TWI887152B - Monitoring system of laser performance and operation method thereof - Google Patents

Abstract

A monitoring system of laser performance and an operation method thereof are provided. The monitoring system comprises a processor, a power adjustment unit, and a power monitoring unit. The power monitoring unit is used to measure the power of the laser and control the rotation angle of the half waveplate to adjust the electromagnetic wave polarization characteristics of the laser to compensate for the average power of the laser.

Description

Laser performance monitoring system and operation method thereof

The present invention relates to a monitoring system and an operating method thereof, and in particular to a laser performance monitoring system and an operating method thereof.

Femtosecond lasers use ultra-high peak power to dissociate processing materials, reduce processing heat accumulation, and make processing precision better than traditional laser processing. However, the quality of this new processing method is affected by laser power and pulse width.

Furthermore, the laser power is usually determined by the preset setting of the equipment. However, the optical components inside the equipment may react with the laser and the hydrocarbons in the environment and the dust caused by the processing application, or the power of the laser source itself may decrease, so that the actual average power may drop from the preset average power output value over time. On the other hand, the laser pulse width is affected by the positive dispersion instability in the pulse laser source and the instability of the beam propagation medium (air disturbance), which causes the pulse width to change and lead to peak power instability. Both the average power and the peak power instability will lead to a decrease in the stability of the processing results.

Based on this, traditional average power and pulse width require regular laser calibration, which is time-consuming and cannot correct average power parameters and pulse width parameters in time, which will lead to a decrease in production yield.

Therefore, in order to overcome the shortcomings and deficiencies in the prior art, it is necessary to provide an improved laser performance monitoring system and its operation method to solve the problems existing in the above-mentioned conventional technology.

The main purpose of the present invention is to provide a laser performance monitoring system and its operation method, which uses a power monitoring unit to measure the power of the laser and control the rotation angle of the half-wave plate, so as to adjust the electromagnetic wave polarization characteristics of the laser to compensate for the average power of the laser.

To achieve the above-mentioned purpose, the present invention provides a laser performance monitoring system, which includes a processor, a power adjustment unit and a power monitoring unit. The power adjustment unit includes a half-wave plate and a polarization beam splitter. The half-wave plate is configured to be rotated by the processor, and the half-wave plate and the polarization beam splitter are sequentially arranged on a first optical path of laser transmission; the power monitoring unit includes a first reflector, a power meter and a working platform. The first reflector and the power meter are arranged on a fifth optical path. The power meter is coupled to the working platform. The processor is connected to the processor, and the first reflector is located between the polarization splitter and the power meter, wherein the laser is split into a transmitted light and a reflected light by the first reflector, and the power meter is configured to measure a transmitted light power of the transmitted light, and the reflected light is transmitted to the working platform; the processor is configured to calculate a reflected light power of the reflected light according to the transmitted light power and the reflectivity and transmittance of the first reflector, and when the reflected light power exceeds a range, the half-wave plate is controlled to rotate to adjust a ratio of the horizontal polarization and the vertical polarization of the transmitted light.

In one embodiment of the present invention, the laser performance monitoring system further includes a width measurement device and a coupling processor. The width measurement device is arranged on a second optical path of the reflected light transmitted by the polarization beam splitter. The width measurement device is configured to measure a pulse time width of the reflected light.

In one embodiment of the present invention, the laser performance monitoring system further includes a width adjustment unit coupled to the processor. The width adjustment unit includes two gratings, a prism and a second reflector. The two gratings are disposed between the prism and the second reflector. The laser enters through the two gratings, is reflected by the prism, and then is output by the two gratings. It is reflected by the second reflector and transmitted along the first optical path. The pulse time width is adjusted by moving a vertical distance between the two gratings.

In one embodiment of the present invention, the laser performance monitoring system further includes an oscillator for generating laser light and transmitting it to the two gratings along a third incident light path.

In one embodiment of the present invention, the second reflector is disposed between the oscillator and the two gratings, the laser light outputted by the two gratings is transmitted along a fourth optical path of the outgoing light, and the incident third optical path and the outgoing fourth optical path are misaligned.

；其中P _R 為反射光功率，P _T 為穿透光功率，R _mirror 為反射率，T _mirror 為穿透率。 In one embodiment of the present invention, the first reflector is a dielectric reflector, and the equation for the reflected light power is:

; Where PR is the reflected light power, PT is the transmitted light power _, Rmirror is _the reflectivity, _and Tmirror is _the transmittance.

In one embodiment of the present invention, the power adjustment unit further includes a rotating base, the rotating base is coupled to the processor, the half-wave plate is arranged on the rotating base, and the rotating base is configured to be controlled by the processor to rotate an angle to drive the half-wave plate to rotate.

To achieve the above-mentioned purpose, the present invention provides an operating method of a laser performance monitoring system, the operating method comprising: step 201: sequentially setting a half-wave plate and a polarization beam splitter on a first optical path of laser transmission, sequentially setting a first reflector and a power meter on a fifth optical path of laser transmission, wherein the laser is split into a transmitted light and a reflected light by the first reflector, and the reflected light is transmitted to a working platform; step 202: measuring a transmitted light power of the transmitted light by the power meter, and transmitting the transmitted light power to a processor; and step 203: using the processor to calculate a reflected light power of the reflected light according to the transmitted light power and the reflectivity of the first reflector, and when the reflected light power exceeds a range, controlling the half-wave plate to rotate to adjust a ratio of the horizontal polarization and the vertical polarization of the transmitted light.

In one embodiment of the present invention, after step 201, the operation method further includes step 204: measuring a pulse time width of the reflected light through a width measuring device disposed on a second optical path of the reflected light transmitted by the polarization splitter, and transmitting the pulse time width to the processor.

In one embodiment of the present invention, after step 204, the operation method further includes step 205: by disposing two gratings between a prism and a second reflector, a vertical distance between the two gratings is moved to adjust the pulse time width.

As mentioned above, the laser performance monitoring system of the present invention uses the laser average power feedback mechanism, that is, the power monitoring unit is used to measure the power of the laser and feedback it to the processor, and then the processor controls the rotation angle of the half-wave plate to adjust the electromagnetic wave polarization characteristics of the laser, which can compensate the average power of the laser in time, increase the convenience for users and increase the production yield. In other words, the reading monitored by the power monitoring unit can be fed back to the power adjustment unit in real time for adjustment, realizing the average power correction function in the process.

2: Processor

3: Power adjustment unit

31: Half-wave plate

32: Polarization spectrometer

33: Rotating base

4: Power monitoring unit

41: First reflector

42: Power meter

43:Working platform

5: Width measuring device

6: Width adjustment unit

61: Grating

62: Prism

63: Second reflector

7: Oscillator

L1: First optical path

L2: Second optical path

L3: The third optical path

L4: The fourth optical path

L5: The fifth optical path

L6: Sixth optical path

S201: Step

S202: Step

S203: Step

S204: Step

S205: Step

FIG1 is a schematic diagram of an embodiment of the laser performance monitoring system according to the present invention.

Figure 2 is a partial schematic diagram of the power adjustment unit of Figure 1.

Figure 3 is a partial schematic diagram of the power monitoring unit of Figure 1.

Figure 4 is a partial schematic diagram of the grating in Figure 1.

FIG5 is a flow chart of an embodiment of the operation method of the laser performance monitoring system according to the present invention.

In order to make the above and other purposes, features and advantages of the present invention more clearly understood, the following will specifically cite the embodiments of the present invention and provide a detailed description in conjunction with the attached drawings. Furthermore, the directional terms mentioned in the present invention, such as up, down, top, bottom, front, back, left, right, inside, outside, side, periphery, center, horizontal, transverse, vertical, longitudinal, axial, radial, topmost or bottommost, etc., are only for reference to the directions of the attached drawings. Therefore, the directional terms used are used to illustrate and understand the present invention, rather than to limit the present invention. It should be noted that the drawings are all simplified schematic diagrams, and therefore, only the components and combination relationships related to the present invention are shown to provide a clearer description of the basic structure or implementation method of the present invention, and the actual components and layout may be more complicated. In addition, for the convenience of explanation, the components shown in the various figures of the present invention are not drawn in proportion to the actual number, shape, and size, and the detailed proportions can be adjusted according to the design requirements.

Referring to FIG. 1 , a schematic diagram of an embodiment of the laser performance monitoring system of the present invention is shown, wherein the laser performance monitoring system includes a processor 2, a power adjustment unit 3 and a power monitoring unit 4, which can provide a stable output average power and pulse width of a nanosecond, picosecond or femtosecond pulse laser. The detailed structure, assembly relationship and operation principle of each component will be described in detail below.

As shown in FIG. 1 and FIG. 2 , FIG. 2 is a partial schematic diagram of the power adjustment unit of FIG. 1 . Specifically, the power adjustment unit 3 includes a half wave plate 31, a polarizing beam splitter 32, and a rotating base 33. The half wave plate 31 is configured to be operated and rotated by the processor 2, and the half wave plate 31 and the polarizing beam splitter 32 are sequentially arranged on a first optical path L1 of laser transmission. In this embodiment, the rotating base 33 is coupled to the processor 2, the half wave plate 31 is arranged on the rotating base 33, and the rotating base 33 is configured to be controlled by the processor 2 to rotate an angle to drive the half wave plate 31 to rotate. The ratio of the polarization electric field intensity of the horizontal and vertical components can be accurately adjusted through the half wave plate 31, and the characteristic of the polarizing beam splitter 32 that only reflects the fixed polarization direction can be used to realize laser power control.

As shown in FIG. 1 and FIG. 3 , FIG. 3 is a partial schematic diagram of the power monitoring unit of FIG. 1 . Specifically, the power monitoring unit 4 includes a first reflector 41, a power meter 42 (Power Meter) and a work station 43 (Work Station). The first reflector 41 and the power meter 42 are arranged on the first optical path L1. The power meter 42 is coupled to the processor 2 . The first reflector 41 is located between the polarization beam splitter 32 and the power meter 42 . The laser is split into a transmitted light and a reflected light by the first reflector 41 .

In this embodiment, the first reflector 41 is a dielectric reflector, the transmitted light is transmitted along a fifth optical path L5, the reflected light is transmitted along a sixth optical path L6, and the reflected light is transmitted to the working platform 43. The power meter 42 is configured to measure a transmitted light power of the transmitted light, that is, the power meter 42 is used to measure the leakage light of the dielectric reflector to monitor the average power of the laser. Specifically, the power meter 42 is a photodiode, a thermoelectric power meter or a pyroelectric nano-power meter, which can record the average power data in an electronic recording device.

Through the above structure, the processor 2 is configured to calculate a reflected light power of the reflected light according to the transmitted light power and the reflectivity and transmittance of the first reflector 41, and when the reflected light power exceeds a range, the half-wave plate 31 is controlled to rotate to adjust a ratio of the horizontal polarization and the vertical polarization of the transmitted light.

As shown in FIG1 , the laser performance monitoring system further includes a width meter 5, a width adjustment unit 6 and an oscillator 7. The width meter 5 is coupled to the processor 2 and is disposed on a second optical path L2 of the reflected light transmitted by the polarization beam splitter 32. The width meter 5 is configured to measure a pulse time width of the reflected light, specifically a laser pulse autocorrelator or a photodiode, and the pulse width can be recorded in an electronic recording device.

As shown in FIG. 1 and FIG. 4 , FIG. 4 is a partial schematic diagram of the grating of FIG. 1 , the width adjustment unit 6 is coupled to the processor 2 , and the width adjustment unit 6 includes two gratings 61 , a prism 62 and a second reflector 63 , wherein the grating 61 is an electrically controllable transmissive grating pair, a reflective grating pair or a prism pair, the prism 62 is a roof prism, and the second reflector 63 is a reflector, and the two gratings 61 are arranged between the prism 62 and the second reflector 63 .

It should be noted that if the pulse width is wider than picoseconds, the width measuring device 5 uses a photodiode, and if the pulse width is narrower than picoseconds, the width measuring device 5 uses a self-correlation instrument for measurement. If the pulse width varies or there are other applications with specific pulse widths, the distance of the dispersion element (reflective grating pair, transmissive grating pair, prism pair) can be set electrically.

The laser enters through the two gratings 61, is reflected by the prism 62, and then is output from the two gratings 61, and is reflected by the second reflector 63 and transmitted along the first optical path L1. The pulse time width of the laser is adjusted by moving a vertical distance between the two gratings 61. The oscillator 7 is used to generate a laser and transmit it to the two gratings 61 along an incident third optical path L3. Specifically, the laser emitted by the oscillator 7 is an ultrashort pulse laser (Ultrashort Laser), which has a high peak power and a narrow pulse width laser pulse, and the oscillator 7 uses titanium sapphire as a gain medium.

Specifically, the laser beam of the oscillator 7 first passes under the second reflector 63, and then enters the two gratings 61 and the prism 62 in sequence. At this time, the optical path of the laser beam output by the prism 62 will return along the original optical path direction, but the optical path height will become higher. After passing through the two gratings 61, it will be reflected by the second reflector 63 to the half-wave plate 31. In other words, the laser beam from the oscillator 7 to the two gratings 61 and the laser beam from the two gratings 61 to the second reflector 63 have the same optical path but opposite directions. By using the different optical path heights, the incident light output by the oscillator 7 can avoid the second reflector 63, and the outgoing light of the two gratings 61 can be reflected by the second reflector 63.

In addition, there is no restriction that the incident light is lower and the outgoing light is higher. The incident light can also be higher and the outgoing light can be lower, or the height of the optical paths of the incident and outgoing lights can be the same. The optical paths of the incident and outgoing lights can be staggered by the prism 62, so that the incident light can pass through the second reflector 63, and the outgoing light can be reflected by the second reflector 63.

As shown in FIG. 1 , in this embodiment, the second reflector 63 is disposed between the oscillator 7 and the two gratings 61 , and the lasers outputted by the two gratings 61 are transmitted along a fourth optical path L4 , and the incident third optical path L3 and the outgoing fourth optical path L4 are misaligned.

；其中P _R 為反射光功率，即工作平台43的光束使用功率，P _T 為穿透光功率，即寬度量測器5的量測功率，R _mirror 為反射率，T _mirror 為穿透率。 In addition, the first reflector 41 is a dielectric reflector, and the equation for the reflected light power is:

; Wherein PR is the reflected light power, that is, the light beam power used by the working platform 43 _, PT is the penetrating light power, that is, the measurement power _of the width measuring device 5, Rmirror is the reflectivity, _and Tmirror is the _{transmittance} .

Specifically, the half-wave plate 31 is an electrically controlled 1/2 λ wave plate, which can change the horizontal and vertical polarization ratio of the light beam, thereby adjusting the power passing through the polarization splitter 32, wherein the first reflector 41 receives a control signal through the processor 2 to operate the rotating base 33 to adjust the rotation angle of the first reflector 41 and return the angle information to the processor 2.

In other embodiments, the width measuring device 5 can also upload the measured value to the cloud database synchronously to increase the process data integration, so that the current processing power can be judged whether it is stable through the real-time reading of the measuring device during the process.

It should be noted that the laser beam transmitted in the first optical path L1 is defined as the superposition of two independent linear polarizations (polarization) (orthogonality). After the incident light passes through an interface and is reflected, the incident and reflected vectors will form a plane. Taking this plane as the reference plane, if the electric field oscillation direction of the beam is parallel to this reference plane, it is horizontal linear polarization; if the electric field oscillation direction of the beam is perpendicular to this reference plane, it is vertical linear polarization. In practice, if the laser beam is horizontally linearly polarized, the incident light will penetrate after passing through the polarization splitter 32. If the laser beam is vertically polarized, it will be reflected after passing through the polarization beam splitter 32. The angle between the incident and the reflected is related to the polarization beam splitter 32. If the polarization beam splitter 32 is a regular cubic structure (i.e., composed of two regular triangular prisms), the angle between the incident and the reflected is 90 degrees. By rotating the angle of the electrically controlled half-wave plate 31, the ratio of the horizontal and vertical polarization of the laser beam can be changed, thereby adjusting the power passing through the polarization beam splitter 32, and thus changing the actual power used. The basic optical properties of the reflected light of the polarization beam splitter 32 are similar to those of the transmitted light of the polarization beam splitter 32, and the main difference is only in the power and polarization properties. Therefore, by transmitting the reflected light through the polarization beam splitter 32 to the width measuring device 5 to measure the time width of the laser pulse, the pulse width of the transmitted light of the polarization beam splitter 32 can be equivalently measured.

According to the above structure, the power meter 42 is used to measure the transmitted light power of the first reflector 41, and the reflectivity of the first reflector 41 is used to push back the power, and the power used by the working platform 43 is monitored. When it is measured that the power used by the working platform 43 is reduced and does not meet the setting conditions, the half-wave plate 31 is electrically controlled to rotate, and the ratio of horizontal and vertical polarization is adjusted, so that the ratio of laser passing through the polarization splitter 32 becomes higher, thereby increasing the power used by the working platform 43 to meet the setting conditions. Conversely, when it is measured that the power used by the working platform 43 increases and does not meet the setting conditions, the half-wave plate 31 is electrically controlled to rotate, and the ratio of horizontal and vertical polarization is adjusted, so that the ratio of laser passing through the polarization splitter 32 becomes lower, thereby reducing the power used by the working platform 43 to meet the setting conditions, thereby solving the problem of unstable actual average power during long-term operation of the processing laser in the process.

The reflected light is transmitted to the width measuring device 5 through the polarization beam splitter 32 to measure the time width of the laser pulse, which can be equivalent to measuring the laser pulse width of the working platform 43. When the laser pulse width of the working platform 43 is measured to be too wide and beyond the setting range, the vertical distance between the two gratings 61 is controlled electrically to lengthen the vertical distance, thereby shortening the laser pulse width of the working platform 43 to meet the setting conditions. On the contrary, when the laser pulse width of the working platform 43 is measured to be too short and beyond the setting range, the vertical distance between the two gratings 61 is controlled to shorten the vertical distance so that the laser pulse width of the working platform 43 is elongated to meet the setting conditions, thereby solving the problem of unstable actual pulse width during long-term operation of the processing laser in the process, resulting in unstable peak power. In addition, the pulse width compensation mechanism can also use the width adjustment unit 6 in combination with the width measurement device 5 to synchronously monitor the current pulse laser state.

Referring to FIG. 5 and in conjunction with FIG. 1 , FIG. 5 is a flow chart of an embodiment of the operation method of the laser performance monitoring system of the present invention, wherein the operation method is performed by the above-mentioned laser performance monitoring system, and the operation method includes step S201, step S202, step S203, step S204 and step S205. The present invention will describe in detail the operation steps and operation principles of each component below.

As shown in FIG. 1 , FIG. 2 and FIG. 3 , in step 201: a half-wave plate 31 and a polarization beam splitter 32 are sequentially arranged on a first optical path L1 of the laser transmission, and a first reflector 41 and a power meter 42 are sequentially arranged on a fifth optical path L5 of the laser transmission. The laser is split into a transmitted light and a reflected light by the first reflector 41, wherein the transmitted light is transmitted along the fifth optical path L5, and the reflected light is transmitted along a sixth optical path L6. to a working platform 43; step 202: measure a transmitted light power of the transmitted light through a power meter 42, and transmit the transmitted light power to a processor 2; and step 203: use the processor 2 to calculate a reflected light power of the reflected light according to the transmitted light power and the reflectivity of the first reflector 41, and when the reflected light power exceeds a range, control the half-wave plate 31 to rotate to adjust a ratio of the horizontal polarization and the vertical polarization of the transmitted light.

As shown in FIG. 1 and FIG. 4 , step 204 measures a pulse time width of the reflected light through a width measuring device 5 disposed on a second optical path L2 of the reflected light transmitted by the polarization splitter 32, and transmits the pulse time width to the processor 2; step 205 adjusts the pulse time width by moving a vertical distance between two gratings 61 disposed between a prism 62 and a second reflector 63. In this embodiment, step 204 is after step 203, but in other embodiments, step 204 can also be arranged after step S201, and is not limited to this embodiment.

As described above, the laser performance monitoring system of the present invention uses the laser average power feedback mechanism, that is, the power monitoring unit 4 is used to measure the power of the laser and feedback it to the processor 2, and then the processor 2 controls the rotation angle of the half-wave plate 31 to adjust the electromagnetic wave polarization characteristics of the laser, which can compensate the average power of the laser in time, increase the convenience for users and increase the production yield. In other words, the reading monitored by the power monitoring unit 4 can be fed back to the power adjustment unit 3 in real time for adjustment, realizing the average power correction function in the process.

Although the present invention has been disclosed by way of embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of the patent application attached hereto.

2: Processor

3: Power adjustment unit

31: Half-wave plate

32: Polarization spectrometer

4: Power monitoring unit

41: First reflector

42: Power meter

43:Working platform

5: Width measuring device

6: Width adjustment unit

61: Grating

62: Prism

63: Second reflector

7: Oscillator

L1, L2, L3, L4, L5, L6: optical path

Claims (10)

A laser performance monitoring system, comprising: a processor; a power adjustment unit, comprising a half-wave plate and a polarization beam splitter, the half-wave plate is configured to be operated and rotated by the processor, and the half-wave plate and the polarization beam splitter are sequentially arranged on a first optical path of laser transmission; and a power monitoring unit, comprising a first reflector, a power meter and a working platform, the first reflector and the power meter are arranged on a fifth optical path, the power meter is coupled to the processor, and the first reflector is located between the polarization beam splitter and the power meter, wherein the laser is split into a transmitted light and a reflected light by the first reflector, the power meter is configured to measure a transmitted light power of the transmitted light, and the reflected light is transmitted to the working platform; The processor is configured to calculate a reflected light power of the reflected light according to the transmitted light power and the reflectivity and transmittance of the first reflector, and when the reflected light power exceeds a range, control the half-wave plate to rotate to adjust a ratio of the horizontal polarization and the vertical polarization of the transmitted light. A laser performance monitoring system as described in claim 1, wherein the laser performance monitoring system further includes a width meter coupled to the processor, the width meter is arranged on a second optical path of the reflected light of the polarization splitter, and the width meter is configured to measure a pulse time width of the reflected light. A laser performance monitoring system as described in claim 2, wherein the laser performance monitoring system further includes a width adjustment unit coupled to the processor, the width adjustment unit includes two gratings, a prism and a second reflector, the two gratings are arranged between the prism and the second reflector, the laser enters through the two gratings, is reflected by the prism, is then output by the two gratings, and is reflected by the second reflector and transmitted along the first optical path, and the pulse time width is adjusted by moving a vertical distance between the two gratings. A laser performance monitoring system as described in claim 3, wherein the laser performance monitoring system further includes an oscillator for generating the laser and transmitting it to the two gratings along an incident third optical path. A laser performance monitoring system as described in claim 4, wherein the second reflector is disposed between the oscillator and the two gratings, the laser output by the two gratings is transmitted along a fourth optical path, and the incident third optical path and the outgoing fourth optical path are misaligned. The laser performance monitoring system as described in claim 1, wherein the first reflector is a dielectric reflector, and the equation for the reflected light power is: ;in is the reflected light power, is the penetrating light power, is the reflectivity, is the penetration rate. A laser performance monitoring system as described in claim 1, wherein the power adjustment unit further includes a rotating base, the rotating base is coupled to the processor, the half-wave plate is disposed on the rotating base, and the rotating base is configured to be controlled by the processor to rotate an angle to drive the half-wave plate to rotate. An operating method of a laser performance monitoring system, the operating method comprising: Step 201: sequentially setting a half-wave plate and a polarization beam splitter on a first optical path of laser transmission, and sequentially setting a first reflector and a power meter on a fifth optical path of the laser transmission, wherein the laser is split into a transmitted light and a reflected light by the first reflector, and the reflected light is transmitted to a working platform; Step 202: measuring a transmitted light power of the transmitted light by the power meter, and transmitting the transmitted light power to a processor; and Step 203: using the processor to calculate a reflected light power of the reflected light according to the transmitted light power and the reflectivity of the first reflector, and when the reflected light power exceeds a range, controlling the half-wave plate to rotate to adjust a ratio of the horizontal polarization and the vertical polarization of the transmitted light. The operating method of the laser performance monitoring system as described in claim 8, wherein after the step 203, the operating method further includes a step 204: measuring a pulse time width of the reflected light through a width measuring device arranged on a second optical path for transmitting the reflected light of the polarization spectrometer, and transmitting the pulse time width to the processor. The operating method of the laser performance monitoring system as described in claim 9, wherein after the step 204, the operating method further includes a step 205: by setting two gratings between a prism and a second reflector, moving a vertical distance between the two gratings to adjust the pulse time width.

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