JP6600201B2 - Velocity measuring device and velocity measuring method - Google Patents
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Description
本発明は、試料中における衝撃波の伝搬速度を測定する装置および方法に関する。 The present invention relates to an apparatus and method for measuring the propagation speed of a shock wave in a sample.
試料への高強度パルスレーザ光の照射による衝撃波発生に基づく高圧状態を利用して試料を改変することができる。また、試料中の衝撃波の伝搬速度を測定することで、試料中の圧力を推定することができる。衝撃波の伝搬速度を測定する技術が非特許文献１に記載されている。この文献に記載された速度測定技術では、ＶＩＳＡＲ（Velocity Interferometer System for Any Reflector）と呼ばれる速度干渉計が用いられる。ＶＩＳＡＲでは、干渉縞の変化をストリークカメラにより撮影し、その撮影した干渉縞の変化に基づいて衝撃波の伝搬速度を測定する。 The sample can be modified using a high-pressure state based on the generation of shock waves by irradiation of the sample with high-intensity pulsed laser light. Further, the pressure in the sample can be estimated by measuring the propagation speed of the shock wave in the sample. A technique for measuring the propagation speed of shock waves is described in Non-Patent Document 1. In the speed measurement technique described in this document, a speed interferometer called a VISAR (Velocity Interferometer System for Any Reflector) is used. In VISAR, changes in interference fringes are photographed by a streak camera, and the propagation speed of shock waves is measured based on the photographed changes in interference fringes.
ＶＩＳＡＲは、ストリークカメラを用いることから、高価である。また、ＶＩＳＡＲでは、撮影される像が時間軸と空間軸とを有しており、そのうち空間軸の方向に干渉縞が現れるので、速度測定の分解能が低い。 VISAR is expensive because it uses a streak camera. Further, in VISAR, a captured image has a time axis and a space axis, and interference fringes appear in the direction of the space axis, so that the resolution of speed measurement is low.
本発明は、上記問題点を解消する為になされたものであり、衝撃波の速度測定の分解能が高く安価に構成することができる速度測定装置および速度測定方法を提供することを目的とする。 The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a speed measuring device and a speed measuring method that can be configured at low cost with high resolution of shock wave speed measurement.
本発明の速度測定装置は、試料中における衝撃波の伝搬速度を測定する装置であって、瞬時周波数が時間的に変化するチャープパルス光を２分岐して第１分岐光および第２分岐光とし、第１分岐光をミラーへ出力し、第２分岐光を試料へ出力し、ミラーで反射された第１分岐光と試料中の衝撃波で反射された第２分岐光とを合波して当該合波光を出力する干渉光学系と、合波光を分光して合波光の周波数干渉縞を求める分光器と、を備え、周波数干渉縞に基づいて衝撃波の伝搬速度を求める。 The velocity measuring device of the present invention is a device for measuring the propagation velocity of a shock wave in a sample, and bifurcates a chirped pulse light whose instantaneous frequency temporally changes into a first branched light and a second branched light, The first branched light is output to the mirror, the second branched light is output to the sample, and the first branched light reflected by the mirror and the second branched light reflected by the shock wave in the sample are combined to perform the combining. An interference optical system that outputs wave light and a spectroscope that divides the combined light to obtain a frequency interference fringe of the combined light are provided, and the propagation speed of the shock wave is obtained based on the frequency interference fringe.
本発明の速度測定方法は、試料中における衝撃波の伝搬速度を測定する方法であって、干渉光学系を用いて、瞬時周波数が時間的に変化するチャープパルス光を２分岐して第１分岐光および第２分岐光とし、第１分岐光をミラーへ出力し、第２分岐光を試料へ出力し、ミラーで反射された第１分岐光と試料中の衝撃波で反射された第２分岐光とを合波して当該合波光を出力し、分光器を用いて合波光を分光して合波光の周波数干渉縞を求め、周波数干渉縞に基づいて衝撃波の伝搬速度を求める。 The velocity measurement method of the present invention is a method for measuring the propagation velocity of a shock wave in a sample, and uses an interference optical system to divide a chirped pulse light whose instantaneous frequency changes with time into a first branched light. And the second branched light, the first branched light is output to the mirror, the second branched light is output to the sample, the first branched light reflected by the mirror and the second branched light reflected by the shock wave in the sample, The combined light is output, and the combined light is dispersed using a spectroscope to determine the frequency interference fringe of the combined light, and the propagation speed of the shock wave is determined based on the frequency interference fringe.
本発明では、パルス光を伸長する伸長部と、その伸長されたパルス光を圧縮する圧縮部とを含む衝撃波発生用光源を用いて、その圧縮されたパルス光を試料に照射して衝撃波を発生させ、伸長部により伸長されて出力されたパルス光の一部を分岐してチャープパルス光として用いるのが好適である。 In the present invention, a shock wave is generated by irradiating a specimen with the compressed pulsed light using a light source for generating a shock wave including an extending part for extending the pulsed light and a compressing part for compressing the extended pulsed light. It is preferable that a part of the pulse light that is output by being extended by the extension unit is branched and used as chirped pulse light.
本発明では、周波数干渉縞に基づいて試料の界面への衝撃波の到達時刻を求め、衝撃波の到達時刻および発生時刻に基づいて衝撃波の伝搬時間を求め、衝撃波の伝搬時間および伝搬距離に基づいて衝撃波の伝搬速度を求めることができる。周波数干渉縞に基づいて試料中の衝撃波の伝搬時間を求め、衝撃波の伝搬時間および伝搬距離に基づいて衝撃波の伝搬速度を求めることもできる。また、周波数干渉縞の周期に基づいて衝撃波の伝搬速度を求めることもできる。 In the present invention, the arrival time of the shock wave at the interface of the sample is obtained based on the frequency interference fringe, the propagation time of the shock wave is obtained based on the arrival time and generation time of the shock wave, and the shock wave is obtained based on the propagation time and propagation distance of the shock wave. Can be obtained. The propagation time of the shock wave in the sample can be obtained based on the frequency interference fringes, and the propagation speed of the shock wave can be obtained based on the propagation time and propagation distance of the shock wave. It is also possible to determine the propagation speed of the shock wave based on the frequency interference fringe period.
本発明によれば、衝撃波の速度測定の分解能が高く安価に装置を構成することができる。 According to the present invention, it is possible to configure a device at a low cost with a high resolution of shock wave velocity measurement.
以下、添付図面を参照して、本発明を実施するための形態を詳細に説明する。なお、図面の説明において同一の要素には同一の符号を付し、重複する説明を省略する。本発明は、これらの例示に限定されるものではなく、特許請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。 DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. The present invention is not limited to these exemplifications, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.
図１は、本実施形態の速度測定装置１の構成を示す図である。速度測定装置１は、干渉光学系１０、分光器２０および衝撃波発生用光源３０を備える。また、速度測定装置１は、ミラー４１〜４６、ビームスプリッタ４７、レンズ５１〜５３および移動部５４を備える。干渉光学系１０は、マイケルソン干渉計を構成しており、ビームスプリッタ１１、ミラー１２、ＮＤフィルタ１３および移動部１４を含む。衝撃波発生用光源３０は、伸長部３１、増幅部３２、圧縮部３３およびビームスプリッタ３４を含む。 FIG. 1 is a diagram showing a configuration of a speed measuring device 1 according to the present embodiment. The velocity measuring device 1 includes an interference optical system 10, a spectroscope 20, and a shock wave generating light source 30. The speed measuring device 1 includes mirrors 41 to 46, a beam splitter 47, lenses 51 to 53, and a moving unit 54. The interference optical system 10 forms a Michelson interferometer, and includes a beam splitter 11, a mirror 12, an ND filter 13, and a moving unit 14. The shock wave generating light source 30 includes an expansion unit 31, an amplification unit 32, a compression unit 33, and a beam splitter 34.
衝撃波発生用光源３０の伸長部３１は、入力したパルス光をパルス伸長して、チャープパルス光を生成する。増幅部３２は、伸長部３１により生成されたチャープパルス光を増幅する。圧縮部３３は、増幅部３２により増幅されたチャープパルス光をパルス圧縮して、高強度の衝撃波発生用レーザ光を生成し出力する。例えば、この衝撃波発生用レーザ光のパルス幅は１ピコ秒以下であり、強度の尖頭値は１０１４Ｗ／ｃｍ２以上である。 The extension unit 31 of the shock wave generating light source 30 generates a chirped pulse light by extending the input pulsed light. The amplification unit 32 amplifies the chirped pulse light generated by the extension unit 31. The compressing unit 33 pulse-compresses the chirped pulse light amplified by the amplifying unit 32 to generate and output a high-intensity shock wave generating laser beam. For example, the pulse width of the laser beam for generating a shock wave is 1 picosecond or less, and the peak value of the intensity is 10 14 W / cm 2 or more.
衝撃波発生用光源３０から出力された衝撃波発生用レーザ光は、ミラー４１，４２およびレンズ５１を経て、試料９０の第１主面９１に照射される。試料９０の第１主面９１に衝撃波発生用レーザ光が照射されると、第１主面９１において衝撃波が発生して高圧状態となり、第１主面９１近傍の領域が改変される。例えば、照射前に単結晶であったものが、照射後に多結晶粒の多層構造に改変される。第１主面９１において発生した衝撃波は、対向する第２主面９２へ伝搬して行く。試料９０中の衝撃波の伝搬速度を測定することで、衝撃波発生用レーザ光の照射に因る試料９０の圧力を推定することができる。 The shock wave generating laser light output from the shock wave generating light source 30 is applied to the first main surface 91 of the sample 90 through the mirrors 41 and 42 and the lens 51. When the first main surface 91 of the sample 90 is irradiated with the laser beam for generating the shock wave, a shock wave is generated on the first main surface 91 to be in a high pressure state, and the region near the first main surface 91 is modified. For example, what was a single crystal before irradiation is changed into a multilayer structure of polycrystalline grains after irradiation. The shock wave generated on the first main surface 91 propagates to the opposing second main surface 92. By measuring the propagation speed of the shock wave in the sample 90, the pressure of the sample 90 due to the irradiation of the shock wave generating laser beam can be estimated.
衝撃波発生用光源３０の伸長部３１と増幅部３２との間にビームスプリッタ３４が設けられている。このビームスプリッタ３４は、伸長部３１により伸長されて出力されたチャープパルス光の一部を分岐して出力する。ビームスプリッタ３４により分岐されて出力されたチャープパルス光は、ミラー４３〜４６、ビームスプリッタ４７およびレンズ５２，５３を経て干渉光学系１０に入力される。 A beam splitter 34 is provided between the extension part 31 and the amplification part 32 of the light source 30 for generating shock waves. The beam splitter 34 branches and outputs a part of the chirped pulse light that has been extended and output by the extension unit 31. The chirped pulse light branched and output by the beam splitter 34 is input to the interference optical system 10 through the mirrors 43 to 46, the beam splitter 47, and the lenses 52 and 53.
ミラー４３とミラー４４との間のチャープパルス光の光路と、ミラー４５とミラー４６との間のチャープパルス光の光路とは、互いに平行である。移動部５４は、前記光路に平行な方向にミラー４４，４５を移動させる。この移動により、試料９０の第１主面９１に衝撃波発生用レーザ光が照射されるタイミングに対して、試料９０の第２主面９２にチャープパルス光が照射されるタイミングを調整することができる。 The optical path of the chirped pulse light between the mirror 43 and the mirror 44 and the optical path of the chirped pulse light between the mirror 45 and the mirror 46 are parallel to each other. The moving unit 54 moves the mirrors 44 and 45 in a direction parallel to the optical path. With this movement, the timing at which the chirp pulse light is irradiated onto the second main surface 92 of the sample 90 can be adjusted with respect to the timing at which the first main surface 91 of the sample 90 is irradiated with the laser light for generating shock waves. .
干渉光学系１０のビームスプリッタ１１は、レンズ５３から到達したチャープパルス光を２分岐して第１分岐光および第２分岐光とし、第１分岐光をミラー１２へ出力し、第２分岐光を試料９０へ出力する。また、ビームスプリッタ１１は、ミラー１２で反射された第１分岐光と試料９０で反射された第２分岐光とを合波して、当該合波光を出力する。試料９０における第２分岐光の反射は、試料９０の第２主面９２で発生する他、第１主面９１で発生する場合があり、試料９０中を伝搬する衝撃波で発生する場合もある。 The beam splitter 11 of the interference optical system 10 bifurcates the chirped pulse light reaching from the lens 53 into the first branched light and the second branched light, outputs the first branched light to the mirror 12, and outputs the second branched light. Output to the sample 90. The beam splitter 11 combines the first branched light reflected by the mirror 12 and the second branched light reflected by the sample 90, and outputs the combined light. The reflection of the second branched light on the sample 90 may occur on the first main surface 91 in addition to the second main surface 92 of the sample 90, and may also occur on a shock wave propagating through the sample 90.
ビームスプリッタ１１とミラー１２との間の第１分岐光の光路上にＮＤフィルタ１３が設けられている。このＮＤフィルタ１３は、ビームスプリッタ１１に戻ってくる第１分岐光および第２分岐光それぞれの強度を互いに同程度として、分光器２０により取得される周波数干渉縞（後述）のコントラストを改善する。移動部１４は、ビームスプリッタ１１とミラー１２との間の光路に平行な方向にミラー１２を移動させる。この移動により、ビームスプリッタ１１による分岐から合波までの第１分岐光と第２分岐光との間の光路長差を調整することができる。 An ND filter 13 is provided on the optical path of the first branched light between the beam splitter 11 and the mirror 12. The ND filter 13 improves the contrast of frequency interference fringes (described later) acquired by the spectroscope 20 by making the intensities of the first branched light and the second branched light returning to the beam splitter 11 comparable. The moving unit 14 moves the mirror 12 in a direction parallel to the optical path between the beam splitter 11 and the mirror 12. By this movement, the optical path length difference between the first branched light and the second branched light from the branching to the multiplexing by the beam splitter 11 can be adjusted.
ビームスプリッタ１１から出力された合波光は、レンズ５３，５２およびビームスプリッタ４７を経て分光器２０に入力される。レンズ５３，５２は、試料９０の像を分光器２０の撮像面に結像する。分光器２０は、その結像された合波光を分光して合波光のスペクトル（周波数干渉縞）を求める。 The combined light output from the beam splitter 11 is input to the spectroscope 20 through the lenses 53 and 52 and the beam splitter 47. The lenses 53 and 52 form an image of the sample 90 on the imaging surface of the spectrometer 20. The spectroscope 20 obtains a spectrum (frequency interference fringes) of the combined light by dispersing the imaged combined light.
本実施形態の速度測定方法は、このような構成の速度測定装置１を用いて、分光器２０により取得された周波数干渉縞に基づいて、試料９０中を伝搬する衝撃波の伝搬速度を求める。 The velocity measuring method of the present embodiment uses the velocity measuring device 1 having such a configuration to obtain the propagation velocity of the shock wave propagating through the sample 90 based on the frequency interference fringes acquired by the spectrometer 20.
次に、分光器２０により取得される周波数干渉縞について数式を用いて説明する。ミラー１２により反射されてビームスプリッタ１１に戻ってきた第１分岐光の電場Ｅ１(ｔ)を下記（１）式で表す。ここで、ｉは虚数単位である。ｔは時刻を表す。τは時間波形の包絡線関数を規定する定数である。ω０は中心周波数を表し、ω０＋ａｔは瞬時周波数を表す。チャープパルス光は、瞬時周波数が時間的に変化する。図２は、（１）式で表される第１分岐光（チャープパルス光）の時間波形の一例を示す図である。（１）式を変形すると下記（２）式のように表される。 Next, frequency interference fringes acquired by the spectroscope 20 will be described using mathematical expressions. The electric field E 1 (t) of the first branched light reflected by the mirror 12 and returning to the beam splitter 11 is expressed by the following equation (1). Here, i is an imaginary unit. t represents time. τ is a constant that defines the envelope function of the time waveform. ω 0 represents the center frequency, and ω 0 + at represents the instantaneous frequency. The instantaneous frequency of chirped pulse light changes with time. FIG. 2 is a diagram illustrating an example of a time waveform of the first branched light (chirp pulse light) represented by the equation (1). When formula (1) is modified, it is expressed as formula (2) below.
試料９０の反射面が静止している場合には、試料９０からビームスプリッタ１１に戻ってきた第２分岐光の電場Ｅ２(ｔ)は、下記（３）式で表される。ここで、２Δｌは、ビームスプリッタ１１による分岐から合波までの第１分岐光と第２分岐光との間の光路長差である。 When the reflecting surface of the sample 90 is stationary, the electric field E 2 (t) of the second branched light returning from the sample 90 to the beam splitter 11 is expressed by the following equation (3). Here, 2Δl is an optical path length difference between the first branched light and the second branched light from the branching to the multiplexing by the beam splitter 11.
ビームスプリッタ１１から出力されて干渉計２０により受光される合波光のパワースペクトルは下記（４）式で表される。ここで、Ｓ０(ω)は第１分岐光のスペクトルであり、Ｐ０(ω)は第１分岐光のパワースペクトルである。試料９０の反射面が静止していている場合、分光器２０は、このような周波数干渉縞を取得することができる。この周波数干渉縞の周期は、第１分岐光と第２分岐光との間の光路長差によって異なる。 The power spectrum of the combined light output from the beam splitter 11 and received by the interferometer 20 is expressed by the following equation (4). Here, S 0 (ω) is the spectrum of the first branched light, and P 0 (ω) is the power spectrum of the first branched light. When the reflecting surface of the sample 90 is stationary, the spectroscope 20 can acquire such frequency interference fringes. The period of this frequency interference fringe differs depending on the optical path length difference between the first branched light and the second branched light.
試料９０の反射面が速度ｖで移動している場合には、試料９０からビームスプリッタ１１に戻ってきた第２分岐光の電場Ｅ２(ｔ)は、下記（５）式で表される。ビームスプリッタ１１から出力されて干渉計２０により受光される合波光のパワースペクトルは下記（６）式で表される。ここで、Ｓ１(ω)は第１分岐光のスペクトルであり、Ｐ２(ω)は第２分岐光のスペクトルである。 When the reflecting surface of the sample 90 is moving at the speed v, the electric field E 2 (t) of the second branched light that has returned from the sample 90 to the beam splitter 11 is expressed by the following equation (5). The power spectrum of the combined light output from the beam splitter 11 and received by the interferometer 20 is expressed by the following equation (6). Here, S 1 (ω) is the spectrum of the first branched light, and P 2 (ω) is the spectrum of the second branched light.
この（６）式の右辺の第３項が周波数干渉縞を表す。この第３項を振幅成分と位相成分とに分離すると、位相成分は２つの干渉項１および干渉項２の和で表される。一方の干渉項１は下記（７）式で表される。ω' は、瞬時周波数ωと中心周波数ω０との差であり、下記（８）式で表される。（７）式の第２項は、パルス光のチャーピングに依存しない初期位相であり、考慮しなくてよい。（７）式の第１項と静止時（ｖ＝０）の位相との差δω１は、下記（９）式で表される。 The third term on the right side of the equation (6) represents a frequency interference fringe. When this third term is separated into an amplitude component and a phase component, the phase component is represented by the sum of two interference terms 1 and 2. One interference term 1 is expressed by the following equation (7). ω ′ is the difference between the instantaneous frequency ω and the center frequency ω 0 and is expressed by the following equation (8). The second term of equation (7) is an initial phase that does not depend on chirping of the pulsed light, and need not be considered. The difference δω 1 between the first term of the equation (7) and the phase at rest (v = 0) is expressed by the following equation (9).
位相成分の他方の干渉項２の位相δω２は下記（１０）式で表される。したがって、試料９０の反射面が速度ｖで移動している場合には、その移動によって、分光器２０により取得される周波数干渉縞の周期（周波数）が変化する。その変化量は、δω１とδω２との和となり、下記（１１）式で表される。この式は、速度ｖにほぼ比例している。本実施形態は、周波数干渉縞に基づいて衝撃波の伝搬速度を求める。 The phase δω 2 of the other interference term 2 of the phase component is expressed by the following equation (10). Therefore, when the reflecting surface of the sample 90 is moving at the speed v, the period (frequency) of the frequency interference fringes acquired by the spectroscope 20 is changed by the movement. The amount of change is the sum of δω 1 and δω 2 and is expressed by the following equation (11). This equation is approximately proportional to the speed v. In the present embodiment, the propagation speed of the shock wave is obtained based on the frequency interference fringes.
図３は、周波数干渉縞の一例を示す図である。分光器２０は、２次元配列された画素構造を有する撮像素子を含む。この図は、分光器２０の撮像素子により取得される周波数干渉縞の計算例を示す。横軸は周波数軸である。チャープパルス光の瞬時周波数ωが時刻ｔによって変化するので、横軸は時間軸でもある。干渉縞は周波数軸方向（時間軸方向）に現れる。縦軸は空間軸である。図３（ａ）と図３（ｂ）とでは周波数干渉縞の周期（周波数）が互いに異なっている。これは、（１１）式に示されるように、周波数干渉縞の周期（周波数）が速度ｖによって異なることによる。 FIG. 3 is a diagram illustrating an example of frequency interference fringes. The spectroscope 20 includes an image sensor having a pixel structure arranged two-dimensionally. This figure shows a calculation example of frequency interference fringes acquired by the imaging device of the spectrometer 20. The horizontal axis is the frequency axis. Since the instantaneous frequency ω of the chirped pulse light changes with time t, the horizontal axis is also the time axis. Interference fringes appear in the frequency axis direction (time axis direction). The vertical axis is the spatial axis. 3A and 3B are different from each other in frequency interference fringe period (frequency). This is because the period (frequency) of the frequency interference fringes varies depending on the speed v as shown in the equation (11).
例えば、チャープパルス光のパルス幅を７１０ｐｓとし、波長の変化幅を５.７ｎｍとし、分光器２０の波長分解能を０.０１ｎｍとする。このとき、時間分解能は１.２５ｐｓ（＝0.01×710／5.7）となる。チャープパルス光のチャープ量を大きくすれば、時間分解能を数十ｐｓにすることができる。これに対し、従来のＶＩＳＡＲの時間分解能は通常ナノ秒オーダである。このように、従来技術と比較すると、本実施形態は、衝撃波の速度測定の分解能が高い。また、本実施形態では、ストリークカメラを用いる必要がなく、安価な構成とすることができる。 For example, the pulse width of the chirped pulse light is set to 710 ps, the wavelength change width is set to 5.7 nm, and the wavelength resolution of the spectrometer 20 is set to 0.01 nm. At this time, the time resolution is 1.25 ps (= 0.01 × 710 / 5.7). If the chirp amount of the chirped pulse light is increased, the time resolution can be several tens of ps. On the other hand, the time resolution of the conventional VISAR is usually on the order of nanoseconds. Thus, compared with the prior art, the present embodiment has a higher resolution of shock wave velocity measurement. In the present embodiment, it is not necessary to use a streak camera, and an inexpensive configuration can be achieved.
本実施形態では、衝撃波の伝搬速度ｖを求めるに際して、周波数干渉縞の周期に基づいて衝撃波の伝搬速度ｖを求めることができる。また、周波数干渉縞に基づいて試料９０の第２主面９２への衝撃波の到達時刻ｔ２を求め、衝撃波の第２主面９２への到達時刻ｔ２および第１主面９１での発生時刻ｔ１に基づいて衝撃波の伝搬時間Ｔ（＝ｔ２−ｔ１）を求め、そして、衝撃波の伝搬時間Ｔおよび伝搬距離（第１主面９１と第２主面９２との間の間隔）ｄに基づいて衝撃波の伝搬速度ｖ（＝Ｔ／ｄ）を求めることもできる。また、周波数干渉縞に基づいて試料９０中の衝撃波の伝搬時間Ｔを求め、衝撃波の伝搬時間Ｔおよび伝搬距離ｄに基づいて衝撃波の伝搬速度ｖを求めることもできる。 In this embodiment, when the propagation velocity v of the shock wave is obtained, the propagation velocity v of the shock wave can be obtained based on the period of the frequency interference fringes. Also, the time of occurrence of the second seek time of arrival t 2 of the shock wave to the principal surface 92, the arrival time t 2 and the first principal surface 91 to the second major surface 92 of the shock waves of the sample 90 based on the frequency interference fringes Shock wave propagation time T (= t 2 −t 1 ) is obtained based on t 1 , and shock wave propagation time T and propagation distance (interval between first main surface 91 and second main surface 92) d The propagation velocity v (= T / d) of the shock wave can also be obtained based on Further, the propagation time T of the shock wave in the sample 90 can be obtained based on the frequency interference fringe, and the propagation velocity v of the shock wave can be obtained based on the propagation time T of the shock wave and the propagation distance d.
次に、実施例について説明する。図４は、実施例で用いた試料９０の構成を示す図である。図４（ａ）に示される試料９０は、チャープパルス光（第２分岐光）が入射する第２主面９２に反射膜９３が設けられたものである。図４（ｂ）に示される試料９０は、衝撃波発生用レーザ光が照射される第１主面９１に反射膜９４が設けられたものである。図４（ｂ）に示される試料９０では、チャープパルス光は、試料９０の第２主面９２で反射する他、試料９０の第１主面９１に設けられた反射膜９４でも反射し、また、伝搬している衝撃波の波面でも反射する。 Next, examples will be described. FIG. 4 is a diagram illustrating the configuration of the sample 90 used in the example. A sample 90 shown in FIG. 4A is obtained by providing a reflective film 93 on a second main surface 92 on which chirped pulse light (second branched light) is incident. A sample 90 shown in FIG. 4B is a sample in which a reflective film 94 is provided on a first main surface 91 irradiated with a laser beam for generating a shock wave. In the sample 90 shown in FIG. 4B, the chirped pulse light is reflected by the second main surface 92 of the sample 90 and also by the reflective film 94 provided on the first main surface 91 of the sample 90. Reflects even the wavefront of the propagating shock wave.
試料９０の材料は任意であるが、本実施例ではジルコニア（厚さ１５０×１０−４ｃｍ）を用いた。反射膜９３，９４の材料は、チャープパルス光を反射させることができるものであれは任意であり、例えばアルミニウム等の金属を用いることができるが、本実施例ではバナジウムを用いた。 The material of the sample 90 is arbitrary, but zirconia (thickness 150 × 10 −4 cm) was used in this example. The material of the reflection films 93 and 94 is arbitrary as long as it can reflect chirped pulse light. For example, a metal such as aluminum can be used, but in this embodiment, vanadium was used.
図４（ａ）に示された試料９０を用いた実施例で取得された周波数干渉縞を図５および図６に示す。図４（ｂ）に示された試料９０を用いた実施例で取得された周波数干渉縞を図７および図８に示す。これらの図は、衝撃波発生用レーザ光の照射前（各図（ａ））、照射中（各図（ｂ））および照射後（各図（ｃ））それぞれの周波数干渉縞を示す。また、各々の周波数干渉縞の横軸は、波長を表すとともに、時刻をも表す。時刻は、衝撃波発生用レーザ光が試料９０の第１主面９１に照射されたタイミングを基準（時刻０）としている。 FIG. 5 and FIG. 6 show the frequency interference fringes obtained in the example using the sample 90 shown in FIG. FIG. 7 and FIG. 8 show frequency interference fringes obtained in the example using the sample 90 shown in FIG. These figures show the frequency interference fringes before irradiation (each figure (a)), during irradiation (each figure (b)), and after irradiation (each figure (c)) of the laser beam for generating a shock wave. In addition, the horizontal axis of each frequency interference fringe represents the wavelength as well as the time. The time is based on the timing at which the first main surface 91 of the sample 90 is irradiated with the shock wave generating laser light (time 0).
図５は、図４（ａ）に示された試料９０を用いた第１実施例で取得された周波数干渉縞を示す図である。衝撃波発生用レーザ光照射中の周波数干渉縞の形状は、衝撃波発生用レーザ光照射前と比べて変化していることが分かる。このことから、この周波数干渉縞の左端の時刻０.１６３ｎｓには、試料９０の第２主面９２に設けられた反射膜９３に衝撃波が既に到達していたことが分かる。それ故、衝撃波の伝搬速度ｖは９.２×１０７ｃｍ／ｓ（＝150x10-4／163x10-12）以上であるという結果が得られた。 FIG. 5 is a diagram showing frequency interference fringes obtained in the first embodiment using the sample 90 shown in FIG. It can be seen that the shape of the frequency interference fringes during the irradiation of the shock wave generating laser beam is changed as compared with that before the irradiation of the shock wave generating laser beam. From this, it can be seen that the shock wave has already reached the reflective film 93 provided on the second main surface 92 of the sample 90 at the time 0.163 ns at the left end of the frequency interference fringes. Therefore, the result that the propagation velocity v of the shock wave is 9.2 × 10 7 cm / s (= 150 × 10 −4 / 163 × 10 −12 ) or more was obtained.
図６は、図４（ａ）に示された試料９０を用いた第２実施例で取得された周波数干渉縞を示す図である。図６（ｂ）の衝撃波発生用レーザ光照射中の周波数干渉縞に対して画像処理をして縞成分のみを抽出したものを図６（ｂ）の下に示しており、また、この図の左にある矢印は衝撃波発生用レーザ光の照射位置を表している。衝撃波発生用レーザ光照射中の周波数干渉縞において、縞が乱れている期間では、衝撃波の伝搬により反射膜９３が移動していると判断することができる。この期間が時刻０.３４３ｎｓ以降であることから、衝撃波の伝搬速度ｖは４.４×１０７ｃｍ／ｓ（＝150x10-4／343x10-12）であるという結果が得られた。 FIG. 6 is a diagram showing frequency interference fringes obtained in the second embodiment using the sample 90 shown in FIG. FIG. 6B shows an image obtained by performing image processing on the frequency interference fringes during the irradiation of the shock wave generating laser beam in FIG. 6B and extracting only the fringe components. The arrow on the left represents the irradiation position of the shock wave generating laser beam. In the frequency interference fringes during irradiation of the shock wave generating laser light, it can be determined that the reflection film 93 is moved by the propagation of the shock waves during the period in which the fringes are disturbed. Since this period is after time 0.343 ns, the result is that the propagation speed v of the shock wave is 4.4 × 10 7 cm / s (= 150 × 10 −4 / 343 × 10 −12 ).
図７は、図４（ｂ）に示された試料９０を用いた第３実施例で取得された周波数干渉縞を示す図である。第３実施例では、第１分岐光より第２分岐光の路長を長くした。各々の周波数干渉縞は、短周期の縞と長周期の縞とが重畳されたものとなっている。短周期の縞は、第１主面９１で反射した第２分岐光および第１分岐光による干渉を表す。長周期の縞は、第２主面９２で反射した第２分岐光および第１分岐光による干渉を表す。衝撃波発生用レーザ光照射中の周波数干渉縞において、短周期の縞が消えている（コントラストが小さくなっている）期間では、衝撃波により第１主面９１からの反射光が小さくなっている期間であると判断することができる。この期間の長さが０.１８６ｎｓであることから、衝撃波の伝搬速度ｖは８.１×１０７ｃｍ／ｓ（＝150x10-4／186x10-12）であるという結果が得られた。 FIG. 7 is a diagram showing frequency interference fringes obtained in the third embodiment using the sample 90 shown in FIG. In the third embodiment, the path length of the second branched light is made longer than that of the first branched light. Each frequency interference fringe is formed by superimposing a short-period fringe and a long-period fringe. The short-period fringes represent interference due to the second branched light and the first branched light reflected by the first main surface 91. The long-period fringes represent interference due to the second branched light and the first branched light reflected by the second main surface 92. In the frequency interference fringes during irradiation of the shock wave generating laser light, the short-period fringes disappear (contrast is low), and the reflected light from the first main surface 91 is small due to the shock waves. It can be judged that there is. Since the length of this period is 0.186 ns, the result is that the propagation velocity v of the shock wave is 8.1 × 10 7 cm / s (= 150 × 10 −4 / 186 × 10 −12 ).
図８は、図４（ｂ）に示された試料９０を用いた第４実施例で取得された周波数干渉縞を示す図である。第４実施例では、第１分岐光より第２分岐光の路長を短くした。各々の周波数干渉縞は、短周期の縞と長周期の縞とが重畳されたものとなっている。短周期の縞は、第２主面９２で反射した第２分岐光および第１分岐光による干渉を表す。長周期の縞は、第１主面９１で反射した第２分岐光および第１分岐光による干渉を表す。図８（ｂ）の衝撃波発生用レーザ光照射中の周波数干渉縞に対して画像処理をして長周期の縞成分のみを抽出したものを図８（ｂ）の下に示す。衝撃波発生用レーザ光照射中の周波数干渉縞において、長周期の縞が消えている（コントラストが小さくなっている）期間では、衝撃波により第１主面９１からの反射光が小さくなっている期間であると判断することができる。この期間の長さが０.１８６ｎｓであることから、衝撃波の伝搬速度ｖは８.１×１０７ｃｍ／ｓ（＝150x10-4／186x10-12）であるという結果が得られた。 FIG. 8 is a diagram showing frequency interference fringes obtained in the fourth embodiment using the sample 90 shown in FIG. In the fourth embodiment, the path length of the second branched light is shorter than that of the first branched light. Each frequency interference fringe is formed by superimposing a short-period fringe and a long-period fringe. The short-period fringes represent interference due to the second branched light and the first branched light reflected by the second main surface 92. The long-period stripes represent interference caused by the second branched light and the first branched light reflected by the first main surface 91. FIG. 8B shows an image obtained by performing image processing on the frequency interference fringes during the irradiation of the shock wave generating laser beam in FIG. In the frequency interference fringes during irradiation of the shock wave generating laser light, the long-period fringes disappear (the contrast is small), and the reflected light from the first main surface 91 is small due to the shock waves. It can be judged that there is. Since the length of this period is 0.186 ns, the result is that the propagation velocity v of the shock wave is 8.1 × 10 7 cm / s (= 150 × 10 −4 / 186 × 10 −12 ).
以上の実施例から、試料９０における衝撃波の伝搬速度は１０７ｃｍ／ｓ以上であると推定された。 From the above examples, it was estimated that the propagation speed of the shock wave in the sample 90 was 10 7 cm / s or more.
１…速度測定装置、１０…干渉光学系、１１…ビームスプリッタ、１２…ミラー、１３…ＮＤフィルタ、１４…移動部、２０…分光器、３０…衝撃波発生用光源、３１…伸長部、３２…増幅部、３３…圧縮部、３４…ビームスプリッタ、４１〜４６…ミラー、４７…ビームスプリッタ、５１〜５３…レンズ、５４…移動部、９０，９０Ａ，９０Ｂ…試料、９１…第１主面、９２…第２主面、９３，９４…反射膜。 DESCRIPTION OF SYMBOLS 1 ... Speed measuring apparatus, 10 ... Interference optical system, 11 ... Beam splitter, 12 ... Mirror, 13 ... ND filter, 14 ... Moving part, 20 ... Spectroscope, 30 ... Light source for shock wave generation, 31 ... Elongation part, 32 ... Amplifying unit 33 ... compression unit 34 ... beam splitter 41-46 ... mirror 47 ... beam splitter 51-53 ... lens 54 ... moving unit 90, 90A, 90B ... sample 91 ... first main surface, 92: second main surface, 93, 94: reflective film.
Claims (10)
瞬時周波数が時間的に変化するチャープパルス光を２分岐して第１分岐光および第２分岐光とし、前記第１分岐光をミラーへ出力し、前記第２分岐光を前記試料へ出力し、前記ミラーで反射された前記第１分岐光と前記試料中の前記衝撃波で反射された前記第２分岐光とを合波して当該合波光を出力する干渉光学系と、
前記合波光を分光して前記合波光の周波数干渉縞を求める分光器と、
を備え、
前記周波数干渉縞に基づいて前記衝撃波の伝搬速度を求める、
速度測定装置。 An apparatus for measuring the propagation speed of a shock wave in a sample,
The chirped pulsed light whose instantaneous frequency changes with time is branched into two to be a first branched light and a second branched light, the first branched light is output to a mirror, the second branched light is output to the sample, an interference optical system for outputting the multiplexed light to multiplexing has been and the second branch light reflected by the shock wave in the sample and the first branch light reflected by the mirror,
A spectroscope that divides the combined light to obtain frequency interference fringes of the combined light;
With
Obtaining a propagation speed of the shock wave based on the frequency interference fringes;
Speed measuring device.
前記伸長部により伸長されて出力されたパルス光の一部を分岐して前記チャープパルス光として用いる、
請求項１に記載の速度測定装置。 A light source for generating a shock wave, which includes a stretching unit that stretches the pulsed light and a compression unit that compresses the stretched pulsed light, and irradiates the sample with the compressed pulsed light;
Branching a part of the pulsed light output by being extended by the extending part and using it as the chirped pulsed light,
The speed measuring device according to claim 1.
前記衝撃波の到達時刻および発生時刻に基づいて前記衝撃波の伝搬時間を求め、
前記衝撃波の伝搬時間および伝搬距離に基づいて前記衝撃波の伝搬速度を求める、
請求項１または２に記載の速度測定装置。 Obtaining the arrival time of the shock wave to the interface of the sample based on the frequency interference fringes,
Obtaining the propagation time of the shock wave based on the arrival time and generation time of the shock wave,
Obtaining a propagation speed of the shock wave based on a propagation time and a propagation distance of the shock wave;
The speed measuring device according to claim 1 or 2.
前記衝撃波の伝搬時間および伝搬距離に基づいて前記衝撃波の伝搬速度を求める、
請求項１または２に記載の速度測定装置。 Determine the propagation time of the shock wave in the sample based on the frequency interference fringes,
Obtaining a propagation speed of the shock wave based on a propagation time and a propagation distance of the shock wave;
The speed measuring device according to claim 1 or 2.
請求項１または２に記載の速度測定装置。 Obtaining a propagation speed of the shock wave based on a period of the frequency interference fringes;
The speed measuring device according to claim 1 or 2.
干渉光学系を用いて、瞬時周波数が時間的に変化するチャープパルス光を２分岐して第１分岐光および第２分岐光とし、前記第１分岐光をミラーへ出力し、前記第２分岐光を前記試料へ出力し、前記ミラーで反射された前記第１分岐光と前記試料中の前記衝撃波で反射された前記第２分岐光とを合波して当該合波光を出力し、
分光器を用いて前記合波光を分光して前記合波光の周波数干渉縞を求め、
前記周波数干渉縞に基づいて前記衝撃波の伝搬速度を求める、
速度測定方法。 A method for measuring the propagation speed of a shock wave in a sample,
Using an interference optical system, the chirped pulse light whose instantaneous frequency changes temporally is branched into two to be a first branched light and a second branched light, the first branched light is output to a mirror, and the second branched light is Is output to the sample, and the first branched light reflected by the mirror and the second branched light reflected by the shock wave in the sample are combined to output the combined light,
Using a spectroscope, the combined light is dispersed to obtain a frequency interference fringe of the combined light,
Obtaining a propagation speed of the shock wave based on the frequency interference fringes;
Speed measurement method.
前記伸長部により伸長されて出力されたパルス光の一部を分岐して前記チャープパルス光として用いる、
請求項６に記載の速度測定方法。 Using a shock wave generating light source including an extension part that extends the pulsed light and a compression part that compresses the extended pulsed light, the shock wave is generated by irradiating the compressed pulsed light to the sample,
Branching a part of the pulsed light output by being extended by the extending part and using it as the chirped pulsed light,
The speed measuring method according to claim 6.
前記衝撃波の到達時刻および発生時刻に基づいて前記衝撃波の伝搬時間を求め、
前記衝撃波の伝搬時間および伝搬距離に基づいて前記衝撃波の伝搬速度を求める、
請求項６または７に記載の速度測定方法。 Obtaining the arrival time of the shock wave to the interface of the sample based on the frequency interference fringes,
Obtaining the propagation time of the shock wave based on the arrival time and generation time of the shock wave,
Obtaining a propagation speed of the shock wave based on a propagation time and a propagation distance of the shock wave;
The speed measuring method according to claim 6 or 7.
前記衝撃波の伝搬時間および伝搬距離に基づいて前記衝撃波の伝搬速度を求める、
請求項６または７に記載の速度測定方法。 Determine the propagation time of the shock wave in the sample based on the frequency interference fringes,
Obtaining a propagation speed of the shock wave based on a propagation time and a propagation distance of the shock wave;
The speed measuring method according to claim 6 or 7.
請求項６または７に記載の速度測定方法。 Obtaining a propagation speed of the shock wave based on a period of the frequency interference fringes;
The speed measuring method according to claim 6 or 7.
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