JP2008146014A - Laser light generating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser light generating device that generates laser light with a desired wavelength as laser light for output by converting the wavelength of the laser light. <P>SOLUTION: The laser light generating device comprises: a first wavelength converting element 8 on which laser light with a first wavelength generated by a laser diode 6 generating the laser light with the first wavelength is made incident and which converts the wavelength of the laser light into a second wavelength; a second wavelength converting element 9 on which the laser light with the second wavelength generated by the first wavelength converting element 8 is made incident and which converts the laser light into the laser light for output as laser light with a third wavelength; a filter 10 which is disposed in the optical path of the laser light for output having been wavelength-converted by the second wavelength converting element 9 and cuts off unnecessary laser light other than the laser light for output; and a diffraction grating 7 provided in the optical path between the laser diode 6 and the first wavelength converting element 8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser light generator that converts the wavelength of laser light generated from a laser diode to generate laser light having a desired wavelength as output laser light.

  2. Description of the Related Art Optical disk apparatuses that can perform signal reading operations and signal recording operations by irradiating a signal recording layer provided on an optical disk with laser light emitted from an optical pickup device have become widespread.

  As an optical disk device, an apparatus using an optical disk called CD or DVD is generally popular, but recently, an optical disk with improved recording density, that is, a Blu-ray standard or an HD DVD (High Definition Digital Versatile Disk) standard. Products that use optical disks have been commercialized.

  In order to improve the density of the signal recorded on the optical disc, it is necessary to reduce the spot diameter of the laser beam irradiated on the signal surface of the optical disc, and for this purpose, it is necessary to shorten the wavelength of the laser beam. An optical pickup device used in an optical disk device incorporates a laser diode that generates laser light.

  The laser beam used for reproducing the signal recorded on the CD standard disc described above uses infrared light, and the laser beam used for reproducing the signal recorded on the DVD standard disc. Red light is used, and blue-violet light is used as a laser beam used for reproducing a signal recorded on a disc of Blu-ray standard or HD-DVD standard.

  The laser diode that can generate the infrared, red, and blue-violet laser light described above has been developed and commercialized, but the laser diode that can generate the green laser light is commercialized. Is late.

The green laser light is used in projectors that project images to form the three primary colors of light and is considered to be used in ink-depositing devices because of its high visibility, but it produces green laser light. Since no laser diode has been developed, green laser light is obtained by converting the wavelength of the laser light. As such a wavelength conversion element for converting the wavelength of laser light, an anisotropic crystal such as Nd: YVO4 or a nonlinear optical crystal such as KTP crystal (KTiOP4) is generally used. (See Patent Document 1)
JP-A-7-58391

  When an anisotropic crystal such as YVO4 or a nonlinear optical crystal such as a KTP crystal is used as the wavelength conversion element, the conversion efficiency is highly dependent on the incident light wavelength, and in order to obtain a stable output laser beam, the incident light It is necessary to stabilize the wavelength. A major cause of the unstable wavelength of incident light is a temperature change, and a method of using a Peltier element is generally used as a method for suppressing such a temperature change as described in the patent literature.

  A conventional technique will be described with reference to FIG. In FIG. 7, reference numeral 1 denotes a laser diode made of an AIGaAs crystal, which generates laser light having a wavelength of 808 nm. Reference numeral 2 denotes a YVO4 crystal on which the laser light emitted from the laser diode 1 is incident, and is configured to excite laser light having a wavelength of 1064 nm.

  Reference numeral 3 denotes a KTP crystal to which the laser beam having a wavelength converted by the YVO4 crystal 2 is incident, and is configured to convert the wavelength into a 532 nm (green) laser beam having a ½ wavelength. Reference numeral 4 denotes a filter provided in the output optical path of the green laser light output from the KTP crystal 3, which cuts off unnecessary wavelength laser light and outputs only the green laser light. is there.

  Reference numeral 5 denotes a Peltier element provided in the vicinity of the YVO4 crystal 2 and the KTP crystal 3, and serves to keep the temperature of the laser diode 1, the YVO4 crystal 2 and the KTP crystal constant.

  When the Peltier element is not used, if the conversion efficiency is used at a low temperature, the output level of the converted laser light is reduced. Therefore, an operation of supplying a large drive current to the laser diode 1 in order to increase the laser output. Done. A current limiting circuit is generally provided because there is a problem that when a large current exceeding the rating is supplied to the laser diode 1, the laser crystal is damaged or the life is shortened.

  When the current limiting circuit is provided, the problem that the laser diode 1 is damaged or the life is shortened can be solved, but the current limiting operation can be performed, that is, the stable operation can be performed. There is a problem that the laser beam is not emitted until the state is reached. FIG. 8 is a characteristic diagram showing the relationship between temperature and light output, and stable laser light can be generated only in a narrow temperature range indicated by a solid line.

  In order to solve such a problem, the operation of making the temperature of the laser diode 1, the YVO4 crystal 2 and the KTP crystal constant by using the Peltier element 5 described above is performed, but the apparatus cannot be downsized. There is a problem of becoming expensive.

  The present invention intends to provide a laser beam generator capable of solving such a problem.

  The present invention provides a first wavelength conversion element that receives a first wavelength laser beam generated from a laser diode that generates a first wavelength laser beam and converts the wavelength of the laser beam to a second wavelength laser beam. A second wavelength conversion element that receives the laser light having the second wavelength converted by the first wavelength conversion element and converts the laser light into output laser light that is laser light having the third wavelength; A filter disposed in an output optical path of the output laser light wavelength-converted by the second wavelength conversion element and blocking unnecessary laser light other than the output laser light; the laser diode; and the first wavelength It comprises a diffraction grating provided in the optical path between the conversion element.

  Further, the present invention is characterized in that the first wavelength conversion element is constituted by an Nd: YVO4 crystal and the second wavelength conversion element is constituted by a KTP crystal.

  The present invention is characterized in that a monitor light-receiving element for detecting the intensity of the laser light is provided at a position where the output laser light wavelength-converted by the second wavelength conversion element is irradiated.

  Further, the present invention is characterized in that a prism for guiding a part of the output laser beam to the light receiving element for monitoring is provided on the emission side of the second wavelength conversion element.

  In the present invention, a filter provided on the emission side of the second wavelength conversion element is disposed to be inclined with respect to the optical axis of the output laser beam, and a part of the output laser beam is reflected by the filter. And is guided to the monitor light-receiving element.

  Further, the present invention is characterized in that the filter is an IR cut filter.

  Further, the present invention is characterized in that the monitor light receiving element receives the third wavelength laser light reflected by the filter.

  Further, the present invention is characterized in that the monitor light receiving element receives the second wavelength laser light remaining in the laser light via the second wavelength conversion element reflected by the filter.

  Further, the present invention is characterized in that the second wavelength conversion element is provided with reflecting means for guiding a part of the output laser beam to the monitor light receiving element itself.

  In the present invention, a wavelength at which a first wavelength laser beam generated from a laser diode that generates a first wavelength laser beam is incident and the wavelength of the laser beam is converted into a second wavelength output laser beam. A conversion element, a filter disposed in an output optical path of the output laser light wavelength-converted by the wavelength conversion element and blocking unnecessary laser light other than the output laser light, the laser diode, and the wavelength It comprises a diffraction grating provided in the optical path between the conversion element.

  Further, the present invention is characterized in that the wavelength conversion element is composed of PPLN or PPKTP.

  The laser beam generator of the present invention receives a first wavelength laser beam generated from a laser diode that generates a first wavelength laser beam and converts the wavelength of the laser beam into a second wavelength laser beam. A first wavelength conversion element and a second wavelength laser beam converted by the first wavelength conversion element are incident thereon, and the second laser beam is converted into an output laser beam that is a third wavelength laser beam. A wavelength converting element, a filter disposed in an output optical path of the output laser light wavelength-converted by the second wavelength converting element and blocking unnecessary laser light other than the output laser light, and the laser diode And a diffraction grating provided in the optical path between the first wavelength conversion element and the laser generated from the laser diode by the diffraction grating Since the wavelength of the light was set to stabilize, it is possible to obtain laser light of stable output without using a Peltier element or the like.

  Since the temperature control means such as a Peltier element is not required, the laser light generating device can be manufactured at a low cost, and the present invention has a great effect for downsizing.

  Moreover, since the laser beam generator of the present invention fixes the wavelength of the laser beam by means of the diffraction grating, the conversion efficiency of the wavelength conversion element can be increased, and as a result, the power consumption can be reduced.

  Furthermore, the laser beam generator of the present invention is provided with the monitor light receiving element for monitoring the output laser beam on the side where the output laser beam is emitted, so that the monitor operation can be performed accurately. As a result, the laser output can be stabilized.

  FIG. 1 is a schematic view showing an embodiment of the laser beam generator of the present invention, and FIGS. 2, 3, 4, 5, and 6 are side views showing the laser beam generator of the present invention.

  In FIG. 1, 6 is a laser diode made of an AIGaAs crystal, which generates laser light having a first wavelength of 808 nm. Reference numeral 7 denotes a diffraction grating provided at a position where the first wavelength laser beam generated from the laser diode 6 is incident, and is composed of elements called VHG (Volume Holographic Grating) and VBG (Volume Bragg Grating). Has been. Such a VHG element has optical grooves periodically cut therein, and is set so that laser light having a predetermined wavelength, that is, a wavelength of 808 nm in this embodiment oscillates.

  The laser beam incident on the VHG element described above oscillates by reciprocating between a groove periodically engraved in the VHG element and an end face of the element piece constituting the laser diode 6. Although such an oscillating operation is well known, its description is omitted. An operation of fixing the wavelength of laser light having a wavelength of 808 nm generated from the laser diode 6 to the first wavelength is performed by performing an oscillation operation in cooperation with the laser diode 6 and the VHG element which is the diffraction grating 7.

  Reference numeral 8 denotes a YVO4 crystal on which the first wavelength laser beam fixed by the diffraction grating 7 is incident, and is configured to excite laser light having a second wavelength of 1064 nm.

  Reference numeral 9 denotes a KTP crystal into which the laser light whose wavelength has been converted by the YVO4 crystal 8 is incident, and is configured to convert the wavelength into a laser light having a third wavelength of 532 nm (green) which is a half wavelength. ing. Reference numeral 10 denotes a filter provided in the output optical path of the green laser light output from the KTP crystal 9, which serves to block the laser light of an unnecessary wavelength and output only the green laser light. is there.

  In the case of a conventional laser beam generator that does not include the diffraction grating 7, the first wavelength of the laser beam generated and emitted from the laser diode 6 changes in the range of 808 nm ± 10 nm, and the temperature characteristic is also 0.3 nm. There is a characteristic of changing at / ° C.

  Compared with such a conventional laser light generator, in the case of the laser light generator of the present invention having the diffraction grating 7, the first wavelength of the laser light generated and emitted from the laser diode 6 is in the range of 808 nm ± 1 nm. It is possible to obtain an excellent characteristic of changing at a low temperature. Further, the laser beam generator of the present invention has an advantage that the temperature characteristic can be suppressed to a slight change of 0.01 nm / ° C.

  As described above, the laser beam generator of the present invention is configured. Next, specific examples of the present invention will be described with reference to FIGS.

  In FIG. 2, reference numeral 11 denotes a base constituting the laser beam generator, and electrode terminals 12, 13 and 14 are fixed. Reference numeral 15 denotes a fixed substrate fixed to the base 11, and the electrode terminal 14 is inserted and fixed therein. Reference numeral 16 denotes a laser fixed substrate fixed to the fixed substrate 15, and the laser diode 6 is fixed thereto. In such a configuration, the drive current to the laser diode 6 is configured to be supplied from the electrode terminal 12 through the lead wire 12a.

  On the fixed substrate 15, the diffraction grating 7, YVO4 crystal 8 and KTP crystal 9 are fixedly arranged as shown. Reference numeral 17 denotes a monitor light-receiving element which is fixed on the fixed substrate 15 and provided at a position where a part of the output laser light converted to the third wavelength by the KTP crystal 9 is irradiated. The monitor signal is output to the electrode terminal 14 through the lead wire 14a.

  Reference numeral 18 denotes a cover which is fixed to the base 11 and covers the laser diode 6, the diffraction grating 7, the YVO4 crystal 8, the KTP crystal 9 and the monitor light receiving element 17, and is placed at a position where the output laser light is irradiated. The filter 10 is provided. According to such a configuration, the output laser light converted to the third wavelength by the KTP crystal 9 is emitted in the direction of arrow A through the filter 10.

  The output laser beam converted to the third wavelength by the KTP crystal 9 is emitted from the KTP crystal 9, but is spread and irradiated in the emission direction, so that it is provided at the illustrated position. A part of the light receiving element 17 for monitoring is irradiated. Therefore, the intensity of the output laser beam can be detected, and a stable laser output can be obtained by controlling the magnitude of the drive current supplied to the laser diode 6 based on the detected intensity.

  FIG. 3 shows another embodiment. In this embodiment, a prism 19 for guiding a part of the output laser beam to the light receiving element 17 for monitoring is provided on the emission side of the KTP crystal 9. A reflective film is provided on the inclined surface 19a of the prism 19 so as to allow most of the output laser light to pass therethrough and reflect a part thereof.

  FIG. 4 shows another embodiment. In this embodiment, by tilting the filter 10 fixed to the cover 18, a part of the output laser light incident on the filter 10 is reflected so as to be used for the monitor. It is configured to guide to the light receiving element 17. A reflection film that allows most of the output laser light to pass therethrough and reflects a part thereof is provided on the incident surface 10 a of the filter 10.

  In this embodiment, an IR cut filter can be used as the filter 10. Further, the monitor light receiving element 7 may receive the third wavelength laser beam (532 nm) reflected by the filter 10 or may remain in the laser beam via the KTP crystal 9. The second wavelength laser beam may be reflected by the filter 10 and received by the monitor light receiving element 7.

  That is, as described above, the KTP crystal 9 receives laser light having a wavelength converted to 1064 nm by the YVO4 crystal, and converts the wavelength of this laser light to laser light having a third wavelength of 532 nm, which is a ½ wavelength. It is configured as follows. However, not all laser light having a wavelength of 1064 nm can be converted into laser light having a wavelength of 532 nm, and some 1064 nm laser light is output from the KTP crystal 9 in addition to the laser light having a wavelength of 532 nm. Therefore, as described above, the monitor light receiving element 7 may be designed to detect the intensity of the output laser light by receiving the 532 nm laser light reflected by the filter 10, or the monitor light receiving element 7. Alternatively, the laser beam of 1064 nm reflected by the filter 10 may be received to detect the intensity of the output laser beam.

  FIG. 5 shows another embodiment. In this embodiment, the surface on the emission side of the KTP crystal 9 is cut obliquely, and a part of the output laser beam is sent to the monitor light receiving element 17 at the inclined portion. Configured to lead to. A reflection film that allows most of the output laser light to pass therethrough and reflects a part thereof is provided on the cut surface 9a.

  In the above-described embodiment, a laser diode that generates a laser beam having a wavelength of 808 nm is used as the laser diode 6. However, a laser diode that generates a laser beam having a wavelength of 1064 nm is used as the laser diode 6 with reference to FIG. To explain.

In the present embodiment, since the laser light generated from the laser diode 6 is a 1064 nm laser beam having a first wavelength, the wavelength conversion element 20 has a second wavelength of 532 nm (
PPLN (Periodically-Poled Lithium Niobate) crystals or PPKTP (Periodically-Poled KTiOP4) crystals that convert to green) can be used. Also, a prism 19 is provided on the output side of the wavelength conversion element 20 to guide a part of the output laser to the monitor light receiving element 17. When the output laser emitted from the wavelength conversion element 20 has a spread in the irradiation direction, the prism 19 can be omitted.

  In this embodiment, YVO4 crystal, KTP crystal, PPLN crystal and PPKTP crystal are used as the wavelength conversion element. However, other crystal elements can be used. Further, in order to obtain green laser light, a laser diode having a wavelength of 808 nm or a laser diode having a wavelength of 1064 nm is used, but the wavelength is not limited.

  In this embodiment, the case where laser light having a wavelength of 532 nm, which is green, is obtained has been described. However, laser light having other wavelengths can also be obtained.

It is the schematic which shows one Example of the laser beam generator of this invention. It is a side view which shows one Example of the laser beam generator of this invention. It is a side view which shows one Example of the laser beam generator of this invention. It is a side view which shows one Example of the laser beam generator of this invention. It is a side view which shows one Example of the laser beam generator of this invention. It is a side view which shows one Example of the laser beam generator of this invention. It is the schematic which shows the conventional laser beam generator. It is a characteristic view which shows the relationship between temperature and light output.

Explanation of symbols

6 Laser diode 7 Diffraction grating 8 YVO4 crystal 9 KTP crystal 10 Filter 15 Fixed substrate 17 Monitor light receiving element 18 Cover 19 Prism 20 Wavelength conversion element

Claims (12)

  A laser diode that generates a laser beam having a first wavelength, and a first wavelength converter that receives the laser beam having a first wavelength generated from the laser diode and converts the wavelength of the laser beam to a laser beam having a second wavelength A second wavelength conversion element that receives the laser light having the second wavelength converted by the first wavelength conversion element and converts the laser light into output laser light that is laser light having the third wavelength; And a laser light generator provided with a filter that is disposed in the output optical path of the output laser light wavelength-converted by the second wavelength conversion element and that blocks unnecessary laser light other than the output laser light. Providing a diffraction grating in the optical path between the laser diode and the first wavelength conversion element, and operating the diffraction grating as a resonator, Laser light generating apparatus, wherein a stabilized wavelength of Za light.   2. The laser beam generator according to claim 1, wherein the first wavelength conversion element is configured by an Nd: YVO 4 crystal, and the second wavelength conversion element is configured by a KTP crystal.   2. The laser light generation according to claim 1, wherein a monitor light-receiving element that detects the intensity of the laser light is provided at a position where the output laser light wavelength-converted by the second wavelength conversion element is irradiated. apparatus.   4. The laser beam generator according to claim 3, wherein a prism for guiding a part of the output laser beam to the light receiving element for monitoring is provided on the emission side of the second wavelength conversion element.   A filter provided on the output side of the second wavelength conversion element is disposed so as to be inclined with respect to the optical axis of the output laser beam, and a part of the output laser beam is reflected by the filter for the monitor. 4. The laser beam generator according to claim 3, wherein the laser beam generator is guided to a light receiving element.   6. The laser beam generator according to claim 5, wherein the filter is an IR cut filter.   The laser light generator according to claim 5 or 6, wherein the light receiving element for monitoring receives a laser beam having a third wavelength reflected by the filter.   7. The monitor light-receiving element receives the laser light having the second wavelength remaining in the laser light that has passed through the second wavelength conversion element reflected by the filter. The laser beam generator described in 1.   4. The laser beam generator according to claim 3, wherein the second wavelength conversion element is provided with reflecting means for guiding a part of the output laser beam to the monitor light receiving element.   A laser diode that generates laser light of a first wavelength, and wavelength conversion that converts the wavelength of the laser light into output laser light of a second wavelength while being incident on the laser light of the first wavelength generated from the laser diode A laser light generator comprising an element and a filter disposed in an output optical path of an output laser light wavelength-converted by the wavelength conversion element and blocking unnecessary laser light other than the output laser light A laser characterized in that a diffraction grating is provided in an optical path between the laser diode and the wavelength conversion element, and the wavelength of the first laser beam is stabilized by operating the diffraction grating as a resonator. Light generator.   The laser beam generator according to claim 10, wherein the wavelength conversion element is composed of a PPLN crystal or a PPKTP crystal.   The laser beam generator according to claim 1 or 10, wherein the output laser beam is green.

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