Abstract: A transmitting and receiving device includes a controller, a driver, a specific pattern generator, a transmitting signal detector, an amplifier, a differential amplifier, an average current detector, and a received signal detector. In a non-signal period, the controller causes a current signal to be input from the driver to a laser diode and causes an optical signal to be output from the laser diode. When an optical signal of a specific pattern output from the other-side laser diode reaches a photodiode over a period of length that depends on an average value of a current signal output from the other-side photodiode that receives the optical signal, the controller adjusts a magnitude of the current signal input from the driver to the laser diode based on the length of the period of the optical signal of the specific pattern.

Abstract: There is provided a semiconductor laser including: a first mirror layer; a second mirror layer; an active layer; a current confinement layer; a first region including a plurality of first oxidized layers; and a second region including a plurality of second oxidized layers, in which, in a plan view, the laminated body includes a first part including the first region and the second region, a second part including the first region and the second region, and a third part disposed between the first part and the second part and resonating light generated in the active layer, the third part includes a fourth part including the first region and the second region and having a first groove, a fifth part including the first region and the second region and having a second groove, and a sixth part disposed between the fourth part and the fifth part and sandwiched between the first part and the second part, in a plan view.

Abstract: Systems and methods for terahertz modulation in a terahertz frequency band from about 0.1 terahertz to about 10 terahertz propagating in a wellbore intersecting a subterranean earth formation. A transmitter generates the EM radiation in the terahertz frequency band. A modulator located in the wellbore receives the EM radiation and generates an amplitude modulated signal with the EM radiation.

Abstract: An optical source unit includes a first optical source for emitting a P-polarized light beam, a first detector for detecting whether the first optical source is normal or abnormal, a second optical source for emitting an S-polarized light beam, a second detector for detecting whether the second optical source is normal or abnormal, and a light beam combining section including a polarization beam splitter for transmitting the P-polarized light beam and reflecting the S-polarized light beam to combine the P-polarized light beam and the S-polarized light beam into an output light beam of the optical source unit.

Abstract: A self-starting, passively modelocked figure-8 fiber laser is specifically configured to self-start into a low noise mode by controlling one or more operating parameters of the laser including, but not limited to, the coupling ratio between the uni-directional fiber loop and the bi-directional mirror loop, the accumulated dispersion within the figure-8 structure, and the amount of power present in the laser cavity. A self-starting passive modelocked figure-8 laser may also be made to self-start by initially increasing the pump current above its lasing threshold. Including a band-pass filter in the uni-directional loop has been found to ensure that the laser will enter a low noise lasing mode.

Abstract: A laser apparatus is provided, which includes an optical reflection and gain unit, an optical modulation unit and a polarizing selection unit. The optical reflection and gain unit includes a gain medium and at least two dichroic surfaces, and is configured to generate a laser beam. The optical modulation unit and the optical reflection and gain unit form a cavity, and the optical modulation unit is configured to adjust phase boundary conditions of the cavity. The optical modulation unit includes portions that respectively correspond to optical phase boundaries in the cavity, so as to allow an optical field in the cavity to pass through the optical modulation unit at least twice. The polarizing selection unit is disposed between the optical reflection and gain unit and the optical modulation unit, and is configured to adjust the polarizing direction of the optical field incident to the optical modulation unit.

Abstract: A dual output semiconductor optical amplifier-based tunable fiber laser is provided that can be switched from low to high power and vice versa. The laser system uses bidirectional semiconductor optical amplifier (SOA) for amplification and hence is able to introduce a unique feature of adjustable dual/single output ports.

Abstract: Optoelectronic oscillator systems and an optoelectronic oscillator noise reduction method. One example of an optoelectronic oscillator system includes an optical source positioned at a first end of a fiber-optic path, the optical source being configured to transmit an optical signal along the fiber-optic path, an optical modulator positioned to receive and modulate the optical signal based on at least a reference signal, a retro-reflector positioned at a second end of the fiber-optic path, the retro-reflector being configured to receive and retro-reflect the optical signal, the retro-reflected optical signal having at least a frequency range of inherent fiber noise canceled, and an optical circulator positioned along the fiber-optic path between the optical modulator and the retro-reflector, the optical circulator being configured to direct the optical signal to the retro-reflector and direct the retro-reflected optical signal along a feedback path to a first photodetector to generate the reference signal.

Abstract: This invention relates to a method of projecting laser light onto a road surface from a vehicle. It also relates to an apparatus for projecting laser light onto a road surface from a vehicle. Said apparatus may be a stand-alone device mounted on a vehicle, or it may be integrally formed with a vehicle.

Abstract: In one embodiment, a lidar system includes a pump laser configured to produce pulses of light at a pump wavelength. The lidar system further includes an optical parametric oscillator (OPO) with an OPO medium configured to: receive the pump pulses from the pump laser; convert at least part of the received pump pulses into pulses of light at a signal wavelength and pulses of light at an idler wavelength; and emit at least a portion of the signal pulses. The lidar system also includes a scanner configured to scan the emitted pulses of light across a field of regard and a receiver configured to detect at least a portion of the scanned pulses of light scattered by a target located a distance from the lidar system. The lidar system also includes a processor configured to determine the distance from the lidar system to the target.

Abstract: A vertical cavity surface emitting laser includes: a laminated body; an insulation layer which is provided over at least a portion of the laminated body; an electrode of which at least a portion is provided over the laminated body; a pad; and a wiring which connects the electrode and the pad, wherein the laminated body includes a first mirror layer, an active layer, and a second mirror layer, the laminated body includes a first distortion imparting portion, a second distortion imparting portion, and a resonance portion which is provided between the first distortion imparting portion and the second distortion imparting portion, in a plan view, the electrode is provided so as to cover at least a portion of the resonance portion, in the plan view, a width of the wiring is greater than a width of the first distortion imparting portion and is smaller than a width of the electrode.

Abstract: Laser apparatus includes an output coupler, a gain medium for generating laser light, a rear optical element, and an input coupler. The input coupler is arranged to direct a pump beam to the gain medium and to define an optical path between the output coupler and the rear optical element. The rear optical element is a spatial light modulator arranged to act as an intra-cavity digital holographic mirror which can be digitally addressed. The spatial light modulator displays selectively a gray-scale image of a hologram thereby to phase-modulate laser light in the cavity, thus making it possible to generate an output laser beam having a desired characteristic. The apparatus includes a computer arranged to generate at least one hologram corresponding to a desired output beam characteristic, and a driver circuit responsive to an output from the computer to generate a corresponding gray-scale image of the hologram on the spatial light modulator.

Abstract: A laser apparatus may include: a master oscillator configured to output a pulsed laser beam at a repetition rate; at least one amplifier disposed on a beam path of the pulsed laser beam; at least one optical shutter disposed on the beam path of the pulsed laser beam; and a controller configured to switch the at least one optical shutter.

Abstract: Provided is a light-emitting element having high luminance and high directivity and emitting light in a controlled polarization state. The light-emitting element comprises substrate 3 and light emitting part 10 disposed on substrate 3 for emitting light in which light intensity of a polarization component in first direction x parallel to substrate 3 is higher than light intensities of polarization components in other directions. Light emitting part 10 includes active layer 12 for generating light and a plurality of structural bodies 14a disposed on a light-emitting side of light emitting part 10 with respect to active layer 12 and arrayed two-dimensionally along a surface substantially parallel to active layer 12. Each of structural bodies 14a has width w1 along first direction x and width w2 along second direction y perpendicular to first direction x, width w1 along first direction x and width w2 along second direction y being different from each other in a cross section parallel to active layer 12.

Abstract: A device for producing a coherent bi-color light source, including: an array substrate, a first laser tube driven by a first direct current signal, a second laser tube driven by a modulation signal coupled by a microwave signal and a second DC signal, a half wave plate, a birefringent crystal, a first quarter wave plate, a partially reflecting plane mirror, and a second quarter wave plate. The first laser tube and the second laser tube are fixed on the array substrate. The half wave plate, the birefringent crystal, the first quarter wave plate, the partially reflecting plane mirror, and the second quarter wave plate are disposed in sequence in an emission direction of a laser beam emitted by the first laser tube. The second laser tube is disposed opposite to the birefringent crystal.

Abstract: A ring laser-resonator generating plane-polarized fundamental-frequency radiation includes an optically nonlinear crystal configured for type-II second-harmonic generation of fundamental-frequency radiation. The resonator is configured such that fundamental-frequency radiation circulating either clockwise or counter-clockwise therein makes two passes through the optically nonlinear crystal per round-trip in the resonator in opposite directions, with polarization planes perpendicular to each other. This arrangement forces unidirectional circulation of radiation in the resonator during which second-harmonic radiation is not generated by the crystal.

Abstract: A laser oscillator includes: a optical resonator having an orthogonal mirror and a partial reflection mirror; a laser gas acting as a laser medium; and a 90-degree folding mirror acting as a polarization selecting element. The orthogonal mirror has two reflecting surfaces orthogonal to each other. The 90-degree folding mirror is arranged such that the polarization direction of the laser oscillated light is parallel to the reference axis set in a plane perpendicular to an optical axis of the optical resonator. The orthogonal mirror is arranged such that the polarization direction of the laser oscillated light is parallel to the valley line of the orthogonal mirror. This configuration can compensate anisotropy of optical characteristics in a laser medium, and stably generate linearly polarized laser light having excellent isotropy in a simple manner.

Abstract: In one embodiment, the invention relates to systems, methods and devices for improving the operation of an electromagnetic radiation source or component thereof. In one embodiment, the source is a laser source. A Fourier domain mode locked laser can be used in various embodiments. The sources described herein can be used in an optical coherence tomography (OCT) system such as a frequency domain OCT system. In one embodiment, laser coherence length is increased by compensating for dispersion. A frequency shifter can also be used in one embodiment to compensate for a tunable filter induced Doppler shift.

Abstract: The invention relates to a laser cavity with central extraction by polarisation for coherent coupling of intense intra-cavity beams. The laser cavity (1) according to the invention comprises an extraction unit (7) with central extraction, which divides the laser cavity (1) longitudinally into two functional portions (P1, P2), namely a first portion (P1) including the active components (3), which amplifies the laser beams (4), and a second portion (P2) which performs coherent coupling of the laser beams (4).

Abstract: There is disclosed a femtosecond laser apparatus including a first laser material comprising Ng, Np and Nm axes spatially perpendicular to each other; a second laser material comprising Np axis, Nm axis and Ng axis; and a first laser diode and second laser diodes, wherein the traveling direction of laser beams generated from the first and second laser materials is substantially parallel to Ng axis of the first laser material and the polarizing direction of laser beams generated from the first and second laser materials is substantially parallel to Np axis of the first laser material, and the traveling direction of laser beams generated from the first and second laser materials is substantially parallel to Np axis of the second material and the polarizing direction of laser beams generated from the first and second laser materials is substantially parallel to Nm axis of the second laser material.

Abstract: The multi-wavelength laser is a ring laser source working at room temperature. The laser has an inner cavity disposed in an outer cavity. A pair of circulators disposed in the inner cavity is configured to assure counter-propagation of light between the inner cavity and the outer cavity. A gain-clamped semiconductor optical amplifier (GC-SOA) is formed by combining a SOA and a Fiber Fabry-Perot Tunable Filter (FFP-TF) with the circulator pair. This configuration in the laser cavity results in an improvement in terms of transient gain excursions by applying an optical feedback. This attribute of the GC-SOA enables realizing a stable multi-wavelength laser source.

Abstract: An optical transmitter includes a laser configured to emit light, a power of the light increasing with temperature decreasing, a Faraday rotator configured to rotate a polarization direction of the light in accordance with the temperature, and a first polarizer that has a principal axis inclined at a given angle and inputs the light output from the Faraday rotator.

Abstract: A main amplifier system includes a first reflector operable to receive input light through a first aperture and direct the input light along an optical path. The input light is characterized by a first polarization. The main amplifier system also includes a first polarizer operable to reflect light characterized by the first polarization state. The main amplifier system further includes a first and second set of amplifier modules. Each of the first and second set of amplifier modules includes an entrance window, a quarter wave plate, a plurality of amplifier slablets arrayed substantially parallel to each other, and an exit window. The main amplifier system additionally includes a set of mirrors operable to reflect light exiting the first set of amplifier modules to enter the second set of amplifier modules and a second polarizer operable to reflect light characterized by a second polarization state.

Abstract: Materials, methods, structures and device including the same can provide a semiconductor device such as an LED using an active region corresponding to a non-polar face or surface of III-V semiconductor crystalline material. In some embodiments, an active diode region contains more non-polar III-V material oriented to a non-polar plane than III-V material oriented to a polar plane. In other embodiments, a bottom region contains more non-polar m-plane or a-plane surface area GaN than polar c-plane surface area GaN facing an active region.

Abstract: In one embodiment, the invention relates to systems, methods and devices for improving the operation of an electromagnetic radiation source or component thereof. In one embodiment, the source is a laser source. A Fourier domain mode locked laser can be used in various embodiments. The sources described herein can be used in an optical coherence tomography (OCT) system such as a frequency domain OCT system. In one embodiment, laser coherence length is increased by compensating for dispersion. A frequency shifter can also be used in one embodiment to compensate for a tunable filter induced Doppler shift.

Abstract: Disclosed is a laser apparatus of amplifying a laser pulse output using an anisotropic laser crystal through chirped pulse amplification. The laser apparatus includes a laser resonator. The laser resonator includes a plurality of anisotropic laser crystals, generates a shorter femtosecond pulse by widening a spectrum bandwidth through a combination of different gain spectrum distributions using the anisotropic laser crystals, and allows a laser beam to travel in axial directions with different thermal characteristics of the anisotropic layer crystals in order to reduce a thermal effect.

Abstract: A system is provided to generate coherent single-frequency and single transverse mode light pulses. A laser produces a linearly-polarized continuous wave beam defined by a single longitudinal and transverse mode. A first rotator processes the beam such that optical polarization is rotated during a first time period and not rotated during a second and third time period. A second rotator is operated during the first period to rotate optical polarization of the beam, during the second period to not rotate the beam, and during the third period to rotate the beam. An optical loop amplifies the beam during the first and second periods. An amplifier device can be added to the loop for amplification. A first beam splitter allows the beam to enter the loop and a second splitter directs the beam along the loop during the first and second periods and out of the loop during the third period.

Abstract: One embodiment of a laser resonator comprises one or more laser resonator components, a container and an ozone generator. The laser resonator components include a non-linear crystal, a beam polarization combiner, an optical lens, a mirror and/or an optical grating. The container encloses the one or more laser resonator components. The ozone generator is configured to introduce ozone gas into the container.

Abstract: The present invention relates to a switchable dual wavelength solid state laser with a solid state gain medium (1) which is selected to emit optical radiation at a first wavelength with a first polarization and of at least a second wavelength with a second polarization different from said first polarization when optically or electrically pumped. A polarizing device (7) is arranged within the laser cavity, said polarizing device (7) being adjustable at least between said first and said second polarization. The two end mirrors (2, 3) of the laser cavity are designed to allow lasing of the solid state laser at the first wavelength when the polarizing device (7) is adjusted to the first polarization, and to allow lasing of the solid state laser at the second wavelength when the polarizing device (7) is adjusted to the second polarization. The proposed solid state laser allows an easy switching between two emission wavelengths.

Abstract: The invention relates to a laser source with an external cavity generating a useful laser beam (Fu), that comprises at least one laser diode DL (10) mounted in an extended optical cavity (30, 82) defined between two reflecting surfaces (92, 48) forming an optical path for a laser beam Fd generated by the laser diode DL, a mode selection filter (44, 86) in the optical path of the cavity for selecting a resonance mode from a range of resonance modes of the laser beam in the cavity.

Abstract: A laser resonator and method for forming the laser resonator are provided. The method comprises placing a housing for the laser resonator in an alignment fixture, attaching a bond plate to an optical component of the laser resonator, attaching a first end of an alignment arm to the bond plate attached to the optical component, attaching a second end of the alignment arm to the alignment fixture such that the optical component is disposed over the housing, aligning, via the alignment fixture and the alignment arm, the optical component relative to the housing, and bonding the aligned optical component to the housing. The first end of the alignment arm may removed once the aligned optical component is bonded to the housing.

Abstract: A high extraction efficiency laser system. The novel laser system includes a laser amplifier and a laser source adapted to provide a laser beam to the amplifier such that polarization states for incident and reflected light within the amplifier are perpendicular one to another. In an illustrative embodiment, the laser beam is input to the amplifier such that the beam reflects back and forth between the side walls of the amplifier with an angle of incidence of about 45 degrees, and the laser beam is linearly polarized in the plane of incidence. This arrangement reduces interference fringes in the amplifier. In an alternative embodiment, the system includes an aberrator adapted to add time-varying aberrations in the laser beam at a rate exceeding an inversed lifetime of an inverted population in the amplifier to increase spatial homogenization of saturation and extraction patterns in the amplifier.

Abstract: The present invention relates to a switchable dual wavelength solid state laser with a solid state gain medium (1) which is selected to emit optical radiation at a first wavelength with a first polarization and of at least a second wavelength with a second polarization different from said first polarization when optically or electrically pumped. A polarizing device (7) is arranged within the laser cavity, said polarizing device (7) being adjustable at least between said first and said second polarization. The two end mirrors (2, 3) of the laser cavity are designed to allow lasing of the solid state laser at the first wavelength when the polarizing device (7) is adjusted to the first polarization, and to allow lasing of the solid state laser at the second wavelength when the polarizing device (7) is adjusted to the second polarization. The proposed solid state laser allows an easy switching between two emission wavelengths.

Abstract: A new and useful attenuating device and method for attenuating a polarized laser beam is provided. At least one attenuating optic is located along, and is rotatable about, a polarized laser beam axis, and is configured to transmit and to reflect portions of the polarized laser beam. The attenuating optic provides predetermined attenuation of the polarized laser beam by changing the ratio between transmission and reflection of the polarized laser beam as a function of the incidence of the polarized laser beam on one or more partially reflective surfaces of the attenuating optic. The attenuating optic is rotatable about the polarized laser beam axis to control the incidence of the polarized laser beam on the one or more partially reflective surfaces of the attenuating optic, thereby to control the ratio between transmission and reflection of the polarized laser beam and provide a range of attenuation of the polarized laser beam.

Abstract: At least one surface of a plate member made of ZnSe has a concave-and-convex structure in which a projecting section and a groove section are formed at a spatial cycle equal to or lower than the wavelength of carbon dioxide laser light to thereby provide a substrate body. On a surface of the concave-and-convex structure, an antireflection film is layered that has a lower refractive index than that of ZnSe to carbon dioxide laser light. By this configuration, the polarization state of transmitted carbon dioxide laser light is converted from a linear polarization to a circular polarization or the like.

Abstract: A solid state laser device is provided. The active element has a double slope portion defining a right angle between the slopes, wherein the pump light beam is directed into one of the slopes, and wherein an output coupler configured to output a laser beam from the active element is located on a portion of the active element, opposite of the double slope portion, the double slope portion is configured such that the laser beam travels at least twice along the long axis of the active element; and a second double slopes portion located at the edge opposite of the first double sloped portion, wherein the second double slopes portion is perpendicular to the first double slopes portion, and wherein the second double slopes portion is configured such that the laser beam travels back and forth along the long axis of the active element at least one more time.

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

Abstract: A harmonic frequency conversion module is disclosed including a polarization maintaining (PM) fiber optical link for providing an output stabilized from power fluctuation by the inclusion of one or more polarizers in the PM fiber optical link. Removing polarization distortions removes noise which has a significant negative effect on the output of harmonic frequency conversion elements. It has been found that the noise in frequency converted light has additional components, caused by mode interaction during conversion. In accordance with the present invention, we are able to remove the spikes in this noise, making it more stable and less dependent on external conditions. If the PM optical fiber route consists of multiple elements creating polarization distortions, a polarizer should be inserted between the most distorting element and the output of the fiber system. If many elements contribute to polarization distortions, several polarizers can be inserted into the system.

Abstract: A slab type laser apparatus has a slab type gas laser medium part formed in a region defined by a pair of electrode flat plates oppositely disposed in parallel with each other in a space to be filled with a gas laser medium which is excited by high-frequency electric power. The apparatus includes an oscillator part including a pair of resonator mirrors oppositely disposed with a part of the gas laser medium part in between, and for amplifying a laser beam to have predetermined light intensity to emit the laser beam, and the amplifier part including a plurality of return mirrors oppositely disposed with a part of the gas laser medium part in between. The incident laser beam goes and returns plural times between the return mirrors, and the laser beam is amplified to have predetermined power.

Abstract: A surface emitting laser includes a plurality of light-emitting portions for emitting laser light beams in different linearly polarized light directions. The light-emitting portions are formed on the substrate and located close to each other. The light-emitting portions include metal opening arrays through which light beams in different linearly polarized light directions respectively pass.

Abstract: Systems and methods are disclosed herein to provide monoblock lasers that may provide improved performance and/or reduce manufacturing costs. For example, in accordance with an embodiment of the present invention, a monoblock laser includes a gain block to generate the light at the first wavelength and a Q switch to receive and polarize the light from the gain block and provide pulsed light that is polarized and at the first wavelength, with the monoblock laser configured in an internal OPO configuration. The monoblock laser may include a film between the gain block and a common substrate and/or include various techniques for aligning various optical elements within the monoblock laser.

Abstract: A diode-pumped intra-cavity frequency-tripled continuous laser device, this device includes: an amplifying medium, a birefringent non-linear medium for frequency doubling, a birefringent non-linear medium for frequency tripling; and a polarizing medium arranged so as to constitute an intra-cavity birefringent filter or Lyot filter, the Lyot filter being adapted to allow monofrequency output emission from the laser device.

Abstract: Semiconductor electrooptic medium shows behavior different from a medium based on quantum confined Stark Effect. A preferred embodiment has a type-II heterojunction, selected such, that, in zero electric field, an electron and a hole are localized on the opposite sides of the heterojunction having a negligible or very small overlap of the wave functions, and correspondingly, a zero or a very small exciton oscillator strength. Applying an electric field results in squeezing of the wave functions to the heterojunction which strongly increases the overlap of the electron and the hole wave functions, resulting in a strong increase of the exciton oscillator strength. Another embodiment of the novel electrooptic medium includes a heterojunction between a layer and a superlattice, wherein an electron and a hole in the zero electric field are localized on the opposite sides of the heterojunction, the latter being effectively a type-II heterojunction.

Abstract: A system for producing a laser light pulse is disclosed. The system includes a travelling wave or ring laser incorporating a gain medium with polarizing means for introducing substantially polarized radiation having a first polarization state into the travelling wave laser and output coupling means to substantially output couple radiation having an output polarization state from the travelling wave laser. The system further includes polarization changing means incorporated into the optical path of the travelling wave laser for changing the polarization of radiation having the first polarization state to a seeding polarization state, wherein radiation with the seeding polarization state seeds the gain medium, and radiation intensity modulation means for modulating the intensity of radiation in the travelling wave laser to vary the feedback of radiation into the gain medium, wherein the radiation intensity modulation means also modulates the radiation with respect to the output coupling means.

Abstract: A horizontal cavity, surface emitting laser (HCSEL) with internal polarization rotation is used in thermally assisted recording in hard disk drives. The desired polarization of the laser is accomplished with two beam reflections off of facets within the diode. The facets are formed in a single ion beam etching step. This device can be used in a thermally assisted recording head to produce polarization incident on the disk aligned with the direction of the tracks on the disk.

Abstract: A single longitudinal-mode laser includes a first mirror and a second mirror that define a laser cavity therein that does not include a linear polarizer. A birefringent gain medium can generate a lasing light at a lasing wavelength along a light propagation direction in response to a pump light at a pumping wavelength. The birefringent gain medium has an optical axis substantially perpendicular to the light propagation direction. A first wave plate positioned between the first mirror and the birefringent gain medium is a quarter wave plate at the lasing wavelength and a whole wave plate at the pumping wavelength. A second wave plate is positioned between the birefringent gain medium and the second mirror. The first wave plat and the second wave plate in part produce a single longitudinal mode in the lasing light.

Abstract: In a cavity-dumped, repetitively-pulsed, solid-state laser cavity dumping is protracted over a predetermined time longer than a round-trip time of the resonator of the laser. The cavity dumping is effected by a Pockels cell optical switch. During a dumping period a voltage applied to the Pockels cell falls in a predetermined time. Varying the voltage fall-time varies the duration of pulses provided by the laser, independent of the pulse-repetition frequency.

Abstract: A regenerative amplifier includes a gain-medium that is optically pumped by CW radiation. The amplifier has primary resonator for amplifying pulses. The primary resonator has an optical switch for opening and closing the primary resonator. The amplifier has a secondary resonator that includes the gain-medium but not the optical switch. When the primary resonator is closed by the optical switch, and pulses are not being amplified, CW radiation is generated in the secondary resonator and prevents the gain-medium from being saturated. When the optical switch is operated to cause the primary resonator to amplify pulses, generation of CW radiation in the secondary resonator ceases.

Abstract: A laser arrangement is provided, in which a Lyot filter arrangement is operative to effect single mode operation. The birefringent element of the Lyot filter arrangement has a cavity folding mirror on one side thereof and a polarizing element on another side thereof, such that the free spectral range of the Lyot filter is improved. Preferably, the Lyot filter arrangement and the laser gain material are located in different branches of the folded cavity.

Abstract: A laser module including a light emitter, a polarizing and filtering unit, a nonlinear optical crystal, and a first filter is provided. The light emitter emits a first beam. The polarizing and filtering unit is disposed on a transmission path of the first beam. A part of the first beam passes through the polarizing and filtering unit to become a second beam with a specific polarization direction. The nonlinear optical crystal is disposed on a transmission path of the second beam from the polarizing and filtering unit. The nonlinear optical crystal converts a part of the second beam into a third beam. The first filter is disposed on a transmission path of a non-converted part of the second beam and the third beam from the nonlinear optical crystal. The non-converted part of the second beam is reflected by the first filter. The third beam passes through the first filter.