JPH02234050A - Light wave measuring device - Google Patents

Abstract

PURPOSE:To effectively utilize pulse light from a pulse light source and to improve time resolution with simple constitution by obtaining a signal which is the reference of the start of measurement from an electric pulse signal for driving the semiconductor laser(light emitting element) of the pulse light source. CONSTITUTION:An ultra short pulse power source 2 generates the electric pulse signal whose rising is fast on the basis of an electric pulse from a pulse generator 1 and gives it to the semiconductor laser LD. Ultra short pulse light LB emitted from the laser LD irradiates a sample 3 and then fluorescence PL is generated. The fluorescence PL is detected by a photodetector PMT and the output of the photodetector is inputted in a time voltage converter 41 as a STOP signal. A detection circuit 21 is added to the power source 2 so as to detect the driving current of the laser LD, which is prescriptively delayed 5 and given to the converter 41 as a START signal. Then, a measuring means 4 constituted of the converter 41 and a pulse height analyzer 42 measures the light wave of the light to be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical waveform measuring device, and is used, for example, to measure the lifetime of fluorescent light generated when a measurement target is irradiated with laser light.

[Conventional technology]

As a conventional optical waveform measurement device with high time resolution,
For example, the following are known.

The first method is called the time-correlated single photon counting method, in which the object to be measured is irradiated with a light pulse of sufficiently short duration, and the fluorescent photons emitted from the object by this irradiation are detected. The device measures the time from when a light pulse is irradiated to when a fluorescent photon is detected. Note that adjustment is made such that at most one photon is detected for one light pulse irradiation. Then, by repeating this time measurement many times (approximately one million times to obtain highly accurate results) and expressing the obtained data in a histogram, the fluorescence lifetime characteristics of the object to be measured can be determined. It has gained.

The second method uses a streak camera device, which measures the waveform of light from an object to be measured using a streak tube that sweeps an electron beam in synchronization with the irradiation of light pulses. According to this, by repeating the light pulse irradiation and the sweeping operation many times, the light waveform can be measured even in the case like the first case. Further, even when a large number of photons are generated from the object to be measured by one pulsed light irradiation, the optical waveform can be measured.

In addition to the above-mentioned optical waveform measuring devices, known optical waveform measuring devices include sampling type optical waveform measuring devices and devices using a pin photodiode or an avalanche photodiode as a photodetector.

For such measurements, a signal must be given that serves as a reference for starting the measurement. For example, with the single photon counting method, measurement is impossible unless a time measurement start signal (start signal) is given, and with a streak camera, measurement is impossible unless a sweep start signal (trigger signal) is given. . Therefore, in the conventional device, a signal serving as a reference for starting measurement is obtained in the following manner. The first is to split the pulsed light from the laser light source using a half mirror, etc.
One side is used as excitation light to irradiate the sample, and the other side is guided to a photodetector to obtain a measurement start signal.

The second method is to take out the signal itself given to the drive circuit of the semiconductor laser constituting the laser light source and use it as a measurement start signal.

[Problem to be solved by the invention]

However, according to the first method, an optical system for branching the optical pulses is required, which complicates the configuration. Furthermore, since the pulsed light is split, the amount of light cannot be used effectively. According to the second method, drift and jitter occur between the electrical signal in the drive circuit of the pulsed light source and the output of the pulsed light, and the temporal relationship between the measurement start signal and the timing of the pulsed light cannot be kept constant. It disappears. For this reason, especially when sampling is performed multiple times, the timing shifts for each sampling, making it difficult to improve the temporal resolution.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical waveform measuring device that has a simple configuration, can effectively utilize the amount of pulsed light from a light source, and can increase temporal resolution.

[Means to solve the problem]

The optical waveform measuring device according to the present invention includes a semiconductor light emitting device that emits pulsed light to be irradiated onto a sample, a pulse power source that outputs an electric pulse signal for driving the semiconductor light emitting device, and a current or current of the electric pulse signal. A pulse detection means for detecting voltage, a photodetector for detecting the light to be measured, and a measurement means for measuring the optical waveform of the light to be measured using the output of the photodetector with the output of the pulse detection means as a reference for starting measurement. It is characterized by being prepared. Here, the measurement means may be a means for measuring the optical waveform by sampling the time from the output of the pulse detection means to the output of the photodetector multiple times,
The structure may include a streak camera device that performs a sweeping operation using the output of the pulse detection means as a trigger signal.

[Effect]

According to the present invention, the reference signal for starting measurement is an electric pulse signal that drives a semiconductor light emitting device (laser) as a pulse light source. Since the pulsed light is obtained from the same source, the timing of the pulsed light and the measurement start signal will not deviate due to drift or jitter of the drive circuit or the like.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram of an optical waveform a constant device according to a first embodiment of the present invention. In the figure, a pulse generator 81 outputs electrical pulses of a predetermined frequency, and an ultra-short pulse power source 22
Based on the electric pulses from the pulse generator 1, a short pulse current (electric pulse signal) with a fast rise of several 100 psec is generated and applied to the semiconductor laser LD. As a result, the semiconductor laser LD emits ultrashort pulses of several tens of psec. Ultrashort pulse light L from semiconductor laser LD
B is the object to be measured (
Sample 3) is irradiated, and as a result, fluorescent light P is emitted from sample 3.
L is generated. This fluorescent light PL is detected by a photodetector PMT consisting of a photomultiplier tube or the like, and the detection output is inputted to the stop terminal of the time-voltage converter 41 as a STOP signal.

On the other hand, a detection circuit 21 is attached to the ultra-short pulse power supply 2,
As a result, the short pulse current itself applied to the semiconductor laser LD as a drive current is detected. This detection output is delayed by a predetermined value in a delay circuit 5, and is then transferred to a time-voltage converter 41.
is given as a START signal to the start terminal of. The time-voltage converter 41 is operated by the above-mentioned STOP and START signals, and provides the result to the pulse height analyzer 42.

The time-voltage converter 41 and the pulse height analyzer 42 constitute the measuring means 4 for measuring the optical waveform, which functions as follows.

First, when a short pulse current is output from the ultra-short pulse power source 2, this is detected by the detection circuit 21 and given to the time-voltage converter 41 as a START signal. This STA
The time point at which the RT signal is applied and the time point at which the sample 3 is irradiated with the ultra-short pulse LB are synchronized by the action of the delay circuit 5. In this case, the START signal is the semiconductor laser L
Since it is generated based on the output of the ultra-short pulse power source 2 applied to D, the above-mentioned synchronization will not be disturbed by drift or jitter of the drive circuit in the ultra-short pulse power source 2.

On the other hand, when the photon of the fluorescent light PL from the sample 3 is detected by the photodetector PMT, the output of the photodetector PMT becomes ST
It is input to the time-voltage converter 41 as an OP signal. Then, the time-voltage converter 41 generates a voltage pulse having a height proportional to the time from the input of the START signal until the input of the STOP signal, and supplies this to the pulse height analyzer . The pulse height analyzer 42 digitizes the input voltage pulse and counts the number of pulses (the number of detected photons) for each pulse height.

FIG. 2 shows an example of the counting results of the pulse height analyzer 42 when a large number of voltage pulses are applied to the pulse height analyzer 42 from the time-voltage converter 41, and the horizontal axis represents the pulse height. The vertical axis is the number of pieces.

In this figure, the vertical axis indicates the probability that a photon (fluorescence PL) is detected at that time, and its value is proportional to the fluorescence intensity at that time. Therefore, this diagram directly represents the temporal change in fluorescence intensity, that is, the fluorescence lifetime characteristics. In reality, light pulse irradiation is performed one million to several tens of millions of times, measurement is continued until approximately one million photons are detected, and the fluorescence lifetime is calculated based on the measurement results.

FIG. 3 is a configuration diagram of an optical waveform measuring device according to a second embodiment.

This differs from the above-described first embodiment in that the detection of the short pulse current given to the semiconductor laser LD from the ultra-short pulse power supply 2 involves the sensor 61 detecting electromagnetic waves generated around the signal line leading to the semiconductor laser LD. This is what is being done. The sensor 61 is composed of, for example, a highly sensitive Hall element, and is amplified by an amplifier circuit 62 and provided to the time-voltage converter 41 as a START signal. In this embodiment as well, since the START signal is generated by the short pulse current itself to the semiconductor laser LD, the influence of drift, jitter, etc. in the ultra-short pulse power supply 2 can be eliminated.

FIG. 4 is a configuration diagram of an optical waveform measuring device according to a third embodiment.

This differs from the first embodiment described above in that a streak camera device 7 is used as the n1 constant means. The streak camera device 7 includes a streak tube 71, a sweep control circuit 72, and a TV camera 73. The streak tube 71 includes a photocathode 74 that emits photoelectrons upon receiving the fluorescent light PL, an acceleration electrode 75 that accelerates the electrons from the photocathode 74, and a focusing electrode (that focuses the electron beam emitted from the photocathode 74 onto the MCP). (not shown) and a deflection electrode 7 that deflects the accelerated electron EB under control from the sweep control circuit 72.
6 and a microchannel plate for multiplying electron EB (
MCP) 77, and a fluorescent surface 78 that emits fluorescent light when irradiated with electrons. The streak image formed on the fluorescent surface 78 is captured by a TV camera 73 composed of, for example, a CCD.

The device of the third embodiment described above operates as follows.

First, when a short pulse current is sent from the ultra-short pulse power source 2 to the semiconductor laser LD, this is detected by the detection circuit 21 and sent to the sweep control circuit 72 of the streak camera device 7 as a trigger signal (TRG). Here, since the trigger signal is generated based on the short pulse current itself output from the ultra-short pulse power source 2, even if there is drift or jitter in the ultra-short pulse power source 2, the emission timing of the semiconductor laser LD and the trigger signal The relationship between the input timings of is kept constant. Therefore, the sweep control circuit 7
2, the streak camera device 7 starts sweeping.

In this example, one ultra-short pulse LB to sample 3
When a large number of photons are emitted as fluorescent light PL by irradiation, it is also possible to observe a light waveform as shown in FIG. 2 by one sweep by the sweep control circuit 72. However, when a large number of photons are not emitted at once, the emission of the semiconductor laser LD and the sweep by the sweep control circuit 72 may be repeated multiple times, and the data of the streak image obtained thereby may be accumulated and integrated. In this case, in the first and second embodiments, the number of photons generated by one ultrashort pulse LB irradiation had to be one or less, but in this embodiment, since the streak tube 71 is used, A plurality of photons may be generated per one irradiation of the ultrashort pulse light LB.

FIG. 5 is a configuration diagram of an optical waveform measuring device according to a fourth embodiment.

In this embodiment, a sensor 61 is installed around the signal line leading to the semiconductor laser LD, detects a short pulse current from the electromagnetic waves generated here, and uses this detection output as a trigger signal for the streak camera device 7. This fourth embodiment also has the same effect as the third embodiment.

Note that a sampling type optical waveform observation means may be used instead of the streak camera device 7 shown in FIGS. 4 and 5.

An example of the structure and operation of this sampling type optical waveform observation means will be briefly explained with reference to FIG. The sampling-type optical waveform observation means shown in FIG. 6 mainly includes a sampling-type streak tube 91 and information processing that processes information regarding the optical waveform of the measured light obtained by extracting a part of the measured light PL using the sampling-type streak tube 91. 100.

The light to be measured PL emitted from the sample and observed by the sampling type optical waveform observation means is focused onto the photocathode 93 of the sampling type streak tube 91 by the lens 92 . This incident light is converted by the photocathode 93 into electrons corresponding to the light intensity, and the converted electrons are accelerated by the accelerating electrode 94, passed between the deflection plates 95, and guided to the slit plate 96. When the electrons pass between the deflection plates 95, they are swept by the sweep voltage applied between the deflection plates 95 and reach the slit plate 96. Since the slit plate 96 has minute slits perpendicular to the sweep direction, only a portion of the electrons that have reached the slit plate 96 pass through this slit and reach the fluorescent surface 97 behind it. The fluorescent surface 97 emits light by collision with electrons. This emission intensity is captured by a photomultiplier tube 98, amplified by an amplifier 99, and output as an electrical signal. In this way, a signal obtained by sampling the light intensity of the light to be measured PL is stored in the information processing section 100.

Such a sampling operation is repeated by slightly sequentially shifting the sweep timing with respect to the incident timing of the light to be measured, and from the obtained information it is possible to obtain the optical waveform as shown in Figure 7. It has become.

Note that the ultrashort pulse power supply 2 can be configured using a device with a high switching speed, such as an avalanche transistor, a tunnel diode, or a step recovery diode. Further, a wavelength conversion element can also be provided on the output side of the semiconductor laser LD.

〔Effect of the invention〕

As explained above in detail, according to the present invention, the signal (START signal, trigger signal) that serves as the reference for starting measurement is obtained from the electric pulse signal itself that drives the semiconductor light emitting device (laser) as the pulse light source. The timing of the pulsed light and the measurement start signal will not deviate due to drift or jitter of the drive circuit or the like. Therefore, the device of the present invention has a simple configuration, can effectively utilize the amount of pulsed light from the light source, and can improve temporal resolution.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an optical waveform measuring device according to a first embodiment of the present invention, FIG. 2 is a diagram showing 8-1 constant results obtained by the device of the first embodiment, and FIG. FIG. 4 is a configuration diagram of the optical waveform measurement device according to the third embodiment, FIG. 5 is a configuration diagram of the optical waveform measurement device according to the fourth embodiment, and FIGS. FIG. 7 is a diagram showing the configuration and operation of an optical waveform measuring device according to another embodiment. 1... Pulse generator, 2... Ultra-short pulse power supply, 21
... detection circuit, 3 ... sample, 41 ... time-voltage converter, 42 ... pulse height analyzer, 5 ... delay circuit, 61
...Sensor, 7...Streak camera device, 71.
...Streak tube, 72...Sweep control circuit, 73...
・TV camera, 91...Sampling type streak tube, LD...Semiconductor laser, PMT...Photodetector, L
B...Ultrashort pulse light, PL...fluorescence. Patent applicant Hamamatsu Photonics Co., Ltd. Representative Patent Attorney
Yoshiki Hasegawa; Q! J Specified Patent Applicant Figure 2 Procedure Amendment Date June 1999 1999 Patent Application No. 55532 Name of the invention Person who amends an optical waveform measuring device Relationship to the case Chamber of Commerce Applicant Hamamatsu Photonics Co., Ltd. (postal code 101) Foresight Building 4th Floor 6, 3-5-2 Iwamoto-cho, Chiyoda-ku, Tokyo Contents of the Invention <<1>> Page 5 of the specification, lines 8 to 9, ``When sampling, etc., each sampling "to" to "
When counting, etc., correct it to `` for each count. (2) Correct "sampling" in the 6th line of page 6 to "counting". "Detailed Description of the Invention" column of the specification subject to the above amendment

Claims (1)

[Claims] 1. An optical waveform measuring device that measures the optical waveform of light to be measured generated when a sample is irradiated with pulsed light, comprising: a semiconductor light-emitting element that emits the pulsed light; and this semiconductor light-emitting element. a pulse power source that outputs an electric pulse signal for driving the electric pulse signal, a pulse detection means that detects the current or voltage of the electric pulse signal, a photodetector that detects the light to be measured, and an output of the pulse detection means. An optical waveform measuring device comprising: a measuring means for measuring the optical waveform of the light to be measured using the output of the photodetector as a reference for starting measurement. 2. The optical waveform measuring device according to claim 1, wherein the measuring means measures the optical waveform by counting the time from the output of the pulse detecting means to the output of the photodetector a plurality of times. 3. The optical waveform measuring device according to claim 1, wherein the photodetector for detecting the light to be measured is a streak camera, and performs a sweeping operation using the output of the pulse detection means as a trigger signal to observe the optical waveform of the light to be measured. . 4. The optical waveform measurement device according to claim 1, wherein the photodetector for detecting the light to be measured and the measurement means include a sampling type optical waveform observation device that operates using the output of the pulse detection means as a trigger signal.