TWI644492B - Pulse controlling apparatus and method for controlling pulses - Google Patents

Abstract

The invention discloses a pulse control device and a pulse control method. Laser vein The impulse control device comprises: a pulsed laser generator that generates a plurality of laser pulses at fixed time intervals; a light modulator that selectively extracts a portion of the laser pulses by driving; the control portion changes over time The drive of the optical modulator is controlled by the electrical signal to the optical modulator; and the optical amplifier is used to amplify the extracted laser pulse.

Description

Pulse control device and pulse control method

The present invention relates to a laser pulse control device and a laser pulse control method, and relates to a method for selectively extracting a laser by adjusting a voltage or a high frequency power applied to a pulse modulator of a pulse control device A laser pulse control device and a laser pulse control method that generate a burst mode in a pulse.

In order to process precision parts such as the electronics industry, laser processing technology has gradually developed into ultra-precision, ultra-high-speed, and large-area processing. In particular, in order to process parts in the microelectronics industry including semiconductors, displays, solar cells, next-generation printed circuit boards (PCBs), and next-generation package industries, ultra-precision machining must not be performed. less.

In order to achieve such micro-scale ultra-precision machining, high-performance laser specifications are also required. In order to achieve micronization processing, it is possible to use a laser in an ultraviolet region or a femtosecond pulse laser having a very short pulse width and a picosecond pulse laser. At the same time, the spatial distribution of the laser beam is required to be a single mode high quality laser. Further, in order to achieve high speed and large area, a pulse laser having a high repetition rate and a high output is required.

As a method of operating the laser in a pulse form, a Q switch and a mode locking method are used. In the laser diode, a method of directly modulating the applied current is used in a pulsed manner.

Previously, in order to generate a laser pulse in a burst mode, a method of generating a burst mode by dividing a pulse using a polarizing element to generate a burst mode is realized. However, in the case of this mode, a pulse is required to be divided, and thus the laser pulse energy is limited. Moreover, in addition to the optical system that needs to divide the laser beam, it is difficult to arbitrarily adjust the number of laser pulses in the burst mode.

An embodiment of the invention provides that the output laser pulse can be operated in a burst mode by changing the electrical signal applied to the optical modulator over time, while adjusting the peak of the laser pulse. Pulse control device and pulse control method.

A pulse control apparatus according to an embodiment of the present invention includes: a pulsed laser generator that generates a plurality of laser pulses at fixed time intervals; and a light modulator that selectively extracts a portion of the laser pulses by driving; The control unit controls the driving of the optical modulator by changing the electrical signal applied to the optical modulator over time; and the optical amplifier amplifies the extracted laser pulse.

The light modulator can include an electro-optical modulator (EOM: electro optics) Modulator).

The electrical signal can include a voltage, and the control unit applies a voltage to the electro-optic modulator that changes over time.

The output of the laser pulse emerging from the optical amplifier can be fixed or varied over time.

The light modulator can include an acoustic optics modulator (AOM).

The electrical signal may include high frequency power, and the control unit applies high frequency power that changes with time to the acousto-optic modulator.

The output of the laser pulse emerging from the optical amplifier can be fixed or varied over time.

A pulse control method according to an embodiment of the present invention includes the steps of: generating a plurality of laser pulses at fixed time intervals; and selectively extracting a portion of the laser pulses by driving the optical modulator; and The step of amplifying the extracted laser pulse; and performing an extraction step by the control portion changing the voltage applied to the optical modulator or the high frequency power over time.

The light modulator may include an electro-optic modulator that is driven by applying a voltage, and the control unit applies a voltage that changes with time to the electro-optical modulator.

The voltage applied to the electro-optic modulator can decrease over time or increase over time.

The output of the amplified laser pulse can be fixed or varied over time.

The light modulator may include an acousto-optic modulator driven by applying high frequency power, and the control unit applies a high frequency power that changes with time to the acousto-optic modulator.

The high frequency power applied to the acousto-optic modulator can decrease over time or increase over time.

The output of the amplified laser pulse can be fixed or varied over time.

According to the above-described means for solving the problem of the present invention, various pulse train patterns can be realized depending on the type of the object to be processed by arbitrarily adjusting the electric signal applied to the optical modulator, whereby productivity can be improved.

Moreover, it is spatially simpler than the case of the burst mode in which the laser system generates a laser pulse.

100‧‧‧pulse control device

110‧‧‧pulse laser generator

120‧‧‧Light modulator

130‧‧‧Control Department

140‧‧‧Optical amplifier

LP‧‧‧Laser pulse

T1, t2‧‧‧ time interval

Ts‧‧‧saturated time

Fig. 1 is a schematic view showing a pulse control device according to an embodiment of the present invention.

Fig. 2a is a graph showing the relationship between the energy accumulated to the amplifying medium and the saturation time when the excitation energy is continuously applied to the optical amplifier.

2b and 2c are graphs showing the energy accumulated to the optical amplifier medium, the input laser pulse, and the output laser pulse when the excitation energy is continuously applied to the optical amplifier to periodically input the laser pulse to amplify the output.

3a to 3d are diagrams showing a pulse control device using an embodiment of the present invention A process map that selectively extracts laser pulses and amplifies them.

4a to 4d are process diagrams showing amplification by selectively extracting a laser pulse by a pulse control device according to an embodiment of the present invention.

5a to 5d are process diagrams showing amplification by selectively extracting a laser pulse by a pulse control device according to an embodiment of the present invention.

Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that they can be easily implemented by those having ordinary knowledge in the technical field to which the present invention pertains. However, the invention can be embodied in many different forms and is not limited to the embodiments described herein. In addition, in order to clearly explain the present invention, the portions that are not related to the description are omitted in the drawings, and the same portions are denoted by the same reference numerals throughout the description.

Throughout the specification, when a part is "connected" to another part, it includes not only the case of "direct connection" but also the case where it is "electrically connected" by other elements. In addition, when a part is "included" to a certain component, unless otherwise stated, it means that it may include other components, and does not mean that other components are excluded.

FIG. 1 is a schematic diagram showing a pulse control device 100 according to an embodiment of the present invention.

Referring to Fig. 1, a pulse control device 100 includes a pulsed laser generator 110, a light modulator 120, a control unit 130, and an optical amplifier 140.

The pulsed laser generator 110 can continuously land at a fixed time interval A plurality of laser pulses LP are generated. The pulsed laser generator 110 can be classified into various laser generators such as a gas laser generator, a liquid laser generator, and a solid laser generator depending on the type of the substance that generates the laser. The time interval between the plurality of laser pulses LP generated by the pulsed laser generator 110 may be 100 ns or less.

The light modulator 120 can function to selectively extract a portion of the laser pulses LP incident on the light modulator 120. The light modulator 120 may include an electro-optical modulator (EOM) and an acoustic optics modulator (AOM).

The control unit 130 can control the driving of the optical modulator 120 by applying an electrical signal to the optical modulator 120. When the optical modulator 120 is an electro-optical modulator, the control unit 130 can apply a voltage. When the optical modulator 120 is an acousto-optic modulator, the high-frequency power can be applied to control the driving of the optical modulator 120. .

In the case where the optical modulator 120 is an electro-optic modulator, the laser pulse LP can be selectively extracted using the Pockels effect. A polarization beam splitter (PBS) (not shown) may be positioned on the light path of the laser beam passing through the electro-optical modulator. When the control unit 130 applies a voltage to the electro-optical modulator, the refractive index of the electro-optical modulator medium changes, whereby the polarization direction of the light can be changed. Only a part of the laser pulses LP generated by the pulsed laser generator 110 can be selectively extracted by the above method, and the intensity of the extracted laser pulses LP can also be adjusted.

For example, the polarizing beam splitter can pass P-type light to reflect the S-type light, and the laser pulse LP through the electro-optic modulator can have a P-type polarization direction. because Therefore, the laser pulse LP cannot pass through the polarization beam splitter until the voltage is applied to the electro-optical modulator by the control unit 130. When the control unit 130 applies a voltage to the electro-optical modulator, the polarization direction of the laser pulse LP is rotated, and the polarizing beam splitter can be passed. Further, by adjusting the magnitude of the voltage, the rotation angle of the polarization direction of the laser pulse LP can be adjusted, whereby the intensity of the extracted laser pulse LP can also be adjusted.

In the case where the optical modulator 120 is an acousto-optic modulator, if the control unit 130 applies high frequency power to the acousto-optic modulator, a periodic change in the refractive index of the acousto-optic modulator medium is generated. Diffraction of light due to diffraction gratings. Thereby, a path difference is generated between the laser pulses LP incident on the acousto-optic modulator, and only a part of the laser pulses LP can be selectively extracted using the path difference. Moreover, the intensity of the extracted laser pulse LP can also be adjusted by adjusting the magnitude of the high frequency power applied to the acousto-optic modulator.

The optical amplifier 140 amplifies and outputs a plurality of laser pulses LP extracted by the optical modulator 120. If the laser pulse LP is input to the optical amplifier 140, the energy of the laser pulse LP can be amplified by expelling the energy of the reversed distribution. The relationship between the energy of the amplifying medium accumulated to the optical amplifier 140 and the amplified laser pulse LP will be described later.

Fig. 2a is a graph showing the relationship between the energy accumulated to the amplifying medium and the saturation time when the excitation energy is continuously applied to the optical amplifier 140.

Referring to Fig. 2a, the accumulated energy continues to increase during a fixed time, that is, until the saturation time ts. The saturation time ts varies according to the amplifying medium, and the rare earth In the case of a class ion, it is usually in the range of a few microseconds (ms: micro second) to several tens of microseconds.

2b and 2c are diagrams showing the energy accumulated in the medium of the optical amplifier 140, the input laser pulse LP, and the output laser pulse LP when the excitation energy is continuously applied to the optical amplifier to periodically input the laser pulse LP to amplify the output. Graph.

Referring to FIG. 2b, the time interval t1 between the laser pulses LP selectively extracted by the optical modulator 120 after the generation of the pulsed laser generator 110 may be greater than or equal to the saturation time ts. That is, the time until the input of the next laser pulse LP after one laser pulse LP is input to the optical amplifier 140 is greater than or equal to the saturation time ts. After the laser pulse LP input first is amplified by the optical amplifier 140, and before the input of the next laser pulse LP, the energy of the amplifying medium accumulated in the optical amplifier 140 can be saturated. Therefore, the laser pulse LP input thereafter can also be sufficiently amplified, whereby the laser pulse LP input first can be the same as the output of the laser pulse LP input later.

Referring to FIG. 2c, the time interval t2 between the laser pulses LP selectively extracted by the optical modulator 120 after the generation of the pulsed laser generator 110 may be less than the saturation time ts. That is, the time until the input of the next laser pulse LP after one laser pulse LP is input to the optical amplifier 140 is less than the saturation time ts. After the first input laser pulse LP is amplified by the optical amplifier 140, and before the input of the next laser pulse LP, the energy of the amplifying medium accumulated in the optical amplifier 140 may be before the saturation state is reached. Therefore, the degree of amplification of the input laser pulse LP afterwards may be smaller than the laser pulse LP input first, whereby the laser pulse LP input first may have a large The output value of the laser pulse LP input afterwards. Further, if the input energy is low, the amplification efficiency also decreases. Therefore, if the laser pulse LP having the time interval t2 smaller than the saturation time ts is continuously input to the optical amplifier 140, the output laser pulse LP exhibits a gradual decrease. Small output.

3a to 3d are process diagrams showing amplification by selectively extracting the laser pulse LP by the pulse control device 100 according to an embodiment of the present invention.

Referring to Figure 3a, the laser pulses LP produced by the pulsed laser generator 110 can have a fixed time interval from each other. The time interval between the laser pulses LP may be 100 ns or less, which may be less than the saturation time ts of the optical amplifier 140.

FIG. 3b is a graph showing voltage or high frequency power applied to the optical modulator 120 by the control unit 130. Referring to FIG. 3b, the control unit 130 may apply a fixed voltage or high frequency power to the optical modulator 120 over a fixed time interval.

FIG. 3c is a diagram showing the laser pulse LP selectively extracted by the optical modulator 120. The control unit 130 has been applied with a fixed voltage or high frequency power over time, so the laser pulses LP extracted by the optical modulator 120 will have the same output. The laser pulse LP is not extracted in a section where no voltage or high frequency power is applied to the optical modulator 120.

FIG. 3d is a diagram showing the laser pulse LP amplified by the optical amplifier 140 after the optical modulator 120 is extracted. Referring to FIG. 3d, the time interval between the laser pulses LP belonging to the same group may be smaller than the saturation time ts of the optical amplifier 140. Therefore, after the laser pulse LP input first is amplified by the optical amplifier 140, and Before the input of the next laser pulse LP, the energy of the amplifying medium accumulated in the optical amplifier 140 may be before the saturation state is reached. Therefore, the degree of amplification of the input laser pulse LP afterwards may be smaller than the laser pulse LP input first, whereby the laser pulse LP input first may have an output value larger than the laser pulse LP input later. Further, if the input energy is low, the amplification efficiency also decreases. Therefore, if the laser pulse LP having a time interval smaller than the saturation time ts is continuously input to the optical amplifier 140, the output laser pulse LP exhibits a gradual decrease. Output. In the section where no voltage or high-frequency power is applied to the optical modulator 120, there is no laser pulse LP input to the optical amplifier 140, and thus the energy of the amplifying medium accumulated in the optical amplifier 140 is again saturated. At this time, if a laser pulse LP having a time interval smaller than the saturation time ts is input to the optical amplifier 140, the laser pulse LP exhibiting a gradually decreasing output is output again.

The laser pulse LP is extracted in a section where the voltage or high frequency power is applied to the optical modulator 120 by the control unit 130, and the time interval between the laser pulses LP can be 100 ns or less. Conversely, the laser pulse LP is not output in a section where no voltage or high frequency power is applied to the optical modulator 120, and the time during which no voltage or high frequency power is applied may be several hundred ns or more. Therefore, the above-described situation can be repeated depending on whether or not the control unit 130 applies a voltage or a high-frequency power to the optical modulator 120 and repeats a group of laser pulses LP having a time interval of 100 ns or less in a period of several hundred ns or more. It is called burst mode. 4a to 4d are process diagrams showing amplification by selectively extracting the laser pulse LP by the pulse control device 100 according to an embodiment of the present invention.

Referring to Figure 4a, the laser pulse LP generated by the pulsed laser generator 110 They can have a fixed time interval from each other. The time interval between the laser pulses LP may be 100 ns or less, which may be less than the saturation time ts of the optical amplifier 140.

4b is a graph showing voltage or high frequency power applied to the optical modulator 120 by the control unit 130. Referring to FIG. 4b, the control portion 130 may apply a voltage or high frequency power that is increased with time to the optical modulator 120 at a fixed time interval.

FIG. 4c is a diagram showing the laser pulse LP selectively extracted by the optical modulator 120. The voltage or high frequency power that has increased with time has been applied to the control portion 130, and thus the laser pulse LP extracted by the light modulator 120 may have an output that increases with time. The laser pulse LP is not extracted in a section where no voltage or high frequency power is applied to the optical modulator 120.

4d is a diagram showing a laser pulse LP amplified by the optical amplifier 140 after being extracted by the optical modulator 120. Referring to FIG. 4d, the time interval between the laser pulses LP belonging to the same group may be less than the saturation time ts of the optical amplifier 140. Therefore, after the first input laser pulse LP is amplified by the optical amplifier 140, and before the input of the next laser pulse LP, the energy of the amplifying medium accumulated in the optical amplifier 140 can be before the saturation state is reached. Therefore, the degree of amplification of the input laser pulse LP afterwards is smaller than that of the first input laser pulse LP. However, referring to FIG. 4c, the output of the first input laser pulse LP exhibits a value smaller than the output of the laser pulse LP input later, and thus the output of the laser pulse LP amplified by the optical amplifier 140 can be the same.

The laser pulse LP is extracted in a section where the voltage or high frequency power is applied to the optical modulator 120 by the control unit 130, and the time interval between the laser pulses LP may be Below 100ns. Conversely, the laser pulse LP is not output in a section where no voltage or high frequency power is applied to the optical modulator 120, and the time during which no voltage or high frequency power is applied may be several hundred ns or more. Therefore, depending on whether the control unit 130 applies a voltage or a high-frequency power to the optical modulator 120, the group of laser pulses LP having a time interval of 100 ns or less is repeated for a period of several hundred ns or longer. In burst mode. According to the above embodiment, various pulse train patterns can be realized depending on the kind of the object to be processed by arbitrarily adjusting the electric signal applied to the optical modulator 120, whereby productivity can be improved. Moreover, it is spatially simpler than the case of generating a burst mode of the laser pulse LP by the optical system.

5a to 5d are process diagrams showing amplification by selectively extracting the laser pulse PL by the pulse control device 100 according to an embodiment of the present invention.

Referring to Figure 5a, the laser pulses LP produced by the pulsed laser generator 110 can have a fixed time interval from each other. The time interval between the laser pulses LP may be 100 ns or less, which may be less than the saturation time ts of the optical amplifier 140.

FIG. 5b is a graph showing voltage or high frequency power applied to the optical modulator 120 by the control unit 130. Referring to FIG. 4b, the control unit 130 may apply a voltage or high frequency power that is increased with time after being applied to the optical modulator 120 at a fixed time interval.

FIG. 5c is a diagram showing the laser pulse LP selectively extracted by the optical modulator 120. The voltage or high frequency power that is increased after decreasing with time has been applied to the control portion 130, and thus the laser pulse LP extracted by the light modulator 120 may have an output that increases as time decreases. No voltage or high frequency is applied to the optical modulator 120 The power interval does not extract the laser pulse LP.

FIG. 5d is a diagram showing the laser pulse LP amplified by the optical amplifier 140 after the optical modulator 120 is extracted. Referring to FIG. 5d, the time interval between the laser pulses LP belonging to the same group may be smaller than the saturation time ts of the optical amplifier 140. Therefore, after the first input laser pulse LP is amplified by the optical amplifier 140, and before the input of the next laser pulse LP, the energy of the amplifying medium accumulated in the optical amplifier 140 can be before the saturation state is reached. Therefore, the degree of amplification of the input laser pulse LP afterwards is smaller than that of the first input laser pulse LP. The section in which the output of the laser pulse LP passing through the optical modulator 120 is reduced and the form of the increased section can be adjusted by adjusting the voltage or the high frequency power input to the optical modulator 120. Thereby, the form of the output of the laser pulse LP outputted by the optical amplifier 140 can be reduced and then increased in a bilaterally symmetrical form.

The laser pulse LP is extracted in a section where the voltage or high frequency power is applied to the optical modulator 120 by the control unit 130, and the time interval between the laser pulses LP can be 100 ns or less. Conversely, the laser pulse LP is not output in a section where no voltage or high frequency power is applied to the optical modulator 120, and the time during which no voltage or high frequency power is applied may be several hundred ns or more. Therefore, the above-described situation can be repeated depending on whether or not the control unit 130 applies a voltage or a high-frequency power to the optical modulator 120 and repeats a group of laser pulses LP having a time interval of 100 ns or less in a period of several hundred ns or more. It is called burst mode.

According to the above embodiment, various pulse trains can be realized according to the kind of the object to be processed by arbitrarily adjusting the electric signal applied to the optical modulator 120. Mode, which increases productivity. Moreover, it is spatially simpler than the case of generating a burst mode of the laser pulse LP by the optical system.

The above description of the present invention is exemplified, and those skilled in the art to which the present invention pertains can be understood, and can be easily modified into other specific forms without changing the technical idea or essential features of the present invention. Therefore, the above described embodiments are to be considered as illustrative only and not limiting. For example, it is explained that each constituent element in a single form can be dispersedly implemented, and the constituent elements in a dispersed form can also be implemented in a combined form.

The scope of the present invention is defined by the scope of the present invention as defined by the appended claims, and the scope of the invention Inside.

Claims (14)

A pulse control device comprising: a pulsed laser generator that generates a plurality of laser pulses at fixed time intervals; and a light modulator that selectively extracts a portion of the plurality of laser pulses by driving Generating a plurality of pulse trains, wherein a first time interval between the plurality of first laser pulses included in each of the pulse trains is equal to a second time interval between the plurality of laser pulses; and the control portion is applied over time Controlling the driving of the optical modulator to the electrical signal of the optical modulator; and an optical amplifier amplifying the extracted plurality of laser pulses, wherein the first time interval is less than the accumulation of the optical amplifier Amplifies the saturation time of the energy of the medium. The pulse control device of claim 1, wherein the optical modulator comprises an electro-optic modulator. The pulse control device according to claim 2, wherein the electrical signal includes a voltage, and the control unit applies the voltage to the electro-optical modulator that changes with time. The pulse control device of claim 3, wherein the output of the plurality of laser pulses emitted from the optical amplifier is fixed or changes with time. The pulse control device of claim 1, wherein the optical modulator comprises an acousto-optic modulator. A pulse control device as claimed in claim 5, wherein The electric signal includes high frequency power, and the control unit applies the high frequency power that changes with time to the acousto-optic modulator. The pulse control device of claim 6, wherein the output of the plurality of laser pulses emitted from the optical amplifier is fixed or changes with time. A pulse control method comprising the steps of: generating a plurality of laser pulses at fixed time intervals; selectively extracting a portion of the plurality of laser pulses by driving a light modulator to generate a plurality of a step of a pulse train, wherein a first time interval between the plurality of first laser pulses included in each of the pulse trains is equal to a second time interval between the plurality of laser pulses; and extracted by an optical amplifier amplification The plurality of laser pulses, wherein the first time interval is less than a saturation time of the optical amplifier accumulating the amplification medium energy; and the voltage applied to the optical modulator by the control portion is changed over time or high The extraction step is performed with the frequency power. The pulse control method of claim 8, wherein the optical modulator comprises an electro-optic modulator driven by applying the voltage, and the control unit applies the electro-optical modulator over time And the voltage that changes. The pulse control method of claim 9, wherein the voltage applied to the electro-optic modulator decreases with time or increases with time. The pulse control method of claim 10, wherein the amplified output of the plurality of laser pulses is fixed or changes with time. The pulse control method of claim 8, wherein the optical modulator comprises an acousto-optic modulator driven by applying the high frequency power, and the control unit modulates the sound and light The device applies the high frequency power that changes over time. The pulse control method of claim 12, wherein the high frequency power applied to the acousto-optic modulator decreases with time or increases with time. The pulse control method of claim 13, wherein the amplified output of the plurality of laser pulses is fixed or changes with time.