JPH02260128A - Optical information recording and reproducing method and production of optical information recording material - Google Patents

Abstract

PURPOSE:To obtain the optical information recording material by making data pulses to an optical recording material to make recording, emitting induction photon echo pulses by reading out pulses to execute reproduction and irradiating Ib type diamond with electron rays to obtain diamond contg. N-V centers. CONSTITUTION:The diamond contg. the N-V centers is used as the information recording material 5. The reference laser pulses 1 having 638nm wavelength and >=-40cm<-1> spectral width are made incident to the material 5. The data pulses 2 of the same wavelength and spectral width as the wavelength and spectral width of the reference pulses are made incident to this material within the phase relaxation time thereof to execute the recording. The reading out pulses 3 are then made incident to the material 5 and the induction photon echo pulses 4 are emitted to execute the reproduction. The reproduction of the optical information is executed by emitting the induction photon echo pulses 4 of 2 to 200MeV to the Ib type diamond. The material 1 is formed by irradiating the Ib type diamond with the electron beam having, for example, 190MeV energy by a beam accelerator, by which the diamond contg. the N-V centers is obtd. and the optical information recording material is produced.

Description

Detailed Description of the Invention [Industrial Field of Application] This invention relates to an optical information recording and reproducing method for recording and reproducing optical information in the time domain using stimulated photon echoes, and an optical information recording and reproducing method used in the method. This invention relates to a method for manufacturing materials.

[Prior art] In recent years, permanent hole burning (PHB)
high-density optical memory capable of recording optical information not only in the spatial dimension but also in the wavelength dimension has been realized. However, using permanent hole burning, instead of the wavelength dimension,
It is also possible to record optical information in the time dimension. The principle of such time-domain optical information recording is 0ptical
Vol. 8 of 0PTIC8LETTER8 published by the 5ociety of America, 7.
No.

2 (February 1982), page 77.

FIG. 1 shows a conceptual diagram of time-domain optical information recording and reproduction described in the above-mentioned 0PTIC3LETTER8. In the figure, number 1 indicates a reference laser pulse, 2 indicates a data laser pulse, 3 indicates a readout laser pulse, 4 indicates a stimulated photon echo pulse, and 5 indicates an optical information recording material. Each laser pulse of 1°2.3 has the same wavelength as the absorption band of the optical information recording material, [and also has a spectral width comparable to the non-uniform width of the optical information recording material. FIG. 2 shows the temporal deviation of each pulse. First, the reference laser pulse 1 is made to enter the optical information recording material 5 at time t. Thereafter, the data laser pulse 2 is made incident on the optical information recording material 5 at time t2. Thereafter, a readout laser pulse 3 is applied at time t3. Note that 1, <12<1. There is a relationship between Assuming that the reference laser pulse 1 and the readout laser pulse 3 are δ-function pulses, and the data laser pulse 2 is a pulse with an arbitrary waveform, at time 1. , +13-1. A stimulated photon echo pulse 4 is then emitted from the optical information recording material 5. Stimulated photon echo pulse 4 has the same waveform as data laser pulse 2.

In order to realize optical information recording and reproduction as described above, it is necessary to satisfy the following phase matching conditions.

K4 = Kl + 2 + 3 In the equation, K is the wave number vector of reference laser pulse 1, K2 is the wave number vector of data laser pulse 2, and K is the read laser pulse 3.
The wave number vector of K4 is the wave number vector of the induced photon echo pulse.

Recording of optical information on the optical information recording material 5 is performed by first making the reference laser pulse 1 and then the data laser pulse 2 incident on the optical information recording material 5. This data writing operation needs to be completed within the phase relaxation time T2 of the optical information recording material 5. In other words,
It is necessary to make the data laser pulse 2 enter the optical information recording material 5 at a time t2 that satisfies the following conditions: t, 2-t, <<'r2.

Regarding the readout laser pulse 3, if i3 j+ is within the lifetime of the hole in the optical information recording material 5, it is possible to make it enter the optical information recording material 5 any number of times. Each time the readout laser pulse 3 is made incident on the optical information recording material 5,
Echoes are induced and optical information is reproduced.

Time-domain optical information recording has the following advantages over wavelength-domain optical information recording.

■ No need for a laser light source with an ultra-fine spectral width.

■ High echo signal strength can be obtained even with weak excitation light.

(2) Write and read operations of optical information can be performed at high speed.

Although time-domain optical information recording has the above-mentioned advantages, it is necessary to write data within the phase relaxation time T2 of the recording material. Therefore, the restriction on this phase relaxation time T2 becomes larger than in the wavelength domain recording method.

Journal of 0ptical S.

city of america B Vo
l.

3, No. 4 (April 1986), page 527, reports on time-domain optical information recording using a dye doped in a polymer as a recording material. Also, Elsevie
r 5science Publishers B
, V,'s 0PTIC8 COMMUNICATIONS
Vol, 65. No. 18 of No. 3 (February 1988)
On page 5, time-domain optical information recording using Eu"":Y203 as a recording material is reported. The methods described in these two publications achieve time-domain optical information recording by bringing the recording material to a temperature below the liquid He temperature.

[Problem to be solved by the invention] The former publication, namely Journal of Opt
ical 5ociety of America
Regarding the time domain optical information recording described in a, the phase relaxation time T2 of the dye used as the recording material is 1.8
Even at K(7) temperature, it is as short as about 300 psec. Another drawback is that when dyes are used as recording materials for a long time, they deteriorate due to fading effects.

The latter publication, namely 0PTIC8COMMUNI
Regarding the time-domain optical information recording described in CATIONS, Eu''' used as a recording material: Y2
In No. 03, the phase relaxation time T2 is several tens of μsec at a temperature of 4.5, which is sufficiently long.

However, when the temperature rises to 15 or above, the holes in the recording material disappear, making it impossible to record and reproduce optical information.

The present invention was made to solve the above-mentioned problems, and its purpose is to provide an optical information recording and reproducing method that can sufficiently record and reproduce optical information even at a temperature higher than the liquid He temperature. An object of the present invention is to provide a method for producing an optical information recording material used in the method.

[Means for Solving the Problems] In the optical information recording and reproducing method according to the present invention, diamond containing an NV center is used as an optical information recording material.

First, a wavelength of 638 nm and a wavelength of 40 nm were added to this optical information recording material.
A reference laser pulse having a spectral width of cm-' or more is made incident. Subsequently, optical information is recorded by making a data laser pulse having the same wavelength and the same spectral width as the reference pulse enter the optical information recording material within the phase relaxation time of the optical information recording material. Further, the optical information is reproduced by making a readout laser pulse having the same wavelength and the same spectral width as the reference pulse enter the optical information recording material on which the optical information is recorded, and emitting a stimulated photon echo pulse.

N-V of diamond used as optical information recording material
The center preferably has an optical density of 0.5 to 1.5.
is within the range of

The optical information recording material used in the above method is produced as follows. 2-200M for type Ib diamond
e An electron beam with an energy of 10'7 to 1018e
The diamond is irradiated with a dose of /cm2, and then the diamond is heat-treated in a vacuum atmosphere at 600 to 1200° C. for 5 hours or more to obtain a diamond containing an N■ center.

Optical information recording materials can also be made by the following method. A type Ib diamond is irradiated with a neutron beam having an energy of 2 to 200 MeV at a dose of 1015 to 1°"n/cm2, and then the diamond is
A diamond containing an N-V center is obtained by heat treatment in a vacuum atmosphere at .degree. C. for 5 hours or more.

[Operations and Effects of the Invention] A diamond containing an NV center used as an optical information recording material has the following characteristics.

First, at temperatures below 120° C., hole recovery in the recording material hardly occurs. The inventor of the present application conducted an experiment to investigate the recovery time of holes in a recording material. The experimental results are shown in FIG. In the figure, the vertical axis indicates the intensity of transmitted light passing through the recording material, and the horizontal axis indicates the passage of time. Note that the experiment was conducted at a temperature of 80°C. In the figure, the recording material was irradiated with a laser beam for making holes at a location indicated by reference number 6, and this irradiation was stopped at a location indicated by reference number 7. ΔIH indicates a state where holes are saturated, and ΔIP indicates a state where holes remain permanently. As shown in FIG. 3, even after 20 minutes or more, the hole has hardly recovered.

In addition, the phase relaxation time T2 of a diamond optical information recording material containing an NV center exhibits temperature dependence of T2'cCT''. Fig. 4 shows the phase relaxation time T2 of the recording material.
2 (n sec) and temperature T (K). As is clear from FIG. 4, the relationship T2cx: "1" a.2 holds over a wide temperature range. When the temperature T is 40, the phase relaxation time T2
is approximately 100 psec.

Furthermore, the absorption wavelength of the zero phonon line at the N-V center of diamond is 638 nm, and the nonuniform width is about 40 cm.
-'. That is, the laser pulse incident on the optical information recording material has the same wavelength as the zero phonon line of the N-■ center, and has a spectral width greater than the unconstrained width of the N-V center.

This condition is a prerequisite for performing stimulated photon echo.

From the experimental results shown in FIGS. 3 and 4, it is possible to determine the temperature range in which optical information can be recorded and reproduced. In order to record and reproduce optical information, the time resolution of the optical receiver must be adjusted by the phase relaxation time T2 of the recording material.
It needs to be much smaller than. When a streak camera is used, since its temporal resolution is about 20 psec, it is possible to record and reproduce optical information at a temperature T of about 40 degrees Celsius.

NV centers are thermally stable and do not suffer from fading problems. The laser pulse incident on the recording material has a wavelength of 638 nm and a spectral width of 40 cm.
'In the above, a laser beam with a pulse width on the order of picoseconds may be used.

The preferred optical density of the NV center is within the range of 0.5 to 1.5. This is based on the following reasons.

Optical information recorded on an optical information recording material is read out using stimulated photon echo.

The echo has the same wavelength as the absorption band of the NV center. Therefore, if the concentration of the NV center is too high, self-quenching will occur when the echo passes through the recording material, diamond, and the intensity of the emitted signal will become weak. Conversely, if the concentration of the NV center is too low, the output signal intensity of the echo signal itself will become weak. Therefore, it is desirable to select the optimal concentration of the NV center to maximize the intensity of the echo signal. Its optimum concentration is an optical density of 0. It is within the range of 5 to 1.5. The optical density can be adjusted by changing the nitrogen concentration of type Ib diamond, the electron beam or neutron beam, the thickness of the diamond crystal, etc.

The method for producing optical information recording materials is characterized by the energy of electron beams or neutron beams. The inventors of the present application have found that when the energy of the electron beam to be irradiated to type Ib diamond differs, the recovery time of the NV center hole generated in the diamond differs. The experimental data shown in Fig. 3 described above is based on the N-
It is based on the V center. The electron beam dose in this case was in the range of 1017 to 10'' e/cm2.

However, using a tandem accelerator, 100% of electron beams with an energy of 1.5 MeV were applied to type Ib diamond.
Even when irradiated with a dose of 17 to 1018 e/Cm2, hardly any holes are formed. This shows that when the energy of the irradiated electron beam is small, the component with an extremely short hole recovery time is dominant.

On the other hand, when the energy of the electron beam to be irradiated is increased, the component with a long hole recovery time becomes dominant.

In order to maintain optical information recording, a sufficiently long hole recovery time is required. In order to satisfy this requirement,
The energy of the electron beam to be irradiated onto type Ib diamond needs to be above a certain level. On the other hand, if the energy of the electron beam is too high, the diamond itself will deteriorate due to irradiation with the electron beam.

Thus, the preferred energy of the electron beam is 2 to 200
It is within the M e V range.

Note that type Ib diamond may be a single crystal or a thin film.

Moreover, neutron beams may be irradiated instead of electron beams. However, when irradiating with neutron beams, a dose in the range of 1015 to 1017 n/cm2 is sufficient due to the difference in the ability to generate vacancies.

As described above, according to the present invention, optical information can be recorded and reproduced even at a temperature higher than the liquid He temperature. Also, N- is used as an optical information recording material.
The V center is thermally stable and does not suffer from problems of fading.

[Example] Example 1 Type Ib diamond synthesized by the temperature difference method had 19
An electron beam with an energy of 0MeV is 1018e/cm2.
The diamond was then irradiated with a dose of 1200
Heat treatment was performed in a vacuum atmosphere at .degree. C. for 5 hours. By changing the nitrogen concentration of type Ib diamond crystal,
NV centers with five types of optical densities were fabricated. These samples are designated as samples 1 to 5.

Using these samples, stimulated photon echoes were observed using the apparatus shown in FIG. Referring to Figure 5, 11
is a mode-locked argon ion laser, 12 is a dye laser, 13, 14, 15, and 16 are semi-transmissive or total reflection mirrors, 17 is a right-angle prism, 18 is an optical information recording material, 1 is a photomultiplier tube, and 20 is a storage Showing an oscilloscope. Mode-locked argon ion laser 11
The laser pulse emitted from the dye laser 12 and converted into a predetermined wavelength by the mirror 13, 14.15.1
6 and a right angle prism 17,
It is divided into three pulses that are time-shifted. E is a reference pulse that first enters the optical information recording material 18,
E2 is the data pulse that enters the optical information recording material 18 second, and E3 is the read pulse that enters the optical information recording material 18 last. 3 pulses E7, E2 and E
, has a wavelength of 638 nm and a spectral width of 80 cm.
-”, the pulse width was a single pulse of about 3 psec.

E is an echo pulse emitted from the optical information recording material 18, and is received by a photomultiplier tube (rising 200 psec) 19 with high-speed response. The waveform of the echo pulse was observed with a storage oscilloscope 20. In addition, the measurement temperature T was 21 degrees. Further, the incident time of the reference pulse E1 to the optical information recording material 18 is tl,
Assuming that the incident time of the data pulse E2 is t2 and the incident time of the read pulse E3 is t3, 12-1. is about 0.1nse
c, t, -t2 was about 5 nsec.

The relationship between the optical density of the NV center and the output of the photomultiplier tube (photomultiplier tube) 19 obtained by the above measurement was as follows.

■ Sample 1 (comparative example) Optical density of N-V center: 0.15 Output of photomal tube (mV): <Q, 3 ■ Sample 2 (example of the present invention) Optical density of N-V center: 0.62 Photomal tube Output of tube (mV): 1°2 ■ Sample 3 (example of the present invention) Optical density of N-V center: 1.20 Output of photomal tube (mV): 2.7 ■ Sample 4 (example of the present invention) N- Optical density of V center: 1.45 Output of photomar tube (mV): l, 7 ■ Sample 5 (comparative example) Optical density of N-V center: 2.03 Output of photomar tube (mV): <Q, 5 Example 2 Ib with nitrogen concentration of about 20 ppm synthesized by temperature difference method
After irradiating the type diamond with an electron beam with an energy of 1.5 MeV at a dose of 10" e/cm2, the diamond was heat-treated in a vacuum atmosphere at 1200°C for 5 hours to form an N-V center. This sample is designated as Sample 6.

Next, the nitrogen concentration synthesized by the temperature difference method was about 20 ppm.
A type Ib diamond was irradiated with an electron beam with an energy of 2.0 MeV at a dose of 10"/cm2, and then the diamond was heated at 1200°C in a vacuum atmosphere for 5
An NV center was formed by heat treatment for a period of time.

This sample is designated as sample 7.

Furthermore, the nitrogen concentration synthesized by the temperature difference method was approximately 20 pp.
m for type Ib diamond, 190 M e V
After irradiating the diamond with an electron beam having an energy of 1018/cm2, the diamond was heat treated in a vacuum atmosphere at 1200 DEG C. for 5 hours to form an NV center. This sample is designated as sample 8.

Using Samples 6.7 and 8, stimulated photon echo was measured using the apparatus shown in FIG.

The measurement conditions are exactly the same as in Example 1. The data obtained by this measurement were as follows.

■ Sample 6 (comparative example) Electron beam energy (MeV): 1.5 Optical density of N-V center: 1.2 Photomultiply tube output (mV): Approx. 0 ■ Sample 7 (invention example) Electron beam energy Energy (MeV): 2°0 N-V center optical density: 0.9 Photomar tube output (mV): 0.8 ■ Sample 8 (example of the present invention) Electron beam energy (MeV): 19O N- Optical density of V center = 1.2 Photomar tube output (mV): 2. 7

[Brief explanation of drawings]

FIG. 1 is a diagram showing the concept of time domain optical information recording and reproduction. FIG. 2 is a diagram illustrating temporal shifts of a reference pulse, a data pulse, a subsequent pulse, and a stimulated photon echo pulse. FIG. 3 is a diagram showing the hole recovery time of the NV center. FIG. 4 is a diagram showing the relationship between the phase relaxation time and temperature of the NV center. FIG. 5 is a diagram showing a schematic configuration diagram of an apparatus for recording and reproducing optical information. In the figure, 1 is a reference laser pulse, 2 is a data laser pulse, 3 is a readout laser pulse, 4 is a stimulated photon echo pulse, 5 is an optical information recording material, 11 is a mode-locked argon ion laser, 12 is a dye laser, 13, 14,
15.16 is a mirror 17 is a right angle prism, 18 is an optical information recording material, 19 is a photomultiplier tube, 20 is a storage oscilloscope, E is a reference pulse, E2 is a data pulse, E3 is a read pulse, E4 is an echo pulse. show.

Claims (4)

[Claims] (1) Diamond containing an N-V center is used as the optical information recording material, and the optical information recording material has a wavelength of 638 nm and a wavelength of 40 cm^-.
After inputting a reference laser pulse having a spectral width of ^1 or more, a data laser pulse having the same wavelength and the same spectral width as the reference pulse is applied to the optical information within the phase relaxation time of the optical information recording material. Recording of optical information is performed by making the optical information enter a recording material, and a readout laser pulse having the same wavelength and the same spectral width as the reference pulse is made to enter the optical information recording material on which the optical information is recorded to generate a stimulated photon echo pulse. An optical information recording and reproducing method that reproduces optical information by emitting light. (2) The optical density of the NV center is 0. The optical information recording and reproducing method according to claim 1, wherein the optical information recording and reproducing method is within the range of 5 to 1.5. (3) Electron beam with energy of 2 to 200 MeV is applied to type Ib diamond at 10^1^7 to 10^1^8e/cm.
The diamond was irradiated with a dose of 60
Obtaining a diamond containing an N-V center by heat treatment in a vacuum atmosphere at 0 to 1200°C for 5 hours or more,
A method for producing an optical information recording material. (4) A neutron beam with an energy of 2 to 200 MeV is applied to type Ib diamond at 10^1^5 to 10^1^7n/c.
irradiated with a dose of m^2 and then the diamond was irradiated with a dose of 6 m^2.
A method for producing an optical information recording material, which obtains a diamond containing an N-V center by heat treatment in a vacuum atmosphere at 00 to 1200°C for 5 hours or more.