JP5075382B2 - Laser oscillator - Google Patents

Description

  The present invention relates to a laser oscillation apparatus that irradiates a laser beam such as a green laser beam or a blue-violet laser beam that is suitable for application to a laser marking device, a laser pointer, or the like and that can be visually recognized by humans.

Conventionally, a semiconductor laser that emits laser light, a solid-state laser that oscillates laser light using laser light emitted from the semiconductor laser as excitation light, and wavelength conversion that converts the wavelength of the laser light emitted from the solid-state laser to a predetermined wavelength There is known a laser oscillation device including an element. In such a laser oscillation device, since the center wavelength of the laser beam emitted from the semiconductor laser has temperature dependence, when the temperature changes, the center wavelength of the laser beam emitted from the semiconductor laser changes, and the solid state The output of the solid-state laser and the wavelength conversion element decreases due to the shift of the wavelength of the laser light incident on the laser. Specifically, when the center wavelength of the laser light emitted from the semiconductor laser is shifted by 1.5 [nm] due to temperature change, the outputs of the solid-state laser and the wavelength conversion element are reduced to half or less of the maximum output. From such a background, the laser beam output from the solid-state laser by the diffraction grating provided on the output side of the wavelength conversion element is returned to the semiconductor laser side, or the light emitted from the semiconductor laser from the incident end face of the solid-state laser is returned. Thus, there has been proposed a wavelength lock structure in which the wavelength of laser light incident on the solid-state laser is fixed to the excitation wavelength of the solid-state laser (see Patent Documents 1 and 2).
JP 7-152055 A JP-A-6-69582

  However, as described above, in the conventional wavelength lock structure, the laser beam output from the solid-state laser is returned to the semiconductor laser side by the diffraction grating provided on the output side of the wavelength conversion element, or from the semiconductor laser from the incident end face of the solid-state laser. Since the wavelength of the laser beam incident on the solid-state laser is fixed by returning the emitted light, the solid state can be obtained only after combining all the components such as the diffraction grating, wavelength conversion element, and solid-state laser. The wavelength of the laser beam incident on the laser cannot be confirmed. Moreover, according to the wavelength lock structure using the diffraction grating, it is necessary to assemble and adjust the component parts in units of nm according to the wavelength of the laser beam incident on the solid-state laser. Met.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to make it possible to easily check and adjust the wavelength of laser light incident on a solid-state laser before combining all the components. Is to provide.

  In order to solve the above-described problems, in the laser oscillation device according to the present invention, the laser oscillation unit configures a semiconductor laser that irradiates laser light and a confocal optical system in which the emission end face of the semiconductor laser is one focal position. Two collimating lenses, a first filter disposed between the two collimating lenses and transmitting only the laser beam having a predetermined fundamental wavelength, and a coat having a higher reflectivity with respect to the laser beam than the reflectivity at the emission end face of the semiconductor laser A second filter disposed at the other focal position of the confocal optical system, and an incident end surface of the solid-state laser oscillator is disposed in contact with the coated surface of the second filter.

  According to the laser oscillation device of the present invention, the wavelength of the laser beam incident on the solid-state laser is fixed by returning the laser beam to the semiconductor laser by reflecting a part of the laser beam emitted from the semiconductor laser on the coating surface. Therefore, it is possible to confirm and adjust the wavelength of the laser light incident on the solid-state laser before combining all the components such as the wavelength conversion element and the solid-state laser. In addition, according to the laser oscillation device of the present invention, the laser oscillation unit forms a confocal optical system, and the beam diameter of the laser beam is the smallest on the coated surface, so that a laser oscillation device with excellent mass productivity is provided. In addition, the laser light having the fundamental wavelength can be efficiently incident on the wavelength conversion element.

  The laser oscillation device according to the present invention can be applied to, for example, a laser oscillation device that emits green laser light (wavelength 532 [nm]). Hereinafter, a configuration of a laser oscillation device according to an embodiment of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, a laser oscillation apparatus according to an embodiment of the present invention includes a laser oscillation unit 1, a solid-state laser oscillator 2, and a wavelength conversion element 3 as main components. The laser oscillation unit 1 includes a semiconductor laser 4 that emits laser light having a fundamental wavelength (808 [nm]), and collimating lenses 5 and 7 that constitute a confocal optical system in which the emission end face of the semiconductor laser 4 has one focal position. And a filter 6 (first filter) which is disposed between the collimating lenses 5 and 7 and has a filter characteristic (see FIG. 2) that transmits the laser light emitted from the semiconductor laser 4 by 90 [%] or more, and reflection with respect to the laser light. A filter 8 having a coated surface 10 having a larger rate than the reflectance on the emitting end face side of the semiconductor laser 4, and the coated surface 10 being disposed at the other focal position of the confocal optical system formed by the collimating lenses 5 and 7. (Second filter) and a power source / drive circuit 9 that supplies power to the semiconductor laser 4 and outputs a drive signal for driving the semiconductor laser 4 to the semiconductor laser 4. That. The laser oscillation unit 1 emits a laser beam fixed to the fundamental wavelength. The solid-state laser oscillator 2 is composed of Nd: YVO 4, and the incident surface is disposed in contact with the coat surface 10 of the filter 8. The solid-state laser oscillator 2 oscillates laser light having a predetermined wavelength (1064 [nm]) using the laser light emitted from the laser oscillation unit 1 as excitation light. The wavelength conversion element 3 is composed of a secondary high frequency generation element (SHG), and converts the wavelength of the laser light oscillated by the solid-state laser oscillator 2 into a ½ wavelength (532 [nm]) and emits it.

  As described above, the laser oscillation apparatus according to the embodiment of the present invention is incident on the solid-state laser oscillator 2 by reflecting a part of the laser light emitted from the semiconductor laser 4 on the coating surface 10 and returning the laser light to the semiconductor laser 4. Since the wavelength of the laser beam to be fixed is fixed, the wavelength of the laser beam incident on the solid-state laser oscillator 2 can be confirmed and adjusted before the wavelength conversion element 3 and the solid-state laser oscillator 2 are combined. In the laser oscillation apparatus according to the embodiment of the present invention, the laser oscillation unit 1 forms a confocal optical system, and the beam diameter of the laser beam becomes the minimum diameter on the coated surface 10, so that laser oscillation with excellent mass productivity is possible. An apparatus can be provided, and laser light having a fundamental wavelength can be efficiently incident on the solid-state laser oscillator 2 and the wavelength conversion element 3.

  The drive signal output from the power supply / drive circuit 9 to the semiconductor laser 4 is a pulse signal having a cycle in the range of 60 [Hz] to 200 [Hz] and a duty ratio of 50 [%] or less. Is desirable. Specifically, the drive signal may be a pulse signal having a pulse width of 6.7 [mS] and a period of 16.7 [mS] (60 [Hz]) as shown in FIG. In general, in order to stably irradiate laser light, the semiconductor laser 4 needs to stably emit laser light having a fundamental wavelength. As a method of stably emitting laser light having a fundamental wavelength to the semiconductor laser 4, a method of driving the semiconductor laser 4 by CW is conceivable. However, when the semiconductor laser 4 is driven by CW, power consumption increases.

  Therefore, by using the pulse signal as the drive signal of the semiconductor laser 4 as described above, the fundamental laser beam can be stably emitted to the semiconductor laser 4 without increasing the power consumption. Further, by setting the period of the pulse signal to 60 [Hz] or more, the irradiation light is recognized as continuous light by the afterimage effect of the human eye even in the case of pulse driving. Further, by setting the cycle of the pulse signal to 200 [Hz] or less, it is possible to recognize the irradiation light as continuous light while reducing power consumption. Further, by setting the duty ratio to 50% or less, it is possible to reduce the end face breakage due to the heat of the semiconductor laser 4 while suppressing the power consumption. When the duty ratio is 50% or more, it is regarded as continuous light emission. When the duty ratio is 50% or less, the reactive power causing heat is reduced according to the duty ratio. The afterimage effect means a phenomenon in which light emitted at a period of 60 [Hz] or more (about 100 [Hz]) is recognized as light continuously emitted by human eyes.

  Further, in this case, as shown in FIG. 4, it is desirable that the laser oscillation device irradiates light having a steep and gentle waveform rising and a predetermined offset in the output level. In general, since the human eye responds strongly to changes in light, by making the rise of the wavelength-converted light output sharp, the change in light can be clearly recognized and the visibility can be further improved. Conversely, by smoothing the fall of the light output, the afterimage effect of the human eye can be enhanced. In addition, by providing a predetermined offset in the output level, it is possible to make a human eye always recognize a certain amount of light, and to recognize it as continuous light even if pulse driving is performed.

  In addition, as shown in FIG. 5, the reflectance of the wavelength conversion light at the end faces of the solid-state laser oscillator 2 and the wavelength conversion element 3 is adjusted to a value that allows a part of the wavelength conversion light to return to the laser oscillation unit 1 side. It is desirable to include a detection element 11 that detects the wavelength-converted light that has returned to the laser oscillation unit 1 side. According to such a configuration, the wavelength-converted light can be detected with a simple configuration. In this case, the power source / drive circuit 9 may adjust the light amount of the laser light emitted from the semiconductor laser 4 in accordance with the light amount of the wavelength-converted light detected by the detection element 11. Specifically, as shown in the flowchart of FIG. 6, the power source / drive circuit 9 outputs a drive pulse signal to the semiconductor laser 4 to emit laser light to the semiconductor laser 4 (step S <b> 1), and then detects the detection element. It is determined whether or not the light amount of the wavelength converted light detected by 11 is equal to or greater than a predetermined threshold (step S2). If the light amount of the wavelength converted light is equal to or greater than the predetermined threshold, for example, driving as shown in FIG. The period of the drive pulse signal is lengthened, such as extending the period of the pulse signal from 5.0 [mS] to 10.0 [mS] (step S3). According to such processing, the amount of wavelength-converted light can be optimized without complicating and increasing the size of the structure.

  The laser oscillation unit 1 preferably includes a mechanism for changing the incident angle of the laser beam to the filter 6. Specifically, the entire laser oscillation unit 1 is constituted by a block 12 having an opening 12a as shown in FIG. 8, the filter 6 is set in a holder 13 having the same shape as the opening 12a, and the filter is opened from the opening 12a. 6 is inserted and the holder 13 is rotated to change the incident angle of the laser beam to the filter 6. In general, there is a variation in the center wavelength of the filter, and this variation causes a decrease in the output of the solid-state laser oscillator and the wavelength conversion element. Therefore, by adjusting the incident angle of the laser beam to the filter 6 and adjusting the incident angle of the laser beam to the filter 6 so that only the fundamental wavelength component is transmitted, the solid-state laser is adjusted. Output reduction of the oscillator and the wavelength conversion element can be suppressed.

  Further, in this laser oscillation device, the laser beam is condensed on the coated surface 10 of the filter 8, but if the beam diameter of the laser beam is not sufficiently reduced on the coated surface 10, the intensity is low as shown in FIG. Since the laser beam in the region is used, the light output is reduced. Therefore, it is desirable to adjust the thickness of the filter 8 so that the coat surface 10 (incident surface of the solid-state laser oscillator 2) is disposed at a position where the beam diameter is minimum (several μm). According to such a configuration, as shown in FIG. 10, the laser beam in the region with the highest intensity can be used, so that the laser beam can be efficiently incident by the solid-state laser oscillator 2 and the output reduction can be suppressed.

  As mentioned above, although the embodiment to which the invention made by the present inventors was applied has been described, the present invention is not limited by the description and the drawings that form part of the disclosure of the present invention according to this embodiment. That is, it should be added that other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the above embodiments are all included in the scope of the present invention.

It is a block diagram which shows the structure of the laser oscillation apparatus used as embodiment of this invention. It is a figure which shows the filter characteristic of the filter (1st filter) shown in FIG. It is a wave form diagram which shows an example of the drive signal of a semiconductor laser. It is a wave form diagram which shows an example of the optical output of a laser oscillation apparatus. It is a block diagram which shows the structure of the application example of the laser oscillation apparatus shown in FIG. It is a flowchart figure which shows the optimization process of the optical output in the laser oscillation apparatus shown in FIG. It is a wave form diagram for demonstrating the control method of a drive pulse signal when the light quantity of wavelength conversion light is more than a predetermined threshold value. It is a schematic diagram which shows an example of the mechanism which changes the incident angle of the laser beam to a filter (1st filter). It is a figure for demonstrating the light output when the beam diameter of a laser beam is not fully restrict | squeezed. It is a figure for demonstrating the light output in case the beam diameter of a laser beam is fully restrict | squeezed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Laser oscillation part 2: Solid state laser oscillator 3: Wavelength conversion element 4: Semiconductor laser 5, 7: Collimating lens 6, 8: Filter 9: Power supply and drive circuit 10: Coated surface 11: Detection element

Claims (7)

A laser oscillation unit for emitting laser light fixed at a predetermined wavelength;
A solid-state laser oscillator that oscillates laser light using the light emitted from the laser oscillator as excitation light;
A wavelength converter that converts the wavelength of the laser light oscillated by the solid-state laser oscillator into a predetermined wavelength, and emits the wavelength-converted laser light as wavelength converted light;
The laser oscillation unit is
A semiconductor laser for irradiating laser light;
Two collimating lenses constituting a confocal optical system having the emission end face of the semiconductor laser as one focal position;
A first filter that is disposed between the two collimating lenses and transmits only laser light having a predetermined fundamental wavelength;
A coating surface having a reflectance with respect to the laser beam greater than that at the emission end surface of the semiconductor laser, and the coating surface having a second filter disposed at the other focal position of the confocal optical system;
The laser oscillation apparatus, wherein an incident end face of the solid-state laser oscillator is disposed in contact with a coat surface of the second filter.   2. The laser oscillation device according to claim 1, wherein a drive signal output from the drive circuit for driving the semiconductor laser to the semiconductor laser has a cycle in a range of 60 [Hz] to 200 [Hz], and a duty ratio. Is a pulse signal of 50 [%] or less.   3. The laser oscillation device according to claim 2, wherein the output waveform is irradiated with light having rising and falling edges that are steep and gentle and having a predetermined offset in the output level.   4. The laser oscillation device according to claim 1, wherein a reflectance with respect to wavelength conversion light at an end face of the solid-state laser oscillator and the wavelength conversion element is a part of the wavelength conversion light. A laser oscillation device characterized by comprising a detection element that is adjusted to a value that can be returned to the oscillation unit side and that detects wavelength-converted light that has returned to the laser oscillation unit side.   5. The laser oscillation device according to claim 4, further comprising a drive circuit that adjusts the amount of laser light emitted from the semiconductor laser in accordance with the amount of wavelength-converted light detected by the detection element. .   6. The laser oscillation device according to claim 1, further comprising a mechanism for changing an incident angle of the laser beam to the first filter. 7.   7. The laser oscillation device according to claim 1, wherein a thickness of the second filter can be adjusted.

Images