JP3952751B2 - Solid state laser equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid-state laser device that excites a solid-state laser crystal by entering light and resonates the excitation light with an optical resonator to cause laser oscillation.
[0002]
[Prior art]
The solid-state laser device uses, for example, a semiconductor laser as an excitation light source, and the laser beam from this is incident on a solid-state laser crystal such as an Nd: YAG crystal that is a laser medium to excite this, and the excitation light is output to an output side mirror. And an optical resonator formed between the crystal and the incident surface mirror to cause laser oscillation and take out the laser light from the output side mirror. An etalon is inserted into the optical resonator for wavelength selection.
[0003]
The length of the optical resonator is extremely important for obtaining stable laser light, and it is desired to suppress the fluctuation range to 40 nm or less. For this reason, the solid laser crystal and the output side mirror are fixed to a metal block or the like to improve the dimensional accuracy. In addition, since the metal block is thermally expanded, the temperature is controlled to be constant so as to suppress the influence. In addition, although the oscillation wavelength of the laser diode and the selective frequency characteristic of the etalon are also slight, they can be controlled by temperature, so that those temperatures are also controlled. That is, these temperatures are detected by a thermistor and the temperature is controlled so that the detected temperature becomes a predetermined value.
[0004]
Further, an automatic output control circuit (Auto Power Control: APC circuit) that controls the drive current of the pumping semiconductor laser so that the output (amplitude) of the laser beam is constant is also provided. A part of the output laser beam is branched and guided to a monitor photodetector, and the monitor output from this photodetector is sent to an APC circuit and compared with a set value, so that the deviation of the excitation semiconductor laser is eliminated. Feedback control is performed to increase or decrease the drive current.
[0005]
Such a solid-state laser device is used for various purposes as a consumer product, and is often used in one large device, or often used in the same facility such as a laboratory or a factory. Therefore, it is necessary to ensure that laser parameters such as laser output and wavelength characteristics are stabilized even during long-term use under various usage environments, and monitoring the operation of a large number of solid-state laser devices individually. And maintenance work needs to be done.
[0006]
[Problems to be solved by the invention]
However, each of the conventional solid-state laser devices is monitored and maintained independently, so that the operation is very complicated, and as a result, many solid-state laser devices are particularly under various environments. When used, there is a problem that it is difficult to ensure stable operation for all of them.
[0007]
In view of the above, the present invention provides an improved solid-state laser device that can easily operate stably over a long period of time even when a large number of solid-state laser devices are used in various environments. The purpose is to provide.
[0008]
Another object of the present invention is to provide a solid-state laser apparatus that can be easily updated such as a version upgrade of a control program.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the solid-state laser device according to claim 1 is excited by a semiconductor laser that generates laser light, a drive circuit that supplies a drive current to the semiconductor laser, and laser light from the semiconductor laser. A solid-state laser crystal having a reflection surface formed on the incident surface, an output-side mirror having a reflection surface that forms an optical resonator between the reflection surface of the laser crystal, and the solid-state laser crystal and the output-side mirror. Are fixed to the resonator block, a wavelength selection etalon inserted into the optical resonator, a monitoring photodetector to which the branched light of the laser beam output from the output side mirror is input, An automatic output adjustment circuit that controls the drive current so that a laser beam having a predetermined output is output to the outside by feeding back the output of the monitoring photodetector to the drive circuit, and the common circuit. A temperature control device for a resonator block that includes a temperature sensor that detects the temperature of the resonator block and controls the temperature of the resonator block to be a set temperature, and a semiconductor laser that includes a temperature sensor that detects the temperature of the semiconductor laser A temperature control device for a semiconductor laser that controls the temperature of the etalon to include a temperature sensor that detects the temperature of the etalon, and a temperature control device for the etalon that controls the temperature of the etalon to be a set temperature. A host computer connected to a network and having a function of judging the presence or absence of an abnormality or failure of a solid-state laser device based on information on the drive current of the semiconductor laser and information on temperatures of the resonator block, semiconductor laser, and etalon in contrast, the information and the resonator Bro for the driving current of the semiconductor laser Click, outputs the information for each temperature of the semiconductor laser and the etalon, a signal from the network, and the from the host computer, the semiconductor laser, the resonator block, and a readjustment of the setting temperature of the etalon A network interface circuit for inputting a command is provided.
[0010]
Since the solid-state laser device has a network interface circuit, it can be connected to the network via this. Through this network interface circuit, it becomes possible to output information about the drive current of the semiconductor laser and information about each temperature of the resonator block, the semiconductor laser, and the etalon to the network, and each temperature from the network. It becomes possible to input a command to the control device. Therefore, it is possible to collect drive current information, temperature information, and the like of a large number of solid-state laser devices in a host computer connected to a network, and to monitor each solid-state laser device collectively with this host computer. It is possible to remotely monitor the abnormality of the drive current and the detected temperature. Then, the host computer issues a command to readjust the temperature by detecting that there is a problem with temperature control even if the drive current is clearly excessive, for example, or detecting a failure even if it is not a failure. Or every time a certain amount of time elapses for each solid-state laser device, a command to readjust the temperature as described above can be issued for each solid-state laser device. Become. As described above, since remote monitoring and maintenance by remote operation for a large number of solid-state laser devices can be performed at once, the work load is reduced, and stable operation over a long period of time can be easily ensured.
[0011]
3. The solid-state laser device according to claim 2, further comprising a replaceable read-only memory, wherein the read-only memory has a resonator block in accordance with a command input from a network via a network interface circuit. The temperature control device for semiconductors, the temperature control device for semiconductor lasers, and the temperature control device for etalon are controlled to read the semiconductor laser drive current when the temperature of the block, semiconductor laser and etalon is changed separately, and the drive current is the least A control program is stored which obtains the respective temperatures and sets them as the set temperatures of the block temperature control device, the semiconductor laser temperature control device, and the etalon temperature control device.
[0012]
With this control program, the temperature tuning operation can be performed in each of the block temperature control device, the semiconductor laser temperature control device, and the etalon temperature control device, and updates such as version upgrades of the control program are read-only. It is simple because the memory itself is exchanged, and the work is also easy.
[0013]
The solid-state laser device according to claim 3, further comprising a rewritable memory, wherein the rewritable memory is used for the resonator block in accordance with a command input from the network via the network interface circuit. The temperature control device, the temperature control device for semiconductor laser, and the temperature control device for etalon are controlled to read the semiconductor laser drive current when the temperature of the block, semiconductor laser and etalon is changed separately, and the drive current is minimized A control program is stored that obtains the temperature separately and performs an operation of setting them as the set temperatures of the block temperature control device, the semiconductor laser temperature control device, and the etalon temperature control device.
[0014]
Therefore, with this control program, it is possible to perform temperature tuning operations in each of the block temperature control device, the semiconductor laser temperature control device, and the etalon temperature control device, and updates such as version upgrades of the control program, This can be done easily by rewriting the rewritable memory online by a host computer or the like via a network interface circuit.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram mainly showing a signal system of a solid-state laser device according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing an arrangement relationship of each part. As shown in FIG. 1, each solid-state laser device includes a network interface circuit 47, and is connected to the network via the network interface circuit 47 so that signals can be exchanged with a host computer 48 or the like.
[0016]
Further, referring also to FIG. 2, the optical resonator 10 is formed by the solid-state laser crystal 11 and the output side mirror 12. The solid-state laser crystal 11 is made of, for example, an Nd: YAG crystal and is excited by the incidence of laser light. A reflection coat 13 is applied to the incident surface to form a reflection surface. As the excitation laser light source, for example, a laser diode (LD) 15 is used, and the laser light enters the solid-state laser crystal 11 through the optical system 16. The output side mirror 12 is made of optical glass or the like, and its surface is polished to a concave surface, and a reflective coating 14 is formed.
[0017]
The solid-state laser crystal 11 is excited by the excitation light, and the generated light is amplified by resonating between the output-side mirror 12 (the reflection coat 14) and the reflection coat (mirror) 13 itself and resonating. As a result, the light intensity increases and laser oscillation occurs. An etalon 17 having a wavelength selection characteristic only for the fundamental wave is inserted into the optical resonator 10 and performs conversion from multimode light to single mode light by transmitting only the fundamental wave of a specific wavelength.
[0018]
Further, in this example, a wavelength conversion crystal 18 is inserted in the optical resonator 10. The fundamental wave light (infrared light) amplified in the optical resonator 10 is wavelength-converted by the wavelength conversion crystal 18 and becomes visible light (green or blue light). The reflection coat 14 of the output side mirror 12 has a wavelength characteristic such that the fundamental wave (infrared light) is totally reflected and the wavelength-converted visible light (green, blue) is transmitted. The light after wavelength conversion through the coat 14 is emitted.
[0019]
A part of the emitted laser beam is branched by the beam splitter 21. The branched laser beam enters a PD (photodiode) 22. The PD 22 is for monitoring the emitted laser beam.
[0020]
These laser crystal 11, output side mirror 12, etalon 17, wavelength conversion crystal 18, beam splitter 21, PD 22, etc. are formed on one integrated block 31 in this example. The block 31 is made of a metal having a small thermal expansion coefficient, and is placed on the temperature control Peltier element 32 to be cooled or heated. The laser diode 15 is also disposed on the Peltier element 33 and its temperature is controlled (cooled or heated). These are housed in one housing 34. Although not shown in the drawing, the casing 34 is provided with an emission port for emitting a laser beam to the outside of the casing 34.
[0021]
The output from the PD 22 is fed back to the LD 15, and the laser beam output through the beam splitter 21 is stabilized. As shown in FIG. 1, the output of the PD 22 is sent to the LD drive circuit 42 through the APC circuit 41 and fed back to the drive current of the LD 15. In the APC circuit 41, the PD22 output is compared with a predetermined set value, and the drive current applied to the LD 15 is increased or decreased so that the deviation is eliminated.
[0022]
On the other hand, the temperature of the block 31 to which the solid-state laser crystal 11 and the output side mirror 12 are fixed is detected by the thermistor 25, and the temperature control circuit 44 controls the Peltier element 32 so that the temperature becomes the set temperature. Since the thermistor 25 is provided in the vicinity of the wavelength conversion crystal 18, the temperature of the wavelength conversion crystal 18 is detected and the temperature is controlled. Similarly, the temperature of the LD 15 is also detected by the thermistor 24, and the detection output is sent to the temperature control circuit 43 to control the Peltier element 33 so that the temperature of the LD 15 becomes the set temperature.
[0023]
Further, the etalon 17 is heated by the heater 23 so as to have a predetermined set temperature. The temperature of the etalon 17 is detected by the thermistor 26, and the detection output is sent to the temperature control circuit 45. Thereby, the temperature control circuit 45 controls the heater 23 so that the temperature of the etalon 17 is maintained at the set value.
[0024]
Information on the drive current of the LD 15 is sent from the drive circuit 42 to the CPU 46, and the temperature of the resonator block 31, the temperature of the LD 15 and the temperature of the etalon 17 captured by the thermistors 25, 24, 26 are also collected in the CPU 46. Has been. The CPU 46 sends these pieces of information to the network via the network interface circuit 47. A host computer 48 on the network receives them and remotely monitors the drive current and each temperature for each of a number of solid state laser devices on the network. Further, the host computer 48 performs cumulative calculation of operation time for each of the solid-state laser devices.
[0025]
In this way, the host computer 48 constantly performs remote monitoring for a large number of solid-state laser devices on the network, and determines whether there is any abnormality or failure from information on the drive current and temperature. Also, in individual solid-state laser devices, as a result of long-term use, the drive current may increase or the temperature may shift, and this is also detected remotely. When the drive current increases, the temperature control becomes inappropriate due to the aging of the thermistors 24 to 26 and the aging of the mechanical dimensions of the resonator block 31 is suspected. An operation command is issued for readjustment. Alternatively, such an operation command may be issued every time the accumulated operation time reaches a certain time.
[0026]
At this time, in the solid-state laser device that has received the command, the CPU 46 monitors the drive current and changes the set temperature that the CPU 46 gives to the temperature control circuits 43 to 45 to change the temperatures of the resonator block 31, LD 15, and etalon 17. Vary individually. Since the optimum temperature is the temperature at which the drive current is the smallest, the optimum temperature can be searched by such a temperature sweep. When the optimum temperature is detected, that temperature is set as the set temperature. As a result, even if there is a secular change of the thermistors 24 to 26 and a mechanical dimension of the resonator block 31, it is possible to compensate for them and maintain the optimum temperature.
[0027]
That is, when the size of the resonator block 31 changes due to mechanical aging and the resonator length changes, the laser output decreases due to the wavelength shift of each part, and the APC circuit 41 compensates for this. As a result, the drive current of the LD 15 increases. Further, even when the temperature control is not properly performed due to the aging of the characteristics of the thermistors 24 to 26, the drive current of the LD 15 increases as a result of the function of the APC circuit 41. On the contrary, if the resonator length is a predetermined length and the wavelength characteristics of each part are kept at the set values, the drive current of the LD 15 becomes the minimum value. This means that if the temperature of each part is adjusted so that the drive current of the LD 15 becomes the minimum value, the resonator length becomes a predetermined value, and the wavelength characteristics of each part become a set value.
[0028]
Therefore, after the CPU 46 takes in information related to the drive current applied to the LD 15, the temperature control circuit 44 controls the Peltier element 32 under the control of the CPU 46 to sequentially change the temperature of the block 31. The temperature at which the drive current is minimized is obtained from the thermistor 25. When the temperature at which the drive current of the LD 15 is minimized can be searched, the temperature is the optimum temperature of the block 31 with a predetermined resonator length. When the optimum temperature is obtained in the CPU 46 in this way, this is set as a set temperature to be determined by the temperature control circuit 44. As a result, mechanical and dimensional secular changes in the block 31 and secular changes of the thermistor 25 are compensated.
[0029]
Further, the control of the temperature of the wavelength conversion crystal 18 as described above also serves to compensate for mechanical and dimensional aging of the block 31. This is because the refractive index of the wavelength conversion crystal 18 is temperature dependent, which means that the refractive index can be changed depending on the temperature, and the equivalent optical path length can be changed. This is because the change in the resonator length due to the mechanical and dimensional change over time of the block 31 can be compensated by the change in the optical path length in the wavelength conversion crystal 18.
[0030]
The temperature of the LD 15 is similarly tuned. The temperature control circuit 43 is controlled by the CPU 46, and the temperature of the LD 15 cooled by the Peltier element 33 is changed. When the driving current of the LD 15 at each temperature (detected by the thermistor 24) at this time is taken into the CPU 46 from the driving circuit 42, the relationship of the driving current with respect to the temperature of the LD 15 is obtained in the CPU 46. The oscillation wavelength of the LD 15 varies depending on the temperature, and when the temperature reaches a predetermined oscillation wavelength, the laser output output to the outside as the solid-state laser device is maximized. That is, the temperature at which the drive current is the smallest is the optimum temperature. When the optimum temperature is obtained in the CPU 46 in this way, this is set as a set temperature to be determined by the temperature control circuit 43. As a result, the secular change of the thermistor 24 is compensated.
[0031]
The same applies to the etalon 17, and the temperature of the etalon 17 heated by the heater 23 is changed to change the selected wavelength. Then, the drive current of the LD 15 at each temperature (detected by the thermistor 26) is obtained, the temperature at which the drive current is the smallest is obtained, and that temperature is given to the temperature control circuit 45 as the set temperature. Such an operation is performed by the CPU 46. The drive current of the LD 15 is minimized when the wavelength selection characteristic of the etalon 17 coincides with the design value, so that the aging of the characteristic of the thermistor 26 is compensated. When such tuning is completed, the temperature control circuit 45 controls the temperature of the etalon 17 to an optimum temperature.
[0032]
A control program for controlling these temperature tuning operations is stored in a ROM (read only memory) 49 connected to the CPU 46. This ROM 49 is attached so as to be exchangeable, and can be exchanged at any time by a traveling worker or the like when a program update or version upgrade occurs.
[0033]
Therefore, since a large number of solid-state laser devices on the network are remotely monitored collectively by a single host computer 48 and receive appropriate commands, management and maintenance work for a large number of solid-state laser devices is automatically performed. As a result, stabilization of operation such as stabilization of laser parameters is ensured over a long period of time.
[0034]
The above description relates to one embodiment of the present invention, and it is needless to say that the present invention is not limited to the configuration described above. For example, in the above description, the wavelength conversion crystal 18 is disposed inside the optical resonator 10, but this wavelength conversion crystal 18 is not necessary when outputting infrared light as a fundamental wave instead of visible light. . Further, a light shielding plate having an opening such as a pinhole or an aperture may be disposed in the optical resonator 10 or immediately after the output side mirror 12 to remove unnecessary light beams.
[0035]
Further, in the above description, the control program is stored in the replaceable ROM 49, but the control program is stored in a rewritable memory (RAM or the like), and the host computer 48 on the network rewrites the RAM or the like. Thus, the program can be updated at the time of version upgrade. This eliminates the need for replacing the ROM 49 and the work load can be further reduced.
[0036]
In addition, although the CPU 46 provided in each solid-state laser device performs the operation for readjustment of the temperature, the CPU 46 only performs signal collection and signal transmission / reception control, as described above. The main operation control of the temperature adjustment can be directly performed by the host computer 48.
[0037]
【The invention's effect】
As described above, according to the solid-state laser device of the present invention, even when a large number of solid-state laser devices are used, monitoring and maintenance of their operation states can be performed in a lump. For solid-state laser devices, stabilization of laser parameters and operation can be ensured over a long period of use. In addition, since the control program can be updated by replacing the replaceable read-only memory or rewriting the rewritable memory, it is easy to update the control program and the like.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a schematic diagram showing an arrangement relationship of each part in the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Optical resonator 11 Solid state laser crystal 12 Output side mirrors 13 and 14 Reflection coat 15 Laser diode (LD)
16 Optical system 17 Etalon 18 Crystal for wavelength conversion 21 Beam splitter 22 PD for monitor
23 Heater 24-26 Thermistor 31 Resonator block 32, 33 Peltier element 34 Case 41 APC circuit 42 LD15 drive circuit 43-45 Temperature control circuit 46 CPU
47 Network interface circuit 48 Host computer 49 ROM

Claims (3)

A semiconductor laser that generates laser light, a drive circuit that supplies a drive current to the semiconductor laser, a solid-state laser crystal that is excited by the laser light from the semiconductor laser and has a reflection surface formed on the incident surface; and the laser An output-side mirror having a reflecting surface that forms an optical resonator with the reflecting surface of the crystal, a resonator block to which the solid-state laser crystal and the output-side mirror are fixed, and a wavelength inserted into the optical resonator The selection etalon, the monitor photodetector to which the branched light of the laser beam output from the output side mirror is input, and the output of the monitor photodetector are fed back to the drive circuit to provide a predetermined output. An automatic output adjustment circuit that controls the drive current so that laser light is output to the outside, and a temperature sensor that detects the temperature of the resonator block are provided. A temperature control device for a resonator block that controls the temperature of the semiconductor laser, and a temperature control device for a semiconductor laser that includes a temperature sensor that detects the temperature of the semiconductor laser and controls the temperature of the semiconductor laser to be a set temperature. And a temperature controller for etalon that includes a temperature sensor that detects the temperature of the etalon and controls the temperature of the etalon to be a set temperature, and is connected to a network, and information about the drive current of the semiconductor laser and the resonance Information on the driving current of the semiconductor laser and the resonator block for a host computer having a function of judging the presence or absence of an abnormality or failure of the solid-state laser device based on the information about the temperatures of the resonator block, the semiconductor laser and the etalon When outputting information about each temperature of semiconductor laser and etalon Moni, a signal from the network, said from the host computer, comprising, a network interface circuit for inputting the semiconductor laser, the resonator block, and an instruction to perform a readjustment of the setting temperature of the etalon A solid-state laser device characterized by the above. Depending on the command, the semiconductor laser driving when the resonator block for temperature control, a semiconductor laser temperature control device and the block by respectively controlling the temperature control device for an etalon, the temperature of the semiconductor laser and the etalon is changed to each other A control program that reads the current, obtains the temperature at which the drive current is minimized, and sets the temperature as a set temperature for the block temperature control device, the semiconductor laser temperature control device, and the etalon temperature control device. The solid-state laser device according to claim 1, further comprising a replaceable read-only memory in which is stored. Depending on the command, the semiconductor laser driving when the resonator block for temperature control, a semiconductor laser temperature control device and the block by respectively controlling the temperature control device for an etalon, the temperature of the semiconductor laser and the etalon is changed to each other A control program that reads the current, obtains the temperature at which the drive current is minimized, and sets the temperature as a set temperature for the block temperature control device, the semiconductor laser temperature control device, and the etalon temperature control device. The solid-state laser device according to claim 1, further comprising a rewritable memory in which is stored.

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