WO2005098529A1 - コヒーレント光源および光学装置 - Google Patents
コヒーレント光源および光学装置 Download PDFInfo
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- WO2005098529A1 WO2005098529A1 PCT/JP2005/004525 JP2005004525W WO2005098529A1 WO 2005098529 A1 WO2005098529 A1 WO 2005098529A1 JP 2005004525 W JP2005004525 W JP 2005004525W WO 2005098529 A1 WO2005098529 A1 WO 2005098529A1
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- light source
- wavelength
- coherent light
- harmonic
- optical system
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
- H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
- H01S3/109—Frequency multiplication, e.g. harmonic generation
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/3501—Constructional details or arrangements of non-linear optical devices, e.g. shape of non-linear crystals
- G02F1/3503—Structural association of optical elements, e.g. lenses, with the non-linear optical device
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/0602—Crystal lasers or glass lasers
- H01S3/0604—Crystal lasers or glass lasers in the form of a plate or disc
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/08—Construction or shape of optical resonators or components thereof
- H01S3/08004—Construction or shape of optical resonators or components thereof incorporating a dispersive element, e.g. a prism for wavelength selection
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/08—Construction or shape of optical resonators or components thereof
- H01S3/08059—Constructional details of the reflector, e.g. shape
Definitions
- the present invention relates to a coherent light source using a wavelength conversion element and an optical device.
- a wavelength conversion element using a semiconductor laser can be miniaturized and have a high output, and the wavelength can be shortened by using wavelength conversion into harmonics.
- the wavelength tolerance of the wavelength conversion element for converting the wavelength with high efficiency is generally very narrow, it is necessary to stabilize the oscillation wavelength of the semiconductor laser in order to stabilize the output.
- the waveguide mode of the semiconductor laser can be controlled by external optical feedback.
- the oscillation wavelength of a semiconductor laser can be fixed by selecting the wavelength of the emitted light of a semiconductor laser using a narrow-band wavelength selection filter or a fiber grating and then feeding it back into the resonator of the semiconductor laser.
- Patent Document 1 a method of controlling the oscillation wavelength of a semiconductor laser by returning external light from an external grating has been proposed (for example, see Patent Document 2).
- FIG. 8 shows an example of a conventional coherent light source.
- Optical feedback is applied to the semiconductor laser 501 using the bandpass filter 504, and the oscillation wavelength of the semiconductor laser is fixed to the transmission wavelength of the bandpass filter 504.
- the dichroic mirror 505 has a characteristic of totally reflecting harmonics and transmitting a fundamental wave, and the band-pass filter 504 is configured to transmit only a selected wavelength of the fundamental wave.
- the fundamental wave emitted from the semiconductor laser 501 is condensed by the condensing optical system 502 and enters the wavelength conversion element 503. A part of the fundamental wave is converted into a harmonic by the wavelength conversion element 503, and the harmonic that has passed through the collimator lens is wavelength-separated by the dichroic mirror 505, and is extracted as a harmonic.
- the fundamental wave emitted from the wavelength conversion element passes through the dichroic mirror 505 after passing through the collimator lens 510, and is selected to a specific wavelength by the band-pass filter 504. After that, the fundamental wave is reflected by the mirror 513, and travels back in the same path to the semiconductor laser 501.
- Feedback is provided in the active layer.
- the power of the feedback wavelength increases, and the loss of the feedback wavelength light in the resonator apparently decreases, so that the oscillation wavelength is fixed to the feedback wavelength. Since the transmission wavelength can be controlled by adjusting the angle of the bandpass filter 504, the oscillation wavelength of the semiconductor laser can be adjusted to the phase matching wavelength of the wavelength conversion element 503 to achieve highly efficient wavelength conversion. It becomes.
- Patent Document 1 JP-A-10-186427
- Patent Document 2 Japanese Patent Application Laid-Open No. 06-102552
- the conventional method has a problem that it is difficult to reduce the size of the optical system and stabilize the optical system because the number of optical components is large and the optical system is complicated.
- the optical axis of the higher harmonic wave had an angle with respect to the optical axis of the fundamental wave incident light, making it difficult to adjust the optical axis.
- a method of applying feedback there is a method of inserting a band-pass filter into a portion where the semiconductor laser is coupled to the wavelength conversion element by using reflection of the incident end face of the wavelength conversion element, thereby realizing miniaturization.
- the fundamental wave to be wavelength-converted is reduced by 20% or more, and the output of the harmonics is reduced by 40% or more.
- the coherent light source of the present invention includes a light source, a wavelength conversion element that converts a part of the fundamental wave emitted from the light source into a harmonic, and a narrow band with respect to a part of the fundamental wave that is not converted into a harmonic.
- a wavelength selection filter having transmission characteristics and transmission characteristics with respect to harmonics.
- a part of the fundamental wave, which is not converted into a harmonic emitted from the wavelength conversion element, is fed back to the light source by the wavelength selection filter, and the harmonic is transmitted to the outside through the wavelength selection filter. .
- a short-wavelength light source having high output, stability, and excellent mass productivity can be realized.
- a wavelength selection filter in a coherent light source has a bandpass filter and a dichroic mirror.
- the bandpass filter has a narrow-band transmission characteristic for a part of the fundamental wave that is not converted into a harmonic, and has a transmission characteristic for a harmonic.
- the dichroic mirror reflects part of the fundamental wave, which is not converted into a harmonic transmitted through the band-pass filter, and the harmonic passes through the band-pass filter and then passes through the dichroic mirror and exits to the outside. It is characterized by being performed. Thereby, the simplification of the optical system becomes possible, and miniaturization and stability are improved.
- the wavelength selection filter in the coherent light source according to the present invention is a confocal optical system, and the dichroic mirror is provided on a focal plane of the confocal optical system.
- the fundamental wave is stably fed back to the semiconductor laser.
- the light source in the coherent light source according to the present invention is a single mode semiconductor laser. Thereby, the light collection characteristics and the conversion efficiency are improved.
- the length force of the cavity of the semiconductor laser is 1 mm or more. This makes it easy to match the wavelength of the semiconductor laser to the phase matching wavelength.
- the semiconductor laser is superimposed at a high frequency. This stabilizes the output.
- the light source in the coherent light source of the present invention may be a fiber laser.
- the wavelength selection filter in the coherent light source of the present invention preferably has a transmittance of a harmonic of 80% or more. Thereby, a decrease in output can be suppressed.
- the wavelength selection filter preferably has a selected wavelength width of 0.2 nm or less. Thereby, a decrease in conversion efficiency can be suppressed.
- the wavelength conversion element in the coherent light source according to the present invention is characterized in that it has a periodically poled structure. This enables high-efficiency conversion.
- At least one end face of the wavelength conversion element is inclined by 3 ° or more with respect to the optical axis of the wavelength conversion element. As a result, noise and output instability can be suppressed.
- the coherent light source of the present invention further includes a light-collecting optical system between the light source and the wavelength conversion element, and the light-collecting optical system has chromatic aberration, and outputs a harmonic and a part of a fundamental wave that is not converted into a harmonic. Light is condensed at different light condensing points. Thus, a high-performance coherent light source can be obtained.
- the wavelength conversion element includes an optical waveguide. This makes it highly effective Rate conversion becomes possible.
- the wavelength conversion element is directly bonded to the light source.
- the light source can be downsized.
- the wavelength selecting filter in the coherent light source according to the present invention is provided inside or at the end face of the optical waveguide. Thereby, miniaturization becomes possible.
- the wavelength conversion element has an optical waveguide.
- the wavelength selection filter has a band-pass filter provided inside or at the end face of the optical waveguide, and a dichroic mirror provided at the end face of the optical waveguide.
- the band-pass filter has a narrow-band transmission characteristic for a part of the fundamental wave that is not converted to a harmonic, and has a transmission characteristic for a harmonic.
- the dichroic mirror reflects a part of the fundamental wave that is not converted into a harmonic transmitted through the non-bass filter. The feature is. Thereby, miniaturization becomes possible.
- the thickness of the dichroic mirror is preferably 1 mm or more. As a result, dust collection characteristics can be suppressed.
- the optical device of the present invention has a coherent light source and an image conversion optical system, and converts light from the coherent light source into a two-dimensional image by the optical system.
- the image conversion optical system preferably comprises a two-dimensional beam scanning optical system.
- the image conversion optical system preferably has a two-dimensional switching force.
- the image conversion optical system is composed of a two-dimensional or one-dimensional optical switch.
- the two-dimensional optical switch is a transmissive or reflective liquid crystal switch, or a movable micromirror (DMD) using a semiconductor micromachine. These are used as an image conversion element of a projector to convert lamp light into an image.
- DMD movable micromirror
- the optical system can be simplified, and the size and stability can be improved.
- FIG. 1 A diagram showing a configuration of a coherent light source according to Embodiment 1 of the present invention.
- FIG. 2 A transmission characteristic diagram of a band-pass filter
- FIG. 3 is a diagram showing a configuration of a coherent light source according to a second embodiment of the present invention.
- FIG. 4 is a diagram showing another configuration of a coherent light source according to a second embodiment of the present invention.
- FIG. 5 is a second embodiment of the present invention.
- FIG. 6 is a diagram showing another configuration of the coherent light source according to FIG. 6.
- FIG. 6 is a diagram showing the configuration of an optical device according to Embodiment 3 of the present invention.
- FIG. 7 is a diagram showing another configuration of the optical device according to Embodiment 3 of the present invention.
- FIG. 8 is a diagram showing a configuration of a conventional coherent light source
- the present invention is a method for fixing the wavelength of a semiconductor laser by optical feedback in a coherent light source that also has the power of a wavelength conversion element with the semiconductor laser.
- FIG. 1 shows a configuration example of the coherent light source of the present invention.
- a wavelength selection filter is a confocal optical system
- the dichroic mirror is provided on the focal plane of the confocal optical system.
- the coherent light source includes a semiconductor laser 101, a focusing optical system 102, a wavelength conversion element 103, a collimating lens 110, a band-pass filter 104, a focusing lens 111, and a dichroic mirror 105.
- the bandpass filter 104 is made of a dielectric multilayer film, and transmits only a specific wavelength with respect to the fundamental wave of the semiconductor laser 101.
- the transmission characteristics can be easily realized by designing the dielectric multilayer film. Details will be described later.
- the dichroic mirror 105 is designed to reflect the fundamental wave and transmit more than 95% of the harmonics!
- the fundamental wave from which the power of the semiconductor laser 101 is also emitted is focused by the focusing optical system 102.
- a part of the fundamental wave collected by the wavelength conversion element 103 is converted into a higher harmonic by the wavelength conversion element 103.
- a light source having a wavelength of 980 nm and an output of 500 mW was used as the semiconductor laser 101.
- the wavelength conversion element 103 is Mg-doped LiNbO using a periodically poled structure.
- This wavelength conversion element 103 can convert a fundamental wave into a second harmonic having a wavelength of 490 nm with a polarization inversion period of 5.4 ⁇ and a conversion efficiency of about 5%.
- the wavelength-converted harmonics are collimated by a collimating lens 110, transmitted through a bandpass filter 104, passed through a condenser lens 111, and a bandpass filter 104, and output to the outside.
- the fundamental wave is focused on the mirror surface of the dichroic mirror 105 by the focusing lens 111.
- Dichroic mirror 1 The fundamental wave reflected at 05 is fed back to the active layer of the semiconductor laser 101 by traveling in the same path backward.
- the fundamental wave is stably fed back to the semiconductor laser 101 because the optical system is a confocal optical system.
- An anti-reflection film for the fundamental wave is formed on the incident surface and the reflective surface of the wavelength conversion element 103, and it is designed so that light in the middle does not feed back to the semiconductor laser 101 and cause noise or output instability Have been.
- the input and output surfaces of the wavelength conversion element 103 are formed obliquely with respect to the optical axis of the element (the axis perpendicular to the polarization inversion). This is also to prevent the reflected light at the end face from being fed back to the semiconductor laser 101.
- the bandpass filter 105 a confocal optical system that focuses on the reflection mirror surface is used, so that a stable system with a large tolerance of the optical system can be realized.
- the optical system of the present invention has the following advantages.
- the number of parts is reduced.
- the dichroic mirror can be used as a fundamental wave reflection mirror and a wavelength separation mirror, so that the number of components can be reduced.
- the number of bandpass mirrors can be reduced from the collimating system, and the volume of the optical system can be significantly reduced.
- the coherent light source can be simplified and downsized, and the stability of the optical system can be greatly improved.
- the emitted harmonic is divergent light.
- the diverging optical system has an advantage that the beam diameter can be easily adjusted with one appropriate lens. The design of the used optical system is facilitated.
- the mirror surface of the dichroic mirror 105 is preferably formed on the condensing side. This is due to the fact that when the power density of light is high, the surrounding dust is collected due to the light trapping effect, and a phenomenon that the characteristics are deteriorated has been observed. Light trapping occurs on the light exit side and depends on the power density. To prevent this, you can increase the power density at the exit surface It is preferable to reduce the temperature. For this reason, the mirror surface is installed inside to reduce the power density at the emission surface. It is also effective to increase the thickness of the substrate of the dichroic mirror 105. If the substrate thickness is 1 mm or more, the power density of harmonics at the emission end face is reduced, and the dust collection characteristics are reduced. As the substrate of the dichroic mirror 105, a block, a prism, or the like can be applied.
- the mirror surface inside is also effective in reducing aberrations.
- the aberration increases because the condensed light passes through the substrate of the dichroic mirror 105.
- the fundamental wave reflected by the dichroic mirror 105 is fed back to the active layer of the semiconductor laser 101.
- the active layer has an m-order shape, and the occurrence of aberration leads to a reduction in the amount of feedback light, and increases output instability.
- it is preferable that the mirror surface is provided on the light collecting side.
- the semiconductor laser 101 used is preferably of a single mode. This is necessary to increase the coupling efficiency with the optical waveguide when used in the optical waveguide. Further, also in the case where the semiconductor laser 101 is used in a balta, if the semiconductor laser 101 is in a multi-mode, the light-collecting characteristics are deteriorated and the conversion efficiency is reduced.
- the beam shaping using a prism pair is used as the condensing optical system.
- the Balta type by shaping the output of the elliptical beam from the semiconductor laser 101 into a circular beam, high efficiency can be achieved.
- FIG. 2 shows the transmission characteristics of the bandpass filter 104.
- the bandpass filter 104 has a sharp transmission characteristic with a narrow half width at around the phase matching wavelength ⁇ of the wavelength conversion element 103.
- the half width ⁇ 1 of the transmission wavelength of the bandpass filter 104 is preferably 0.6 nm or less. Although this depends on the allowable wavelength range of the wavelength conversion element 103, generally, the allowable range of the wavelength that can be converted by the wavelength conversion element is about 0.1 nm. For this reason, if one wavelength of the band-pass filter exceeds lnm, the tolerance of the wavelength conversion element is greatly exceeded, and the conversion efficiency is reduced.
- the width of the transmission wavelength of the fundamental wave of the bandpass filter 104 is preferably 0.6 nm or less. Further, the thickness is preferably 0.2 nm or less. By setting the thickness to 0.2 nm or less, stable output characteristics can be obtained. On the other hand, high transmittance is required as a characteristic for harmonics (here, wavelength of ⁇ 2). Because the transmittance is low, the output is reduced, so a transmittance of at least 80% is required. Another important point is that, as shown in Fig. 1, a broad transmission characteristic S is required for harmonics. As shown in the configuration of FIG.
- the bandpass filter 104 adjusts the transmission wavelength of the fundamental wave by changing the angle, and matches the fundamental wavelength to the phase matching wave of the wavelength conversion element 103. It is necessary to design so that the transmission characteristics of harmonics are kept at 80% or more over the entire range of such angle adjustment.
- the half-width ⁇ ⁇ 2 of the transmission wavelength near the wavelength of the harmonic is preferably 10 nm or more.
- the transmittance of the bandpass filter 104 for the fundamental wave is preferably 30% to 80% or less. If the transmittance is high, the condensing power density at the dichroic mirror 105 increases, and the reliability of the mirror surface deteriorates.
- the transmittance is too low, the feedback of the semiconductor laser decreases, and stable optical feedback cannot be realized. Since the fundamental wave passes through the bandpass filter twice, if the transmittance is less than 30%, the feedback light will be less than 10%, making it difficult to stably fix the wavelength.
- the end face reflectivity of the semiconductor laser 101 is desirably 1% or less. This is because the external optical feedback sufficiently feeds back into the active layer.
- the length of the active layer of the semiconductor laser 101 is desirably lmm or more. In other words, it is preferable that the length of the cavity of the semiconductor laser is lmm or more. Since the oscillation wavelength of the semiconductor laser 101 is determined by the composite cavity including the resonator of the semiconductor laser and the resonator force of external feedback, the longitudinal mode interval is inversely proportional to the length of the active layer. Because the allowable width of the transmission wavelength of the non-volatile filter 104 is as narrow as 0.2 nm or less, if the longitudinal mode interval of the semiconductor laser 101 is too narrow, the semiconductor laser 101 is controlled by changing the angle of the band-pass filter 104 to control the wavelength. The output fluctuation of the laser 101 increases.
- phase matching wavelength tolerance of the wavelength conversion element 103 is as narrow as about 0.1 nm, it is difficult to accurately adjust the wavelength of the semiconductor laser 101 to the phase matching wavelength if the longitudinal mode interval of the semiconductor laser 101 is wide. Problem arises. To prevent this, it is necessary to make the length of the active layer of the semiconductor laser 101 lmm or more and narrow the longitudinal mode interval.
- a high frequency be superimposed on the semiconductor laser 101.
- the power light source described for the semiconductor laser as the light source of the fundamental wave is not limited to this.
- a solid-state laser or a fiber laser can be used.
- a Yb-doped fiber laser can perform high-efficiency laser excitation with a wide and absorption wavelength range.
- the oscillation wavelength is very wide, the conversion efficiency of the wavelength conversion element decreases. To prevent this, it is important to narrow the wavelength by optical feedback.
- the present invention is also effective for such a method.
- the wavelength conversion element 203 includes a periodic polarization inversion 208 and an optical waveguide 209.
- the fundamental wave emitted from the semiconductor laser 201 is focused on the optical waveguide 209.
- the fundamental wave propagating in the optical waveguide 209 is wavelength-converted by the periodic polarization inversion 208 to become a harmonic.
- the conversion efficiency is as high as about 50%, and a 200 mW harmonic (wavelength 490 ⁇ m) is realized from the power of the semiconductor laser 201 (output 500 mW) having a wavelength of 980 nm.
- a direct junction type configuration as shown in FIG. 4 can be realized.
- the semiconductor laser 301 is directly bonded to the optical waveguide 302.
- the coupling efficiency becomes about 90%, and high efficiency coupling becomes possible.
- the distance between the elements became very short, and stable coupling was realized.
- harmonics emitted from the wavelength conversion element 308 are condensed on the dichroic mirror 305 through the collimator lens 310, the bandpass filter 304, and the condenser lens 311. Since the dichroic mirror 305 transmits harmonics, the harmonics are output to the outside as they are.
- the fundamental wave is wavelength-selected by the band-pass filter 304, then reflected by the dichroic mirror 305, travels in the same path in the opposite direction, and is fed back to the semiconductor laser 301.
- the incident side end face of the wavelength conversion element 308 is perpendicular to the optical waveguide 302 to improve the coupling efficiency with the semiconductor laser 301.
- the emission side is polished obliquely, and the polishing angle is preferably 3 ° or more. As a result, the reflected light at the end face can be reduced to 0.1% or less, and noise generation and output instability due to return light with a strong end face force to the semiconductor laser 301 can be eliminated.
- the collimating lens 310 and the condensing lens 311 are configured to generate chromatic aberration with respect to a fundamental wave and a harmonic. For this reason, the focal points of both lights on the dichroic mirror 306 are shifted by about the depth of focus. Further, a dichroic mirror 306 is provided at the focal point of the fundamental wave, and adjustment is made so that the fundamental wave is fed back to the active layer of the semiconductor laser 301. This is because when the fundamental wave and the harmonic wave are condensed at the same point by the dichroic mirror 306, the harmonic wave is fed back to the semiconductor laser 301 because of the confocal optical system, and the noise of the semiconductor laser 301 This is because it causes occurrence.
- the occurrence of noise can be prevented by utilizing the chromatic aberration of the lens.
- the power density of the light on the surface of the dichroic mirror 306 can be reduced to prevent the reliability of the dichroic mirror 306 from deteriorating due to surface damage.
- the focal point of the harmonic is located closer to the focal point of the fundamental wave. This is because the harmonics are focused in front of the dichroic mirror 306, and the power density of the harmonics at the exit surface of the dichroic mirror is reduced. is there.
- the band-pass filter 304 is fitted in a groove formed in the middle of the waveguide.
- Waveguide A dichroic mirror 306 is provided on the output end face of the mirror to reflect a fundamental wave and transmit a harmonic wave.
- the fundamental wave reflected by the dichroic mirror 306 is fed back to the semiconductor laser 301 through the waveguide to fix the oscillation wavelength to the transmission wavelength of the filter.
- FIG. 5B a bandpass filter 304 and a dichroic mirror 306 are deposited on the end face of the waveguide.
- the phase matching wavelength can be controlled by changing the temperature of the wavelength conversion element 308, and the phase matching wavelength can be adjusted to the transmission wavelength of the filter.
- LiNbO and LiTaO with stoichiometric structure are promising for high efficiency conversion.
- Arbitrary wavelength conversion is possible by changing the conversion structure, and high-efficiency conversion can be performed.
- By using an optical waveguide structure higher conversion efficiency can be realized.
- a 1060 nm wavelength semiconductor laser can generate green light of 530 nm, and a semiconductor laser near 900 nm can generate blue light. If a near-infrared or red semiconductor laser of 780 nm or 680 nm is used, ultraviolet light can be generated.
- These semiconductor lasers have been increasing in output power and have also secured reliability, so that various laser light sources can be realized in combination with a wavelength conversion element.
- the transmission wavelength can be changed by the angle of the bandpass filter. Since the transmission wavelength changes by adjusting the angle of the bandpass filter, the oscillation wavelength of the semiconductor laser can be controlled to match the phase matching wavelength by adjusting the angle.
- the wavelength conversion element includes an optical waveguide.
- this configuration is applicable to a Balta-type wavelength conversion element.
- a laser display will be described as an optical device using the coherent light source of the present invention.
- a display with high color reproducibility can be realized by using an RGB laser.
- a laser light source a high-power red semiconductor laser has been developed.
- blue has not achieved high output, and green has difficulty in forming a semiconductor laser itself. Therefore, blue and green light sources using wavelength conversion are required.
- the coherent light source of the present invention since a wide-stripe semiconductor laser can be used, high-output blue and green light can be realized in combination with a wavelength conversion element.
- a 880 nm semiconductor laser can be wavelength-converted to produce 440 nm blue light
- a 1060 nm semiconductor laser can be wavelength-converted to produce 530 nm green light.
- a two-dimensional image can be projected (Fig. 6).
- a MEMS using a micro machine, a liquid crystal switch, or the like can be used as the two-dimensional switch 802.
- the output depends on the screen size, but several tens of mW and several tens of OmW are required.
- a small short-wavelength light source can be realized by the coherent light source of the present invention, and the laser display can be downsized and highly efficient.
- the method shown in FIG. 7 is also effective as a laser display device.
- the laser light draws a two-dimensional image on the screen by scanning with mirrors 902 and 903.
- the laser light source needs a high-speed switch function, and high-speed output modulation is possible by modulating the output of the semiconductor laser.
- the coherent light source of the present invention can achieve high output and is promising for laser display applications.
- the vertical mode and the horizontal mode are fixed to a single mode, so that the output modulation of the laser can be performed at high speed.
- a scanning laser display can be realized.
- the embodiment of the present invention has been described above with reference to an example in which an SHG element is used for a waveguide optical device.
- high-power semiconductor lasers are used as semiconductor lasers. Therefore, if a wide-stripe semiconductor laser can be used as the high-output laser, a compact and high-output light source can be realized. Therefore, high output and stabilization can be realized by using the structure of the present invention.
- the waveguide type optical device is not particularly limited to the SHG element.
- various functions and configurations of a waveguide type optical device such as a high-speed modulation element, a phase shifter, a frequency shifter, and a polarization control element can be considered.
- the waveguide type optical device of the present invention can be applied to all optical systems using such a waveguide type optical device and a coherent light source.
- the present invention is effective for an optical disk device and a measuring device in addition to the power described for a laser display as an optical device.
- the present invention is effective for an optical disk device, because the laser output is required to be improved by increasing the writing speed. Since the light source of the present invention has high output and high coherence, it can be miniaturized and is effective for application to an optical disk or the like.
- the coherent light source of the present invention has an effective configuration for wavelength conversion of a semiconductor laser.
- a narrow-band bandpass filter is used, and the oscillation wavelength of the semiconductor laser is controlled by selectively setting the transmission wavelength of the bandpass filter.
- the bandpass filter is provided with the transmission characteristics of harmonics, the number of optical components can be reduced, and the optical system can be reduced in size and stabilized. As a result, a short-wavelength light source with high output, stability, and excellent mass productivity can be realized.
- this coherent light source is used, a high-output small-sized RGB light source can be realized, so that it can be applied to various optical devices such as a laser display and an optical disk device.
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- Electromagnetism (AREA)
- Nonlinear Science (AREA)
- Engineering & Computer Science (AREA)
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- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
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Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/576,210 US7426223B2 (en) | 2004-04-09 | 2005-03-15 | Coherent light source and optical device |
JP2006511945A JPWO2005098529A1 (ja) | 2004-04-09 | 2005-03-15 | コヒーレント光源および光学装置 |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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JP2004115278 | 2004-04-09 | ||
JP2004-115278 | 2004-04-09 |
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PCT/JP2005/004525 WO2005098529A1 (ja) | 2004-04-09 | 2005-03-15 | コヒーレント光源および光学装置 |
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JP (1) | JPWO2005098529A1 (ja) |
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Cited By (2)
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JP2008304932A (ja) * | 2006-08-11 | 2008-12-18 | Seiko Epson Corp | レーザ光源装置及びそのレーザ光源装置を備えたプロジェクタ |
JP2010093211A (ja) * | 2008-10-10 | 2010-04-22 | Ricoh Co Ltd | 波長変換レーザ装置 |
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JP2008135689A (ja) * | 2006-10-30 | 2008-06-12 | Seiko Epson Corp | レーザ光源装置及びそのレーザ光源装置を備えた画像表示装置 |
US20080310465A1 (en) * | 2007-06-14 | 2008-12-18 | Martin Achtenhagen | Method and Laser Device for Stabilized Frequency Doubling |
US7729394B2 (en) * | 2007-07-20 | 2010-06-01 | Corning Incorporated | Conversion efficiency expansion in wavelength converting optical packages |
WO2009047888A1 (ja) * | 2007-10-10 | 2009-04-16 | Panasonic Corporation | 固体レーザー装置及び画像表示装置 |
JP5330261B2 (ja) * | 2007-11-21 | 2013-10-30 | パナソニック株式会社 | 波長変換装置およびそれを用いた画像表示装置 |
US8358460B2 (en) * | 2010-04-13 | 2013-01-22 | I Shou University | Quasi-phase matched optical waveguide for preventing back conversion |
JP4980454B2 (ja) * | 2010-09-10 | 2012-07-18 | パナソニック株式会社 | レーザ光源装置 |
US10378006B2 (en) | 2017-04-19 | 2019-08-13 | The Florida International University Board Of Trustees | Near-infrared ray exposure system for biological studies |
US10084282B1 (en) | 2017-08-14 | 2018-09-25 | The United States Of America As Represented By The Secretary Of The Air Force | Fundamental mode operation in broad area quantum cascade lasers |
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Also Published As
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US20070053388A1 (en) | 2007-03-08 |
US7426223B2 (en) | 2008-09-16 |
JPWO2005098529A1 (ja) | 2008-02-28 |
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