JP4714967B2 - Semiconductor laser pumped solid-state laser device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor laser pumped solid-state laser device, and more particularly to detection of deterioration or failure of a semiconductor laser.
[0002]
[Prior art]
A conventional semiconductor laser pumped solid state laser device will be described with reference to FIG. FIG. 4 is a schematic diagram showing the configuration of a conventional semiconductor laser-pumped solid-state laser device described in, for example, Japanese Patent Laid-Open No. 10-294513.
In the figure, 1 is a solid-state laser medium (YAG), 2 and 3 are resonator mirrors for constituting a resonator, 4 (4a to 4h) are semiconductor lasers for exciting the solid-state laser medium 1, and 5 is a semiconductor laser. 4 is a power source for driving 4. Further, 6 (6a to 6h) is a heat sink, 7 is a cooling water channel, and 8 is a cooler.
[0003]
The semiconductor laser 4 for exciting the solid-state laser medium 1 obtains a large output by configuring the light emitting part in an array or a stack. At present, the output of the arrayed semiconductor laser 4 is generally 20 W to 50 W.
[0004]
On the other hand, the output of the solid-state laser medium 1 has several W to several kW class, and it is impossible to excite with a single semiconductor laser 4 in order to construct a laser device with these outputs. The method of exciting with the semiconductor laser 4 is used.
[0005]
First, a power connection method for simultaneously exciting a plurality of semiconductor lasers will be described.
Generally, when a plurality of loads are connected to a power supply in parallel, the power supply to be driven has a low voltage and a large current, whereas when connected in series, a high voltage and a low current are obtained.
In the case of a 20 W to 50 W class semiconductor laser, the operating voltage is about 2 V, the operating current is 40 A to 60 A, and the semiconductor laser operates at a relatively low voltage and large current.
In the semiconductor laser excitation solid-state laser device shown in FIG. 4, one solid-state laser medium 1 is excited by eight semiconductor lasers 4. Assuming that the operating voltage and operating current of one semiconductor laser 4 is 2V-50A, the power source required for operating eight semiconductor lasers in parallel is 2V-400A. On the other hand, when operating in series, 16V-50A. As described above, in the case of the semiconductor lasers 4, even if a plurality of semiconductor lasers are connected in series, a relatively medium voltage and medium current power source can be used.
[0006]
Low-voltage, high-current power supplies are not only difficult to obtain, but also extremely disadvantageous in terms of circuit losses. The electric wire for supplying the electric current has a slight electric resistance Re, and the electric power lost in the electric wire becomes I ² · Re with respect to the current value I, and increases in proportion to the square of the electric current. In order to overcome this, there is a method of increasing the cross-sectional area of the electric wire to lower the electric resistance, but it is very disadvantageous to wire a thick electric wire in the excitation head.
[0007]
As described above, a high voltage and low current system with little loss is generally adopted for power supply. From the above, as a method of exciting a plurality of semiconductor lasers 4 at the same time, a method of operating the semiconductor lasers 4 connected in series is common.
[0008]
Next, the configuration of the excitation head having the solid laser medium 1 and the semiconductor laser 4 will be described.
In general, in order to increase the pumping efficiency of the solid-state laser medium 1, all the light output from the semiconductor laser 4 is irradiated toward the solid-state laser medium 1 and confined in a condenser.
[0009]
If the pump head is configured to be monitored by light leaking from the semiconductor laser 4 to the outside, the semiconductor laser 4 that has deteriorated or failed can be identified by detecting the light leaked from each semiconductor laser 4.
If a plurality of semiconductor lasers 4 are connected in parallel to the power supply 5, a circuit that supplies power to each semiconductor laser 4 can be cut off independently. Therefore, if the output of the solid-state laser medium 1 does not change even when the circuit to the semiconductor laser 4 is cut off, it can be determined that the semiconductor laser 4 has deteriorated or failed (hereinafter referred to as deterioration as appropriate).
[0010]
However, as described above, the pump head is configured so that light from the semiconductor laser 4 does not leak to the outside, and a semiconductor laser having a system in which a plurality of semiconductor lasers 4 are connected in series and operated by a single power source 5. In the pumped solid-state laser device, when the output of the solid-state laser medium is reduced due to deterioration of the semiconductor laser 4 or the like, it is difficult to identify the deteriorated semiconductor laser.
[0011]
[Problems to be solved by the invention]
Since the conventional semiconductor laser pumped solid-state laser device has the configuration described above, in order to know which of the plurality of semiconductor lasers has deteriorated, the pump head is disassembled. There was a problem that all the semiconductor lasers were taken out and the output characteristics of each semiconductor laser had to be individually measured.
[0012]
The present invention has been made to solve the above-described problems, and obtains a semiconductor laser excitation solid-state laser device that can identify a deteriorated semiconductor laser from a plurality of semiconductor lasers with a simple configuration. It is.
[0013]
[Means for Solving the Problems]
A semiconductor laser pumped solid-state laser device according to the present invention detects a temperature of a solid-state laser medium, a plurality of semiconductor lasers connected to a power source and pumping the solid-state laser medium, and a predetermined semiconductor laser among the plurality of semiconductor lasers A temperature detection means and a deterioration detection means for detecting the deterioration state of the semiconductor laser based on the output of the temperature detection means are provided.
[0014]
The plurality of semiconductor lasers are electrically connected in series.
[0015]
The temperature detecting means detects the temperatures of all the semiconductor lasers.
[0016]
In addition, deterioration notifying means for notifying the deterioration state of the semiconductor laser based on the output from the deterioration detecting means is provided.
[0017]
The temperature detecting means is provided on a heat sink for cooling the semiconductor laser.
[0018]
The temperature detecting means is a thermocouple.
[0019]
The temperature detecting means is a thermal paper.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
A semiconductor laser pumped solid-state laser device according to a first embodiment of the present invention will be described.
First, the principle of semiconductor laser deterioration detection in the present invention will be briefly described.
In a semiconductor laser, energy corresponding to an energy gap existing in the PN junction is converted into light by recombination of electrons and vacancies supplied from a power source in the PN junction. If the semiconductor crystal structure constituting the semiconductor laser is broken for some reason, the energy gap at the PN junction changes, and the energy due to recombination of electrons and vacancies cannot be converted to light. The energy that can no longer be converted into light is generated as heat from the PN junction.
Thus, the deterioration of the semiconductor laser only changes the energy emission form from light to heat, and the change in electrical characteristics, that is, current / voltage characteristics is small.
[0021]
As described above, the semiconductor laser has the property that the current / voltage characteristics do not change even if the output characteristics thereof are lowered. The reduced output becomes heat as it is and is accumulated in the semiconductor laser. Therefore, when the semiconductor laser is operated under a certain condition, the output deterioration appears as a temperature rise of the semiconductor laser itself. By detecting this temperature increase by the temperature detecting means, it becomes possible to identify the semiconductor laser whose output has decreased.
[0022]
In the case of a semiconductor laser capable of obtaining a light output of P (W) when driven under a certain condition, for example, a constant current value with direct current, the thermal resistance from the light emitting part to the position where the temperature detecting means is attached, this is the light emission This is determined only by the material and mechanical structure from the position to the position of the temperature detecting means, and this is R (° C./W). When the light output is converted into heat due to the deterioration of the semiconductor laser, the temperature rise of the temperature detecting means appears as P × R (° C.).
[0023]
In 20W to 50W class semiconductor laser products that are currently commercialized, the thermal resistance from the light emitting part to the heat sink attached to dissipate heat is generally about 0.7 to 1.0 ° C / W. Is. When a semiconductor laser having a 20 W output and a thermal resistance of 0.7 ° C./W deteriorates, a temperature increase of 20 W × 0.7 ° C./W=14° C. occurs on the heat sink. In the case of a semiconductor laser having an output of 60 W and a thermal resistance of 1.0 ° C./W, the temperature rises by 60 ° C.
[0024]
Therefore, the deterioration detection of the semiconductor laser may be performed by detecting a relatively large temperature change such as 10 ° C. or more, and can be sufficiently handled by an inexpensive and simple temperature detecting means such as a thermocouple or thermal paper.
[0025]
Next, a specific configuration of the semiconductor laser pumped solid-state laser device according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a semiconductor laser pumped solid-state laser device according to a first embodiment of the present invention.
In the figure, reference numerals 1 to 5 are the same as or equivalent to those of the conventional example, and detailed description thereof is omitted. Reference numeral 10 (10a to 10h) denotes a thermocouple as temperature detecting means attached in the vicinity of the oscillation part of each semiconductor laser 4. 11 (11a to 11h) is a comparator provided corresponding to each thermocouple 10, and the other input is connected to the reference temperature setter 12.
Denoted by 13 is a deterioration notification means for notifying the operator of the deterioration or failure of the semiconductor laser 4 based on the output of the comparator 11, such as a dedicated display panel, a warning light, a warning sound generating speaker, and the like. The deterioration detection means is constituted by the comparator 11, the reference temperature setting device 12, and a processing circuit (not shown) that processes the output signal from the comparator 11 and outputs the processed signal to the deterioration notification means 13. Further, the processing circuit (not shown) may be configured so as to be integrated with the deterioration notification means 13.
[0026]
The semiconductor laser 4 is driven by a power source 5 and generates light having a wavelength corresponding to the absorption band of the solid-state laser medium 1. When the solid-state laser medium 1 is Nd: YAG, a semiconductor laser 4 whose oscillation wavelength is in the vicinity of 808 nm is used. The solid-state laser medium 1 is excited by a semiconductor laser 4 and oscillates by a resonator constituted by resonator mirrors 2 and 3.
[0027]
The thermocouple 10 is attached to each semiconductor laser 4 and constantly monitors its temperature. In the case of the semiconductor laser 4 having an output of about 40 W, it generally operates at 2V-50A. The power extracted as semiconductor laser light is 40 W with respect to the power of 100 W supplied to the semiconductor laser 4, and the remaining 60 W is accumulated in the semiconductor laser 4 as heat. This accumulated amount of heat is carried out to the outside using some cooling method.
[0028]
When any one of the semiconductor lasers 4 is deteriorated, the change in the current / voltage characteristics is negligible, and only the optical output is reduced. That is, the power originally extracted as the optical output is accumulated in the semiconductor laser 4 as the amount of heat. The amount of heat accumulated in the semiconductor laser 4 increases due to the deterioration, and appears as a temperature rise of the semiconductor laser 4. This temperature rise can be detected by the thermocouple 10 provided in the semiconductor laser 4.
[0029]
The comparator 11 compares the output from the thermocouple 10, that is, the temperature of the semiconductor laser 4 with a reference temperature preset in the reference temperature setter 12, and the temperature of the semiconductor laser 4 rises and exceeds the set reference temperature. When it becomes, it outputs to a processing circuit (not shown). The output signal processed by the processing circuit is further output to the deterioration notification means 13, and the user is notified of the deterioration of the semiconductor laser 4 by the operation of the deterioration notification means 13.
[0030]
As described above, according to the semiconductor laser excitation solid-state laser device of this embodiment, even if the semiconductor lasers 4 are connected in series and driven by one power source 5, the temperature of each semiconductor laser 4 is monitored and By detecting the rise, it can be determined which semiconductor laser 4 has deteriorated.
[0031]
FIG. 2 shows the configuration of each semiconductor laser 4. In the semiconductor laser 4, the heat sink 6 and the semiconductor laser element 14 are integrated, and the semiconductor laser element 14 is always cooled by the heat sink 6.
FIG. 3 shows a case where the thermal paper 15 is pasted on the surface of the heat sink 6 as temperature detecting means.
[0032]
Although not shown, when a water-cooled heat sink is used, the temperature of each semiconductor laser is increased based on the change in the temperature difference between the cooling water supply side and the discharge side of the cooling water to the heat sink. It is also possible to detect.
[0033]
Furthermore, although not shown, it is also possible to detect the temperature rise of each semiconductor laser by non-contact temperature detecting means such as an infrared camera.
[0034]
In the above-described embodiment, when the temperature of the semiconductor laser 4 rises and becomes equal to or higher than the set reference temperature, it is output from the processing circuit to the deterioration notification means 13 and the user is notified of the semiconductor laser 4. Although the case where the deterioration is notified is shown, as a countermeasure when the deterioration of the semiconductor laser 4 is detected, not only the user is notified but also a process such as stopping the apparatus by turning off the power source 5 is performed. May be.
[0035]
【The invention's effect】
As described above, according to the present invention, by detecting the temperature of each semiconductor laser, it is possible to identify a deteriorated or failed semiconductor laser from a plurality of semiconductor lasers with a simple configuration. Play.
[0036]
In addition, in order to detect the deterioration or failure of the semiconductor laser, it is only necessary to detect a relatively large temperature change. As the temperature detecting means, a temperature detecting means having a relatively simple structure such as a thermocouple or a thermal paper. There is an effect that can be used.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a semiconductor laser pumped solid-state laser device according to an embodiment of the present invention.
FIG. 2 is an explanatory view showing the structure of a semiconductor laser with a heat sink according to an embodiment of the present invention.
FIG. 3 is an explanatory diagram showing a structure in which a thermal paper is provided on a semiconductor laser with a heat sink according to an embodiment of the present invention.
FIG. 4 is a schematic configuration diagram of a conventional semiconductor laser excitation solid-state laser device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Solid-state laser medium 2, 3 Resonator mirror 4 Semiconductor laser 5 Power supply 6 Heat sink 10 Thermocouple 11 Comparator 12 Reference temperature setting device 13 Degradation notification means 14 Semiconductor laser element 15 Thermal paper

Claims (5)

A solid state laser medium;
A plurality of semiconductor lasers connected in series and electrically connected in series to excite the solid state laser medium;
A plurality of temperature detecting means provided in each of the plurality of semiconductor lasers for detecting the temperature of each semiconductor laser;
A comparator for comparing the output of these temperature detecting means with a preset reference temperature,
A deterioration detecting means for detecting that the semiconductor laser provided with the temperature detector is deteriorated when the output of any of the plurality of temperature detecting means exceeds a reference temperature by the comparator ; A semiconductor laser-excited solid-state laser device comprising: 2. The semiconductor laser pumped solid state laser device according to claim 1, further comprising a deterioration notifying unit for notifying a deterioration state of the semiconductor laser based on an output from the deterioration detecting unit. 3. The semiconductor laser pumped solid state laser device according to claim 1, wherein the temperature detecting means is provided in a heat sink for cooling the semiconductor laser. Temperature detecting means, a semiconductor-laser-pumped solid-state laser apparatus according to claim paragraphs 1 through claim 3, characterized in that the thermocouple. A solid state laser medium;
A plurality of semiconductor lasers connected in series and electrically connected in series to excite the solid state laser medium;
A plurality of thermal papers are attached to the surface of each of the plurality of semiconductor lasers to detect the temperature of each semiconductor laser, and
A semiconductor laser excitation solid-state laser device capable of detecting which of the plurality of semiconductor lasers is deteriorated by the thermal paper .

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