Classifications

• • 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
• • 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
• • 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
  • H01S3/0606—Crystal lasers or glass lasers with polygonal cross-section, e.g. slab, prism
• • 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
  • H01S3/09—Processes or apparatus for excitation, e.g. pumping
  • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
  • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
  • H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
  • H01S3/09415—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping
• • 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
  • H01S3/102—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
  • H01S3/1022—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation by controlling the optical pumping

Definitions

• the present invention is used in the field of optical electronics, particularly in a laser printer device, an optical shaping device, an optical disk, a DNA sequencer device, and a personal computer device.
• the present invention relates to a laser resonator, a laser device, a laser application device, and a laser oscillation method. ⁇ technique
• the conversion efficiency from the input power of the laser device to the laser beam is low, and the power consumption is large, so the cooling device is required because it becomes mature and the size of the laser application device becomes large. there were .
• the displacement of the optical system due to the vibration of the cooling means deteriorates the reliability of the laser application device.
• the life of the laser device was short due to the deterioration of the gas and the like, and the life of the laser application device was also short.
• Second harmonic generation which converts the laser beam into a half wavelength of the first laser beam (hereinafter sometimes referred to as a fundamental wave), which is a solid-state laser oscillation wave, to generate a second laser beam (SHG: Second Harmonic Generation), for example, has been tried to solve the problems with gas lasers described above by applying wavelength conversion techniques such as 8 ⁇ 0 ⁇ 9 0 0 nm band Ru les one the crystalline der can oscillate in the wavelength region Ti: Al 2 0 3 (Ti- Sapphire; referred to hereinafter simply Ti- Sap) or Cr: LiSrAlF 6 (chromium added
• LiSAF Futsudani lithium strontium aluminum
• the lifetime of the laser medium alone was greatly improved by changing from a laser beam to a solid crystal.
• the pumping light source of the latter iSAF laser is a Kr (crypton) laser, that is, a gas laser, and the conventional problems still remain.
• the excitation light source for the TiSap laser is a Q switch Nd: YAG (neodymium-doped indium aluminum garnet) laser, which has a green color as a fundamental wave. SHG laser is used. Therefore, the life of the laser light source was improved because the entire laser light source was solidified.
• the SHG output is a pulse output, so if it is used for laser printers such as laser printer stereolithography equipment and optical disk equipment, for example, signal discontinuities may occur. There were problems such as occurrence.
• a birefringent filter used as a wavelength tuning element for selecting the wavelength of an iSF laser and extracted it from the resonator of the iSF laser.
• a birefringent filter is arranged in a laser resonator in a laser capable of wavelength tuning, such as a Li SAF laser, and has a reflection loss such as an oscillation beam having a wavelength other than a desired wavelength among the oscillation beams. It has a function of giving a loss and selecting a laser beam having a desired wavelength. Therefore, Qi Zhang et al. Added a resonator dedicated to wavelength tuning, including a birefringent filter, after the resonator of the LiSAF laser.
• the wavelength tuning can be performed without giving any loss due to the Li SAF laser resonator.
• US Pat. No. 5,218,610 The loss noted here by Qi Zhang et al. Is mainly the reflection loss due to the birefringent filter. Although this method can improve the above-mentioned loss, there is a possibility that the device is complicated and large.
• the excitation light source is a Kr laser, and a pulse SHG laser with an average of 7.4 mW is applied using a 3.3 W average excitation.
• the SHG laser output is obtained, the SHG laser output must be continuous wave as described above. The required output varies depending on the equipment, but it is considered that about 10 mW is required.
• currently available semiconductor lasers capable of exciting a Li SAF laser can be up to 500 mW class in a single stripe. .
• the fundamental power can be reduced to about 1 / by changing the pump light source from a Kr laser to a semiconductor laser. It becomes 6. Also, since the SHG output is proportional to the square of the fundamental wave power, the expected SHG output is about 1/36, that is, 0.2 mW pulse output, and the efficiency is greatly improved. If not, it will be understood that the SHG output that can be used practically cannot be obtained. Also, compared to Kr lasers, semiconductor lasers have a remarkably flat output beam shape, ie, a mode, so that even if the beam shaping technology is applied, the pumping efficiency is expected to deteriorate. A further decline is expected.
• the near-infrared semiconductor laser output is used as a first oscillation wave, that is, a fundamental wave, and external resonance is applied.
• vessel in to resonate (simply referred to as SHG crystal for handling cormorants wavelength conversion Ri taken below are all SHG) der Ru KN nonlinear-optic crystal therein; a (KNb0 3 niobium oxide Li um)
• a method of obtaining a blue laser beam, which is a second oscillating wave, that is, an SH wave by arranging it, has been proposed (W. J. Koz 1 ovsky and W.
• the semiconductor laser in order to stably adjust the oscillation wavelength of the semiconductor laser, which is susceptible to disturbance, to a wavelength at which the conversion efficiency of KN is maximized, the semiconductor laser must be converted from reflected light. It is necessary to insert an optical isolator 102 in order to protect the external resonator, and to control the resonator length of the external resonator including KN on the order of the wavelength of the fundamental wave. There are advanced technical issues such as receiving the reflected light with the photodetector 105 and stably oscillating the semiconductor laser by the feedback circuit 106 with the electrical output. It is expected that the solution at the commercialization level will be quite difficult.
• the oscillation wavelength of the semiconductor laser which is easily affected by disturbance, is stably adjusted to the wavelength at which the conversion efficiency of KN is maximized, and the resonator length of the external resonator including KN is basically determined. It is expected that the two technical issues of controlling in the order of wave wavelength will be difficult to solve at the commercialization level.
• Li SAF laser can be used as a broadband wavelength tunable laser by using a wavelength control element.
• a method for generating an iSAF laser as the first oscillation wave (fundamental wave) and using a nonlinear crystal as the second oscillation wave as SHG light in the blue region we examined two problems.
• FIG 11 shows the input / output characteristics of a semiconductor laser-pumped tunable solid-state laser device (hereinafter simply referred to as LiSAF laser) using a LiSAF crystal.
• the solid line shows the input / output characteristics of the LISAF laser with the wavelength control element, and the dotted line shows the input / output characteristics without the wavelength control element.
• the wavelength control element is composed of three quartz plates of different thicknesses used in dye lasers and T1 sapphire lasers, so the wavelength band that can pass through the quartz plate Can be made as narrow as 3 nm or less, and the wavelength of the laser oscillation can be controlled to 0.1 ⁇ or less.
• Fig. 11 Inserting a wavelength control element with a narrower transmission wavelength range than in Fig. 11 increases the loss in the resonator and increases the oscillation threshold by more than 10 times. In order to obtain the same output, more than 10 times the pump input is required, so a large semiconductor laser is required, the equipment for driving and cooling the semiconductor laser is large, and power consumption is large. It will be many.
• the oscillation wavelength width without the wavelength control element was about 100 nm, which was more than 100 times that with the wavelength control element.
• the second problem is that the conventionally used KN crystal, which is a nonlinear crystal that can obtain blue SHG light, has a phase matching wavelength half-width, which is the phase wavelength width at which SHG waves are generated, as shown in Fig. 12.
• the crystal propagation loss is as high as 0.5% / ctn, so the loss in the resonator becomes large and the oscillation threshold becomes high. That is, sufficient SH output cannot be obtained even if it is inserted into the ISSF laser as described above.
• the present inventors have studied the loss inside the resonator, and as a result, have found that the loss has some relationship with the size of the aperture of the optical component. It means the effective area of the optical surface of the optical component in the resonator. In other words, it has been considered that there is no problem in an ordinary laser device if the aperture of the optical component is larger than the laser beam diameter. However, in the case of a new laser, the Li SAF laser, it has been found that loss occurs even if the opening of the optical component is of a conventional size, and the present invention was reached. .
• the present invention relates to a laser resonator comprising a laser crystal made of fluoride containing Cr and at least one optical component, wherein the opening inside the resonator is substantially the same as the above.
• a laser resonator characterized in that the diameter is at least five times the diameter of the first laser beam generated by emission of light from the laser crystal.
• Figure 1 3 is Ru Oh a typical solid state laser N'd: Y V0 4 (neo Jiumu oxide nosed Jiumui Tsu Application Benefits um> laser and by that oscillation efficiency drops openings in the resonator of L i SAF laser additives Fig. 13 The upper part shows the shape of the resonator used in the experiment.
• the cavity is formed by a plane mirror and a concave mirror formed on the end face of the laser crystal.
• the diameter of the oscillating beam is determined by the radius of curvature and the distance of the mirror that forms the resonator.
• the beam diameter is the smallest on the plane side, and the concave
• the radius of curvature of the concave mirror, which is the largest in this case, is 150 mm, and the effective optical path length between the cavity mirrors is slightly shorter than the radius of curvature of the mirror.
• the horizontal axis in FIG. 13 shows the distance from the plane mirror, and the vertical axis on the right side shows the beam diameter.
• the beam diameter in the resonator is TEM in the transverse mode. In the case of a perfect circular beam in the 0 mode, it can be calculated from the minimum beam diameter obtained by the following equation 1 and the beam diameter at each position obtained by the following equation 2. Equation 1 Equation 2
• Equation 1 w 0 is the minimum beam diameter, ⁇ is the wavelength of the first beam, d is the resonator length, and R 1 and R 2 are the radius of curvature of the mirror.
• w (z) represents the beam diameter at a distance z away from the minimum beam diameter position.
• the calculated beam diameter was a minimum of about 0.2 m ⁇ and a maximum of about 0.8 mm.
• an opening of ⁇ 2.5 mm was inserted into the resonator, the oscillation beam intensity was adjusted to be the maximum, and the oscillation beam intensity was measured.
• the vertical axis on the left shows the ratio of the oscillating beam intensity when the aperture is inserted and when the aperture is not inserted.
• Nd Y V0 4 3 times the apertures of the internal resonator beam diameter at Les one The, i.e. oscillatable der even 90% or more efficiency when the beam diameter is it is max of 0 8 mm.
• the efficiency of the Li SAF laser was reduced to about 80% by setting the aperture inside the resonator to less than 5 times the beam diameter.
• the beam diameter when the transverse mode is Ru have I light intensity
• Do the Gaussia emission distribution in TEM 0 0 mode one de perfect circle is defined by the diameter of l Z e 2 or more ranges of peak intensity ing .
• the beam transverse mode is TEM 0 0 or more of Otherwise, the beam diameter is defined as the maximum length connecting the outermost circumference of the boundary where the light intensity is 1 / e 2 or less of the beak.
• the above is the regulation on the lower limit of the opening, but the upper limit is to ensure the maximum crystal growth size, stable processing size and quality of the coating. Limited by size. According to common sense, it is desirable to be about 1 ⁇ 100 times.
• the present inventors have found that a saturation phenomenon exists in the input / output characteristics of the LiSAF laser.
• FIG. 15 is a diagram for comparing and explaining the input / output characteristics of the Li SAF laser with and without temperature control of the Li SAF crystal.
• the solid line shows the input / output characteristics when the temperature of the Li SAF crystal is controlled at 15 ⁇ 5 ° C, and the dotted line shows the input / output characteristics when the temperature is not controlled. It can be seen from Fig. 15 that by controlling the temperature of the laser crystal, the linear region can be expanded and a stable solid-state laser output can be obtained.
• Figure 15 shows the input / output characteristics when the temperature of the Li SAF crystal is 15 C. The input and output when the crystal temperature is changed to 10, 20, 30, and 40 ° C are shown.
• the lower limit of the temperature control range is a temperature at which the laser crystal does not condense under the operating conditions.
• the upper limit is a temperature at which the oscillation quenching phenomenon is not observed under the operating conditions. It is desirable that the temperature T of the laser crystal be controlled within a range of 0 ⁇ T ⁇ 50 X>.
• At least one of a plurality of mirrors forming the resonator is formed on one end face of the laser crystal.
• At least one of the optical components is a wavelength control element.
• the laser device is composed of:
• the optical component includes a wavelength control element and a nonlinear optical crystal.
• a birefringent crystal inclined at the Brewster angle may be used as a control element for controlling the oscillation wavelength of the solid-state laser crystal.
• Crystal (S i 0 2) to, L i N b O a, Izure of L i T a ⁇ 3; ⁇ may be put use to.
• a single crystal plate having a thickness of 0.4 to 3 mm is used as the birefringent crystal.
• the control element for controlling the oscillation wavelength of the solid-state laser crystal may be a resonator mirror for resonating the first radiation, and the reflectance of the resonator mirror may be 9%. It is preferable that the wavelength bandwidth of the first oscillation wave of 9.9% or more is 10 nm or less with respect to the center wavelength.
• a birefringent crystal is used as a control element for controlling the oscillation wavelength of a solid-state laser crystal
• the inventors of the present invention have proposed a wavelength control element that causes an increase in the oscillation threshold.
• the transmission wavelength width of the refraction crystal was studied.
• the oscillation characteristics of a laser resonator depend on the loss in the resonator. If the loss is high, the threshold value before oscillation is increased.
• the transmission bandwidth of the wavelength control element is narrow, the loss in the resonator increases, and the oscillation threshold value increases.
• Figure 16 shows the calculation of the transmission wavelength width according to the number of combined birefringent crystals of the crystal inclined at the Brewster angle.
• the birefringent crystal thickness under each condition is that the number of birefringent crystals is increased as shown in Fig. 16, that is, the transmission wavelength width is narrowed by increasing the birefringent crystal thickness. Understand .
• the transmission wavelength width can be increased and the oscillation threshold can be reduced. It was found that it had the effect of
• Fig. 17 shows a birefringent crystal with a single crystal plate. !
• the laser oscillation wavelength interval with respect to the thickness is shown.
• the laser oscillation wavelength interval is an interval between wavelengths at which laser oscillation can be performed at the same time, and depends on the gain characteristic with respect to the wavelength of the laser medium. Due to the wide wavelength range, laser oscillation may occur at the same time depending on the transmission wavelength interval of the wavelength control element. It can be seen from Fig. 17 that when the thickness is larger, the lasing wavelength interval of the laser oscillation wavelength becomes narrower. This is because if the thickness is large, the wavelength interval between adjacent laser oscillations becomes narrow, and a laser that can oscillate over a wide band like a Li SAF laser can be used at two or more oscillation wavelengths at the same time. Oscillation may occur.
• the reflection bandwidth of a general laser mirror is about 50 nm, to suppress two or more simultaneous oscillations, about 25 nm, which is about half of the above-mentioned reflection bandwidth, is required. Since the above oscillation wavelength interval is required, the thickness of the birefringent crystal must be 3 mm or less according to Fig.17. In addition, the wavelength control becomes difficult if the crystal thickness is too thin, and the oscillation wavelength width of the Li SAF laser is about 20 nm. It must be at least 4 mm. Therefore, the thickness of the birefringent crystal can further reduce the oscillation threshold in the range of 0.4 to 3 mm.
• the oscillation threshold was reduced by using a birefringent crystal, but the oscillation wavelength width was increased by increasing the transmission wavelength width. Therefore, it becomes larger than the phase matching half width of the SHG crystal, and SHG cannot be generated with high efficiency. Is found present inventors to Me others is increased efficiency, the to a relatively wide phase matching half width BO (L i B;, ⁇ 5) crystal or BB 0 ( ⁇ ⁇ B a B 2 0 4) crystal or CLB ⁇ ⁇ C s L i B 6 0 1 0) were conceived and this can be resolved by the this using crystals.
• Figure 18 shows the half bandwidth of the phase matching wavelength of the LBO crystal.
• the transmission wavelength width is set to about 10 nm, and in order to eliminate the loss in the resonator, it is inserted at an angle to the pre-use angle. Satisfactory SH output can be obtained.
• the LB0 crystal has a small change in phase matching width of less than 0.1 nm / ° C even with temperature, so there is no need to control the temperature, and the propagation loss is 0.1% Z cm. Because of its small size, the ratio of loss in the resonator is low. The same effect as the LB0 crystal can be obtained by using the BB0 crystal or the CLB0 crystal. However, it is clear that more stable SH output can be achieved by controlling the temperature of the SH crystal.
• a birefringent crystal is not used as a control element for controlling the oscillation wavelength of the solid-state laser crystal, and the wavelength bandwidth where the reflectivity of the resonator mirror is 99.99 or more is greater than the center wavelength. It is also possible to use a material having a diameter of less than 10 nm.
• the laser resonator comprises at least two or more resonator structures, and at least one of the mirrors forming the resonator structure has a second oscillation wavelength shift.
• a non-linear optical crystal having an opening at least five times the diameter of the first laser beam inserted into the resonator, a wavelength control element, the non-linear optical crystal, and the laser crystal
• a laser device having means for simultaneously or independently controlling the temperature of the laser beam and the nonlinear optical crystal, and means for extracting a second laser beam converted to a different wavelength from a portion of the first laser beam It is preferable that
• the nonlinear optical crystal is L i B 3 0 5 (three boric acid Lithium), Cs L i Be O io ( cesium Li Chiumubore DOO), / 3 - BaB 2 0 4 ( boric San'noku Li c beam), KN b 0 3 (niobium oxide Li um>, KTa O 3 ⁇ 4 (data down barrel 'oxide Li um ), K-Li-Nb-0 (lithium-niobate-potassium), K-Ta-Nh-0 (two-year butyric acid, monolithium tantalate), or LH0 3 It is preferable to be any one of (lithium iodate).
• the laser resonator and the laser device according to the present invention are used for a laser aligner device, an optical shaping device, an optical disk device, a particle counter device, a DNA sequencer device, and the like.
• a small and stable device can be provided.
• FIG. 1 is a diagram for explaining one embodiment of the present invention.
• FIG. 2 is a diagram for explaining another embodiment in which the temperature control of the laser crystal, which is another means for improving the efficiency of the present invention, is applied.
• FIG. 3 is a diagram for explaining an SHG laser according to another embodiment of the present invention.
• FIG. 4 is a diagram for explaining an application in which an embodiment of the present invention is used in a laser printer.
• FIG. 5 is a diagram for explaining an application example in which an embodiment of the present invention is used in a stereolithography apparatus.
• FIG. 1 is a diagram for explaining an application example in which an embodiment of the present invention is used in an optical disk device.
• FIG. 7 is a diagram for explaining an embodiment of the present invention.
• FIG. 8 is a diagram for explaining one embodiment of the present invention.
• FIG. 9 is a diagram for explaining one embodiment of the present invention.
• FIG. 10 is a diagram for explaining a conventional example.
• FIG. 11 is a diagram for comparing and explaining the input / output characteristics depending on the presence or absence of a wavelength control element in a semiconductor laser pumped solid-state laser device using a LiSAF crystal.
• FIG. 12 is a diagram for explaining the phase matching wavelength width of the KN crystal.
• Figure 1 3 is a typical solid state laser Oh Ru in Nd: Ru YV0 4 Les chromatography THE and L i SAF FIG der the order to explain the phenomenon of by that oscillation efficiency drops openings in the resonator of the laser.
• Figure 15 is a diagram for comparing and explaining the input / output characteristics of the LiSAF laser with and without temperature control of the LiSAF crystal.
• Figure 16 is a diagram for comparing and explaining the transmission wavelength width depending on the number of birefringent crystals.
• FIG. 17 is a diagram for explaining the oscillation wavelength interval with respect to the thickness of the birefringent crystal.
• Figure 18 is a diagram for explaining the phase matching wavelength width of the L B ⁇ crystal.
• FIG. 1 is a diagram for explaining one embodiment of the present invention.
• the excitation beam 31 emitted from the semiconductor laser 11 is condensed by the condensing optical system 12 and excites the laser crystal 21.
• the semiconductor laser 11 uses an AlGalnP semiconductor laser manufactured by SDL (Sectra Diode Lab.), And has an output of 500 mW and an oscillation wavelength of 670 nm.
• the condensing optical system 12 is composed of a semiconductor laser collimator (focal length 8 mm), an anamorphic prism pair (magnification: 6 times), and a single lens (focal length 3 mm). 0 mm).
• the excited laser crystal 21 is a solid-state laser resonator 20 composed of an incident-side resonator mirror 24 and an output mirror 25 formed on the end face of the laser crystal. Then, the first laser beam 32 is oscillated. A laser crystal 21 and a wavelength tuning element 23 as a wavelength control element are arranged in the solid-state laser resonator 20. The wavelength of the first laser beam 32 oscillating in the resonator is tuned by the wavelength tuning element 23.
• the resonator structure 20 is a plano-concave resonator, and the output mirror 25 has a radius of curvature of 150 mm, and the effective optical path length is slightly shorter than the radius of curvature.
• the loss can be greatly improved by setting the aperture in the resonator of the iSAF laser to be at least five times the diameter of the first laser beam as shown in FIG. 13. This was demonstrated. Based on this, the laser crystal was set to ⁇ 3 mm, the aperture of the wavelength tuning element 23 was set to ⁇ S mm, and the aperture of the output mirror was set to ⁇ 10 mm.
• a single birefringent filter made of a quartz plate is used for the wavelength tuning element 23, and the Brewster angle at which the reflection loss is minimized with respect to the first laser beam 32. It was arranged so that it might become.
• the wavelength of the first laser beam 32 can be tuned by rotating the birefringent filter around the optical axis.
• the wavelength tuning range is about 860 ⁇ 50 nm
• the wavelength selection width was about 0.5 nm.
• the wavelength selection width is arbitrary within a range in which the output of the first laser beam does not significantly decrease.
• the wavelength tuning element may use a prism, etalon, or external injection locking, or a combination thereof, in addition to the birefringent filter.
• the allowable wavelength range of absorption of the Li SAF crystal 21 is as wide as about 100 nm. While no wavelength tuning was performed on the pumping semiconductor laser using a temperature control element or the like, the maximum absorption wavelength was not increased. Wavelength tuning may be used to match the above.
• the condensing optical system of the semiconductor laser can be replaced by using an optical component having a beam shaping function such as a cylindrical lens or an optical fiber.
• FIG. 2 is a diagram for explaining another embodiment in which the temperature control of a laser crystal, which is another means for improving the efficiency of the present invention, is applied.
• Excitation light source 11, condensing optical system 12, laser crystal 21, wavelength tuning element 23, and resonator configuration 20 are the same as those in the first embodiment. Further, the aperture in the resonator, the wavelength tuning range, and the like are the same as in the first embodiment.
• the Li SAF crystal has a thermoelectric cooler and a thermistor.
• the temperature was controlled to 15 C using a heater.
• the lower limit of the control temperature is the temperature at which the laser crystal begins to condense, and can be set arbitrarily within a range where the laser output does not become saturated under the operating conditions.
• FIG. 3 is a diagram for explaining an SHG laser according to another embodiment of the present invention.
• the pumping optical system including the semiconductor laser I 1 used was the same as in Example 1.
• the pumped laser crystal 21 is a solid-state laser resonator 20 consisting of an incident-side resonator mirror 24 and an output mirror 25 formed at the end face of the laser crystal.
• a fundamental wave 32 which is a solid-state laser oscillation wave
• a laser crystal 21, a nonlinear optical crystal 22 for converting a part of the fundamental wave into an SHG wave, and a wavelength tuning element 23 are arranged in the solid-state laser resonator 2 ⁇ .
• the non-linear optical crystal 22 is made of LiB 0 5 (lithium borate; hereinafter simply referred to as LB ⁇ ) and has a size of 3 x 3 x 5 mm with respect to the fundamental and SHG wavelengths. AR coating of 2% or less was performed.
• the temperature of the iSAF crystal 21 and the LBO crystal 22 was simultaneously controlled at 25 ° C and 0.1 ° C using a temperature control element.
• the output mirror 25 has an HR coating of 99% or more with respect to the fundamental wave and an AR coating with respect to the SHG wave.
• the other optical components were the same as those in Example 1.
• the wavelength of the fundamental wave 32 oscillating in the resonator is tuned by the wavelength tuning element 23 to a wavelength at which the wavelength conversion efficiency of the nonlinear optical crystal 22 is maximized.
• a part of the fundamental wave 32 is converted into the SHG wave 33 by the nonlinear optical crystal 22 and emitted from the output mirror 25. According to the present invention, an SHG output of 10 mW was obtained when the semiconductor laser input was 4.55 mW.
• the wavelength tuning range was about 860 ⁇ 70 nm, and the wavelength selection range was 0.5 nm.
• the wavelength tuning range is near the wavelength at which the conversion efficiency of the LB0 crystal is maximized, and the wavelength selection range is arbitrary within a range where the output of the SHG laser does not significantly decrease.
• CsLiB 6 0io cesium Li Chiumubore one DOO>, KNbC (niobium Bed acid strength Li um), K - L i - N b - 0 ( niobate Li Chiumuka Trim), was or L i I 0 3 ( Any of non-linear optical crystals that can be phase-matched as a wavelength conversion element in any of the wavelength tuning regions of the fundamental wave, such as lithium iodate, may be used.
• the characteristics were compared using a conventional gas laser having the same output as that of the above embodiment.
• the output of the gas laser dropped to 50% in 2000 to 500 hours, whereas the output of the SHG laser was 100%. No decrease in output was observed even after operation for more than ⁇ hours. Therefore, the life was extended by 2 to 5 times according to the present embodiment.
• the SHG laser was 0.3 liters in contrast to the force laser in the size range of 10 to 15 li ... Therefore, according to the present embodiment, the size was reduced to 1/50 to 1/30.
• the power consumption of the gas laser was 100 to 200 W, whereas that of the SHG laser was 5 W. Therefore, according to this embodiment, the power consumption can be reduced to 1Z400 to 1, 20 '.
• Table 1 shows a characteristic comparison table between the above gas laser and the SHG laser of this example. Table 1 Comparison of specifications of gas laser and SHG laser of the present invention
• FIG. 4 is a diagram for explaining an application example in which one embodiment of the present invention is used in a laser printing apparatus.
• the SHG laser output 33 emitted from the SHG laser light source 100 described in FIG. 3 is an acousto-optic (hereinafter simply referred to as A A; Acousto-Opti ca 1) modulator 51, a beam exhaust, and the like.
• a A acousto-optic
• the light passes through a cylinder 52, a rotating polygon mirror 53, and an f-lens 54, and is focused on a photosensitive drum 55.
• a 0 modulator 51 modulates SHG output 43 according to image information.
• the rotating polygon mirror 53 scans in the horizontal (in the plane of the paper) direction. With this combination, the two-dimensional information is recorded on the photosensitive drum 55 as a partial potential difference.
• the photosensitive drum 55 rotates with the toner attached thereto in response to the potential difference, and reproduces information on recording paper.
• the photosensitive member applied to the photosensitive drum 55 is selenium (Se), and the output wavelength of the SHG laser light source 100 is 420 nm, which is relatively high in sensitivity of the photosensitive member.
• the output was 10 mW.
• the photoreceptor may be other than Se.
• FIG. 5 is a diagram for explaining an application example in which an embodiment of the present invention is used in an optical shaping apparatus.
• the SHG laser light source 100 described in FIG. 3 was used as the light source.
• the container is filled with the blue cured resin 61, and laser light is two-dimensionally scanned on the liquid surface. At this time, the blue cured resin 61 hardens only at the liquid surface portion 61-a where the light is absorbed.
• the elevator b2 descends, and forms the next fault continuously.
• a three-dimensional model 63 of the desired shape was created.
• the SHG laser light source had a wavelength of 430 nm and an output of 10 mW.
• FIG. 5 is a diagram for explaining an application example in which an embodiment of the present invention is applied to an optical disk device.
• the SHG laser light source 1 ⁇ 0 described in Fig. 3 was used.
• the optical disk device employs a magneto-optical recording method.
• the SHG laser output 33 emitted from the SHG laser light source 100 is expanded by the beam expander 52 and becomes parallel light.
• the light partially rejected by the beam splitter 72 is taken into the front monitor 73.
• the beam that has passed through the beam splitter 72 is condensed on the medium 75 by the condensing optical system 74, and the reflected light is partially reflected by the beam splitter 72, and then the two beams. And are taken into the two detectors 76, respectively.
• the front monitor 73 monitors the SHG laser output 33 to control the SHG laser output 33.
• the beam splitter 7 2 Each of the detectors 76 performs autofocus and signal detection. A constant magnetic field is applied to the medium 75, and the SHG laser output 33 is modulated to raise the focal point temperature up to the Curie temperature of the medium 75 and invert the magnetization. More records were made. When the output is turned on, the magnetic field of the medium is inverted, and when the output is turned off, the magnetic field is not inverted and signal recording becomes possible. The recording frequency was set to 10 MHz. At the time of signal reproduction, a good reproduction signal was obtained by using the same SHG laser light source 100 as at the time of recording.
• FIG. 7 is a diagram for explaining one embodiment of the present invention.
• the excitation beam 14 1 emitted from the semiconductor laser 11 1 is condensed by the condensing optical system 11 2 to excite the laser crystal 12 1.
• the semiconductor laser 111 uses an Al Gain P-based semiconductor laser manufactured by SDL (Spectra Diode Lab.), And has an output of 500 mW and an oscillation wavelength of 670 nm.
• the pumped laser crystal 122 is a solid-state laser resonator 120 composed of the incident-side resonator mirror 122 and the output mirror 124 formed on the end face of the laser crystal. Generates 2.
• a laser crystal 121, an SHG crystal 131, and a wavelength control element 125 are arranged in the solid-state laser resonator 120.
• the solid-state laser resonator 120 was a plano-concave resonator, the radius of curvature of the output mirror 124 was 150 mm, and the resonator length was 144 mm.
• As the laser crystal 121 a Li SAF crystal (3 ⁇ 5 mm) with a Cr content of 1.5 mo 1% was used.
• Anti-reflection (AR) coating with a reflectance of 2% or less for the excitation wavelength on the front end face of the crystal, and a reflectance of 99% or more for the fundamental wavelength. Total reflection (hereinafter simply HR; High-Reflection) coating was applied. An AR coating with a reflectance of 0.2% or less for the fundamental wave wavelength was applied to the rear end face, and an incident side resonator mirror 122 was formed. In the SHG crystal 31, a 3 ⁇ 3 ⁇ 5 mm LB ⁇ crystal was arranged immediately after the Li SAF crystal 121. AR coatings with a reflectance of 0.2% or less for the fundamental wavelength and a reflectance of 1% or less for the SH wavelength were applied to both end faces of the LB ° crystal.
• the wavelength control element 125 a birefringent crystal consisting of a single quartz plate with a thickness of 0.5 rnm was used, and it was arranged at one corner of the brister with respect to the optical axis to rotate the optical axis.
• the wavelength was controlled by rotating the laser to adjust the wavelength so that the conversion efficiency of the LB ⁇ crystal, which is the SHG crystal 131, was maximized.
• the SHG crystal 1331 partially converts it into a SH wave 144 and takes it out of the resonator as an SH output from the output mirror 124.
• the oscillation threshold value was about twice that in the case where the wavelength control element in FIG. 12 was not provided, and an SH output of 10 mW was obtained.
• the positions of the SHG crystal 1331 and the wavelength control element 125 inserted inside the resonator in FIG. 7 can be switched back and forth.
• the allowable wavelength range of absorption of the Li SAF crystal 121 is as wide as about 100 nm. While the excitation semiconductor laser was not wavelength-controlled using a temperature control element or the like, it was controlled to match the maximum absorption wavelength. You may do it.
• a wavelength control element 125 was a single crystal plate having a thickness of 5 mm, and a KN crystal was used as a SHG crystal 1331. Since the laser oscillation wavelength interval by the wavelength control element of the quartz plate with a thickness of 5 mm is as narrow as 12 nm, the fundamental wave oscillating in the Li SAF crystal, which is the laser crystal 121, has a wavelength of 1 nm. Four or five lines oscillated simultaneously at 2 nm intervals.
• KN which is an SHG crystal
• KN has a narrow phase matching wavelength half-width of 0.4 nm, so that even if only one of the wavelengths of the fundamental wave is tuned to the K ⁇ crystal, laser oscillation occurs at other wavelengths.
• the SH output was only about several nW because the fundamental wave power was dispersed.
• FIG. 8 is a diagram for explaining another embodiment of the present invention.
• Semiconductor The excitation optical system composed of the laser 111 and the condensing optical system 112 is the same as in the seventh embodiment.
• the excited laser crystal 1 2 1 is an incident-side resonator mirror formed on the end face of the laser crystal] 2 2, a concave mirror 1 2 b, and a planar output mirror 1 2 3.
• a solid-state laser resonator 120 consisting of a mirror generates a fundamental wave 142.
• the laser crystal 12 1 and the SHG crystal 13 1 between the incident-side resonator mirror 122 and the plane output mirror 123 have a plane output.
• a wavelength control element 125 is arranged between the mirror 123 and the concave mirror 126.
• the materials, shapes, and coatings of the laser crystal 122 and the SHG crystal 131 used in this case are the same as those in the seventh embodiment.
• the same wavelength control element as that of the seventh embodiment was used as the wavelength control element 125.
• the concave mirror 1226 was coated with an HR coating with a reflectivity of at least 99% at the fundamental wavelength.
• the planar output mirror 123 has an HR coating with a reflectivity of at least 99% for the fundamental wavelength, and an AR coating with a transmittance of at least 85% at the SH wavelength.
• the ring was applied.
• the wavelength is controlled by rotating the wavelength control element 125 around the optical axis to adjust the wavelength to maximize the conversion efficiency of the LB0 crystal, which is the SHG crystal 131.
• the structure is converted into SH waves 144 by the SHG crystal 131, and extracted from the planar output mirror 123 to the outside of the resonator as SH output 144.
• FIG. 9 is a diagram for explaining another embodiment of the present invention.
• the excitation optical system composed of the semiconductor laser 111 and the condensing optical system 112 is the same as in the seventh embodiment.
• the excited laser crystal 122 is formed by a solid-state laser resonator 120 composed of an incident-side resonator mirror 122 and an output mirror mirror 124 formed on the end face of the laser crystal.
• a fundamental wave 14 2 is generated.
• the materials, shapes and coatings of the laser crystal 122 and the SHG crystal 131 used here The ringing is the same as in Example 7.
• the output mirror 124 has a HR coating with a reflectivity of 99.9% or more with respect to the fundamental wavelength at a center wavelength of 860 nm and a soil of 5 nm.
• Oscillation wavelength can be controlled without using.
• An AR coating with a transmittance of 85% or more is applied to the SH wavelength.
• the half-width of the phase matching wavelength of the LB 1 crystal, which is the SHG crystal 131 is as wide as 8 nm, so that SH light can be obtained efficiently without any particular wavelength control.
• the efficiency of the laser diode pumped LiSAF laser is greatly improved by performing the resonance I design of the LiSAF laser in consideration of the opening inside the resonator.
• an SHG laser with an output of 1 OmW was realized.
• the life can be greatly improved to 2 to 5 times, the size to 1/50 to: IZ30, and the power consumption to 1400 to 1/200.
• the oscillation threshold value is reduced by increasing the transmission wavelength width of the wavelength control element.
• the LB0 crystal which is an SHG crystal with a wide phase matching width
• the efficiency and reliability of the second harmonic generation device as a laser device were improved.
• this second harmonic generator as a light source, the reliability of laser printers and the like as applied products has been improved.
• a laser application device such as a laser resonator, a laser device, a laser printer device, etc., which is small and has excellent stability.

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• 1995
  • 1995-12-06 WO PCT/JP1995/002491 patent/WO1997021259A1/ja active Application Filing
  • 1995-12-06 KR KR1019960705293A patent/KR100246274B1/ko not_active IP Right Cessation

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