Abstract: A fiber amplifier in which the active core is surrounded by a cladding and coupling of radiation between a core mode and cladding modes is suppressed to minimize cladding mode losses in a short wavelength range. An index profile is established in the active core and in the cladding such that the core exhibits a loss above a cutoff wavelength ?c and positive gains in the short wavelength range below the cutoff wavelength ?c. Suppression of cladding mode losses is achieved by an arrangement for suppressing the coupling of radiation in the short wavelength range between a core mode supported the active core and a cladding mode supported by the cladding. The arrangement for suppressing can include an absorbing material or a scattering material distributed in the cladding. The arrangement for suppressing can include a non-phase-matched length section of the fiber amplifier in which the core mode and the cladding modes are not phase matched.

Abstract: A fiber amplifier in a depressed cladding or W-profile fiber. The fiber has a core doped with the active material and defined by a core cross-section and a refractive index no. A depressed cladding of index n1 surrounds the core and a secondary cladding of index n2 surrounds the depressed cladding. The fiber amplifier is pumped to a level of high relative inversion, such that the active material exhibits positive gains in a short wavelength band and high gains in a long wavelength band. The core cross-section, the depressed cladding cross-section and the refractive indices no, n1, and n2 are selected to obtain a roll-off loss curve about a cutoff wavelength ?c. The roll-off loss curve yields losses at least comparable to the high gains in the long wavelength band and losses substantially smaller than the positive gains in the short wavelength band.

Abstract: An optical communication system such as a Wavelength-Division-Multiplexed (WDM) or Dense Wavelength-Division-Multiplexed (DWDM) communication system using Erbium doped fiber amplifiers (EDFAs) for amplifying signals in the S-band. The fiber amplifier has a core doped with Erbium and defined by a core cross-section and a refractive index n0. The fiber amplifier has a depressed cladding surrounding the core and a secondary cladding surrounding the depressed cladding. The depressed cladding has a depressed cladding cross-section and a refractive index n1, and the secondary cladding has a secondary cladding cross-section and a refractive index n2. The fiber amplifier has a pump source for pumping the Erbium to a level of high relative inversion D such that the Erbium exhibits positive gains in the S-band and high gains in a long wavelength band longer than the S-band, i.e., in the C- and L-Bands.

Abstract: A Thulium-doped silica fiber normally has its strongest gain at 1.9 microns and thus is not suitable for communication use. By engineering a W-profile or depressed cladding fiber with an appropriate index profile having a fundamental mode cut-off between 1.9 microns and the shorter wavelength of desired operation, an optical amplifier based on the W-profile Thulium-doped silica fiber operates at wavelengths shorter than conventional amplifiers, just above what is currently called the Erbium L-band. In a preferred embodiment, the cut-off wavelength is at or near 1.7 ?m, eliminating longer wavelengths from the fiber. Amplifiers engineered according to the principles and techniques of the present invention can operate in the wavelength range between about 1.6 to 1.8 microns, which is particularly useful for telecommunications.

Abstract: A source that employs an Erbium-Doped Fiber Amplifier (EDFA) for generating light in an S-band of wavelengths. The EDFA uses a fiber having a core with a core cross section surrounded by a depressed cladding with a depressed cladding cross section and a secondary cladding with a secondary cladding cross section. A pump source is provided for pumping the Erbium contained in the core of the fiber to a high relative inversion D, such that the Erbium exhibits positive gains in the S-band and high gains in a long wavelength band longer than the S-band. The core cross-section, the depressed cladding cross-section, and the refractive indices no, n1, and n2 are selected to produce losses at least comparable to the high gains in the long wavelength band and losses substantially smaller than the positive gains in the S-band.

Abstract: A system and method for using pulses of laser light delivered in a non-overlapping sequence of first pulses at a green wavelength, second pulses at a blue wavelength and semi-continuous pulses at a red wavelength to illuminate a color generation unit for generating a color. Typically, the color generating unit is an image generating unit for producing color images and is equipped with transmissive or reflective pixels which are adjusted to select portions of the laser light generated at the green, blue and red wavelengths to obtain a desired output color. The first and second pulses preferably have a narrow pulse width and an interpulse separation equal to at least 100 times the narrow pulse width, while the semi-continuous pulses at the red wavelength have a wide pulse width equal to at least 100 times the narrow pulse width.

Abstract: A tunable light source equipped with an optical parametric amplifier (OPA) placed in a cavity for performing an optical parametric oscillation (OPO) driven by a pump beam at a pump frequency selected within a certain range such that the OPO is driven near degeneracy. An adjustment mechanism adjusts the pump frequency within a wavelength tuning range to select a gain spectrum of the OPO and a spectral control mechanism sets a resonant frequency of the cavity within that gain spectrum. Thus, only one of the idler and signal beams within the passband set by the narrowband tuner is supported inside the cavity. Other nonlinear frequency conversion operations can also be performed within the cavity in conjunction with the OPO. The light source can be operated in cw, near-cw and pulsed operation modes as a broadly tunable narrowband source covering a wavelength window of 250 nm.

Abstract: A system employing a solid state light source for writing Bragg gratings in fibers and for other photolithographic applications. The solid state light source preferably has a passively Q-switched laser, a fiber amplifier and two or more nonlinear conversion elements for delivering a pulsed exposure beam at an exposure wavelength in the UV wavelength range. The exposure beam is generated in a single pass through the nonlinear elements, for example by cascaded second harmonic generation yielding the fourth harmonic. The system is effective at covering the UV wavelengths from 200 nm to 330 nm and particularly effective at producing an exposure wavelength between 240 and 250 nm at average power levels of 500 milliWatts and more within a photosensitive range of fiber cores in which Bragg gratings are to be written.

Abstract: An optical fourth-harmonic generation system includes a resonant cavity configured to support electromagnetic radiation of a fundamental frequency and a fourth-harmonic generator disposed within the resonant cavity produces electromagnetic radiation of a fourth-harmonic frequency by an interaction with radiation of the fundamental frequency. The fundamental radiation is characterized by a p polarization that is complementary to an s polarization that characterizes the fourth-harmonic radiation. The fourth-harmonic generator has an output facet oriented substantially at a Brewster's angle with respect to the fundamental radiation to separate the fundamental radiation from the fourth-harmonic radiation as they emerge from the output facet.

Abstract: This invention provides a tunable laser in which a plurality of gain elements (e.g., semiconductor diodes) with a plurality of gain spectra are optically coupled to a splitting-combining means (e.g., a wavelength router or fiber-optic coupler) in parallel, and the splitting-combining means is in optical communication with a wavelength-selecting means (e.g., a diffraction grating optically coupled to a movable mirror). The tunable laser of the present invention further comprising an optical fiber, optically coupling the splitting-combining means to the wavelength-selecting means. The use of a plurality of distinct gain spectra greatly enhances the tuning range of the tunable laser in the present invention.

Abstract: An optical resonator has a piezoelectric element attached to a quasi-monolithic structure. The quasi-monolithic structure defines an optical path. Mirrors attached to the structure deflect light along the optical path. The piezoelectric element controllably strains the quasi-monolithic structure to change a length of the optical path by about 1 micron. A first feedback loop coupled to the piezoelectric element provides fine control over the cavity length. The resonator may include a thermally actuated spacer attached to the cavity and a mirror attached to the spacer. The thermally actuated spacer adjusts the cavity length by up to about 20 microns. A second feedback loop coupled to the sensor and heater provides a “coarse” control over the cavity length. An alternative embodiment provides a quasi-monolithic optical parametric oscillator (OPO). This embodiment includes a non-linear optical element within the resonator cavity along the optical path.

Abstract: An intracavity frequency converted, Q-switched laser and method for operating such laser to obtain high output power in secondary pulses at a converted frequency. The secondary pulses are generated by a intracavity frequency conversion element from primary pulses at the fundamental wavelength. In accordance with the invention, after the primary and secondary pulses are generated the Q-switch is turned back on before the gain is fully depleted in the generation of the primary pulse. In particular, the Q-switch is turned back on such that a certain amount of energy of the primary pulse is retained in the laser, but late enough so that a majority of the secondary pulse is out-coupled from the laser. The Q-switched laser is well-suited for use at pulse repetition rates larger than 1/&tgr;, where &tgr; is an upper state lifetime (fluorescence lifetime) of the laser. Specifically, the laser can be operated at repetition rates of 10 kHz and higher, e.g.

Abstract: An approach to blue light in a single, integrated system is disclosed. An oscillator generates source radiation at a wavelength near 0.91 microns and a few milliwatts of power. This power is amplified to multi-Watt levels in a Neodymium-doped cladding-pumped fiber device that has its gain suppressed at 1.05 microns. A harmonic generator frequency-doubles the output of the fiber device to produce radiation at a blue wavelength near 0.455 microns. Mirrors, gratings or other means in the fiber expel wavelengths of light at or near 1.05 microns while allowing 0.91 micron radiation to remain in the fiber. Gain at 1.05 microns may alternatively be suppressed by adjusting the refractive index profile of the fiber to eliminate bound-modes at 1.05 microns or by bending the fiber to attenuate radiation at 1.05 microns. The laser may include a high brightness pump to enhance the transition that produces 0.91 micron radiation.

Abstract: An optical resonator has an axial mode frequency tuning rate with respect to temperature matching the peak gain frequency tuning rate, so that mode hops are eliminated. The resonator contains a composite cavity consisting of a gain medium and free space. Preferably, the resonator is a single-frequency solid state laser containing a solid state gain medium defining a physical path length Lg. The optical cavity is defined by a high reflector and output coupler surrounding the gain medium and defining a physical cavity path length Lo. The high reflector and output coupler are mounted on a substrate so that Lo is temperature insensitive. Preferably, the substrate is a thermally insensitive material having a negligible coefficient of thermal expansion; for example, it may be Invar™, Super-Invar™, ULE™ Glass, Zerodur™, and fused silica. Alternately, the substrate is a thermally isolated material that is temperature controlled and insulated from the gain medium.

Abstract: An apparatus and a method for separating a light of a first wavelength &lgr;1 from a second wavelength &lgr;2, where &lgr;1<&lgr;2, in a waveguide such as an optical fiber is described. The apparatus includes a core surrounded by a depressed cladding, which itself is surrounded by a secondary cladding. The core cross-section, the depressed cladding cross-section, the secondary cladding cross-section, and the refractive indices of the core, the depressed cladding and the secondary cladding are selected to produce a fundamental mode cutoff wavelength &lgr;c such that &lgr;1&lgr;c<&lgr;2, and produce a high loss at the secondary wavelength &lgr;2. The apparatus can be used as a filter, an amplifier, a laser, or in a nonlinear optical switch.

Abstract: Optical, opto-mechanical and electro-optical elements (OE) of a Laser resonance assembly (LRA) are positioned and fixated in close proximity on an assembly plate by clamping the OE in a vacuum chuck that holds the OE on a clamping portion on the very top of it. The OE is brought into the predetermined position while a lateral attaching surface of the OE is kept in a predetermined angle relative to the assembly plate. A side mount is placed between the mirror and the assembly plate after an UV-curing adhesive has been applied. The attaching surface s and the adhesive have a specific relation between areal extension, surface roughness, uncured viscosity and uncured cohesive force.

Abstract: Compact solid state laser apparatus that includes a laser diode pump, beam forming optics, a laser gain medium and optical resonator, a photodetector to vary the power supplied to the laser diode pump to suppress relaxation oscillations that might otherwise appear in the laser gain medium output light beam, an optical isolator and laser output optics. Each of the optical components has an independently activatable heater to allow optical alignment of that component. Each of the laser diode pump and laser gain medium has an independently activatable thermoelectric cooler to allow optical alignment (laser gain medium only) and to provide thermal tuning of the output wavelength of that device. An optical platform, which is thermally conductive, electrically non-conductive and has low thermal expansion, supports the other components, provides a substrate for electrical traces that provide power for operation of the apparatus and contains the heaters for the optical components.

Abstract: Apparatus for end-pumping of a solid-state laser with a source of high optical brightness. A stack of diode laser bars are excited, and each bar emits a light beam of a selected pump wavelength in a chosen direction. The light beam output of the diode bar stack is divided into a plurality of smaller, approximately rectangular light beams, which serve as extended light sources, by a plurality of mirrors that are positioned to receive one or more of these smaller beams and redirect such beams onto first, light-receiving ends of one or more optical fibers. Light collection optics receive the beams issuing from the mirrors and focus these beams onto a light-receiving end of an optical fiber with beam convergence angles that are appropriate for the numerical aperture of that fiber.

Abstract: Method and apparatus for stabilization of pulse energies produced by a continuously pumped, Q-switched, solid-state or gas laser, through control of the optical power delivered by an optical pump to the laser, in order to limit the energy emitted in any single laser pulse as a result of Q-switching. The laser pump is driven at full strength for a selected initial refresh time t.sub.r. If a Q-switch trigger signal is received by the laser before the elapsed time .DELTA.t has reached the refresh time t.sub.r, the laser emits a pulse with the reduced energy stored in the laser at that time. If the elapsed time reaches or exceeds the refresh time t.sub.r, the optical pump power subsequently delivered to the laser is reduced to a lower level, which may be time-dependent, that is sufficient to maintain the net energy stored in the laser at a predetermined value so that the energy in a subsequently emitted laser pulse does not exceed a selected limit.