Disclosure of Invention
In view of this, an embodiment of the present invention provides a near-field thermal reflection measurement apparatus, so as to solve the problem that the existing thermal reflection measurement apparatus can only reduce the influence of environmental vibration, but cannot reduce the influence on the beam transmission direction caused by the instability of each optical component.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect of the present invention, there is provided a near-field thermal reflection measurement apparatus, comprising: the device comprises a laser generator, a light beam correction system, a near-field measurement system and a computer; the laser generator transmits a laser signal to the beam correction system; the beam correction system corrects the direction of the laser signal and transmits the corrected laser signal to the near-field measurement system; the near field measurement system obtains an electric signal representing thermophysical information of a sample to be measured according to the corrected laser signal and transmits the electric signal to the computer; and the computer obtains the thermophysical property information of the sample to be detected according to the electric signal and the prestored light intensity of the laser signal.
With reference to the first aspect, in a first implementation of the first aspect, the beam correction system includes: a mirror, a beam splitter and a position sensor; the reflecting mirror reflects the laser signal and transmits the reflected laser signal to the beam splitter; the beam splitter splits the reflected laser signal and transmits the laser signal reflected by the beam splitter to the position sensor; the position sensor receives the laser signal reflected by the beam splitter, obtains position information of the laser signal reflected by the beam splitter, and transmits the position information to the computer; and the computer compares the position information with preset position information and adjusts the orientation of the reflector according to a comparison result.
With reference to the first embodiment of the first aspect, in a second embodiment of the first aspect, the beam correction system further includes: a photodetector; the photoelectric detector monitors the corrected laser signal to obtain the light intensity of the corrected laser signal, and transmits the light intensity of the corrected laser signal to the computer; and the computer corrects the prestored light intensity of the laser signal according to the corrected light intensity of the laser signal.
With reference to the first embodiment of the first aspect or the second embodiment of the first aspect, in a third embodiment of the first aspect, the near-field thermal reflection measurement apparatus further includes: the optical transmission system is arranged between the laser generator and the light beam correction system and comprises a first beam splitter, a frequency multiplier, an optical delay stage and an electro-optical modulator; the first beam splitter divides the laser signal into detection light and pumping light, and transmits the detection light and the pumping light to the frequency multiplier and the electro-optic modulator respectively; the frequency multiplier is used for carrying out frequency multiplication on the detection light and transmitting the detection light after frequency multiplication to the optical delay stage; the optical delay stage includes a retroreflector, adjusts an optical path length of the probe light by movement of the retroreflector, and transmits the adjusted probe light to the beam correction system; the electro-optical modulator electro-optically modulates the pumping light and transmits the modulated pumping light to the light beam correction system.
With reference to the third implementation manner of the first aspect, in a fourth implementation manner of the first aspect, the beam correction system includes: a first correction module and a second correction module; the first correction module corrects the adjusted orientation of the detection light and transmits the corrected detection light to the near-field measurement system; and the second correction module corrects the orientation of the modulated pumping light and transmits the corrected pumping light to the near-field measurement system.
With reference to the fourth implementation manner of the first aspect, in the fifth implementation manner of the first aspect, the first correction module and the second correction module each include: two mirrors, two beam splitters, and two position sensors.
With reference to any one of the third to fifth embodiments of the first aspect, in a sixth embodiment of the first aspect, the near-field thermal reflection measurement apparatus further includes: and the second beam splitter is arranged between the light beam correction system and the near field measurement system and is used for combining the corrected detection light and the corrected pumping light and transmitting a combined laser signal to the near field measurement system.
With reference to the sixth implementation manner of the first aspect, in the seventh implementation manner of the first aspect, the near-field measurement system includes: a near-field detection system and a photoelectric detection processing system; the near-field detection system irradiates the corrected laser signal to a sample to be detected and transmits the laser signal reflected by the sample to be detected to the photoelectric detection processing system; and the photoelectric detection processing system obtains the electric signal representing the thermophysical information of the sample to be detected according to the laser signal reflected by the sample to be detected, and transmits the electric signal to the computer.
With reference to the seventh implementation manner of the first aspect, in an eighth implementation manner of the first aspect, the near-field detection system includes: the device comprises an objective lens, a near-field probe and a three-dimensional workpiece table, wherein a sample to be detected is arranged on the three-dimensional workpiece table; the objective lens converges the converged laser signals, collects reflection signals of the converged laser signals, transmits the reflection signals of the converged laser signals to the photoelectric detection processing system, and the reflection signals of the converged laser signals are obtained by reflecting the converged laser signals after the converged laser signals are incident to the surface of the sample to be detected through the near-field probe.
With reference to the eighth implementation manner of the first aspect, in the ninth implementation manner of the first aspect, the photodetection processing system comprises an optical filter, a photomultiplier tube, and a lock-in amplifier; the optical filter filters pumping light in the reflected signals of the combined laser signals, and transmits the obtained detection light in the reflected signals to the photomultiplier; the photomultiplier converts the detection light in the reflected signal into the electric signal and transmits the electric signal to the lock-in amplifier; and the phase-locked amplifier collects the signal component with the same frequency as the modulated pumping light in the electric signal and transmits the collected signal component to the computer.
Compared with the prior art, the technical scheme of the invention at least has the following advantages:
the embodiment of the invention provides a near-field heat reflection measuring device, which corrects the direction of a laser signal emitted by a laser generator through a light beam correction system, obtains an electric signal representing the thermophysical information of a sample to be measured according to the corrected laser signal by the near-field measuring system, transmits the electric signal to a computer, and obtains the thermophysical information of the sample to be measured according to the electric signal and the prestored light intensity of the laser signal by the computer. The near-field heat reflection measuring device provided by the embodiment of the invention not only can reduce the influence of environmental vibration, but also can reduce the influence on the transmission direction of the light beam caused by the instability of each optical component, thereby ensuring the reliability and accuracy of the near-field heat reflection measuring device.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; the two elements may be directly connected or indirectly connected through an intermediate medium, or may be communicated with each other inside the two elements, or may be wirelessly connected or wired connected. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
An embodiment of the present invention provides a near-field thermal reflection measurement apparatus, as shown in fig. 1, the near-field thermal reflection measurement apparatus includes: a laser generator 100, a beam correction system 300, a near field measurement system, and a computer; the laser generator 100 transmits laser signals to the beam correction system 300, the laser generator 100 can be a femtosecond pulse laser generator with the output wavelength of 800 nanometers, and the width and the repetition frequency of the transmitted pulse laser signals are respectively 100 femtoseconds and 80 megahertz; the beam correction system 300 corrects the azimuth of the laser signal and transmits the corrected laser signal to the near-field measurement system; the near field measurement system obtains an electric signal representing the thermophysical information of the sample to be measured according to the corrected laser signal and transmits the electric signal to the computer; and the computer obtains the thermophysical information of the sample to be detected according to the electric signal and the prestored light intensity of the laser signal.
According to the near-field thermal reflection measuring device provided by the embodiment of the invention, the direction of the laser signal emitted by the laser generator 100 is corrected by the light beam correction system 300, the near-field measuring system obtains the electric signal representing the thermophysical information of the sample to be measured according to the corrected laser signal and transmits the electric signal to the computer, and the computer obtains the thermophysical information of the sample to be measured according to the electric signal and the prestored light intensity of the laser signal, so that the influence of environmental vibration can be reduced, the influence of instability of each optical component on the transmission direction of the light beam can be reduced, and the reliability and the accuracy of the near-field thermal reflection measuring device are ensured.
In a preferred embodiment, the beam calibration system 300 comprises: a mirror, a beam splitter and a position sensor; the reflecting mirror reflects the laser signal and transmits the reflected laser signal to the beam splitter; the beam splitter splits the reflected laser signal and transmits the laser signal reflected by the beam splitter to the position sensor; the position sensor receives the laser signal reflected by the beam splitter, obtains the position information of the laser signal reflected by the beam splitter, and transmits the position information to the computer; and the computer compares the position information with preset position information and adjusts the orientation of the reflector according to a comparison result.
It should be noted that the working process of the light beam correction system 300 is a process of closed-loop operation, after the computer adjusts the orientation of the mirror according to the comparison result, the light beam is reflected to the position sensor through the mirror and the beam splitter again, the position sensor transmits the position information to the computer again, the computer compares the position information with the preset position information until the obtained position information is the same as the preset position information, and the adjustment of the orientation of the mirror is stopped.
It should be noted that, before the beam calibration system 300 operates in a closed loop, the calibrated and aligned thermal reflection measurement device is in a good working state, the position sensor transmits the position information of the calibrated optical path to the computer as the preset position information, and the computer may adjust the orientation of the mirror according to the comparison result between the position information transmitted by the position sensor and the preset position information by using a method in the prior art, which is not described in detail herein.
In a preferred embodiment, as shown in fig. 2, the beam calibration system 300 further comprises: a photodetector 31; the photoelectric detector 31 monitors the corrected laser signal to obtain the light intensity of the corrected laser signal, and transmits the light intensity of the corrected laser signal to the computer; and the computer corrects the light intensity of the laser signal stored in advance according to the corrected light intensity of the laser signal.
In a preferred embodiment, as shown in fig. 1 and fig. 2, the near-field thermal reflection measurement apparatus provided in the embodiment of the present invention further includes: a light transmission system 200 disposed between the laser generator 100 and the beam correction system 300, the light transmission system 200 comprising: a first beam splitter 2, a frequency multiplier 3, an optical delay stage 6 and an electro-optical modulator 17; the first beam splitter 2 divides the laser signal into detection light with 400 nm wavelength for detecting a sample to be detected and pumping light with 800 nm wavelength for heating the sample to be detected, and transmits the detection light and the pumping light to the frequency multiplier 3 and the electro-optical modulator 17 respectively; the frequency multiplier 3 multiplies the frequency of the detection light and transmits the frequency-multiplied detection light to the optical delay stage 6; the optical delay stage 6 is an electric control optical delay stage which is controlled by a computer and provided with a retroreflector, the optical path length of the detection light can be adjusted through the high-precision movement of the retroreflector, so that the optical path difference between the pumping light and the detection light is adjusted, the adjusted detection light is transmitted to the light beam correction system 300 to adjust the time difference between the detection light and the time when the pumping light reaches a sample to be measured, the optical path difference of one micron can realize the time difference of 3.3 femtoseconds, and the dynamic measurement of high time resolution is realized; the electro-optical modulator 17 electro-optically modulates the pump light and transmits the modulated pump light to the beam correction system 300. The optical transmission system 200 divides the pulse laser into detection light for detecting a sample to be detected and pumping light for heating the sample to be detected, and multiplies the frequency of the detection light, and modulates the pumping light, so that the subsequent near-field measurement system can effectively separate the pumping light from the detection light and obtain data which has high signal-to-noise ratio and reflects the thermophysical property of the sample to be detected.
In a preferred embodiment, as shown in fig. 1 and 2, the beam correction system 300 comprises: a first correction module 301 and a second correction module 302; the first correction module 301 corrects the adjusted orientation of the probe light and transmits the corrected probe light to the near-field measurement system; the second correction module 302 corrects the orientation of the modulated pump light and transmits the corrected pump light to the near-field measurement system. The first correction module 301 and the second correction module 302 each include: two mirrors, two beam splitters, and two position sensors, the first correction module 301 includes: mirror 9, mirror 10, beam splitter 11, beam splitter 12, position sensor 15, and position sensor 16, and second correction module 302 includes: mirror 19, mirror 20, beam splitter 21, beam splitter 22, position sensor 25, and position sensor 26.
In a preferred embodiment, as shown in fig. 2, the near-field thermal reflection measurement apparatus provided in the embodiment of the present invention further includes: and the second beam splitter 14 is disposed between the beam correction system 300 and the near-field measurement system, and is configured to combine the corrected probe light and the corrected pumping light, and transmit a combined laser signal to the near-field measurement system.
In a preferred embodiment, as shown in fig. 2, the near field measurement system comprises: a near field detection system 400 and a photo detection processing system 500; the near-field detection system 400 irradiates the corrected laser signal to the sample to be detected, and transmits the laser signal reflected by the sample to be detected to the photoelectric detection processing system 500; the photoelectric detection processing system 500 obtains an electrical signal representing the thermophysical information of the sample to be detected according to the laser signal reflected by the sample to be detected, and transmits the electrical signal to the computer.
In a preferred embodiment, as shown in fig. 2, the near field detection system 400 comprises: the device comprises an objective lens 32, a near-field probe 33 and a three-dimensional workpiece table 35, wherein a sample 34 to be detected is arranged on the three-dimensional workpiece table 35, and the sample 34 to be detected loaded on the three-dimensional workpiece table 35 and the near-field probe 33 always keep a constant distance, which is usually less than 20 nanometers, by controlling the movement of the three-dimensional workpiece table 35; the objective lens 32 converges the converged laser signal, collects a reflection signal of the converged laser signal, and transmits the reflection signal of the converged laser signal to the photoelectric detection processing system 500, the reflection signal of the converged laser signal is obtained by transmitting the converged laser signal to the surface of the sample to be detected 34 through the aperture of the near-field probe 33 and then reflecting the converged laser signal, the diameter of the aperture of the near-field probe 33 is about 100 nm-500 nm, the sample to be detected 34 absorbs pumping light penetrating through the aperture of the near-field probe 33 to increase the temperature, the detection light passes through the aperture of the near-field probe 33 and then irradiates the sample region to be detected under the action of the pumping light, and the pumping light and the detection laser reflected by the sample to be detected 34 return through the aperture of the near-field probe 33 and are collected by the objective lens 32.
In a preferred embodiment, as shown in fig. 2, the photo-detection processing system 500 includes: a filter 28, a photomultiplier 29, and a lock-in amplifier 36; the optical filter 28 filters pumping light in the combined reflection signal of the laser signal, and transmits probe light in the obtained reflection signal to the photomultiplier 29; the photomultiplier 29 converts the probe light in the reflected signal into an electrical signal and transmits the electrical signal to the lock-in amplifier 36; the lock-in amplifier 36 collects a signal component having the same frequency as the modulated pumping light in the electric signal and transmits the collected signal component to the computer.
The following describes in detail the specific principle of the near-field thermal reflection measurement apparatus provided by the embodiment of the present invention with reference to fig. 2.
The pulse laser emitted by the laser generator 100 is divided into two laser beams by the first beam splitter 2 of the optical transmission system 200, one laser beam is frequency-doubled by the frequency doubler 3 to become a probe light, the probe light is used for sensing the heat reflection information of the sample to be measured, and the other laser beam is used as a pumping light for heating the sample. In the operation process of the near-field thermal reflection measuring device, due to instability of a laser, an optical element and a moving part, pumping light and detection light deviate from a preset optical axis, and the light intensity changes. Two beam correction modules arranged in the beam correction system 300 respectively correct the detection light and the pumping light, each beam correction module comprises two reflectors, one reflector can adjust the beam direction in two dimensions of X and Y, and the combination of the two reflectors can realize the adjustment of the four dimensions of X, Y position and angle alpha and angle beta; each beam correction module comprises two position sensors, one position sensor defining the spatial position of the light spot and two position sensors defining the position and the propagation direction of the light beam. Therefore, the two double-shaft adjustable reflectors and the two position sensors can realize the adjustment of light in any direction, and can correct light beams and transmit the light beams according to a preset optical axis. A key parameter measured by the heat reflection measuring device is the light intensity of the detection light, when the laser signal emitted by the laser generator 100 and the light transmission system 200 are unstable, the light intensity of the detection light changes, and in order to eliminate the influence of instability of the light intensity, the light beam correction system 300 is further provided with a photoelectric detector 31 for monitoring the light intensity in real time, and transmitting the light intensity to a computer to correct the light intensity of the laser signal stored in advance, so as to eliminate the influence of instability of the light beam on the measurement result, and ensure the accuracy of the detected heat reflection signal.
It should be noted that a computer mentioned in the embodiment of the present invention is not shown in fig. 1 and fig. 2, and those skilled in the art should understand that the connection relationship, the signal transmission process, and the like between the computer and the optical delay stage 6, each position sensor, the photodetector 31, and the lock-in amplifier 36 can all adopt the methods in the prior art, and the embodiment of the present invention is not limited thereto.
The following describes a specific implementation process of the near-field thermal reflection measurement apparatus provided in the embodiment of the present invention with reference to fig. 2.
The pulse laser 100 generates a pulse laser beam with a wavelength of 800 nanometers, two beams of light are obtained through the first beam splitter 2, the first laser beam obtains pulse laser with a wavelength of 400 nanometers through the frequency multiplier 3, the first laser beam is used as detection light for sensing parameters such as thermophysical properties of a sample and the like, the detection light is irradiated onto the optical delay stage 6 through the reflecting mirror 4 and the reflecting mirror 5 in a changed direction, the movement of a retroreflector in the optical delay stage 6 is controlled by a computer, the retroreflector is moved to a corresponding position according to the time delay between the detection light and pumping light, then the detection light is incident into the second beam splitter 14 through the reflecting mirror 7, the reflecting mirror 8, the reflecting mirror 9, the reflecting mirror 10, the beam splitter 11, the beam splitter 12 and the reflecting mirror 13, the laser reflected by the beam splitter 11 is irradiated onto the position sensor 15, the laser reflected by the beam splitter 12 is irradiated onto the position sensor 16, and the measured position, the computer controls and drives the reflector 9 and the reflector 10 according to the position information monitored in real time to enable the detection light positions measured by the position sensor 15 and the position sensor 16 to be consistent with the preset positions; the second laser beam from the first beam splitter 2 is used as pumping light, the pumping light becomes modulated pulse laser after passing through the electro-optical modulator 17, the modulated pulse laser output by the electro-optical modulator 17 passes through the reflecting mirror 18, the reflecting mirror 19, the reflecting mirror 20 and the beam splitter 21, the beam splitter 22, the reflecting mirror 23 and the reflecting mirror 24 and then enters the second beam splitter 14, the laser reflected by the beam splitter 21 irradiates the position sensor 25, the laser reflected by the beam splitter 22 irradiates the position sensor 26, the position sensor 25 and the position sensor 26 feed back the measured position information to the computer, and the computer controls and drives the reflecting mirror 19 and the reflecting mirror 20 according to the real-time monitored position information to enable the pumping light positions measured by the position sensor 25 and the position sensor 26 to be consistent with the preset positions. The probe light and the pumping light combined by the second beam splitter 14 irradiate the objective lens 32 through the beam splitter 27 and the beam splitter 30, converge and irradiate the near-field probe 33, and enter the surface of a sample to be measured 34 through a diaphragm hole of the near-field probe 33, and the sample to be measured 34 is installed on a three-dimensional workpiece table 35. Part of the reflected light from the beam splitter 30 enters the photodetector 31, and the photodetector 31 monitors the stability of the intensity of the laser light entering the objective lens 32 and transmits the monitored intensity of the laser light to the computer. The pumping light reflected from the surface of the sample to be measured 34 and the detection light with the sample thermophysical parameter information return through the diaphragm hole of the near-field probe 33, are collected by the objective lens 32, pass through the beam splitter 30, the beam splitter 27 and the optical filter 28, and enter the photomultiplier 29, the optical filter 28 filters the pumping light, the photomultiplier 29 converts the collected detection light into an electrical signal, the electrical signal is connected to the lock-in amplifier 36, the output signal of the lock-in amplifier 36 is transmitted to the computer, and the computer obtains thermophysical parameters and the like according to the output signal and the light intensity of the corrected prestored laser signal.
It should be noted that, the computer obtains the thermophysical information of the sample to be measured according to the output signal of the lock-in amplifier and the light intensity of the laser signal which is stored in advance after being corrected, which may be a method in the prior art, and this part does not belong to the important point of the embodiment of the present invention, and is not described in detail here.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.