Abstract: The invention relates to a broadband Terahertz (THz) radiation generation and detection system and method. THz radiation is generated by optical rectification of an ultrashort pump pulse of a first wavelength having a duration in the picosecond- or sub-picosecond range in a first nonlinear optical crystal. The THz radiation is detected by electro-optic sampling or another appropriate method of a probe beam having a second wavelength in a second nonlinear optical crystal. According to the invention, at least one of the following conditions is fulfilled: a) the first wavelength is different from the second wavelength; b) the material of the first nonlinear optical crystal is different from the material of the second nonlinear optical crystal.

Abstract: An optical antenna assembly including multiple optical antenna elements, each of the optical antenna elements are arranged in a regular pattern and carried by a supporting body. The regular pattern of the plurality of optical antenna elements is nonuniform. Certain ones of the optical antenna elements are configured to respond to the one or more waves of light.

Abstract: A wavelength conversion device is disclosed. The wavelength conversion device includes at least a fundamental wave light source and an external resonator, where a reflectance Rin of an input coupling element that inputs light from the fundamental wave light source to the external resonator is selected as represented by the equations 1 and 2, when a frequency jitter of the fundamental wave light source is ?fjitter, a resonator length of the external resonator is Lcav, a frequency line width of the external resonator is ??cav, a total internal loss of the external resonator is ?, and a speed of light is c.

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.

Abstract: A wavelength converter of the present invention is provided with a laser resonator including a fiber containing an laser-active material and a fiber grating formed in the fiber, a laser light source for emitting an excitation light to the fiber, and a wavelength conversion element for converting a fundamental wave of a laser beam emitted from the laser resonator into a harmonic, wherein the fiber is coiled and has the outer side thereof coated with a heat radiating member having a reflection surface for reflecting light having a wavelength of an excitation light. The wavelength converter is designed to prevent an efficiency reduction caused by the heat generation of a rare-earth doped fiber in a wavelength converter.

Abstract: The present invention relates to a device for modifying, e.g. narrowing the wavelength range of a spectrum of light.

Abstract: This invention relates to methods and apparatus for generating an optical frequency comb. In embodiments a passive mode locked optical waveguide comb uses electrical or optical tuning for the mode spacing frequency (df) and the carrier envelope offset frequency (fceo). We describe a passive mode locked optical comb frequency source comprising: an optical cavity having an optical driver and an optical output to provide an optical comb; an absorbing element coupled to said optical cavity for producing said optical comb; and an optically or electrically controllable element in said optical cavity; and wherein said optically or electrically controllable element has an optically or electrically controllable refractive index such that said refractive index is variable to vary one or both of a mode spacing and a carrier envelope offset frequency of said optical comb.

Abstract: A surface plasmon element comprising an array of metal nanoparticles (1) with an adsorbed layer of resonant material and the use of such material to activate said array.

Abstract: The present invention relates to a large-sized and high-quality bismuth-zinc-borate (Bi.sub.2 ZnB.sub.2 O.sub.7) single crystal, preparation methods and applications thereof. The crystal has cross-sectional dimensions greater than one centimeter, a nonlinear optical effect of about 3-4 times that of KH.sub.2 PO.sub.4 (KDP), and an optical transmission wavelength range of 330-3300 nm. The crystal can be grown from a compound melt by a Czochralski method, a Kyropoulos method or a Bridgman method with the raw material being the synthetic compound Bi.sub.2 ZnB.sub.2 O.sub.7. Alternatively, the crystal may be grown from a high-temperature solution method by using Bi.sub.2 O.sub.3 as a flux. The crystal may be applied in nonlinear optical devices such as frequency doubling generators, frequency upconverters or downconverters, and optical parametric oscillators.

Abstract: An allowable temperature range satisfying phase matching conditions of a wavelength conversion device is widened. A wavelength conversion light source includes a semiconductor laser diode device (1) applied with an antireflection film (3), a lens (4) arranged opposite to the semiconductor laser diode device (1), an optical fiber (5) having a Bragg grating (6) arranged in a core thereof, and a wavelength conversion device (8) formed of a nonlinear optical crystal on which light from the semiconductor laser diode device (1) is incident. In the wavelength conversion light source, the semiconductor laser diode device (1) oscillates in coherent collapse mode.

Abstract: A wavelength-converted light generating apparatus 1A includes: an excitation light source 10 supplying excitation light L0 of a predetermined wavelength; and a wavelength conversion element 20, in which an aggregate 22 of crystals of a dye molecule is held by a holding substrate 21 and which, by incidence of the excitation light L0, generates converted light L1 that has been wavelength-converted. The excitation light source 10 supplies the excitation light L0 of a wavelength longer than an absorption edge of the dye molecule to the wavelength conversion element 20. The wavelength conversion element 20, by incidence of the excitation light L0 on the crystal aggregate 22, generates and outputs the converted light (for example, visible light) L1 that has been wavelength-converted to a shorter wavelength than the excitation light (for example, near-infrared light) L0.

Abstract: A wavelength conversion device that obtains, from an input light, a wavelength-converted light with a wavelength shift by a wavelength shift amount of ?? is disclosed. The device comprises first and second wavelength converters. The first wavelength convertor shifts a central wavelength of a first wavelength-converted light by a first wavelength shift amount of ??1 relative to a central wavelength of an input light. The second wavelength convertor shifts a central wavelength of a second wavelength-converted light by a second wavelength shift amount of ??2 relative to a central wavelength of the first wavelength-converted light. The first wavelength shift amount of ??1 and the second wavelength shift amount of ??2 satisfy ??1+??2=??.

Abstract: The present invention relates to a composition for photon energy up-conversion, a system comprising said composition and to uses of said composition and said system.

Abstract: A laser light source device includes: a light source; an external resonator; a wavelength conversion element converting the wavelength of part of incident light having the first wavelength into the second wavelength which is different from the first wavelength; and an optical-path conversion element causing the light that has been converted into light of the second wavelength in the process of traveling to the light source due to reflection from the external resonator to be separated into a second optical-path different from the first optical-path, and emitting a second laser light of the second wavelength. In the laser light source device, and the height of the wavelength conversion element is greater than a distance between an optical-axis of the first laser light on an end face of the wavelength conversion element which is close to the external resonator and an optical-axis of the second laser light.

Abstract: An optical homodyne communication system and method in which a side carrier is transmitted along with data bands in an optical data signal, and upon reception, the side carrier is boosted, shifted to the center of the data bands, and its polarization state is matched to the polarization state of the respective data bands to compensate for polarization mode dispersion during transmission. By shifting a boosted side carrier to the center of the data bands, and by simultaneously compensating for the effects of polarization mode dispersion, the provided system and method simulate the advantages of homodyne reception using a local oscillator. The deleterious effects of chromatic dispersion on the data signals within the data bands are also compensated for by applying a corrective function to the data signals which precisely counteracts the effects of chromatic dispersion.

Abstract: A light source device includes: a first light source unit and a second light source unit emitting light; and a wavelength conversion element converting wavelengths of lights emitted from the first light source unit and from the second light source unit. Chief ray of light emitted from the first light source unit and transmitted through the wavelength conversion element is not parallel with chief ray of light emitted from the second light source unit and transmitted through the wavelength conversion element.

Abstract: Walk-off corrected (WOC) non-linear optical (NLO) components, devices and systems including one or more engineered WOC NLO crystal doublets. Such systems and devices advantageously increase the efficiency of an OPO operation. Devices are applicable to any uniaxial and biaxial NLO crystals in a wide range of wavelengths, e.g., from far ultraviolet to visible to far infrared. Devices employing engineered WOC NLO components according to embodiments of the present invention include any conventional frequency converting architectures. Systems and methods are also provided to unambiguously determine and correct walk-off for any arbitrary uniaxial and biaxial crystal orientation. The correct crystal orientation is also experimentally confirmed. This allows the use of WOC crystal doublet assemblies for a wide range of wavelengths and NLO crystals that until now have not been used because of low efficiency due to walk-off and inability of readily correcting walk-off.

Abstract: A device for generating a high power frequency converted laser beam includes a nonlinear optical crystal having an entrance surface and a curved surface. The nonlinear optical crystal is configured to receive at least one laser beam at the entrance surface and provide a frequency converted beam through a frequency conversion process. The device also includes an optical coating coupled to the curved surface. The reflectance of the optical coating is greater than 50% at a wavelength of the frequency converted beam. Additionally, the far field divergence angle of the frequency converted beam increases after reflection off the curved surface. The device further includes a heat sink in thermal contact with the optical coating.

Abstract: A nonlinear optical system comprises a metallic film having a first side and a second side. The nonlinear optical system further comprises a regular array of slits in the metallic film. The slits connect the first and second sides of the metallic film. The array is configured to selectively transmit through the metallic film light having frequencies of a selected frequency band. The nonlinear optical system still further comprises a nonlinear optical material situated within the slit.

Abstract: An apparatus includes one or more optical couplers, an optical medium, and an optical pump source. The optical medium behaves as a negative refractive index material over a frequency range. The one or more optical couplers are configured to provide first and second optical inputs to the optical medium and to provide an optical output from the optical medium. The optical pump source is coupled by one of the one or more optical couplers to deliver pump light to the optical medium.

Abstract: A wavelength conversion optical device is provided with a fundamental wave light source (301) which outputs a fundamental wave (L11) including a P polarized light and an S polarized light that are perpendicular to each other, and two wavelength conversion mechanisms (303a, 303b) each having a polarization inversion formation part which wavelength-converts the fundamental wave (L11) to generate harmonic waves, and the first-stage wavelength conversion mechanism (303a) performs wavelength conversion of the P polarized light of the fundamental wave (L11) while the second-stage wavelength conversion mechanism (303b) performs wavelength conversion of the S polarized light of the fundamental wave (L11), whereby absorption of a second harmonic wave (green light) due to a third harmonic wave (ultraviolet light) is reduced, and stability and reliability of the wavelength-converted light output are enhanced, thereby providing a wavelength conversion optical device which can output a wavelength-converted light capable o

Abstract: A wavelength converting apparatus that improves output performance of laser light subjected to wavelength conversion while improving the efficiency of laser light wavelength conversion. Wavelength converting apparatus (100) has: nonlinear optical crystal (110) converting wavelength of laser light propagating inside wavelength converting apparatus (100); right angle prism (130) deflecting laser light emanating from nonlinear optical crystal (110) and causing the laser light to be incident on nonlinear optical crystal (110) again, and to propagate in parallel and in opposite directions at a predetermined distance with respect to laser light before emanation from nonlinear optical crystal (110); and first dichroic mirror (120) separating laser light subjected to wavelength conversion inside nonlinear optical crystal (110) from the laser light before incidence on nonlinear optical crystal (110) for a second time.

Abstract: The present invention concerns a fiber device capable of shifting an oscillation wavelength of a fundamental wave of a laser emitted therefrom, and is provided with a laser cavity including a fiber containing a laser active substance and having at least one fiber grating formed therein, and a laser light source for introducing an excitation light to the fiber. The laser cavity is constructed to be able to shift the oscillation wavelength of the fundamental wave of the laser emitted therefrom.

Abstract: This device for optically regenerating pulses includes a synchronous intensity modulator to provide time synchronization for pulses passing through it and to stabilize intensity fluctuations in the pulses. In addition, it includes noise suppression circuitry in the form of a saturable absorber that is distinct from the synchronous intensity modulator and the intensity fluctuations stabilizer.

Abstract: A wavelength conversion member which can achieve high color purity and optimize color temperature according to environmental changes, a light source assembly including the wavelength conversion member, and a liquid crystal display (LCD) including the light source assembly. The light source assembly includes a light-emitting chip which generates light and a wavelength conversion member which includes wavelength conversion particles that convert the light into light having a predetermined wavelength, the predetermined wavelength being determined according to the size of the wavelength conversion particles.

Abstract: In one embodiment of the present invention, a quantum entangled photon-pair producing device is disclosed which includes a superposed state generating device for generating a superposed state of photon-pairs entering through N (N?2) different incident optical paths and being composed of photons having different polarization directions, and a light-guide device for separating the photon-pairs entering through the N (e.g. N is two) incident optical paths into photons having a first polarization direction (e.g. horizontally polarized light) and those having a second polarization direction (e.g. vertically polarized light) and guiding the photons having the first polarization direction and entering through the i-th (1?i?N) (e.g. the first) incident optical path and photons having the second polarization direction and entering through the (N?i+1) (e.g. the second) incident optical path to the i-th (e.g. the first) exit optical path through optical paths having the same optical path length.

Abstract: A light-emitting device which includes a semiconductor light-emitting element, and a plurality of plate-like wavelength conversion members which are disposed to face the semiconductor light-emitting element and are inclined with respect to the optical axis of excitation light emitted from the semiconductor light-emitting element, the plate-like wavelength conversion members containing respectively a fluorescent material which is capable of absorbing the excitation light and outputting light having a different wavelength from that of the excitation light, and the plate-like wavelength conversion members as a whole emitting visible light.

Abstract: A system for producing frequency converted light includes a first seed laser operable to provide a first laser signal and a second seed laser operable to provide a second laser signal. The system also includes an optical combiner optically coupled to the first seed laser and the second seed laser. The optical combiner is operative to combine the first laser signal and the second laser signal into a combined laser signal. The system further includes a power amplifier optically coupled to the optical combiner. An intensity of both the first laser signal and the second laser signal are increased by the power amplifier. The system additionally includes a harmonic converter optically coupled to the power amplifier.

Abstract: The present invention aims to provide a tuning light source apparatus including a multiple-optical resonator, where the resonance frequencies of the respective optical resonators in a multiple-optical resonator are exactly coincided with the set frequency, and the frequency of the output laser beam is locked within a range of about 1 GHz from the set frequency. Current is flowed to TO phase shifters based on lights detected by light receiving elements, and the resonance wavelengths of resonators are adjusted in an aim of obtaining a state in which an intensity of an oscillation light becomes a maximum and at the same time an intensity of a light from a through port becomes a minimum.

Abstract: A WDM communication system having two optical-frequency comb sources (OFCSs) that are substantially phase-locked to one another, with one of these OFCSs used at a transmitter to produce a WDM communication signal and the other OFCS used at a receiver to produce multiple local-oscillator signals suitable for homodyne detection of the WDM communication signal received from the transmitter. In one embodiment, the transmitter has (i) a first OFCS adapted to generate a first frequency comb and (ii) an optical modulator adapted to use the first frequency comb to generate a WDM communication signal having at least two beacon lines for transmission to the receiver. The receiver has a second OFCS adapted to produce a second frequency comb having the beacon frequencies, with the phases of the corresponding comb lines being locked to the phases of the beacon lines of the received WDM signal.

Abstract: A light emitting device includes a first unit having a first excitation light source including a laser element emitting blue wavelength band excitation light, and a first wavelength converting member including at least one type of fluorescent material and which absorbs at least a portion of a first excitation light, converts the wavelength, and releases light with a wavelength longer than the first excitation light, and a second unit having a second excitation light source including a laser element which emits excitation light with a wavelength band shorter than the blue wavelength band excitation light, and a second wavelength converting member which includes at least one type of fluorescent material and which absorbs at least a portion of a second excitation light, converts the wavelength, and releases light with a wavelength longer than the second excitation light. The first unit and the second unit are combined using a bundle fiber.

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 as 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 the other part of the second beam and the third beam from the nonlinear optical crystal. The other part of the second beam is reflected by the first filter. The third beam passes through the first filter.

Abstract: A method and apparatus for accurately retrieving the position of an optical feature. The method uses the optical properties of biaxial crystals to conically refract the optical feature and transform the image of the optical feature to a circular ring structure. The position of the optical feature is then calculated by locating a center point associated with the circular ring structure.

Abstract: The present invention aims to provide a wavelength converter capable of stably obtaining a W-class high-output green laser beam and a 2D image display device using this wavelength converter. By causing a polarization direction of a laser light source for generating an excitation light and that of a light emitted from an oscillator to orthogonally intersect, the deterioration of an excitation light source by an ASE is suppressed by a polarization splitting element provided between a laser resonator and the laser light source.

Abstract: A technique for generating variable pulse delays uses one or more nonlinear-optical processes such as cross-phase modulation, cross-gain modulation, self-phase modulation, four-wave mixing or parametric mixing, combined with group-velocity dispersion. The delay is controllable by changing the wavelength and/or power of a control laser. The delay is generated by introducing a controllable wavelength shift to a pulse of light, propagating the pulse through a material or an optical component that generates a wavelength dependent time delay, and wavelength shifting again to return the pulse to its original wavelength.

Abstract: To induce a targeted non-linear optical effect by a high-peak-power light by using a light pulse from a semiconductor laser without using a light pulse from a large, high-average-power solid laser such as titanium sapphire laser. A semiconductor laser pulse beam with a wavelength of 1550 nm (for example, repeatability of 1 MHz) from a semiconductor laser (laser diode: LD) is efficiently amplified in two stages, front-end and main EDFAs. An optical filter removes a spontaneous emission light component that is noise. An optical filter picks up, from the amplified pulse beam, second harmonic light pulse produced by the non-linearity of an optical device (frequency polarization inversion Mg-added LiNbO3:PPMgLN) to produce a super-continuum light in a 800 nm wavelength region from a photonic crystal fiber (PCF).

Abstract: An optical antenna collects, modifies and emits energy at light wavelengths. Linear conductors sized to correspond to the light wavelengths are used. Nonlinear junctions of small dimension are used to rectify an alternating waveform induced upon the conductors by the lightwave electromagnetic energy. The optical antenna and junctions are effective to produce harmonic energy at light wavelengths. The linear conductors may be comprised of carbon nanotubes that are attached to a substrate material, which may then be connected to an electrical port.

Abstract: A laser system for a spectroscopic catheter system uses multiple semiconductor gain media having gain peaks at different wavelengths. The output from the gain media is preferably coupled into single-mode fiber using conventional opto-electronic packaging techniques. As a result, the laser oscillator source has a spectral output that is wider than the gain bandwidth of a single medium to enable it to access the entire spectrum of interest, which is presently in the near infrared. Moreover, the semiconductor gain media can be packaged in a stable and controlled environment for long-term performance.

Abstract: A laser system (10) for use in photonic excitation investigation of a target object, in which the target object interacts with incident photons and emits a corresponding photon which is detected and used to generate an image of the target object. The laser system (10) includes a pulsed fiber laser (14) for producing a laser beam, and a non-linear photonic crystal fiber (16) for carrying the laser beam from the laser (14) to an instrument (18) for photonically exciting the target object. The photonic crystal fiber (16) allows for switching, or tuning, the wavelength of the laser beam. In two-photon microscopy, the laser system (10) allows for providing multiple wavelengths for exciting a plurality of different fluorophores simultaneously. In coherent Raman imaging and spectroscopy, the laser system (110) allows for using a single laser to provide two laser beams of different wavelengths.

Abstract: In detection and sensing, light is transmitted through layers or structures that vary laterally, such as with a constant gradient or a step-like gradient. After transmission, a position of a transmitted portion of the light or of output photons can be used to determine wavelength change or to obtain other photon energy information. The light can be received, for example, from a stimulus-wavelength converter such as an optical fiber sensor or another optical sensor. A component that propagates the light from the converter to a transmission structure can spread the light across the transmission structure's entry surface. At the exit surface of the transmission structure, photosensor components can sense or detect transmitted light or output photons, such as with a photosensor array or a position sensor. A photosensed quantity can be compared, such as with another photosensed quantity or with a calibration quantity. A differential quantity can be obtained using photosensed quantities.

Abstract: When a domain inversion part is produced by means of electric field polling process, damage in the vicinity of the forward end of a comb electrode and deviation of width of each domain inversion part are to be reduced. A polarization domain inversion structure has polarization domain inversion parts is produced by electric field poling process using a comb electrode formed on one surface of a substrate of a ferroelectric single crystal and of a single domain, and the comb electrode has a plurality of electrode portions and feeding portion. Each of the electrode portions corresponds with each domain inversion part of the domain inversion structure. The electrode portion has a plurality of low resistance pieces arranged in a direction “F” intersecting the longitudinal direction “E” of the electrode portion and spaced apart with each other.

Abstract: A nonlinear optical signal-treating apparatus can suppress the distortion of pulse light to be inputted into an optical fiber to an allowable level or less. The apparatus comprises a pulse light source for outputting first pulse light, a first optical fiber, a second optical fiber that is spliced with the first optical fiber and has a mode-field diameter smaller than that of the first optical fiber, and a light-introducing system for inputting the first pulse light into the first optical fiber. The second optical fiber receives the first pulse light and generates second pulse light having a newly produced wavelength. The peak power ratio of the first pulse light outputted from the first optical fiber to that inputted into the first optical fiber and the pulse width ratio of the first pulse light outputted from the first optical fiber to that inputted into the first optical fiber are 0.5 to 1.5.

Abstract: A single cavity may be used to produce up-converted, quantum-entangled beams relying on the common field of the pumping energy stimulating to up-converting material to produce the quantum entanglement.

Abstract: The invention relates to a fiber laser and harmonic frequency conversion module incorporating a 90 degree Polarization Maintaining (PM) fiber fusion splice therebetween for providing temperature insensitive power stabilization. The present invention has found that incorporating at least one 90 degree splice of the transmission axes of the PM fiber, coupling a fast axis to a slow axis, to create substantially equal optical path lengths of the two transmission axes of the fiber coupling can nearly eliminate output amplitude fluctuation within a practical operating temperature range.

Abstract: A metamaterial structure for light processing includes a light guide and a composite resonant electromagnetic (EM) structure having a resonant frequency. The composite resonant EM structure is arranged to interact with light propagating along the light guide to upconvert a frequency of the light to the resonant frequency, which generates second and higher harmonics of the light frequency. Method of processing light are also disclosed.

Abstract: Proposed is a light source having a conversion element (2) disposed at one end of an optical waveguide (1) and a semiconductor light source (3) disposed at the other end. The optical waveguide includes a heat-conducting layer (4) at its end proximate the converter.

Abstract: A wavelength converting method of a wavelength tunable light source that is performing a phase modulation for a light output is disclosed. The wavelength converting method has an amplitude of a phase modulation have an amplitude value that is temporarily greater during a wavelength conversion than a phase modulation amount during non conversion. Therefore, an erroneous lock resulting from an abnormal oscillation wavelength can be prevented without spending the cost or time.

Abstract: A light source device includes a light source having a plurality of light emitting sections, a plurality of wavelength conversion elements each having a periodic polarization inversion structure, and for converting wavelengths of light beams emitted from the plurality of light emitting sections into predetermined wavelengths, a temperature control medium for controlling temperature of the plurality of wavelength conversion elements, a holding member having a housing space for housing the temperature control medium, and for holding the plurality of wavelength conversion elements, and a temperature control section for controlling the temperature of the plurality of wavelength conversion elements with the temperature control medium, and the temperature control section controls the temperature of the wavelength conversion elements so that the wavelength of the light beam emitted from at least one of the plurality of wavelength conversion elements is different from the wavelength of the light beam emitted from ano

Abstract: A wavelength conversion element with a Quasi-Phase Matching structure which can suppress the ripples of fluctuation pulse waveforms of a change efficiency in a frequency band of the waveform conversion, without controlling the positions and dimensions of the polarization regions at high precision. The wavelength conversion element of the present invention has a plurality of first and second polarization regions, formed so that dielectric polarizations are inverted from each other, and an optical wave guide which is formed so as to pass through the first and second polarization regions, in a nonlinear optical substrate. And an absolute value of the wavelength conversion efficiency is set by adjusting the positional coordinates of the first and second polarization regions in a light traveling direction.

Abstract: The present invention provides a semiconductor light source module including: a semiconductor light source for emitting a light flux with a predefined wavelength; a SHG element for converting an incident light flux entering onto an incident end surface of the SHG element into an outgoing light flux having a different wavelength from the incident light flux; a light converging optical system for converging a light flux emitted from the semiconductor light source onto the incident end surface of the SHG element; a light receiving element for receiving a part of a light flux emitted from the SHG element; and a drive device for driving an optical element in the light converging optical system based on a light flux received by the light receiving element.