Abstract: Cladding-pumped fibers are used for chirped pulse amplification of ultrashort optical pulses, increasing the average output power by one order of magnitude and substantially decreasing the cost of pump sources. Broad-area multimode diode pumped Er/Yb codoped fiber amplifiers and MOPA pumped high-power Er-doped fiber amplifiers are used to achieve chirped pulse amplification.

Abstract: A polarization independent optical isolator for transmitting a signal ray in a forward direction and suppressing backward transmission comprises: a first and second optical isolation unit for receiving, transmitting, and outputting signal rays in the forward direction and for suppress backward transmission of any rays; and a reflection unit for coupling to first and second optical isolation unit by directing the outputted signal ray from the first optical isolation unit to the second optical isolation unit, the signal ray received by the first optical isolation unit transmitting in the opposite direction to the outputted signal ray from the second optical isolation unit. A reflection protection unit may be provided to prevent undesired reflection at inlet of the optical isolator. A optical filter for reflecting a component having a predetermined wavelength and transmitting remaining component may be used for the reflection unit. An optical detector may be used for monitoring the remaining component.

Abstract: A polarization independent optical isolator for transmitting a signal ray in a forward direction and suppressing backward transmission comprises: a first and second optical isolation unit for receiving, transmitting, and outputting signal rays in the forward direction and for suppress backward transmission of any rays; and a reflection unit for coupling to first and second optical isolation unit by directing the outputted signal ray from the first optical isolation unit to the second optical isolation unit, the signal ray received by the first optical isolation unit transmitting in the opposite direction to the outputted signal ray from the second optical isolation unit. A reflection protection unit may be provided to prevent undesired reflection at inlet of the optical isolator. A optical filter for reflecting a component having a predetermined wavelength and transmitting remaining component may be used for the reflection unit. An optical detector may be used for monitoring the remaining component.

Abstract: A method of mass-producing reliable, optical isolators, which allows reliable soldering and metallization in large quantities. The method comprises forming grooves (2) wider than a cutting margin along predetermined cut lines for cutting out a plurality of optical devices on the surface of an optical material block (1), forming then an antireflection film and a metallized film (3), and cutting the block along the grooves (2) ino optical elements (5).

Abstract: A low noise optical fiber Raman amplifier (FRA) comprises an upstream and a downstream length of silica-based amplifier fiber, of combined length >200 m, typically >1 km, with an optical isolator disposed between the upstream and downstream lengths of amplifier fiber such that passage of backscattered signal radiation from the latter to the former is substantially blocked. In preferred embodiments counter-propagating pump radiation is coupled into the downstream length of amplifier fiber, and wavelength-selective means are provided for shunting the pump radiation around the optical isolator. The described FRA is advantageously incorporated into optical fiber communication systems. Exemplarily it can serve as power amplifier, as pre-amplifier, or as in-line amplifier. For instance, it can be used to replace conventional opto-electronic repeaters in existing 1.3 .mu.m fiber communication systems, or it can be used as power amplifier in a multi-subscriber optical fiber CATV system.

Abstract: A laser diode package couples laser diode outputs into a plurality of fibers, and these are bundled and brought to an output face that produces a divergent composite beam from the fiber ends. The beam end pumps a solid-state laser across a gap, and the divergence allows a wide tolerance in alignment of the pump and crystal. Preferably, one cavity mirror is a focusing mirror that reconcentrates residual pump light in the desired mode. In a preferred embodiment, the output face of the package is at a short stub or ferrule that provides a simple and effective pump beam centering alignment. The solid-state laser may be a rod or crystal and is preferably sufficiently short, in relation to pump beam diameter and divergence in the rod, that the pump beam within the rod lies in the TEM.sub.OO mode volume of the laser cavity. A concave mirror then refocuses residual pump light back into that mode. The rod preferably has a high index at the pump wavelength, but need not have high absorption.

Abstract: A fiberoptic coupler capable of many functions is presented. The basic fiberoptic coupler has a first sleeve, a second sleeve, a first collimating GRIN or conventional lens, and a second collimating GRIN or conventional lens. The first sleeve holds end sections of two or more input optical fibers along the longitudinal axis of the sleeve. The second sleeve holds an end section of at least one output optical fiber. The end face of the second sleeve faces the first sleeve end face. The first collimating GRIN or conventional lens in front of the first sleeve end face collimates light signals from the input optical fibers and the second collimating GRIN or conventional lens in front of the second sleeve end face focusses light signals from at least one of the input optical fibers into the single output fiber, or at least one of the output optical fibers. With only one output fiber the coupler operates as a combiner.

Abstract: An optical isolator includes an optical isolator unit including a main polarization discriminator in concatenation with a Faraday rotator, and an auxiliary polarization discriminator disposed in series with the optical isolator unit. One of the polarization discriminators initially divides an applied optical signal propagating in a forward direction along a reference axis into two polarized signals subsequently experiencing polarization dispersion and differential transverse deflection, while the other polarization discriminator eventually eliminates the polarization dispersion. The auxiliary discriminator includes a plate of a uniform thickness inclined at a tilt angle with respect to the reference axis selected so that the transverse deflection difference incurred during the passage through the one polarization discriminator is eliminated in the other polarization discriminator. This facilitates achieving very low polarization dependent loss in the isolator.

Abstract: A low noise optical fiber Raman amplifier with integral Raman laser (FRA) is disclosed. The FRA typically comprises a fiber ring with at least two amplifier stages, with strictly counter-propagating pump radiation. Relatively short wavelength (e.g., 1060 nm) pump power is provided to the Raman laser portion of the fiber ring. Appropriately selected and placed Bragg gratings provide one or more optical cavities in the fiber ring, such that the input pump radiation is converted to the desired amplifier pump radiation (e.g., 1240 nm, suitable for amplification of 1310 nm signal radiation). The FRA can, for instance, advantageously serve as power amplifier in digital or analog fiber communication systems, or it can serve as pre-amplifier or in-line amplifier.

Abstract: Optical isolator, circulator, switch or the like, including a Faraday rotator to which a magnetic field is applied which is oriented along the direction of propagation of light and which is arranged between a preceding polarization filter and a succeeding polarization filter whose planes of polarization enclose an angle with respect to each other such that light can only traverse in one direction, the Faraday rotator having different propagation constants .beta..sub.TE and .beta..sub.TM in a TE plane and a TM plane, respectively. The elaborate technique for adapting the propagation constants of the TE wave and the TM wave is mitigated in that the TE plane of the Faraday rotator is aligned in such a way that it extends between the planes of polarization of the polarization filters.

Abstract: An optical device includes a body of a semiconductor material having a waveguide therein along which light flows and means for providing gain to the light. A layer of an amorphous or polycrystalline metallic-ferromagnetic material extends along the waveguide and means, such as a permanent magnet, provides a magnetic field to the metallic-ferromagnetic material layer. This provides an optical isolator of the Faraday rotation type which can be integrated with a variety of material systems including those commonly used to fabricate semiconductor lasers, arrays and amplifiers.

Abstract: A non-reciprocal optical device for interconnecting single mode optical fiber waveguides so that a light beam can pass between the fibers in a forward direction but a reverse beam, such as might be caused by unwanted reflections, is displaced away the input fiber, includes a focussing lens unit and at least one non-reciprocal optical element in series between respective ends of an input optical fiber and an output optical fiber. The focussing lens unit has a focal length such that a light beam from the input optical fiber will be focussed onto the end of the output optical fiber. The focussing lens unit may comprise, for example, a half-pitch grin-rod lens. The non-reciprocal device is positioned adjacent one or other of the foci of the focussing lens unit. The focussing lens unit may comprise several lens elements, for example a pair of quarter pitch collimating lenses, allowing additional optical elements, such as filters, to be interposed.

Abstract: A polarization independent optical isolator for use in optical communication systems is provided. This optical isolator functions to provide dual-way optical isolation wherein an input optical signal entering in the isolation direction is transmitted through the optical isolator twice using a reflecting member, and includes a magnetooptic plate and a birefringent plate disposed between the magnetooptic plate and the reflecting member.

Abstract: A broadband thermal optical limiter disposed between a laser oscillator and laser amplifier system for protecting optical components in the laser oscillator from damage due to amplified optical feedback from the laser amplifier system at all near ultraviolet, visible and near infrared wavelengths is disclosed.

Abstract: A new optical diode is disclosed that permits unidirectional transmission of light, the direction of transmission depending on the direction of incidence. The diode comprises a stack of alternating layers of a low-index material and a high-index material. The layers are arranged within the stack such that there is spatial anisotropy of optical pathlengths in the stack and at least the low-index layers or the high-index layers have an optical nonlinearity, either inherently or by doping. At sufficiently high incident intensifies and appropriate wavelengths, such a diode exhibits partial transmission of input light incident from one direction while reflecting almost totally input light incident from the opposite direction.

Abstract: An optical isolator comprises a non-reciprocal rotator disposed between a pair of birefringent wedges, an input wedge and an output wedge. In order to reduce walk-off between the ordinary and extraordinary rays at the output of the isolator in one embodiment, the input signal is made incident on the input wedge at an angle above the normal to the wedge. At a particular angle related to various parameters of the isolator the relative walk-off can be reduced to essentially zero. In another embodiment, the input angle and various isolator parameters are mutually adapted so that the ordinary and extraordinary rays intersect within the isolator.

Abstract: The present invention provides for a compensating element in the form of a birefringent plate in an optical isolator which uses a first GRIN lens to collimate the light signal from an input optical fiber, a first birefringent polarizer wedge, an optical Faraday rotator, a second birefringent polarizer wedge, and a second GRIN lens to recollimate the light signal to an output optical fiber. Polarization mode dispersion through said optical isolator is substantially reduced by arranging the fast optical axis of the plate to be perpendicular to the fast optical axis of the polarizer on the same side of the Faraday rotator as the plate and selecting the thickness of the plate in a predetermined manner. The present invention also allows for minimization of "walk-off", which also contributes to some polarization mode dispersion through the isolator.

Abstract: Wavelength division multiplexed couplers are provided with the ends of input and output optical fibers arranged with respect to GRIN lens so that light from one input fiber is directed toward one output fiber with little crosstalk. An integrated wavelength division multiplexed coupler and isolator device useful for connecting fiberoptic amplifiers to pump lasers is also provided with one version of the WDM coupler. The integrated WDM coupler and isolator device has a tap coupler component created by a planar grating which deflects a small portion of the light through the device toward a photodetector circuit for monitoring purposes. The integrated device also may be combined with a laser diode subassembly can be combined to eliminate a pump laser connection for the fiberoptic amplifier.

Abstract: A passively mode-locked fiber ring laser (LAS) is disclosed for generating optical pulses whose repetition frequency is settable. The mode-locked fiber ring laser (LAS) contains an erbium-doped fiber (ER), a ring resonator (RES), a pump-light source (PUMP), an optical modulator (MOD), and a feedback loop (RS). A portion of the signal light, which is produced by stimulated emission and is composed of a plurality of pulse repetition frequencies, is processed in the feedback loop (RS) into a drive signal which is coupled to the control input of the optical modulator (MOD). The feedback loop (RS) includes an adjustable filter which filters the desired pulse repetition frequency from the signal light. Thus, optical pulses of a given repetition frequency are developed in the ring resonator (RES) and at the output (OUT) of the passively mode-locked fiber ring laser (LAS).

Abstract: An optically pumped bistable laser (LAS) with an active laser condition and an excited inactive condition is presented. The bistable laser (LAS) comprises an erbium-doped fiber (ER), a resonator (RES), a pumping light source (PUMP), and optical isolator (ISO), a wavelength-dependent coupler (WDM) and an asymmetrical fiber coupler (FC). Excitation from the excited condition is created by pumping light from the pumping light source (PUMP) into the erbium-doped fiber (ER), to place the bistable laser into the excited inactive condition. Optical pulses, which are coupled in through input (IN), activate the bistable laser (LAS) and enable it to operate both as a pulse generator and a trigger circuit, as a function of pulse duration and/or pulse frequency.

Abstract: An optical isolator obtains reduced ripple due to Fabry-Perot reflections by using a polarization mode dispersion compensation element with first and second antireflection coatings designed to minimize reflections for first and second polarizations for first and second wavelengths.

Abstract: An optical isolator is disclosed that is particularly useful in the visible, infrared, and near-infrared portions of the electromagnetic spectrum. The rotator portion of the isolator produces a highly uniform magnetic intensity across its clear aperture. The optical isolator comprises a Faraday rotator that defines an optical axis, a respective polarizer on each end of the Faraday rotator and positioned on the optical axis, and a housing containing the Faraday rotator and the polarizers. The Faraday rotator comprises an optical rotator rod that defines the optical axis and a magnet assembly surrounding the optical rotator rod. The magnet assembly comprises eight trapezoidal cross section magnet sections arranged in a first group of four and a second group of four.

Abstract: An optical isolator device comprises a magnet having a rectangular channel and a rectangular optical isolator element fitted in the channel and fixed to the magnet by adhesive filled up in a gap around the element in the channel. In order to avoid an increased thickness of the adhesive layer which is caused by round corners of the rectangular channel in production of the magnet by injection molding, the magnet is formed with a small slit outwardly extending from each corner of the rectangular channel. Thus, the optical isolator element is fitted in the channel without interference of the channel corners and is in close contact with at least one of flat inner surfaces of the channel to form a thin gap of 10 microns or less therebetween. Accordingly, the optical isolator element is strongly adhered to the inner surface of the channel by the thin adhesive layer of 10 microns or less in the thin gap.

Abstract: An optical fiber terminal fitted with an optical isolator in close proximity in a unitary structure comprises an optical fiber, a ferrule which holds the optical fiber in position, at least one magneto-optical element located as aligned with the optical fiber, and a cylindrical permanent magnet that applies a magnetic field to the magneto-optical element. The magneto-optical element is disposed axially outside of the magnet, and the end face of the optical fiber is located in the hollow of the magnet or in the space between the magnet and the magneto-optical element, so that the overall outside diameter and length can be decreased. The ferrule, made of a soft magnetic material, increases the magnetic field strength of the magnet.

Abstract: An object of the present invention is to provide an optical passive component having a polarization-independent optical isolator for constituting an optical fiber amplifier and exhibiting an optical isolator function. At least first and second optical fibers for input and output of light rays, a birefringent crystal, a lens for converting the input light rays into nearly collimated rays, a magnetooptical crystal for receiving a magnetic field so as to rotate by .pi./8+N.pi./4(n=0, 1, . . . ) the polarization direction of the input light rays, and a reflector are disposed in order. A half wave plate is provided to cover one portion of the ray path between the above described birefringent crystal and the above described lens.

Abstract: The present invention relates to a tuneable ring laser with an output having a fixed, stable linear state of polarization with a fixed and known azimuth. The state of polarization at the output is fixed by careful splice and component orientation that compensates for component birefringence of the various ring elements that alter the polarization state and azimuth. Further, such polarization transformation is minimized by careful deployment of the non-polarization component.

Abstract: We have discovered that at least some optical waveguide lasers such as Er-doped fiber lasers are subject to excessive output amplitude fluctuations, including severe fluctuations when the laser is subjected to mechanical shock. We have determined that these highly undesirable fluctuations are due to a resonance phenomenon, and that the fluctuations can be at least substantially reduced by means of a feedback loop that makes the amplitude of the output of the pump laser responsive to the amplitude of the output of the waveguide laser. We have also discovered that the operation of a pump laser/waveguide laser combination is frequently improved if an appropriate non-reciprocal element (e.g., an isolator or a tilted wavelength filter) is placed between the two lasers. An exemplary embodiment of the invention comprises the feedback loop as well as the non-reciprocal element.

Abstract: An element for an optical isolator which is formed by alternately bonding together at least one flat plate-shaped Faraday rotator and two or more flat plate-shaped polarizers, the optical isolator element having an outer peripheral surface which is cut such that, when the outer peripheral surface is disposed parallel to an optical axis, incidence and emergence planes of the element are inclined at a predetermined angle with respect to a plane perpendicular to the optical axis. The optical isolator element is accommodated in a cylindrical magnet having an inner peripheral surface of the same shape as the outer peripheral surface of the optical isolator element, thereby forming an optical isolator.

Abstract: At least one non-reciprocal rotation element is interposed between two adjacent walk off crystal members to form an optical isolator. Light in the forward direction is separated into two rays of linear polarizations where there is substantially no optical path length difference between the two rays. Light transmitted in the reverse direction is reduced. A conventional optical isolator which does not preserve optical path length difference is converted into one which does by adding a birefringent plate to compensate for the optical path length difference introduced by the conventional isolator. A pair of collimating lenses may be introduced between any pair of non-reciprocal rotation elements.

Abstract: A high dynamic range laser diode modulation scheme employs two laser diodes connected so that their outputs are added in a single optical fiber. The first diode is modulated over its dynamic range. The second diode is also modulated over its dynamic range, and is attenuated with a filter to provide fine level adjustment to the coarse levels provided by the first diode.

Abstract: A polarization-independent optical isolator comprises three Faraday rotators and four birefringent elements. An optical arrangement of these elements is determined on the basis of the appropriate values derived from the analysis for polarization-independency. A transmission loss characteristic, which is most important in practical use of the optical isolator, is maintained at an excellent level even in presence of variation in temperature and wavelength and in presence of fluctuation in working precision. Deterioration of various isolator properties can be avoided.

Abstract: An optical isolator comprising first through fourth plate-like birefringent substances. Each plate-like birefringent substance receives and transmits incident light, and has a corresponding optical axis which is inclined with respect to a direction of the incident light. The optical isolator also has first and second magneto-optical materials, each for rotating a plane of polarization of the incident light. The optical axis of the second plate-like birefringent substance is rotated by one of -45.degree. and 135.degree. about a first axis which is perpendicular to a surface of the first plate-like birefringent substance. The optical axis of the third plate-like birefringent substance is rotated by one of 45.degree. and 225.degree. about a second axis which is perpendicular to the surface of the first plate-like birefringent substance. The optical axis of the fourth plate-like birefringent substance is rotated by one of -90.degree. and 90.degree.

Abstract: An element for an optical isolator which is formed by alternately bonding together at least one flat plate-shaped Faraday rotator and two or more flat plate-shaped polarizers, the optical isolator element having an outer peripheral surface which is cut such that, when the outer peripheral surface is disposed parallel to an optical axis, incidence and emergence planes of the element are inclined at a predetermined angle with respect to a plane perpendicular to the optical axis. The optical isolator element may be formed with a rectangular configuration in conformity to the arranged form of a plurality of laser active regions of a laser array.

Abstract: An optical isolator not dependent on the plane of polarization of an incident beam and does not allow the plane of polarization to change on the outgoing side. The optical isolator comprises a first parallel flat double refractive crystal substance; a first Faraday rotor for rotating the plane of polarization of a beam; a second parallel flat double refractive crystal substance; a second Faraday rotor for rotating the plane of polarization in a direction opposite to that in which said first Faraday rotor rotates the plane of polarization; a third parallel flat double refractive substance; a fourth parallel flat double refractive substance; and permanent magnets for magnetizing the Faraday rotor and second Faraday rotors. Since a pair of Faraday rotors for rotating the plane of polarization in opposite directions, the plane of polarization on the incident side does not change on the outgoing side.

Abstract: In an optical isolator device comprising a plurality of optical isolator elements each of which comprises a pair of polarizers and a magneto-optical element disposed between said polarizers, the optical isolator elements have element cutoff wavelength bands which are different from one another. The optical isolator elements are arranged in series with an optical axis in common. Each element cutoff wavelength band is defined by an element cutoff central wavelength for a return light beam. The optical isolator device has a device cutoff wavelength band for the return light beam that is defined by a device cutoff central wavelength. When the optical isolator elements are equal in number to two, both of the optical isolator elements have a common wavelength area where the element cutoff wavelength bands overlap each other.

Abstract: An optical amplifier comprises first (22) and second (24) lengths of erbium-doped fibre connected in series via an isolator 20 which reduces the transmission of backward-travelling ASE from the second length to the first length when pump power in inputted in to the first length.

Abstract: Optical passive components comprising: a first optical fiber for outputting pumping light; a second optical fiber for receiving the pumping light and either outputting or receiving signal light; a third optical fiber for either receiving or outputting the signal light; a wavelength selecting filter which transmits therethrough the pumping light and reflects the signal light; a mirror which reflects most of the signal light reflected by the wavelength selecting filter and transmits therethrough a portion of the signal light reflected by the wavelength selecting filter such that the wavelength selecting filter and the mirror form an optical assembly; an optical isolator which passes therethrough the signal light reflected by the mirror so as to output the signal light; and a semiconductor optical detecting device for detecting the signal light transmitted through the mirror; wherein the first, second and third optical fibers are disposed at one side of the optical assembly.

Abstract: An optical isolator comprises two birefringent plates one of which separates two light components whose planes of polarization are perpendicular to each other to make the two light components spatially separate between the two birefringent plates and pass through two separate optical paths and the other of which thereafter combines the two separate light components, two Faraday rotators disposed between the two birefringent plates and having a Faraday rotation angle of approximately 45 degrees, a polarizer disposed between the two Faraday rotators and having a predetermined polarized-light transmitting angle, and a magnetic field device for applying an external magnetic field to the two separate optical paths in the two Faraday rotators to magnetize respective regions near the two optical paths in each of the rotators in opposite magnetization directions to each other.

Abstract: An optical isolator comprises a polarizer, a Faraday rotator, an analyzer and a magnet for applying a magnetic field to the Faraday rotator wherein the polarizer is incorporated into a first metal cylinder to form a polarizer unit, the Faraday rotator is incorporated into a cylindrical magnet to form a Faraday rotator unit and the analyzer is incorporated into a second metal cylinder to form an analyzer unit, the polarizer, Faraday rotator and analyzer units being arranged within an outer cylinder and the first metal cylinder and the second metal cylinder being joined to the outer cylinder through an adhesive component. The optical isolator can easily be produced, the adhered and supported portion thereof is not peeled off and it has high reliability.

Abstract: A non-reciprocal unit and a parallel-surfaced flat birefringent plate are provided between incident side and outgoing side fiber collimators. The non-reciprocal unit is formed by disposing two tapered birefrigent plates, one on each side of a 45.degree. Faraday rotator consisting of a cylindrical permanent magnet and a magneto-optical element housed in the magnet. The optical axes of the parallel-surfaced flat birefringent plate and adjacent tapered birefringent plate are staggered from each other by 90.degree.. The thickness of the parallel-surfaces birefringent plate is set equal to the sum of the thicknesses of the two tapered birefringent plates.

Abstract: A polarizer, a Faraday rotator and an analyzer are fixed by fused glass applied on an outer periphery of the polarizer to be contacted with the Faraday rotator and on an outer periphery of the analyzer to be contacted with the Faraday rotator. No adhesive exists between contact planes of the polarizer and the Faraday rotator and those of the Faraday rotator and the analyzer.

Abstract: In a polarization dependency type optical isolator comprising wedgelike polarizing prisms 3 and 5 and a Faraday rotator 4, the mode field diameters of an input side fiber 1 and an output side fiber 7 are the same as that of a transmission fiber and an erbium-doped fiber to be connected to them. The shape and other features of each lens are controlled so that the spot size of a parallel ray which is converted from an incident ray by an input side lens 2 is equal to the spot size of a parallel ray which is converted by an output side lens 6 when a reference beam is irradiated from the fiber 7. In a rare-earth-doped fiber optical amplifier using an optical isolator which is configured in a manner similar to this, the connecting portion of the fiber and the optical isolator can be spliced by fusion without increasing the insertion loss of the optical isolator in the forward direction and the connection loss due to a difference in the mode field diameter is reduced.

Abstract: A high quality small-sized polarization independent optical isolator for use in an optical fiber communication system, wherein a pair of magneto-optical elements having Faraday rotation angle of 45.+-.5 are contained in permanent magnets and arranged between a pair of birefringent crystal plates for splitting and combining an optical path of a laser light, and two polarizers arranged in parallel as being bounded on the midpoint of separated optical paths are interposed between the pair of magneto-optical elements, whereby a degree of worsening the optical isolation can be kept minimum against variations of an environmental temperature and wave length.

Abstract: An apparatus for creating an optical noise of a predetermined bandwidth that uses an optical amplifier which amplifies optical noise components and produces unpolarized optical noise by spontaneous emission, a mirror to reflect the optical noise components back to the optical amplifier and a filter that filters out optical noise components outside the predetermined optical bandwidth. The filter is located so that optical noise components passed by the filter are amplified in the optical amplifier during an additional amplification. Optionally, a polarizer and Faraday rotator are used in the apparatus. The optical noise created in the optical amplifier is polarized in the polarizer after two amplifications, rotated in the Faraday rotator, then amplified two more times before leaving the apparatus.

Abstract: An optical source particularly suitable as a pump is provided. A gain medium such as a thulium doped fiber has an input end and an output end. The input end is optically coupled to a reflector to cause spontaneous emissions within a predetermined band exiting the input of the gain medium to be reflected back into the medium. Spontaneous emissions outside of the predetermined band are lost. An optical isolator can be provided to prevent the optical source from lasing, resulting in a moderate bandwidth optical pump. A cascaded embodiment is disclosed, in which the gain medium is followed by an optical amplifier for increased power.

Abstract: A spherical multicomponent optical isolator having a first spherical segment lensing region, including a base, a second spherical segment lensing region, including a base, a first polarizer attached to the base of the first segment lensing region, a second polarizer attached to the base of the second spherical segment lensing region and A Faraday rotator disposed between the first and second polarizers, wherein the combination of the first and second spherical segments, the first and second polarizers and the Faraday rotator forms the spherical optical isolator having a spherical outer surface.

Abstract: An electrically tunable optical oscillator. An acoustooptically tunable filter is located in a feedback path of an optical oscillator. The filter non-collinearly diffracts the light signal to selectively tune the oscillator. In one embodiment the light signal passes twice through a single filter in a single transit around the feedback path. In another embodiment the light passes through a pair of filters which are arranged such that any frequency shift created by one is cancelled by the other.

Abstract: A solid-state tunable laser having a ND:YAG pumping source, a chromium-doped fosterite crystal lasing medium, a birefringent filter for selecting a specific fundamental wavelength, a pair of harmonic generating crystals mounted on counter-rotating platforms driven by stepper motors under the control of a computer, a partially reflective, partially transmissive mirror for directing the output of the pumping source through the lasing medium so that the lasing medium produces radiation having a range of fundamental wavelengths, and a fully reflective mirror for directing the radiation of the specific fundamental wavelength through the birefringent filter and the pair of crystals so as to produce radiation of a harmonic wavelength of the specific fundamental wavelength.

Abstract: An optical system in which optical circulators with polarization plates are used for light modulation of plane polarized light waves. The light modulation is used for black and white printing, grey scale printing and for adjustment of beam intensity of plane polarized light waves.

Abstract: An apparatus and method for flattening the gain of an optical fiber amplifier (18) doped with an ion such as erbium and which is pumped by a pump laser (20). Optical couplers (32, 34) inserted before and after the fiber amplifier couple the main optical path to an optical ring passing through the fiber amplifier so as to form a ring laser. An optical isolator (32) placed in the ring causes the lasing light to only counterpropagate relative to the optical signal being amplified. When the fiber amplifier primarily exhibits inhomogeneous broadening and the ring lases, the lasing light clamps the gain to a value determined by the loop loss, and the value of the clamped gain is relatively uniform across a wide bandwidth.