interface and its waveguiding with the inner cladding of the fiber. The FSDM coupler comprises an optical material in optical contact or integrated with the inner cladding and having a refractive index substantially equal to n2. The coupler medium may also be employed with a fiber having no core and where the inner cladding would function as a multimode core.

Abstract: All-fiber coupling architectures include at least one fiber gain media, e.g. a fiber amplifier or a fiber laser, providing for the coupling light from one or more multi-wavelength pump sources propagating in a multimode core fiber at multiple points along a double clad fiber or at least at one point along multiple double clad fibers having their inner claddings fused to the multimode core fiber. The latter arrangement provides for a low cost utility multi-signal fiber amplifier for telecommunication applications.

Abstract: Power scaling by multiplexing multiple fiber gain sources with different wave-lengths is useful in printing applications requiring higher optical powers to perform the printing function, such as through thermal inducement in thermal ablation, thermal fusion, thermal diffusion or thermal transfer. A marking system is disclosed using a plurality of laser sources operating at different wavelengths with their respective outputs coupled into a respective single mode fiber. At least one WDM combiner is coupled to receive and combine the laser source outputs into a single output. The combined power single output provides sufficient power intensity to induce thermal marking on a marking medium.

Abstract: Optical pumping arrangements are provided for the broadband or multiple wavelength pumping of optical sources. Sources may be based on Raman gain media and may use multiple output couplers to couple out different wavelength ranges. Cascaded Raman resonator (CRR) configurations may also be used. Overlapping resonators at different wavelengths may be configured to share gain media, and may have separate portions in separate optical paths. Attenuation filters may also be used that are matched to the gain profile of a gain medium, to flatten the gain spectrum and allow equalization of gain to different output wavelengths. In one embodiment, polarization maintaining fiber is used to develop resonant conditions at different wavelengths in different polarization states. Wideband output gratings may be substituted for narrowband gratings to provide CRR configurations with a broader output band. Broadband amplification may also be provided by using a laser source operating in coherence collapse.

Abstract: The effectiveness of reflected light to stabilize the operational characteristics of a semiconductor diode laser varies with the polarization orientation of the reflected light. Stabilization failure can occur if the polarization orientation of the reflected light is orthogonal to the polarization of the light emitted by the laser source. The use of multiple reflectors can reduce the probability of stabilization failure by arranging the reflectors to return to the laser source portions of light having polarization orientations that are statistically independent with respect to each other.

Abstract: A frequency conversion system includes at least one source providing a first near-IR wavelength output including a gain medium for providing high power amplification, such as double clad fiber amplifier, a double clad fiber laser or a semiconductor tapered amplifier to enhance the power output level of the near-IR wavelength output. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Ra-man/Brillouin amplifier or oscillator between the high power source and the NFM device.

Abstract: A frequency conversion system comprises first and second gain sources providing first and second frequency radiation outputs where the second gain source receives as input the output of the first gain source and, further, the second gain source comprises a Raman or Brillouin gain fiber for wave shifting a portion of the radiation of the first frequency output into second frequency radiation output to provided a combined output of first and second frequencies. Powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

Abstract: Power scaling by multiplexing multiple fiber gain sources with different wavelengths, pulsing or polarization modes of operation is achieved through multiplex combining of the multiple fiber gain sources to provide high power outputs, such as ranging from tens of watts to hundreds of watts, provided on a single mode or multimode fiber.

Abstract: A number of variations are provided of a device that provides an amplified single polarization optical signal. Each of these relies on the use of a non-polarization maintaining gain medium through which the signal is directed, and a polarization shifter and reflector that direct the signal back through the same gain medium with a shifted polarization state. An input polarization beamsplitter directs the returning optical signal away to an output, based on its shifted polarization state. The embodiments of the invention include the use of double-clad fiber. Multiple stages may be used to provide specific amplification parameters. In particular, a fiber with a relatively large mode field diameter may be used to enable high pulse power applications. Wavelength selective components are used in certain embodiments of the invention, to allow for wavelength selectivity, as well as a single polarization state, in amplifiers, lasers and amplified spontaneous emission (ASE).

Abstract: Power scaling by multiplexing multiple fiber gain sources with different wavelengths, pulsing or polarization modes of operation is achieved through multiplex combining of the multiple fiber gain sources to provide high power outputs, such as ranging from tens of watts to hundreds of watts, provided on a single mode or multimode fiber.

Abstract: Laser diode pumped mid-IR wavelength sources include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

Abstract: Coherent light sources combining a semiconductor optical source with a light diverging region, such as a flared resonator type laser diode or flared amplifier type MOPA, with a single lens adapted to correct the astigmatism of the light beam emitted from the source is disclosed. The lens has an acircular cylindrical or toroidal first surface and an aspheric or binary diffractive second surface. The first surface has a curvature chosen to substantially equalize the lateral and transverse divergences of the astigmatic beam. Sources with an array of light diverging regions producing an array of astigmatic beams and a single astigmatism-correcting lens array aligned with the beams are also disclosed. The single beam source can be used in systems with frequency converting nonlinear optics. The array source can be stacked with other arrays to produce very high output powers with high brightness.

Abstract: Apparatus for providing a laser source optically coupled to an optical waveguide, such as an optical fiber, having a reflective grating positioned from the output facet of the laser source a distance equal to or greater than the coherence length of the laser source providing a portion of reflective feedback into the laser source optical cavity to maintain wavelength operation of the laser source in spite of changes in the laser operating temperature or drive current based upon coherence collapse in the laser operation. In cases where the fiber grating is positioned in the fiber within the coherence length of the laser source, intermittent coherence collapse, as opposed to continuous coherence collapse, is unavoidable. In cases where such a laser source is a pumping source for a solid state gain medium, such as an optical amplifier or laser having an active gain element, e.g.