A laser ablation method and apparatus

Abstract

The application discloses a laser ablation method and device, the laser ablation device includes: femtosecond laser module, galvanometer system and field lens, the galvanometer system includes X-axis galvanometer and Y-axis galvanometer;The X-axis galvanometer adjusts the position of laser focusing on the sample surface along the X-axis direction, and the Y-axis galvanometer adjusts the position of laser focusing on the sample surface along the Y-axis direction;The X-axis direction and Y-axis direction are perpendicular to each other;The X-axis galvanometer and Y-axis galvanometer can be high-frequency axis reciprocating rotation at a predetermined frequency to switch the laser focal point between multiple positions;The field lens is used to focus laser pulses on the sample.The laser ablation device of the application can ablate different areas of the sample in nanosecond period, for homogeneous sample, the number of particles produced is more, and the sensitivity of element analysis is higher;For different samples, the sample information obtained when element analysis is richer after the particles produced are mixed.

Description

Technical Field

[0001] This invention belongs to the field of laser ablation technology, and particularly relates to a laser ablation method and apparatus. Background Technology

[0002] As laser ablation systems mature, their applications are becoming increasingly widespread, and they are becoming more and more common as a solid sample introduction method. Current techniques typically use an objective lens to focus the laser onto a specific area of ​​the sample, then ablate the sample into microparticles, which are then transported into the elemental analysis system via a carrier gas. However, ordinary laser ablation systems cannot solve the problem of needing to ablate different areas extremely quickly.

[0003] Currently, for the technology of quantitatively determining the elemental content of samples using laser ablation, it is difficult to find standard samples that match the sample matrix, and the concentration of the standard sample differs greatly from that of the sample. Therefore, the technological progress in quantitatively determining the elemental content of samples using laser ablation is very slow. Existing methods for quantitatively determining the elemental content of samples using laser ablation involve alternating measurements of the sample and the standard sample, i.e., the ablation signal of the standard sample is measured after the sample is tested. The difficulty lies in matching the standard sample to the sample matrix, and the significant difference between the sample concentration and the standard sample concentration. This method results in low accuracy and low precision in quantifying the elemental concentration of samples.

[0004] Therefore, how to ensure high accuracy in analysis and testing while simultaneously achieving ultra-fast sample ablation is a problem that urgently needs to be solved. Summary of the Invention

[0005] In view of this, one of the objectives of the present invention is to provide a laser ablation method that, by combining galvanometer technology and field lens technology, can achieve the goal of setting different pulse numbers on samples, high-content standards, and low-content standards, thereby fulfilling the objective of the standard addition method.

[0006] Another objective of this invention is to provide a sample detection method for the aforementioned laser ablation method, which combines a field lens focusing on different regions of the sample, and then uses an ultra-short pulse width femtosecond laser to ablate the sample in multiple pulses to generate mixed particles, which are then analyzed and tested by an elemental analysis system.

[0007] Another object of the present invention is to provide a laser ablation device for ablating samples by using a femtosecond laser ablation instrument set in different regions and within ultra-fast time periods (nanoseconds) to excite multi-pulse lasers.

[0008] To achieve the above objectives, the first aspect of the present invention provides a laser ablation method, comprising the following steps:

[0009] S1: A femtosecond laser module, an X-axis galvanometer, a Y-axis galvanometer, and a field mirror are provided. The X-axis galvanometer and the Y-axis galvanometer can reciprocate around their axes at high frequency. The laser pulse emitted by the femtosecond laser module is focused on the focal plane of the object side after being reflected by the X-axis galvanometer and the Y-axis galvanometer and refracted by the field mirror.

[0010] S2: Place at least one sample on the sample stage and adjust the position of the focal plane to coincide with the upper surface of the sample;

[0011] S3: Set the ratio of the period of the laser pulse emitted by the femtosecond laser module, the period of the high-frequency reciprocating rotation of the X-axis galvanometer, and the period of the high-frequency reciprocating rotation of the Y-axis galvanometer to an integer ratio, and set the amplitude of the high-frequency reciprocating rotation of the X-axis galvanometer and the amplitude of the high-frequency reciprocating rotation of the Y-axis galvanometer, so that when the laser pulse is focused on the plane corresponding to the sample surface, its focal point switches back and forth at different positions, and at least two of the focal points are located on the upper surface of the sample.

[0012] S4: Control the femtosecond laser module to emit laser pulses to ablate the sample surface, and collect the mixed particles generated by the laser pulse ablation for analysis and testing.

[0013] Preferably, step S2 specifically includes:

[0014] At least two samples are placed on the sample stage, with the upper surfaces of the samples flush, and the position of the focal plane is adjusted to coincide with the upper surface of the sample.

[0015] The phrase "at least two of the focal points are located on the upper surface of the sample" in step S3 specifically means:

[0016] The positions of at least two of the focal points are respectively on the upper surface of different samples.

[0017] A second aspect of the present invention provides a sample inspection method for the above-mentioned laser ablation method, comprising the following steps:

[0018] S1: Prepare a high-content standard sample containing the element to be tested at a concentration of C1 and a low-content standard sample containing the element to be tested at a concentration of C2, where C1 and C2 are preset known concentrations, and C1>C2>0;

[0019] S2: Set the pulse frequency of the femtosecond laser module, the frequency of the reciprocating rotation of the X-axis galvanometer and the frequency of the reciprocating rotation of the Y-axis galvanometer, so that the laser focus periodically switches on the high-content standard sample, the low-content standard sample and the upper surface of the sample. The number of pulses focused on the high-content standard sample, the low-content standard sample and the upper surface of the sample in one cycle are X, Y and Z, respectively, where X, Y and Z are positive integers. Collect the mixed particles generated by laser pulse ablation for analysis and testing, and obtain the total signal value U. Calculate the standard addition concentration according to formula (1).

[0020] C(p) = (C1 X + C2 Y) / Z (1);

[0021] Where C(p) is the standard concentration added.

[0022] S3: Repeat step S2 several times, keeping the Z value constant in each test and the (X+Y) value constant, and the X value different in at least two tests. Use C(p) of each test as the x-coordinate and the total signal value U as the y-coordinate to perform linear fitting, and obtain the absolute value of the x-axis intercept as the content of the element to be measured in the sample.

[0023] A third aspect of the present invention provides a laser ablation device, comprising a femtosecond laser module, a galvanometer system and a field mirror, wherein the galvanometer system comprises an X-axis galvanometer and a Y-axis galvanometer;

[0024] The X-axis galvanometer adjusts the focusing position of the laser on the sample surface along the X-axis direction, and the Y-axis galvanometer adjusts the focusing position of the laser on the sample surface along the Y-axis direction.

[0025] The X-axis direction and the Y-axis direction are perpendicular to each other;

[0026] The X-axis and Y-axis galvanometers can reciprocate around the axes at a preset frequency, allowing the laser focus to switch between multiple positions.

[0027] The field lens is used to focus the laser pulse onto the sample.

[0028] The present invention has the following beneficial effects:

[0029] (1) The laser ablation method of the present invention sets the period of the laser pulse emitted by the femtosecond laser module, the period of the high-frequency reciprocating rotation of the X-axis galvanometer, the period of the high-frequency reciprocating rotation of the Y-axis galvanometer, the amplitude of the high-frequency reciprocating rotation of the X-axis galvanometer, and the amplitude of the high-frequency reciprocating rotation of the Y-axis galvanometer, so that when the laser pulse is focused on the plane corresponding to the sample surface, its focal point switches back and forth at different positions, thereby achieving the objective of the standard addition method.

[0030] (2) The sample detection method of the present invention controls the number of particles in the sample and the added standard sample at different concentrations by setting the number of laser pulses on the upper surface of the high-content standard sample, low-content standard sample, and sample, thereby achieving a concentration gradient. The results obtained overcome the problem of inaccurate results caused by different ionization efficiencies of elements in the plasma due to different matrix. The problem of large differences between standard sample concentration and sample concentration is solved by setting the number of pulses.

[0031] (3) The laser ablation device of the present invention can ablate samples in different regions within a nanosecond time period. For homogeneous samples, more particles are generated, resulting in higher sensitivity during elemental analysis. For different samples, the generated particles are mixed and the sample information obtained during elemental analysis is richer. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the laser ablation apparatus disclosed in this invention;

[0034] Figure 2 This is a schematic diagram of the high-frequency reciprocating rotation of the X-axis galvanometer in the laser ablation method disclosed in this invention.

[0035] Figure 3 This is a schematic diagram of the high-frequency reciprocating rotation of the Y-axis galvanometer in the laser ablation method disclosed in this invention.

[0036] The components include: 1. Femtosecond laser module; 2. X-axis galvanometer; 3. Y-axis galvanometer; 4. Field mirror; 5.1 Sample; 5.2 High-content standard sample; 5.3 Low-content standard sample; 6. Laser pulse. Detailed Implementation

[0037] One of the core aspects of this invention is to provide a laser ablation method that, combined with galvanometer and field microscope technologies, enables the setting of different pulse numbers on samples, high-content standards, and low-content standards, thereby achieving the goal of the standard addition method.

[0038] Another core aspect of this invention is to provide a sample detection method based on the aforementioned laser ablation method. This method combines a field lens to focus on different regions of the sample, and then uses an ultra-short pulse width femtosecond laser to ablate the sample in multiple pulses to generate mixed microparticles, which are then analyzed and tested using an elemental analysis system.

[0039] Another core aspect of this invention is to provide a laser ablation device that uses a femtosecond laser ablation instrument to excite multi-pulse lasers in different regions and within ultra-fast time periods (nanoseconds) to ablate samples.

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Please refer to the following first. Figure 1 The laser ablation method disclosed in this embodiment is applied in a laser ablation device. Those skilled in the art will understand that the laser ablation device includes a femtosecond laser module 1, a galvanometer system, and a field lens 4. The galvanometer system includes an X-axis galvanometer 2 and a Y-axis galvanometer 3. The X-axis galvanometer 2 adjusts the position where the laser is focused on the surface of sample 5-1 along the X-axis direction, and the Y-axis galvanometer 3 adjusts the position where the laser is focused on the surface of sample 5-1 along the Y-axis direction. The X-axis direction and the Y-axis direction are perpendicular to each other. The X-axis galvanometer 2 and the Y-axis galvanometer 3 can reciprocate around the axis at a preset frequency to switch the laser focus between multiple positions. The field lens 4 is used to focus the laser pulse 6 onto sample 5-1.

[0042] In actual use, the sample 5-1 to be tested is first placed on the sample stage. Then, the height is adjusted so that the upper surface of the sample 5-1 is on the focal plane after the laser pulse field lens is focused. Then, the frequency of the high-frequency vibration of the X-axis galvanometer 2 and the Y-axis galvanometer 3 and the amplitude of the high-frequency reciprocating rotation of the X-axis galvanometer 2 and the Y-axis galvanometer 3 are set. Finally, the femtosecond laser module 1 is controlled to emit laser pulse 6 to ablate the sample, generating microparticles for analysis and testing.

[0043] This invention utilizes a femtosecond laser ablation instrument to excite multi-pulse lasers in different regions and within ultra-fast time periods (nanoseconds) to ablate sample 5-1, collecting the resulting microparticles for analysis. The advantages of this approach are twofold: firstly, it allows for multi-pulse scanning of homogeneous samples, generating a larger number of microparticles and improving the sensitivity of elemental analysis; secondly, it allows for multi-pulse scanning of different samples, ensuring the resulting particles are homogenized before entering the elemental analysis system, thus providing richer sample information.

[0044] The laser ablation method disclosed in this invention includes the following steps:

[0045] S1: Set up a femtosecond laser module 1, an X-axis galvanometer 2, a Y-axis galvanometer 3 and a field mirror 4. The X-axis galvanometer 2 and the Y-axis galvanometer 3 can reciprocate around the axis at high frequency. The laser pulse 6 emitted by the femtosecond laser module 1 is focused on the focal plane of the object after being reflected by the X-axis galvanometer 2 and the Y-axis galvanometer 3 and refracted by the field mirror.

[0046] S2: Place at least one sample 5-1 on the sample stage and adjust the position of the focal plane to coincide with the upper surface of the sample 5-1;

[0047] S3: Set the ratio of the period of the laser pulse 6 emitted by the femtosecond laser module 1, the period of the high-frequency reciprocating rotation of the X-axis galvanometer 2, and the period of the high-frequency reciprocating rotation of the Y-axis galvanometer 3 to an integer ratio, and set the amplitude of the high-frequency reciprocating rotation of the X-axis galvanometer 2 and the amplitude of the high-frequency reciprocating rotation of the Y-axis galvanometer 3 so that when the laser pulse is focused on the plane corresponding to the surface of sample 5-1, its focal point switches back and forth at different positions, and at least two focal points are located on the upper surface of sample 5-1.

[0048] S4: Control the femtosecond laser module to emit laser pulse 6 to ablate the surface of sample 5-1, and collect the mixed particles generated by laser pulse 6 for analysis and testing.

[0049] in, Figure 2 and Figure 3 The radiation patterns of laser pulse 6 after high-frequency reciprocating rotation of X-axis galvanometer 2 and Y-axis galvanometer 3 around their axes are shown respectively. In this embodiment of the invention, a device combining femtosecond laser module 1 with galvanometer system and field lens 4 is used to etch out microparticles from sample 5-1, high-content standard sample 5-2, and low-content standard sample 5-3 within a nanosecond time period, which are then mixed and tested in the elemental analysis system.

[0050] In some other preferred embodiments, step S2 specifically involves: placing at least two samples 5-1 on the sample stage, with the upper surfaces of the samples flush, and adjusting the position of the focal plane to coincide with the upper surface of the sample; in step S3, "the positions of at least two focal points are on the upper surface of the sample" specifically means that the positions of at least two focal points are respectively on the upper surfaces of different samples.

[0051] The femtosecond laser module 1 in this embodiment of the invention has a very narrow pulse width (femtosecond). Combined with galvanometer technology and field lens technology, it is possible to set different pulse numbers on sample 5-1, high-content standard 5-2 and low-content standard 5-3. The advantage of doing so is that the matrix matching of sample 5-1, high-content standard 5-2 and low-content standard 5-3 is basically the same and the concentration difference is not large. Therefore, the accuracy and precision of quantitative sample element concentration are high.

[0052] In addition, this invention also discloses a sample detection method using laser ablation, comprising the following steps:

[0053] S1: Prepare a high-content standard sample 5-2 containing the element to be tested at a concentration of C1 and a low-content standard sample 5-3 containing the element to be tested at a concentration of C2, where C1 and C2 are preset known concentrations, and C1>C2>0;

[0054] S2: Set the pulse frequency of the femtosecond laser module 1, the reciprocating rotation frequency of the X-axis galvanometer 2 and the reciprocating rotation frequency of the Y-axis galvanometer 3, so that the laser focus periodically switches on the upper surface of the high-content standard sample 5-2, the low-content standard sample 5-3 and the sample 5-1. The number of pulses focused on the upper surface of the high-content standard sample 5-2, the low-content standard sample 5-3 and the sample 5-1 in one cycle are X, Y and Z, respectively, where X, Y and Z are positive integers. Collect the mixed particles generated by the laser pulse 6 ablation for analysis and testing, and obtain the total signal value U. Calculate the standard addition concentration according to formula (1).

[0055] C(p) = (C1 X + C2 Y) / Z (1);

[0056] Where C(p) is the standard concentration added.

[0057] S3: Repeat step S2 several times, keeping the Z value constant in each test and the (X+Y) value constant, and the X value different in at least two tests. Use C(p) of each test as the x-coordinate and the total signal value U as the y-coordinate to perform linear fitting, and obtain the absolute value of the x-axis intercept as the content of the element to be measured in the sample.

[0058] This invention achieves a concentration gradient by controlling the number of pulses added to the surfaces of sample 5-1, high-content standard sample 5-2, and low-content standard sample 5-3 during surface ablation, while ensuring a consistent total number of pulses. By measuring the number of mixed particles and using the known elemental concentrations and pulse counts of high-content and low-content standard samples 5-2 and 5-3, the elemental concentration in the unknown sample 5-1 can be calculated. According to formula (1), a linear fit is performed with C(p) as the x-axis and the total signal value U as the y-axis. The absolute value of the x-axis intercept is the content of the element to be measured in sample 5-1. This method solves the problem of inaccurate results caused by different ionization efficiencies of elements in plasma due to different substrates, and addresses the issue of large differences between standard and sample concentrations by setting the pulse count.

[0059] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0060] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sample inspection method using laser ablation, characterized in that, The laser ablation method includes: The setup includes a femtosecond laser module, an X-axis galvanometer, a Y-axis galvanometer, and a field mirror. The X-axis and Y-axis galvanometers can each perform high-frequency reciprocating rotations around their axes. The laser pulses emitted by the femtosecond laser module are focused onto the focal plane of the object side after reflection from the X-axis and Y-axis galvanometers and refraction from the field mirror. At least two samples are placed on the sample stage, with their upper surfaces flush. The focal plane is adjusted to coincide with the upper surface of the samples. The periods of the laser pulses emitted by the femtosecond laser module, the high-frequency reciprocating rotations of the X-axis galvanometer, and the high-frequency reciprocating rotations of the Y-axis galvanometer are set. The ratio of the reciprocating rotation periods is an integer ratio, and the amplitudes of the high-frequency reciprocating rotation of the X-axis galvanometer and the Y-axis galvanometer are set so that when the laser pulse is focused on the plane corresponding to the sample surface, its focal point switches back and forth at different positions, and at least two of the focal points are located on the upper surfaces of different samples; the femtosecond laser module is controlled to emit laser pulses to ablate the sample surface, and the mixed particles generated by the laser pulse ablation are collected for analysis and testing. The mixed particles are obtained by multi-pulse scanning with the focal point switching back and forth on different samples; The sample detection method includes the following steps: S1: Prepare a high-content standard sample containing the element to be tested at a concentration of C1 and a low-content standard sample containing the element to be tested at a concentration of C2, where C1 and C2 are preset known concentrations, and C1>C2>0; S2: Set the pulse frequency of the femtosecond laser module, the frequency of the reciprocating rotation of the X-axis galvanometer and the frequency of the reciprocating rotation of the Y-axis galvanometer, so that the laser focus periodically switches on the high-content standard sample, the low-content standard sample and the upper surface of the sample. The number of pulses focused on the high-content standard sample, the low-content standard sample and the upper surface of the sample in one cycle are X, Y and Z, respectively, where X, Y and Z are positive integers. Collect the mixed particles generated by laser pulse ablation for analysis and testing, and obtain the total signal value U. Calculate the standard addition concentration according to formula (1). C(p) = (C1X + C2Y) / Z (1); Where C(p) is the standard concentration; S3: Repeat step S2 several times, keeping the Z value constant in each test and the (X+Y) value constant, and the X value different in at least two tests. Use C(p) of each test as the x-coordinate and the total signal value U as the y-coordinate to perform linear fitting, and obtain the absolute value of the x-axis intercept as the content of the element to be measured in the sample.

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