JP2008145896A - Laser pointer using semiconductor laser excitation solid laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser pointer using semiconductor laser excitation solid laser, where a driving current for a semiconductor laser and a cooling power for the semiconductor laser are minimized, and a laser output is stabilized. <P>SOLUTION: The semiconductor laser (1) of a single mode both in a vertical mode and in a horizontal mode is used. The semiconductor laser includes a wavelength that makes absorptance of a solid laser medium (3) the maximum, and also, three or more vertical modes of the semiconductor laser (1) lie within the wavelength range having less fluctuation of the absorptance. The semiconductor laser having the single mode both in the vertical mode and the horizontal mode has a low oscillation threshold and high electrooptic conversion efficiency, then, the driving current and the cooling power can be minimized, and a portable use by the dry battery drive can be made available. Even when mode-hopping among the three vertical modes lying within the wavelength range is performed, since the absorptance fluctuation of the solid laser medium is small, the output is stabilized by the drive current control circuit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser pointer using a semiconductor laser-pumped solid-state laser, and more particularly, the drive current of the semiconductor laser and the power for cooling the semiconductor laser can be minimized, portable use by dry cell drive and laser output are possible. The present invention relates to a laser pointer using a stable semiconductor laser pumped solid-state laser.

Conventionally, a solid-state laser medium is excited by a laser beam of a semiconductor laser, a fundamental wave is oscillated by an optical resonator including the solid-state laser medium, and the wavelength is converted to a second harmonic by a nonlinear optical crystal. There is known a laser pointer that emits (see, for example, Patent Document 1 and Patent Document 2).
Japanese Patent No. 2500573 JP 2004-281932 A

The conventional laser pointer uses a so-called gain-guided semiconductor laser that is multimode in both the longitudinal mode and the transverse mode. However, the gain-guided semiconductor laser has a high oscillation threshold and high electro-optical conversion efficiency. Since it is low, the driving current becomes large. Further, the gain-guided semiconductor laser has a linear pattern of several μm × several tens to several hundreds of μm in light emission pattern. It is difficult to sufficiently overlap the cavity mode (mode matching), which is a fundamental Gaussian mode having a circular cross section to be excited by the mode. As a result, it is a cause of reducing excitation efficiency. Further, since the electro-optical conversion efficiency is low, the heat generated by the semiconductor laser is large, which causes the power required for cooling to increase.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a laser pointer using a semiconductor laser pumped solid-state laser that can minimize the driving current and cooling power of a semiconductor laser, can be used portablely by dry cell drive, and has a stable laser output. It is to provide.

In a first aspect, the present invention relates to a semiconductor laser that oscillates in a zeroth-order fundamental mode in both a longitudinal mode and a transverse mode, a solid-state laser medium that is excited by laser light output from the semiconductor laser, and the solid-state laser medium. A nonlinear optical crystal that outputs a second harmonic of a fundamental wave oscillated by the optical resonator, a drive current control unit that controls a drive current of the semiconductor laser, and a semiconductor laser Temperature control means for controlling the temperature, including a wavelength at which the absorptance of the solid-state laser medium is maximum, and within a wavelength range in which the intensity fluctuation of the second harmonic falls within a specification value range. Provided is a laser pointer using a semiconductor laser pumped solid-state laser, wherein there are three or more longitudinal modes of the semiconductor laser.
In the laser pointer using the semiconductor laser pumped solid state laser according to the first aspect, a single mode semiconductor laser is used for both the longitudinal mode and the transverse mode. A single-mode semiconductor laser in both the longitudinal mode and the transverse mode has a low oscillation threshold and a high electro-optical conversion efficiency, so that the drive current can be minimized. Further, since the transverse mode is a single mode, the mode matching characteristic with the resonator mode is good, and high excitation efficiency is obtained. Further, since the electro-optical conversion efficiency is high, the heat generated by the semiconductor laser is small, and the power for cooling can be minimized. Therefore, portable use by dry cell drive becomes possible.

However, in general, a single mode semiconductor laser has a mode between three longitudinal modes: a longitudinal mode of the center wavelength, a longitudinal mode adjacent to the shorter wavelength side than the center wavelength, and a longitudinal mode adjacent to the longer wavelength side of the center wavelength. Since the hopping occurs, if the change in the absorptance of the solid-state laser medium with respect to the wavelength jump due to the mode hop is large, the output becomes unstable in the control by the drive current control circuit.
Therefore, in the laser pointer using the semiconductor laser-pumped solid-state laser according to the first aspect, the intensity variation of the second harmonic falls within the specification value range including the wavelength at which the absorption rate of the solid-state laser medium is maximized. Three or more longitudinal modes of the semiconductor laser exist in such a wavelength range. Even if mode hopping is performed between three longitudinal modes within the wavelength range, the output of the solid-state laser medium with respect to the wavelength jump is small, so that the output can be stabilized by the control by the drive current control circuit.

In a second aspect, the present invention relates to a laser pointer using the semiconductor laser pumped solid-state laser according to the first aspect, wherein the wavelength range is centered around a wavelength at which the absorption rate of the solid-state laser medium is maximum. Provided is a laser pointer using a semiconductor laser pumped solid-state laser characterized by being in a wavelength range of 0.5 nm.
In the laser pointer using the semiconductor laser-pumped solid-state laser according to the second aspect, a wavelength range of ± 0.5 nm centering on the wavelength at which the absorptance of the solid-state laser medium is maximized is obtained. Variation in the absorptance of the solid-state laser medium can be reduced.

In a third aspect, the present invention provides a laser pointer using the semiconductor laser-pumped solid-state laser according to the first or second aspect, wherein the solid-state laser medium has an end surface on the anti-nonlinear optical crystal side and the nonlinear optical crystal. Provided is a laser pointer using a semiconductor laser-pumped solid-state laser, wherein an end face on the anti-solid laser medium side is mirror-coated with respect to a fundamental wave, and an optical resonator is constituted by the both end faces.
In the laser pointer using the semiconductor laser pumped solid-state laser according to the fifth aspect, the end face of the solid-state laser medium and the end face of the nonlinear optical crystal are mirror-coated with respect to the fundamental wave, and an optical resonator is formed on each end face. The structure can be simplified and the temperature control object can be made compact. Therefore, the power required for temperature control can be reduced.

In a fourth aspect, the present invention relates to a laser pointer using the semiconductor laser-pumped solid state laser according to the third aspect, wherein an end surface of the solid-state laser medium that is not mirror-coated and a mirror coat of the nonlinear optical crystal are provided. Provided is a laser pointer using a semiconductor laser-pumped solid-state laser, characterized in that an end surface which has not been applied is bonded.
Since the laser pointer using the semiconductor laser pumped solid state laser according to the fourth aspect has a structure in which the solid state laser medium and the nonlinear optical crystal are bonded together, the temperature control target can be made more compact. Therefore, the power required for temperature control can be further reduced.

In a fifth aspect, the present invention relates to a laser pointer using a semiconductor laser pumped solid state laser according to any one of the first to fourth aspects, wherein the laser pointer using the semiconductor laser pumped solid state laser is driven by a dry cell. A laser pointer using a semiconductor laser pumped solid-state laser is provided.
Since the laser pointer using the semiconductor laser excitation solid-state laser according to the fifth aspect is driven by a dry cell, it can be used in a portable manner, and a portable laser marking device can be realized.

  According to the laser pointer using the semiconductor laser pumped solid-state laser of the present invention, since a single mode semiconductor laser having a low oscillation threshold and a high electro-optical conversion efficiency is used, the power required for driving current and temperature control can be minimized, Portable use by dry cell drive becomes possible. In addition, since there are three or more longitudinal modes in the wavelength range where the variation of the absorptance is small, the variation of the absorptance of the solid-state laser medium with respect to the wavelength jump is small even when mode hopping between them, and the control by the drive current control circuit Can stabilize the output.

  Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited thereby.

FIG. 1 is a configuration diagram illustrating a laser pointer 100 according to the first embodiment.
The laser pointer 100 includes a semiconductor laser 1 that emits laser light, a lens 2 that condenses the laser light, a solid-state laser medium 3 that is excited by the condensed laser light and emits a fundamental wave, and a fundamental wave. Nonlinear optical crystal 4 that converts to second harmonic, mirror 5 that constitutes one end of optical resonator 6 and transmits the second harmonic, and beam splitter that extracts a portion of the second harmonic transmitted through mirror 5 7, an infrared cut filter 8 that cuts infrared rays from the second harmonic wave that has passed through the beam splitter 7, a beam expander 9 that expands the beam diameter that has passed through the infrared cut filter 8 and makes a parallel beam, and a beam splitter 7. The photodiode 10 that receives the extracted second harmonic and converts it into an electrical signal, and the intensity of the electrical signal at the photodiode 10 is constant. An APC (Auto Power Control) circuit 11 for controlling the drive current of the semiconductor laser 1, a base 12 for supporting the semiconductor laser 1, the condenser lens 2, the solid-state laser medium 3, the nonlinear optical crystal 4 and the mirror 5, and a base 12 A Peltier element 13 for heating / cooling; a thermistor 14 for detecting the temperature of the base 12; a temperature control circuit 15 for driving the Peltier element 13 so that the temperature detected by the thermistor 14 becomes a predetermined temperature; A dry battery 16 as a power source, a cylindrical casing 17 of a size that can be carried by a person, and a spring 18 are provided.

The semiconductor laser 1 is a single mode semiconductor laser for both the longitudinal mode and the transverse mode, and emits light in a wavelength range (for example, 808 nm to 809 nm) centered on the absorption peak wavelength (for example, 808.5 nm) of the solid-state laser medium 3. Temperature tuned.
FIG. 2 shows the output characteristics of the semiconductor laser 1.
As indicated by the solid line, the oscillation threshold is 60 mA or less.
For comparison, the characteristics of a multimode semiconductor laser are indicated by broken lines.

The solid-state laser medium 3 is Nd: YVO ₄ .
The semiconductor laser side end face of the solid-state laser medium 3 is coated with a high transmittance at 808.5 nm and a high reflectance at 1064 nm. An optical resonator 6 is formed between the end surface of the solid-state laser medium 3 on the semiconductor laser side and the mirror 5, and a 1064 nm laser beam oscillates.
FIG. 3 shows the absorptance characteristics of the solid-state laser medium 3.
The absorption peak wavelength is 808.5 nm.
In general, the intensity fluctuation of the beam output from the laser pointer 100 is not noticeable up to about 10%. In order to suppress the intensity fluctuation of the second harmonic to about 10%, the intensity fluctuation of the fundamental wave may be suppressed to within 5%. Then, since the absorption rate is 0.9 at the absorption peak wavelength of 808.5 nm, the wavelength fluctuates in the wavelength range from the wavelength 807.9 nm to the wavelength 809.1 nm where the absorption rate decreases by 5% to 0.855. Also good. Therefore, it is sufficient that three or more longitudinal modes of the semiconductor laser 1 exist within the wavelength range of 807.9 nm to 809.1 nm, preferably within the wavelength range of 808 nm to 809 nm. In other words, if the semiconductor laser 1 having a resonator length in which three or more longitudinal modes exist in the wavelength range is adopted, the intensity fluctuation of the second harmonic is within a specification value (for example, 10%). Fits in.

The nonlinear optical crystal 4 is a quasi phase matching element in which a polarization inversion structure is formed with a polarization inversion period so that phase matching can be performed within a temperature range controlled by the temperature control circuit 15. The quasi phase matching element is obtained, for example, by subjecting LiNbO ₃ , LiTaO ₃ , MgO: LiNbO ₃ , MgO: LiTaO ₃ , KNbO ₃ , KTiOPO ₄ to polarization inversion. Pseudo phase matching elements having different polarization inversion periods are prepared in advance and selected according to the temperature of the semiconductor laser 1 to be used as the nonlinear optical crystal 4.
The 1064 nm laser light passing through the nonlinear optical crystal 4 is converted into light of 532 nm, which is the second harmonic, and output from the optical resonator 6.

The base 12 is formed by shaping a good thermal conductor such as aluminum, copper, or copper tungsten.
The spring 18 urges the base 12 to be pressed against the casing 17 with the Peltier element 13 interposed therebetween, and supports the base 12 so that other portions of the base 12 are floated from the casing 17.
The whole of the spring 18 or the portion that contacts the base 12 is made of a polymer material so that the spring 18 does not transfer heat.
A heat conductive grease or a heat conductive sheet is sandwiched between the base 12 and the Peltier element 13 and between the Peltier element 13 and the housing 17 to improve heat conduction. The base 12 and the Peltier element 13 may be bonded or soldered.

  If necessary, the parallel beam output from the beam expander 9 is converted into a fan-shaped beam by using a cylindrical lens having an AR coating for 532 nm on its surface to prevent ghosting.

FIG. 4 shows the green laser output characteristics.
The solid line is the laser pointer 100 using the semiconductor laser pumped solid state laser of the present invention, and the broken line is the laser pointer using a multimode semiconductor laser.
As can be seen from the comparison, the present invention can reduce the drive current by about 70 mA.

According to the laser pointer 100 according to the first embodiment, the following effects can be obtained.
(1) A single mode semiconductor laser in both the longitudinal mode and the transverse mode has a low oscillation threshold and a high electro-optical conversion efficiency, and therefore can minimize the drive current. Further, since the electro-optical conversion efficiency is high, the heat generated by the semiconductor laser is small, and the power required for temperature control can be minimized.
(2) Since there are three or more longitudinal modes of the semiconductor laser 1 within a wavelength range in which the variation of the absorptance is small, the variation of the absorptance of the solid-state laser medium 3 with respect to the wavelength jump is small even if mode hopping between them The output can be stabilized by the control by the APC circuit 11.
(3) It is possible to drive a dry battery, and to realize a green beam laser marking device that can be portable and has good visibility.
(4) Since the temperature of the base 12 is controlled by the Peltier element 13, the semiconductor laser 1, the solid-state laser medium 3 and the nonlinear optical crystal 4 are kept at a constant temperature without being affected by the body temperature of the person carrying them or the ambient temperature. Can be kept. Accordingly, there is no need to drive the semiconductor laser 1 with an excess margin, the driving current of the semiconductor laser 1 can be minimized, and dry cell driving is possible. In addition, the electric power for driving the Peltier element 13 can be small, the electric power required for temperature control can be minimized, and dry cell driving is possible. Further, since there is no temperature change in the emission direction of the second harmonic generated by the nonlinear optical element 4, the direction of the laser output does not change.

FIG. 5 is a configuration diagram illustrating a laser pointer 200 according to the second embodiment.
In this laser pointer 200, the solid-state laser medium 3 and the nonlinear optical crystal 4 are bonded with an adhesive or the like, and the end surface of the nonlinear optical crystal 4 on the anti-semiconductor laser side has a high reflectance at 1064 nm and a low reflectance coating at 532 nm. It has been subjected. That is, the optical resonator 6 is configured inside the crystal. The mirror 5 is omitted. The rest is the same as the laser pointer 100 according to the first embodiment.

  According to the laser pointer 200 according to the second embodiment, the temperature control target can be made compact by bonding the solid-state laser medium 3 and the nonlinear optical crystal 4, so that the power required for temperature control can be further reduced. I can do it.

As the solid-state laser medium 3, Nd: GdVO ₄ , Nd: YLF, Nd: YAG single crystal, ceramic YAG obtained by sintering fine crystals of Nd: YAG, or the like may be used instead of Nd: YVO ₄ .

  The laser pointer using the semiconductor laser excitation solid-state laser of the present invention can be used for a laser marking device.

FIG. 3 is an explanatory diagram illustrating a laser pointer according to the first embodiment. It is an output characteristic view of a semiconductor laser. It is an absorptivity characteristic view of a solid laser medium. 6 is a green laser output characteristic diagram of the laser pointer according to Embodiment 1. FIG. FIG. 10 is an explanatory diagram illustrating a laser pointer according to a second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor laser 3 Solid state laser medium 4 Nonlinear optical crystal 6 Optical resonator 12 Base 13 Peltier element 14 Thermistor 15 Temperature control circuit 16 Dry cell 100,200 Laser pointer using semiconductor laser excitation solid state laser

Claims (5)

A semiconductor laser that oscillates in a zeroth-order fundamental mode in both the longitudinal mode and the transverse mode, a solid-state laser medium that is excited by laser light output from the semiconductor laser, and an optical resonator that includes the solid-state laser medium and is contained in the optical resonator A nonlinear optical crystal that outputs a second harmonic of a fundamental wave oscillated by an optical resonator; drive current control means for controlling the drive current of the semiconductor laser; and temperature control means for controlling the temperature of the semiconductor laser. And there are three or more longitudinal modes of the semiconductor laser in the wavelength range including the wavelength at which the absorptance of the solid-state laser medium is maximum and the intensity fluctuation of the second harmonic falls within the specification value range. A laser pointer using a semiconductor laser pumped solid-state laser. 2. The laser pointer using the semiconductor laser pumped solid-state laser according to claim 1, wherein the wavelength range is a wavelength range of ± 0.5 nm centering on a wavelength at which the absorption rate of the solid-state laser medium is maximum. A laser pointer using a semiconductor laser pumped solid-state laser. 3. A laser pointer using the semiconductor laser-pumped solid-state laser according to claim 1 or 2, wherein an end face of the solid-state laser medium on the anti-nonlinear optical crystal side and an end face of the non-linear optical crystal on the anti-solid laser medium side are fundamentally provided. A laser pointer using a semiconductor laser-pumped solid-state laser, wherein a mirror coat for waves is applied and an optical resonator is formed by the both end faces. 4. A laser pointer using the semiconductor laser pumped solid-state laser according to claim 3, wherein an end surface of the solid-state laser medium that is not mirror-coated and an end surface of the nonlinear optical crystal that is not mirror-coated are bonded together. A laser pointer using a semiconductor laser pumped solid-state laser. 5. A laser pointer using the semiconductor laser pumped solid laser according to claim 1, wherein the laser pointer using the semiconductor laser pumped solid laser is driven by a dry cell. Laser pointer using a laser.

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