JP7841726B2 - Measurement system and detector used in the measurement system - Google Patents

Description

This invention relates to a measurement system, etc., for performing time-resolved measurement of a target object.

Streak cameras are known as devices for measuring phenomena that occur within extremely short timeframes. Non-Patent Document 1 below describes the operating principle of a streak camera. A streak camera focuses the light to be measured onto the photocathode of a streak tube, generating photoelectrons corresponding to its intensity. These photoelectrons are then accelerated by an accelerating electrode and moved towards the fluorescent screen. During this process, the streak camera applies a sweeping electric field perpendicular to the acceleration direction, spatially resolving the photoelectron cluster. The streak camera then converts this photoelectron cluster into light on the fluorescent screen, generating a streak image of this light. Streak cameras have extremely high time resolution; for example, some can measure light with a time resolution of 1 picosecond.

"Operating Principle | Streak Camera | Hamamatsu Photonics" [Accessed May 19, 2020] Internet <URL: https://www.hamamatsu.com/jp/ja/product/photometry-systems/streak-camera/operating-principle/index.html>

As described above, a streak camera is configured to focus the light to be measured onto the photocathode of a streak tube. Therefore, there are limitations to the light intensity that can be measured by a streak camera, making it difficult to apply to measuring high-intensity light.

One aspect of the present invention aims to realize a measurement system that can perform time-resolved measurements of various measurement targets, such as high-intensity light and lasers, which are difficult to measure with streak cameras.

To solve the above problems, a measurement system according to one aspect of the present invention is a measurement system for performing time-resolved measurement of a measurement target, comprising a detection laser emitter, a detector equipped with a Pockels element and an optical fiber, and an analysis device. The detection laser emitter emits linearly polarized laser light consisting of pulses whose wavelength continuously changes over time. The measurement target is incident on the detector, generating an electric field around the Pockels element. The optical fiber guides the laser light to the Pockels element and also guides the transmitted light, which has passed through the Pockels element, to the analysis device. The analysis device analyzes the transmitted light based on its wavelength and polarization state.

Furthermore, a detector according to one aspect of the present invention is a detector used in a measurement system that performs time-resolved measurement of a measurement target, comprising a Pockels element and an optical fiber. The optical fiber guides linearly polarized laser light, consisting of pulses whose wavelength continuously changes over time, to the Pockels element, and also guides the transmitted light, which has passed through the Pockels element, to an analytical device that analyzes the transmitted light based on its wavelength and polarization state.

To solve the above problems, a measurement system according to one aspect of the present invention is a measurement system for performing time-resolved measurement of a measurement target, and includes a detection laser emitter, a detector equipped with an optical fiber and an electro-optic element that generates an electro-optic effect using an electric field, and an analysis device. The detection laser emitter emits laser light consisting of pulses whose wavelength continuously changes over time, the optical fiber guides the laser light to the electro-optic element where an electro-optic effect is generated by the electric field produced by the measurement target incident on the detector, and the transmitted light that has passed through the electro-optic element is guided to the analysis device, and the analysis device analyzes the transmitted light based on its wavelength.

Furthermore, a detector according to one aspect of the present invention is a detector used in a measurement system that performs time-resolved measurement of a target to be measured, and comprises an optical fiber and an electro-optic element that generates an electro-optic effect using an electric field. The optical fiber guides laser light consisting of pulses whose wavelength continuously changes over time to the electro-optic element, and also guides the laser light to an analytical device that analyzes the transmitted light after it has passed through the electro-optic element based on its wavelength.

According to one aspect of the present invention, time-resolved measurement can be performed even for high-intensity measurement targets.

This figure shows an example configuration of a measurement system according to one embodiment of the present invention. This figure shows the measurement principle and an example of the configuration of the analytical device in the above measurement system. This figure shows another example configuration of the analytical device described above. This figure shows an example of the output of measurement results from the above measurement system. This figure shows an example of a detector configuration. This figure illustrates a simulation used to verify the detection sensitivity and resolution of the measurement system described above. This figure shows an example of a detector configuration with a grip. This figure shows an example configuration of a measurement system equipped with multiple detectors. This figure illustrates an overview of a measurement system according to Embodiment 2 of the present invention. This figure shows the structure of a photoelectric polymer, an example of an electro-optic element that produces the Stark effect, and its light absorption characteristics. This diagram shows the schematic configuration of the measurement system used in an experiment to perform time-resolved measurements of ultrafast electrons and X-rays using the Stark effect. This figure shows the time-series changes in the intensity of ultrafast electrons and X-rays, generated using the data shown in Figure 11.

[Embodiment 1]
[System Configuration]
The configuration of a measurement system according to one embodiment of the present invention will be described with reference to Figure 1. Figure 1 is a diagram showing an example of the configuration of the measurement system 1. As will be explained in detail below, the measurement system 1 makes it possible to measure electromagnetic waves, electrons, ions, neutrons, gamma rays, X-rays, visible light, etc., with an ultra-high time resolution of about 1 picosecond. Such measurements are extremely useful, for example, in scientific research and industry dealing with ultrashort pulse phenomena.

The measurement system 1 shown in Figure 1 includes a detection laser emitter 11, a fiber circulator 13, a detector 15, and an analysis device 16. The detection laser emitter 11 includes a laser oscillator 111 and a polarizer 112, and the detector 15 includes an optical fiber 151.

The detection laser emitter 11 emits linearly polarized laser light consisting of pulses whose wavelength continuously changes over time. More specifically, the laser oscillator 111 emits laser light consisting of pulses whose wavelength continuously changes over time, and this laser light becomes linearly polarized by passing through the polarizer 112 and is emitted from the detection laser emitter 11.

A pulse whose wavelength continuously changes over time is called a chirp pulse. A chirp pulse can be obtained, for example, by chirpening an ultrashort pulse laser beam using a wavelength chirp device consisting of a diffraction grating. Hereinafter, the laser beam emitted from the detection laser emitter 11 will be referred to as a chirp pulse laser. The chirp pulse laser is used to detect the object to be measured by the detector 15. The chirp pulse laser emitted from the detection laser emitter 11 is incident on the fiber circulator 13. The polarizer 112 may be built into the laser oscillator 111.

The fiber circulator 13 guides the chirp pulse laser emitted by the detection laser emitter 11 to the detector 15. Furthermore, since the chirp pulse laser reflects back within the detector 15, the fiber circulator 13 guides this reflected light to the analysis device 16.

The detector 15 detects the object to be measured. Figure 1 shows an enlarged view of the detector 15's configuration. As shown in the figure, the detector 15 comprises an optical fiber 151, a Pockels element 152, a reflector 153, and a coating portion 154. Although Figure 1 shows the end face of the optical fiber 151 and the Pockels element 152 separated, they are fixed in close contact. The same applies to the Pockels element 152 and the reflector 153.

The optical fiber 151 guides the chirp-pulsed laser light to the Pockels element 152. The optical fiber 151 also guides the transmitted light from the chirp-pulsed laser, after it has passed through the Pockels element 152, to the analysis device 16 via the fiber circulator 13. A single-mode optical fiber, which does not change the polarization state of light passing through its interior, is used as the optical fiber 151.

The Pockels element 152 is an element that exhibits the Pockels effect when an electric field is applied. The Pockels effect is a phenomenon in which birefringence occurs when an electric field is applied. When light passes through the Pockels element 152 exhibiting the Pockels effect, its polarization state changes. As the Pockels element 152, various crystals that exhibit birefringence when an electric field is applied can be used, such as DAST (4'-dimethylamino-N-metyl-4-stilbazolium tosylate) crystals. Such crystals are also called Pockels crystals.

The reflector 153 reflects light. The reflector 153 is connected to the end face of the Pockels element 152 opposite to the end face to which the optical fiber 151 is connected, as shown in Figure 1. In other words, the Pockels element 152 is positioned between the reflector 153 and the end face of the optical fiber 151.

Therefore, the chirp pulse laser incident from the optical fiber 151 to the Pockels element 152 passes through the Pockels element 152, is reflected by the reflector 153, and then passes through the Pockels element 152 again to return to the optical fiber 151. By providing the reflector 153, most of the chirp pulse laser incident on the Pockels element 152 can be returned to the optical fiber 151 as reflected light.

Furthermore, as shown in Figure 1, the reflector 153 is positioned between the measurement target and the Pockels element 152, and therefore also functions as a protective material to prevent the measurement target from entering the Pockels element 152 or the optical fiber 151. In the measurement system 1, the measurement target does not enter the Pockels element 152 or the optical fiber 151, and therefore does not enter the analysis device 16. For this reason, even if the measurement target is, for example, a high-intensity laser pulse, the analysis device 16 and other components will not be damaged by its intensity.

Furthermore, even without the reflector 153, the polarized laser light is reflected back to the optical fiber 151 by the end face of the Pockels element 152 (the end face on the side not connected to the optical fiber 151). Therefore, the reflector 153 can be omitted.

The coating portion 154 is formed to cover the tip of the Pockels element 152 and the optical fiber 151. While providing the coating portion 154 is not essential, it is preferable to provide it to improve measurement sensitivity and the durability of the detector 15.

For example, if the measurement target is light, a coating portion 154 can be formed using a light-reflecting metal or similar material to prevent the light being measured from entering the Pockels element 152 or optical fiber 151. Alternatively, if the measurement target is neutrons, a coating portion 154 that shields against electromagnetic waves can be formed to prevent the influence of electromagnetic waves on neutron measurement. In this way, by shielding against noise in the measurement using the coating portion 154, the measurement sensitivity can be improved.

The analysis device 16 analyzes the transmitted light that has passed through the Pockels element 152 based on its wavelength and polarization state. The computer 17 then outputs the analysis results from the analysis device 16 and performs calculations based on those results. Details of the analysis device 16 will be described later.

[Measurement principle and example of analytical device configuration 1]
Figure 2 shows the measurement principle in the measurement system 1 and an example of the configuration of the analysis device 16. In Figure 2, the chirp pulses that make up the chirp pulse laser emitted by the detection laser emitter 11 are shown as P1 to P5. The chirp pulses P1 to P5 each have different wavelengths. Specifically, chirp pulse P1 has the shortest wavelength, and the wavelengths gradually increase from P5 onwards.

The chirp pulses P1 to P5 travel through the optical fiber 151 and enter the Pockels element 152. The chirp pulses P1 to P5 that enter the Pockels element 152 are then reflected by the reflector 153 and return to the optical fiber 151, after which they enter the analysis device 16.

Here, when the object to be measured is incident on the reflector 153 during the period when chirp pulses P1 to P5 are passing through the Pockels element 152, an electric field is generated in the Pockels element 152 due to the incident. In the example in Figure 2, a negative charge is generated on the end face of the Pockels element 152 on the side where the reflector 153 is located, and this generates an electric field between it and the other end face of the Pockels element 152.

When an electric field is generated in this way, the Pockels effect occurs in the Pockels element 152. Therefore, among the chirp pulses P1 to P5 that pass through the Pockels element 152, those transmitted during the period when the electric field is generated, i.e., the period when the object being measured was incident, undergo a change in polarization state. Specifically, the chirp pulse laser incident during the period when the object being measured was incident changes from linearly polarized to elliptically polarized, and its polarization axis rotates. This rotation angle of the polarization axis is proportional to the electric field strength. On the other hand, the polarization state of those transmitted during other periods remains linearly polarized.

Here, there is a time lag between the generation of the electric field and the occurrence of the Pockels effect, but this time lag is extremely short, about 10 femtoseconds or less. Therefore, by considering the period during which the polarization state of the chirp pulse laser changes as the period during which the object being measured was incident, extremely high-precision time-resolved measurements become possible.

For example, in the example shown in Figure 2, of the chirp pulses P1 to P5 that passed through the Pockels element 152, only chirp pulses P3 and P4 are elliptically polarized, while the others remain linearly polarized. Therefore, the period during which chirp pulses P3 and P4 passed through the Pockels element 152 can be considered as the period during which the object being measured was incident.

The analytical apparatus 16 shown in Figure 2 includes a polarization separator 161 and a wavelength spectrometer 162. The wavelength spectrometer 162, also called a wavelength spectroscopic camera, includes a wavelength spectroscopic element 1621 and an image sensor 1622. The wavelength spectroscopic element 1621 may be, for example, a diffraction grating. The image sensor 1622 may be, for example, a CCD (Charge-Coupled Device) element.

The polarization separator 161 transmits chirp pulses P3 and P4, which are the optical components with changed polarization states from the chirp pulses P1 to P5 contained in the transmitted light that has passed through the Pockels element 152, and outputs them to the wavelength spectrometer 162. The polarization separator 161 may, for example, include a quarter-wave plate and a polarization beam splitter.

Here, the chirp pulses P3 and P4 emitted from the polarization separator 161 have different wavelengths. Therefore, after passing through the wavelength spectrometer 1621, the chirp pulses P3 and P4 travel in different directions and are separated and imaged on the image sensor 1622. Since the emission angle of light from the wavelength spectrometer 1621 is determined according to the wavelength of that light, the image formation position on the image sensor 1622 indicates the wavelengths of the chirp pulses P3 and P4.

Furthermore, in a chirp-pulsed laser, wavelength and time correspond one-to-one; therefore, a change in wavelength can be directly interpreted as a change in time. Thus, the time interval between chirp pulses P3 and P4 can be determined from the positions of the images of chirp pulses P3 and P4 formed on the image sensor 1622. In this way, by using the wavelength spectrometer 162, the positions of the chirp pulse images formed on the image sensor 1622 can be determined, and the time evolution of the Pockels effect can be calculated from the determined image positions.

Furthermore, the time resolution of the measurement system 1 is extremely high. For example, suppose the detection laser emitter 11 emits a laser with a pulse width of 0.1 ps, and through chirpening, generates a 100 nm chirp pulse where the wavelength changes at a rate of 1 ps/1 nm over a pulse width of 100 ps. In this case, if the wavelength spectrometer 162 has a resolution of 1 nm, the time resolution of the measurement system 1 becomes 1 ps. Previously, the only equipment capable of such high-level time-resolved measurement was the extremely expensive, top-of-the-line streak camera.

Furthermore, by changing the pulse width from 100 ps to 10 ps, a chirp pulse with a wavelength change of 0.1 ps/1 nm is obtained. Therefore, the time resolution of the measurement system 1, when using a spectrometer with a resolution of 1 nm, becomes 0.1 ps. Such changes to the chirp pulse can be easily achieved by adjusting the detection laser emitter 11.

Furthermore, as described above, the rotation angle of the polarization axis when light passes through the Pockels element 152 is proportional to the electric field strength. Also, the electric field strength generated in the Pockels element 152 is proportional to the intensity of the ultrashort pulse being measured. Therefore, when the transmitted light that has passed through the Pockels element 152 enters the polarization separator 161, light with an intensity corresponding to the intensity of the measured object is emitted from the polarization separator 161.

For example, if the polarization separator 161 includes a quarter-wave plate, the intensity of the light emitted from the polarization separator 161 is proportional to the rotation angle of the polarization axis. Furthermore, if the polarization separator 161 does not include a quarter-wave plate and consists only of a polarizer, for example, the intensity of the light emitted from the polarization separator 161 is proportional to the square of the rotation angle of the polarization axis.

In other words, the rotation angle of the polarization axis as it passes through the Pockels element 152 is determined by the intensity of the object being measured, and the intensity of the light emitted from the polarization separator 161 is determined by the rotation angle of the polarization axis. Therefore, the intensity of the light imaged by the image sensor 1622 represents the intensity of the object being measured.

Furthermore, if the pulse width and intensity of the target object can be measured, the waveform can also be derived. Note that the calculation of the pulse width and intensity of the target object and the derivation of the waveform may be performed by the analysis device 16, or by a device other than the analysis device 16, such as a computer 17.

As described above, the measurement system 1 includes a detection laser emitter 11, a detector 15 equipped with a Pockels element 152 and an optical fiber 151, and an analysis device 16. The detection laser emitter 11 emits chirp pulses, which are linearly polarized laser light consisting of pulses whose wavelength continuously changes over time. The object to be measured is incident on the detector 15, generating an electric field around the Pockels element 152. The optical fiber 151 guides the chirp pulse laser to the Pockels element 152 and also guides the transmitted light that has passed through the Pockels element 152 to the analysis device 16. The analysis device 16 analyzes the transmitted light based on its wavelength and polarization state.

According to the above configuration, the detector 15 includes a Pockels element 152. Therefore, when the object to be measured enters the detector 15, the electric field generated by the object causes the Pockels effect to occur in the Pockels element 152. When the Pockels effect occurs, the polarization state of the light passing through the Pockels element 152 changes.

Here, since the light transmitted through the Pockels element 152 is a chirp-pulsed laser, its wavelength changes over time. Therefore, by analyzing the transmitted light that has passed through the Pockels element 152 based on its wavelength and polarization state, it becomes possible to measure the target object.

Furthermore, the measurement system 1 detects changes in polarization state caused by the Pockels effect generated by the object being measured, and the object being measured does not enter the analysis device 16. Therefore, the measurement system 1 makes it possible to perform time-resolved measurements of various objects, such as high-intensity light and lasers, which are difficult to measure with a streak camera.

Furthermore, the measurement target can be anything that generates an electric field in the Pockels element 152, such as charged particles (electrons, ions, etc.). Also, as will be described in detail later based on Figure 5, it is possible to measure electromagnetic waves such as gamma rays and X-rays, neutrons, light, etc.

Furthermore, the analysis device 16 only needs to analyze transmitted light based on its wavelength and polarization state, and various analysis devices 16 can be applied depending on the application of the measurement system 1. For example, if the measurement target is laser light, an analysis device 16 that analyzes the wavelength and polarization state of the transmitted light and outputs data indicating the pulse width and waveform of the laser light may be applied. Alternatively, for example, an analysis device 16 that analyzes the wavelength and polarization state of the transmitted light and detects whether or not the measurement target has entered the detector 15 may be applied.

Furthermore, the above configuration enables extremely high-speed time-resolved measurements. This is because, as mentioned above, the time delay between the generation of an electric field in the Pockels element and the appearance of the Pockels effect is said to be less than 10 femtoseconds.

Other advantages include the fact that the measurement system 1 does not have expensive components such as streak tubes, and therefore can be manufactured at a significantly lower cost compared to streak cameras. Furthermore, the detector 15 is detachable from the measurement system 1 and easily replaceable. Therefore, it can be applied to applications such as measuring the time evolution of X-rays, neutrons, ions, and electrons in laser fusion by bringing the detector 15 into contact with the fusion plasma. In this case, the detector 15 can be replaced and disposed of after each measurement.

Furthermore, as described above, the detector 15 used in the measurement system 1 comprises a Pockels element 152 and an optical fiber 151. The optical fiber 151 guides the chirp pulse laser to the Pockels element 152 and also guides the transmitted light from the chirp pulse laser through the Pockels element 152 to the analysis device 16. This makes it possible to perform time-resolved measurements of various measurement targets, such as high-intensity light and lasers, which are difficult to measure with a streak camera. Moreover, since the optical fiber 151 is lightweight and compact, and the Pockels element 152 only needs to have a width approximately the same as the diameter of the optical fiber 151, the overall size of the detector 15 can be made extremely small and lightweight.

[Example of analytical device configuration 2]
Figure 3 shows another example of the configuration of the analytical apparatus 16. The analytical apparatus 16a shown in Figure 3 includes a quarter-wave plate 161a, a polarizing beam splitter 162a, and a wavelength spectrometer 163a.

The transmitted light that passes through the Pockels element 152 first enters the quarter-wave plate 161a. This transmitted light is then emitted from the quarter-wave plate 161a after its polarization axis is rotated by 45°. While the quarter-wave plate 161a is not essential, its inclusion can improve detection sensitivity.

The light emitted from the quarter-wave plate 161a is incident on the polarizing beam splitter 162a, where it is split into horizontally polarized and vertically polarized components. The horizontally polarized component is then input to the horizontal polarization channel of the wavelength spectrometer 163a, and the vertically polarized component is input to the vertical polarization channel of the wavelength spectrometer 163a.

The horizontal polarization component input to the horizontal polarization channel of the wavelength spectrometer 163a is spectrally analyzed by the optical system within the wavelength spectrometer 163a based on its wavelength, and imaged at a position on the image sensor, such as a CCD element, corresponding to the wavelength of the vertical polarization component. Similarly, the vertical polarization component input to the vertical polarization channel of the wavelength spectrometer 163a is also imaged at a position on the image sensor corresponding to the wavelength of the vertical polarization component. Note that the image sensor for imaging the vertical polarization component and the image sensor for imaging the horizontal polarization component may be provided by a single imaging device, or by separate imaging devices.

Thus, in the analysis device 16a, the transmitted light that has passed through the Pockels element 152 is polarized using the quarter-wave plate 161a, and then the signals of two orthogonal polarization components obtained by the polarization beam splitter 162a are detected. In this case, by calculating the difference between the two orthogonal polarization component signals, noise components can be canceled out, thereby improving measurement accuracy. This calculation may be performed by the analysis device 16, or it may be performed by a device other than the analysis device 16, such as a computer 17.

[Example of measurement result output]
Figure 4 shows an example of the output of measurement results by the measurement system 1. The analyzer 16a shown in Figure 3 may output the analysis results as an image as shown in Figure 401. In image 401, the left-right direction represents wavelength, and the brightness value represents intensity. In addition, in image 401, the measurement results for light input to the vertical polarization channel and the measurement results for light input to the horizontal polarization channel are shown side by side in the vertical direction.

As can be seen from Image 401, changes in brightness values are observed in the same wavelength range for both the light input to the vertical polarization channel and the light input to the horizontal polarization channel. This indicates that the polarization state of the chirp pulses in this wavelength range, which constitute the chirp pulse laser, has changed.

Alternatively, a graph like the one shown in Figure 402 may be generated from data such as that in Image 401, and this graph may be output as the measurement result. Graph 402 is a graph with time on the horizontal axis and intensity on the vertical axis.

As described above, the left-right direction in image 401 represents wavelength, and the wavelength of the pulses constituting the chirp pulse laser changes over time. Therefore, by converting the left-right position in image 401 to time and the brightness value to intensity, a graph like 402 can be generated, showing the waveform of the measured object with time on the horizontal axis and intensity on the vertical axis.

Graph 402 shows the results of an experiment in which a DAST crystal was used as the Pockels element 152, and terahertz radio waves generated when this DAST crystal was irradiated with laser light were measured.

In this experiment, the laser beam emitted from the laser device was split into two; one beam was used as a chirp pulsed laser, and the other was incident on a DAST crystal. When the laser beam is incident on the DAST crystal, terahertz radio waves are generated from the crystal. These terahertz radio waves cause the DAST crystal to exhibit birefringence, and this change in state alters the polarization state of pulses at certain wavelengths of the chirp pulsed laser that passes through the DAST crystal. This change was detected by the analysis device 16a, and graph 402 was created based on the detection results.

Graph 402 in Figure 4 shows the signal waveform of the terahertz radio waves measured as described above, as well as the limiting resolution in this measurement and the waveform of the detection laser. Because the wavelength width of the detection laser used in this experiment was 8 nm, the time resolution was limited to approximately 90 ps (11 GHz). However, the time resolution can be further improved by using a laser with a wider wavelength width.

[Example of detector configuration]
Figure 5 shows an example of the configuration of the detector 15. The detector 15a shown in Figure 5 differs from the detector 15 shown in Figure 1 in that the electron conversion material 155 is provided on the outside of the reflector 153 (on the opposite side of the Pockels element 152, with the reflector 153 in between).

The electron conversion material 155 converts incident light into electrons. More specifically, the electron conversion material 155 emits a number of electrons corresponding to the intensity of the incident light. Therefore, when light strikes the electron conversion material 155, electrons are emitted from it, and the electric field generated by these emitted electrons causes the Pockels effect in the Pockels element 152. Consequently, by using a detector 15a containing the electron conversion material 155, measurements can be performed using light as the object being measured. For example, visible light can also be measured.

Similarly, electromagnetic waves, such as high-energy X-rays, can also be measured using an electron conversion material that converts them into electrons. In this case, a high-Z material such as gold can be used as the electron conversion material. The electron conversion material 155 should be positioned and placed in a range such that the electrons emitted by the electron conversion material 155 cause the Pockels effect in the Pockels element 152. For example, a portion of the coating 154 may be made of the electron conversion material 155.

Furthermore, the detector 15b shown in Figure 5 differs from detector 15a in that it is equipped with a proton conversion material 156 instead of an electron conversion material 155. The proton conversion material 156 converts incident neutrons into protons. More specifically, the proton conversion material 156 emits a number of protons corresponding to the intensity of the neutrons incident on it. Therefore, when neutrons are incident on the proton conversion material 156, protons are emitted from it, and the electric field generated by these emitted protons causes the Pockels effect in the Pockels element 152. Thus, by using detector 15b, which includes the proton conversion material 156, the measurement target can be measured as neutron beams.

The proton conversion material 156 can be any material that converts neutrons into protons; for example, plastic may be used as the proton conversion material 156. Furthermore, the proton conversion material 156 should be positioned and placed in a range such that the protons emitted by the proton conversion material 156 cause the Pockels effect in the Pockels element 152. For example, a portion of the coating 154 may be made of the proton conversion material 156. In this way, by changing the configuration of the detector 15, the range of objects that can be measured can be broadened.

Furthermore, the detector 15c shown in Figure 5 has a Pockels element 152c at the end of the core of the optical fiber 151. Such a Pockels element 152c can be produced by polling (more specifically, glass polling) the glass core of the optical fiber 151. Such a detector 15c does not require microfabrication of Pockels crystals or attachment to the optical fiber 151 during manufacturing, thus reducing processing time and material costs. Also, the size (length) of the Pockels element 152c can be easily adjusted. However, if detection sensitivity is to be improved, it is preferable to have a configuration in which the Pockels element 152 is attached to the optical fiber 151, as shown in detectors 15, 15a, and 15b.

[Regarding detection sensitivity and resolution]
A simulation was performed to verify the detection sensitivity and resolution of measurement system 1. The results will be explained based on Figure 6. Figure 6 is a diagram illustrating the simulation used to verify the detection sensitivity and resolution of measurement system 1.

Here, the measurement target is assumed to be the laser pulse oscillated by an ultrashort pulse laser diode oscillator, and its pulse width is to be measured. A photocathode 18 is formed on one side of an optical fiber 151, and the laser pulse is irradiated onto it. The photocathode 18 emits photoelectrons upon irradiation with the laser pulse, and these photoelectrons cause the Pockels effect. The photocathode 18 can be formed, for example, by depositing a bialkali metal onto the surface of the optical fiber 151.

Furthermore, the detector 15c shown in Figure 5 will be used as the detector 15. The length of the Pockels element 152c in the detector 15c will be L, and the diameter of the optical fiber 151 will be D.

Here, it is known that the half-wavelength voltage of the Pockels element generated by ultraviolet poling is 100 V/cm. This means that when laser light is incident on a Pockels element to which a voltage of 100 V is applied, the polarization axis rotates by 90° while the laser light travels 1 cm through the Pockels element. If the rotation angle of the polarization axis is within the range of 0 to 90°, the change in light (signal) that has passed through the polarization separator 161 can be within the range of 0 to 1, making it suitable for polarization measurement.

When a laser is shone onto the photocathode 18, a number of photoelectrons corresponding to the laser intensity are generated from the photocathode 18. For example, when a laser with an energy of 1 nJ and a pulse width of 10 ps is shone, 2.5 × ^10⁹ photons hit the photocathode 18. In this case, assuming a photoelectron quantum efficiency of 20% for the photocathode 18, a total of 5 × ^10⁸ photoelectrons are generated from the photocathode 18 across the entire pulse width.

Figure 6 shows Model M1, a simplified model of the state in which photoelectrons are generated from the photocathode 18. As shown in Model M1, the generation of photoelectrons from the photocathode 18 forms a capacitor between the photocathode 18 and the opposite side of the Pockels element 152c in the optical fiber 151. The electrode area of this capacitor is D × L, and the electrode gap is D.

For example, if D = 125 μm, L = 100 μm, and the relative permittivity of the capacitor is 3, then 5 × ^10⁸ electrons will accumulate on the photocathode 18, which is one electrode of the capacitor, and the voltage of this capacitor will be 1500 V. Figure 6 also shows a graph illustrating the change in this voltage over time.

Furthermore, the rotation angle of the polarization axis is calculated by the product of the voltage and the optical path length. Since the chirp pulse laser makes one round trip through the Pockels element 152c, the optical path length through which the chirp pulse laser passes is 2 × L. Therefore, if L = 100 μm, the optical path length is 200 μm (0.02 cm).

Therefore, if the capacitor voltage is 1500V, the rotation angle of the polarization axis will be 1500V × 0.02cm = 30Vcm. As mentioned above, the half-wavelength voltage of the Pockels element 152c is 100V/cm, and at 100V, the rotation angle of the polarization axis is expected to rotate 90° for every 1cm. Therefore, the rotation angle at 30Vcm is predicted to be approximately 27°. Thus, it can be seen that laser pulses of the magnitude simulated in this study are sufficiently detectable by the measurement system 1.

Furthermore, the time resolution of the measurement system 1 depends on the pulse width setting of the chirp pulse laser and the thickness of the Pockels element used. For example, in the case of a Pockels element 152c with a length of 0.1 mm as used in the above simulation, the resolution is 1 ps, which is the time it takes for the chirp pulse laser to travel back and forth within the Pockels element 152c.

When a laser pulse with a pulse width of 10 ps is measured using measurement system 1, which has a time resolution of 1 ps, the pulse width of the resulting signal is expected to be 10.1 ps, based on the relationship √( ^10² + ^1² ). This degree of difference can be ignored as an error in pulse width measurement. The graph shown at the bottom of Figure 6 was created based on the calculation prediction, and this graph shows the time evolution of the electric field generated in the Pockels crystal, with the horizontal axis representing time and the vertical axis representing the electric field.

[Detector component configuration]
Measurement system 1 enables broadband, high-precision electromagnetic wave measurement. For example, advances in advanced information science are leading to higher frequencies of electromagnetic waves used in mobile and communication devices, and in the future, the use of electromagnetic waves in the THz range is becoming a possibility. Since 1 THz has a repetition period of 1 ps, measurement system 1 can also be used to measure 1 THz electromagnetic waves.

In measurement system 1, since the detector 15 is located at the tip of the optical fiber 151, the detector 15 is easy to handle. For example, with measurement system 1, it is easy to bring the detector 15 close to the communication unit of a mobile device and measure the waveform of the electromagnetic waves emitted by the communication unit.

Furthermore, by providing a grip on the detector 15, the usability of the measurement system 1 can be further improved. This will be explained with reference to Figure 7. Figure 7 shows an example configuration of the detector 15 equipped with a grip 20.

The grip 20 has a cylindrical shape that tapers towards the tip, resembling a pen. The center of the grip 20 is hollow, and the optical fiber 151 is inserted through this hollow. The optical fiber 151 is fixed within the hollow so that the Pockels element 152 is located near the tip of the grip 20.

By providing such a grip 20, the user of the measurement system 1 can stably hold the detector 15, and the Pockels element 152 can be easily brought close to the source of the electromagnetic waves to be measured. For example, delicate tasks such as measuring the waveform of electromagnetic waves emitted by a small communication unit in a mobile device at a very close distance to the communication unit can be easily performed with the detector 15 equipped with the grip 20.

[Spatial resolution time change measurement]
Measurement system 1 can perform multi-channel simultaneous measurement using multiple detectors 15, thereby enabling spatially resolved time-varying measurement. This will be explained with reference to Figure 8. Figure 8 shows an example configuration of measurement system 1a equipped with multiple detectors 15. Note that measurement system 1a also includes a detection laser emitter 11 and a fiber circulator 13, similar to measurement system 1, but these are omitted in Figure 8.

Measurement system 1a differs from measurement system 1 in that it includes multiple detectors 15 and an image generation device 30. To achieve spatially resolved measurement, multiple optical fibers 151 are bundled together, and the relative arrangement of the detectors 15 at their ends is fixed.

In the example shown in Figure 8, we assume a scenario where a laser with a non-uniform spatial pattern in front of the detector 15, where the time waveform differs at each location, is being measured. Specifically, this pattern is the three letters "ILE".

Multiple detectors 15 measure this pattern. In the example shown in Figure 8, 50 optical fibers 151 are bundled together. As schematically shown in Figure 8, which depicts the detector 15 viewed from the front, a total of 50 Pockels elements 152, each attached to the tip of one optical fiber 151, are fixed in an arrangement of 5 rows (rows 1 to 5) x 10 columns (columns A to J) on the same plane.

This 5x10 two-dimensional array is rearranged into a 1x50 one-dimensional array before reaching the analysis device 16. The analysis device 16 then records the time changes of the 1x50 measurement results (measurement results from row 1-column A to row 5-column J). The image generation device 30 then rearranges the above measurement results back into a 5x10 two-dimensional array. This allows for the recording of spatially resolved time changes.

As described above, the measurement system 1a includes multiple detectors 15. The analysis device 16 then analyzes the transmitted light that simultaneously passes through the Pockels elements 152 in each of the multiple detectors 15. This configuration allows for the measurement of the spatial distribution of the object being measured at the moment the transmitted light passes through each Pockels element 152. This is because the spatial positions of the Pockels elements 152 in each detector 15 are different.

Furthermore, the analysis device 16 detects whether or not the object to be measured has entered the detector 15 by analyzing the transmitted light. The image generation device 30 then generates an image in which the detection results from the analysis device 16 for each of the multiple detectors 15 are reflected in the pixel values of the pixels according to the spatial arrangement of the detectors 15.

This configuration allows for the automatic generation of an image showing the spatial distribution of the object being measured at the moment the transmitted light passes through each Pockels element 152. Such an image is suitable for applications such as understanding the behavior of the object being measured.

[Embodiment 2]
Other embodiments of the present invention will be described with reference to Figures 9 to 12. Components similar to those in the above embodiments will be given the same reference numerals, and their descriptions will be omitted. The measurement system 1d according to this embodiment differs from the measurement system 1 described in the above embodiments in that it uses the Stark effect instead of the Pockels effect to perform time-resolved measurement.

〔overview〕
Figure 9 is a diagram illustrating the overview of the measurement system 1d. As shown in the figure, the measurement system 1d includes a detector 15d and an analyzer 16d. Although not shown in the figure, the measurement system 1d also includes a detection laser emitter 11, similar to the measurement system 1.

The detector 15d is for detecting the object to be measured and comprises an optical fiber 151d, an electro-optic element 152d that generates an electro-optic effect using an electric field, and a reflector 153d. More specifically, the optical fiber 151d is connected to the electro-optic element 152d, and the electro-optic element 152d is connected to the reflector 153d. The reflector 153d has the same configuration as the reflector 153 in Embodiment 1 and reflects incident light. For example, silicon can be used as the reflector 153d.

As described above, the electro-optic element 152d is positioned between the reflector 153d and the end face of the optical fiber 151d. This configuration ensures that light incident from the optical fiber 151d toward the electro-optic element 152d (a chirp pulse laser, as detailed later) passes through the electro-optic element 152d, is reflected by the reflector 153d, and the reflected light passes through the electro-optic element 152d again and returns to the optical fiber 151d.

Specifically, the electro-optic element 152d is an element that generates the Stark effect in the presence of an electric field. The electro-optic element 152d can be any element that generates the Stark effect in the presence of an electric field; for example, an electro-optic polymer (EO) may be used as the electro-optic element 152d.

The analysis device 16d is a device that analyzes the detection results of the detector 15d, and includes a wavelength spectrometer 161d and an image sensor 162d. The analysis device 16d differs from the analysis device 16 of Embodiment 1 in that it does not include a polarization analyzer optical system. In the analysis device 16d, the wavelength spectrometer 161d spectrally separates the light emitted from the detector 15d (transmitted light that has passed through the electro-optic element 152d, as will be described in detail later) by wavelength and forms an image on the image sensor 162d.

[Measurement principle]
Next, the measurement principle of the measurement system 1d will be explained based on Figure 9, as described above. In the measurement system 1d, as with the measurement system 1 of Embodiment 1, a detection laser emitter 11 is used that emits laser light consisting of pulses whose wavelength changes continuously over time, i.e., a chirp pulse laser. Note that the chirp pulse laser used in this embodiment does not need to be linearly polarized.

The chirp pulse laser emitted by the detection laser emitter 11 is guided to the electro-optic element 152d via the optical fiber 151d. The chirp pulse laser then passes through the electro-optic element 152d, is reflected by the reflector 153d, and passes through the electro-optic element 152d again to return to the optical fiber 151d.

Here, when the object to be measured is incident on the reflector 153d during the period when it is passing through the electro-optic element 152d, an electric field is generated in the electro-optic element 152d due to the incident light, and the Stark effect occurs. As a result of the Stark effect, the peak wavelength of light absorption of the electro-optic element 152d shifts to a longer or shorter wavelength. In other words, as shown in graph 901 of Figure 9, the absorption rate of the electro-optic element 152d changes during the period when the object to be measured is incident.

As a result, a portion of the wavelength range of the chirp pulse laser that passes through the electro-optic element 152d is affected by the change in the absorption rate of the electro-optic element 152d. More specifically, the intensity of the chirp pulse laser that passes through the electro-optic element 152d changes in the wavelength range that passes through during the period when the electric field is generated, i.e., during the period when the object being measured was incident.

Furthermore, the time lag between the generation of the electric field and the occurrence of the Stark effect is extremely short, similar to the Pockels effect. Therefore, by considering the period during which the intensity of the chirp pulse laser changes as the period during which the object being measured was incident, extremely high-precision time-resolved measurements become possible.

Specifically, as shown in Figure 9, a chirp-pulsed laser that has passed through the electro-optic element 152d is incident on the wavelength spectrometer 161d via the optical fiber 151d. The chirp-pulsed laser that has passed through the wavelength spectrometer 161d is spectrally separated according to its wavelength and imaged on the image sensor 162d. Since the emission angle of the light from the wavelength spectrometer 161d is determined according to the wavelength of the light, the image formation position on the image sensor 162d indicates the wavelength of the chirp-pulsed laser. The image sensor 162d can record the light intensity for each wavelength, as shown in Graph 902.

Furthermore, in chirp pulse lasers, wavelength and time correspond one-to-one. That is, as shown in graph 903 of Figure 9, time t can be expressed in terms of wavelength λ, and wavelength changes can be directly interpreted as time changes. Therefore, from the light intensity data for each wavelength shown in graph 902, the time changes in light intensity shown in graph 904 can be identified.

Thus, time-resolved measurements can be performed using the measurement system 1d. Furthermore, the time resolution of the measurement system 1d, like that of the measurement system 1, depends on the pulse width of the chirp pulse laser used. For example, when using a chirp pulse laser with a pulse width of 100 ps (wavelength changes at 0.1 ps/1 nm) and a wavelength spectrometer 161d with a resolution of 1 nm, the time resolution of the measurement system 1d is 1.0 ps.

[Specific examples of electro-optical elements]
A specific example of the electro-optic element 152d will be explained based on Figure 10. Figure 10 shows the structure of a photoelectric polymer 101, which is an example of an electro-optic element 152d that produces the Stark effect, and its light absorption characteristics.

The structure of the portion of the photoelectric polymer 101 enclosed by the dashed line changes due to the electric field. This change in the structure of that portion alters the absorption spectrum of the photoelectric polymer 101.

Specifically, the absorption spectrum of the photoelectric polymer 101, unaffected by an electric field, is a downward-sloping curve shown by the dashed line graph 1021 in Figure 10. When a positive electric field (+E) is applied to the photoelectric polymer 101, the absorption spectrum shifts to the longer wavelength side, resulting in the curve shown by the dashed line graph 1022. Conversely, when a negative electric field (-E) is applied to the photoelectric polymer 101, the absorption spectrum shifts to the shorter wavelength side, resulting in the curve shown by the double-dashed line graph 1023. The amount of shift depends on the strength of the electric field (the stronger the electric field, the greater the shift).

Therefore, if laser light with a wavelength within the range in which the absorption spectrum of the photoelectric polymer 101 fluctuates due to the electric field is incident on the photoelectric polymer 101, the effect of the fluctuation in the absorption spectrum will appear in the transmitted light after the laser light passes through the photoelectric polymer 101.

For example, if a laser beam with the laser spectrum shown as 1024 in Figure 10 is incident on the photoelectric polymer 101, and a positive electric field is simultaneously applied to the photoelectric polymer 101, most of the laser beam will be absorbed by the photoelectric polymer 101. Therefore, in this case, the period during which the intensity of the transmitted light passing through the photoelectric polymer 101 is relatively low can be said to be the period during which a positive electric field was applied.

On the other hand, if this laser light is incident on the photoelectric polymer 101 and a negative electric field is applied to the photoelectric polymer 101 simultaneously, most of the laser light will pass through the photoelectric polymer 101. Therefore, in this case, the period during which the intensity of the transmitted light that has passed through the photoelectric polymer 101 is relatively high can be said to be the period during which the negative electric field was applied.

From the above, it can be seen that the wavelength of the chirp pulse laser and the type of the electro-optic element 152d should be selected such that the influence of fluctuations in the electric field around the electro-optic element 152d is reflected in the wavelength of the chirp pulse laser transmitted through the electro-optic element 152d.

[Experimental Example]
An experiment was conducted to perform time-resolved measurements of ultrafast electrons and X-rays using the Stark effect. This experiment will be explained with reference to Figure 11. Figure 11 is a schematic diagram of the measurement system 1e used in the experiment.

The measurement system 1e shown in Figure 11 includes a detection laser emitter 11e, a detector 15e, and an analysis device 16e. The measurement system 1e also includes an optical fiber 21e connected to the detection laser emitter 11e, and an LFEX (Laser for Fast Ignition Experiment) laser oscillator 22e that emits ultrafast electrons and X-rays to be measured. Furthermore, the measurement system 1e includes a vacuum feedthrough 23e, a timing delay adjuster 24e, a fiber circulator 13e, a Yb fiber amplifier 25e, and an optical shutter 26e. The optical fiber 21e is a polarization-maintaining fiber.

Furthermore, the detection laser emitter 11e includes a pulse stretcher 111e, an optical shutter 112e, and a regenerative amplifier 113e. The detector 15e includes an optical fiber 151e, an electro-optic element 152e, and a reflector 153e. The electro-optic element 152e is the photoelectric polymer shown in Figure 10. The optical fiber 151e may also be a polarization-maintaining fiber, similar to the optical fiber 21e, but polarization retention is not required for the optical fiber 151e.

The LFEX laser oscillator 22e is an oscillator capable of emitting an ultra-high-intensity laser. In the measurement system 1e, the ultrafast electrons and X-rays generated by the LFEX laser oscillator 22e are detected by the detector 15e inside the vacuum feedthrough 23e.

In this experiment, the detector 15e, specifically the electro-optic element 152e, was positioned 65 mm away from the focal point of the LFEX laser oscillator 22e. However, the electro-optic element 152e may be positioned as close to the focal point as possible. Furthermore, in the measurement system 1e, the object to be measured may be incident on the front of the electro-optic element 152e, as shown in the figure. This is because, unlike the Pockels effect, the Stark effect does not produce differences in effect depending on the direction of incidence of the object being measured. This is very advantageous for experimental setups involving ultra-high-intensity lasers.

Furthermore, if a high-intensity object to be measured is incident on the front of the electro-optic element 152e, the detector 15e may be damaged. However, even in such a case, the chirp pulse laser that passes through the electro-optic element 152e reflects the influence of the Stark effect, so the measurement results are not affected. Also, since the object to be measured does not incident on the analysis device 16e, the analysis device 16e is not damaged, and measurement can be repeated by replacing the damaged detector 15e.

Furthermore, the reflector 153e and electro-optic element 152e can be miniaturized to approximately 1 mm, making it possible to install them in extreme environments such as the focal point of the LFEX laser oscillator 22e. Thus, the measurement system 1e can be used in environments where conventional measurement devices are incapable, while also achieving significant cost reductions.

In the measurement system 1e, a portion of the oscillator light (chirp pulsed laser) from the LFEX laser oscillator 22e is emitted to the detection laser emitter 11e via the optical fiber 21e. The pulse width of this oscillator light is adjusted by the pulse stretcher 111e. After pulse width adjustment, the emitted light is energized by the regenerative amplifier 113e via the optical shutter 112e and emitted to the time delay adjuster 24e. The detection laser emitter 11e is adjusted so that the emitted emitted light is a chirp pulsed laser with a wavelength of 1010-1050 nm (full width at half maximum of 20 nm), an energy of 100 nJ, and a pulse width of 500 ps.

Furthermore, the timing of the chirp pulse laser emitted from the detection laser emitter 11e entering the electro-optic element 152e and the timing of the ultrafast electrons and X-rays generated by the LFEX laser oscillator 22e entering the detector 15e were synchronized (more precisely, the chirp pulse laser was transmitted through the electro-optic element 152e during the period when the electric field change caused by the ultrafast electrons and X-rays occurred) using the time delay adjuster 24e.

The chirp pulsed laser, after time adjustment by the time delay adjuster 24e, is incident on the electro-optic element 152e via the fiber circulator 13e, Yb fiber amplifier 25e, and optical fiber 151e. The energy of the chirp pulsed laser at the time of incidence was 1 μJ. Furthermore, the energy of the chirp pulsed laser when it was reflected by the reflector 153e and returned to the optical fiber 151e was 1 nJ.

The chirp pulse laser reflected by the reflector 153e is amplified by the Yb fiber amplifier 25e and then incident on the analyzer 16e via the fiber circulator 13e and optical shutter 26e. At this time, the energy of the chirp pulse laser was less than 100 nJ.

Furthermore, the total length of the optical fiber 151e is 40m, and the analysis device 16e is located in a different room from the room where the LFEX laser oscillator 22e is installed. Thus, the measurement system 1e can bring the detector 15e to the location where the detection target occurs to perform detection, and the analysis of the detection results can be performed away from the location where the detection target occurs.

The configuration of the analyzer 16e is the same as that of the analyzer 16d shown in Figure 9, and it performs spectral analysis using a wavelength spectrometer and detects the signal with an image sensor. The analyzer 16e may also be a CCD spectrometer using, for example, a CCD (charge-coupled device) image sensor. Figure 11 shows data 110, which represents the analysis results obtained by the analyzer 16e. The horizontal axis of data 110 represents wavelength, and the brightness value represents intensity. Thus, the analyzer 16e allows obtaining a signal as a wavelength spectrum from a wavelength spectrometer.

As mentioned above, wavelength can be converted to time. In this experimental example, as shown by the upper and lower scales of data 110, the wavelength range of 1010 nm to 1050 nm corresponds to the time range of 800 ps to 0 ps. Therefore, data 110 can be said to represent the results of time-resolved measurement.

[Time-series changes in the intensity of the detected target]
Figure 12 shows the time-series changes in the intensity of ultrafast electrons and X-rays generated using the data 110 shown in Figure 11. More specifically, graph 1202 in Figure 12 shows the time-series changes in the intensity of ultrafast electrons and X-rays.

As shown in graphs 1021-1023 of Figure 10, the absorption rate of the photoelectric polymer decreases as the wavelength increases. Therefore, before measuring data 110, measurements were performed by emitting only a chirp pulse laser to the detector 15e without incidenting the object to be detected. Using this measurement result as a baseline, the measurement results shown in data 110 were processed to obtain graph 1202 shown in Figure 12.

Furthermore, Figure 12 includes Graph 1203, which shows the time resolution of the measurement system 1e, along with Graph 1202. Graph 1203 indicates that the time resolution of the measurement system 1e is approximately 4 ps. The time resolution of the measurement system 1e is determined by the pulse width of the chirp pulse laser used and the resolution of the wavelength spectrometer equipped in the analysis device 16e. This time resolution is significantly lower than the previous highest time resolution of 25 ps in high-energy electron and X-ray measurements in this field.

Furthermore, Figure 12 also shows graph 1203, which illustrates the time-dependent changes in the charge of X-rays and ultra-high-energy electrons generated by the LFEX laser oscillator 22e, calculated through simulation.

Graph 1202 shows a downward-convex peak near 0 ps and an upward-convex peak near 50 ps. The downward-convex peak is understood to correspond to X-rays propagating at the speed of light, while the upward-convex peak corresponds to electrons. Graph 1202 clearly shows how electrons are incident 50-80 ps after the X-rays traveling at the speed of light. This is in good agreement with the simulation results shown in Graph 1203.

Furthermore, we have successfully obtained measurement results similar to those in Graph 1202 multiple times. It has also been confirmed that when the timing of incident on the object being measured and the timing of incident on the chirp-pulsed laser are staggered, measurement results like those in Graph 1202 cannot be obtained.

As described above, the measurement system 1e enables time-resolved measurements of X-rays and ultrafast electrons. Of course, the measurement system 1e is not limited to X-rays and ultrafast electrons; it can be used to measure any target that generates an electric field in the electro-optic element 152e. Such measurements are extremely useful, for example, in scientific research and industry dealing with ultrashort pulse phenomena. Furthermore, the detectors 15d and 15e of this embodiment can also be used as detectors in the measurement system 1a shown in Figure 8.

〔summary〕
Each of the measurement systems described in Embodiments 1 and 2 above is a measurement system that performs time-resolved measurement of a measurement target, and includes a detection laser emitter, a detector equipped with an optical fiber and an electro-optic element that generates an electro-optic effect using an electric field, and an analysis device. The detection laser emitter emits laser light consisting of pulses whose wavelength changes continuously over time, the optical fiber guides the laser light to the electro-optic element where an electro-optic effect is generated by the electric field generated by the measurement target incident on the detector, and also guides the transmitted light that has passed through the electro-optic element to the analysis device, and the analysis device is configured to analyze the transmitted light based on its wavelength.

According to the above configuration, laser light consisting of pulses with continuously changing wavelengths over time is guided to an electro-optic element where the electro-optic effect occurs due to the electric field generated by the object being measured. Therefore, some wavelength components of the laser light transmitted through the electro-optic element are affected by the electro-optic effect. Consequently, by guiding the transmitted light through the electro-optic element to an analysis device and analyzing the transmitted light based on its wavelength, it becomes possible to determine the presence or absence of wavelength components affected by the electro-optic effect and to identify those wavelength components.

Furthermore, the above configuration uses laser light consisting of pulses whose wavelength continuously changes over time. In other words, in this laser light, there is a one-to-one correspondence between wavelength and time. Therefore, if the wavelength component affected by the electro-optic effect in the laser light can be identified, the time during which the electro-optic effect occurred, i.e., the time during which the object being measured was near the detector, can be determined. Thus, the above configuration makes time-resolved measurement possible.

Furthermore, with the above configuration, the light entering the analysis device is the transmitted light from the detection laser emitter that has passed through the electro-optic element; the object to be detected does not enter the analysis device. Therefore, it becomes possible to perform time-resolved measurements of various measurement targets, such as high-intensity light and lasers, which are difficult to measure with streak cameras.

Furthermore, the detectors described in Embodiments 1 and 2 above are detectors used in a measurement system that performs time-resolved measurement of a target object, and each detector comprises an optical fiber and an electro-optic element that generates an electro-optic effect using an electric field. The optical fiber guides laser light consisting of pulses whose wavelength continuously changes over time to the electro-optic element, and also guides the laser light to an analytical device that analyzes the transmitted light after it has passed through the electro-optic element based on its wavelength.

As described above, by using such detectors, it becomes possible to perform time-resolved measurements of various measurement targets, such as high-intensity light and lasers, which are difficult to measure with streak cameras.

Furthermore, as described in Embodiment 2, the electro-optic element may be an element that generates the Stark effect by an electric field. In this case, the analytical apparatus may comprise a wavelength spectrometer for spectrally analyzing the transmitted light and an image sensor, and the optical components of the transmitted light spectrally analyzed by the wavelength spectrometer may be imaged at a position on the image sensor corresponding to the wavelength of those optical components.

As described above, in transmitted light passing through an electro-optic element where the Stark effect occurs, the intensity of some frequency components changes. Therefore, with the above configuration, which images the optical components of the transmitted light spectrally separated by a wavelength spectrometer at a position on the image sensor corresponding to the wavelength of those optical components, an image showing wavelength components affected by the Stark effect can be obtained. The laser light incident on the electro-optic element consists of pulses whose wavelength changes continuously over time, and since there is a one-to-one correspondence between wavelength and time, the above image shows the result of time-resolved measurement. In other words, time-resolved measurement is realized with the above configuration.

Furthermore, as described in Embodiment 1, the electro-optic element may be an element that generates the Pockels effect by an electric field. In this case, the analysis apparatus may comprise a polarization separator, a wavelength spectrometer, and an image sensor. The polarization separator emits the light component whose polarization state has changed after passing through the Pockels element into the wavelength spectrometer, and the wavelength spectrometer images the light component at a position on the image sensor corresponding to the wavelength of the light component. With this configuration, an image showing the wavelength component affected by the Pockels effect can be obtained. This image also shows the results of time-resolved measurement.

Furthermore, the electro-optic element described above may be an element that generates electro-optic effects other than the Pockels effect and the Stark effect. For example, an element that generates the Kerr effect may be used as the electro-optic element. In this case, time-resolved measurement can be performed with the same configuration as in Embodiment 1.

The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of the present invention.

1, 1a, 1d, 1e Measurement system 11, 11e Detection laser emitter 15, 15a, 15b, 15c, 15d, 15e Detector 151, 151d, 151e Optical fiber 152, 152c Pockels element 153, 153d, 153e Reflector 155 Electron conversion material 156 Proton conversion material 16, 16a, 16d, 16e Analysis device 161 Polarization separation device 162 Wavelength spectrometer 162a Polarization beam splitter 163a Wavelength spectrometer 30 Image generation device 152d, 152e Electro-optic element 161d Wavelength spectrometer 162d Image sensor

Claims (2)

A measurement system that performs time-resolved measurement of the object to be measured,
It includes a detection laser emitter, a detector equipped with an electro-optic element that generates an electro-optic effect using an optical fiber and an electric field, and an analysis device.
The above-mentioned detection laser emission device emits laser light consisting of pulses whose wavelength continuously changes over time.
In the above detector, the electro-optic element is fixed to the end face of the optical fiber.
The optical fiber guides the laser light to the electro-optic element where an electro-optic effect occurs due to the electric field generated by the object to be measured that is incident on the detector, and also guides the transmitted light that has passed through the electro-optic element to the analysis device.
The above analytical device analyzes the transmitted light based on its wavelength.
The above detector is removable from the above measurement system.
The above electro-optic element is an element that generates the Stark effect by an electric field.
The above-mentioned analytical device is a measurement system comprising a wavelength spectrometer for spectrally analyzing the transmitted light and an image sensor, wherein the optical components of the transmitted light spectrally analyzed by the wavelength spectrometer are imaged at a position on the image sensor corresponding to the wavelength of the optical components . A detector used in a measurement system that performs time-resolved measurement of the object to be measured,
It comprises an electro-optic element that generates an electro-optic effect using an optical fiber and an electric field,
The above electro-optic element is fixed to the end face of the optical fiber.
The optical fiber guides laser light consisting of pulses whose wavelength continuously changes over time to the electro-optic element, and also guides the laser light to an analytical device that analyzes the transmitted light after it has passed through the electro-optic element based on its wavelength.
It can be removed from the above measurement system.
The above electro-optic element is a detector that generates the Stark effect using an electric field .