JP3458414B2 - Organic nonlinear optical element and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to optical communication, optical disks,
The present invention relates to an organic nonlinear optical element used in an optoelectronic system such as optical information processing, more specifically to a waveguide type nonlinear optical element and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, attention has been paid to optoelectronic systems such as optical communication, optical disks, and optical information processing capable of transmitting and processing a large amount of information. Then, in order to establish these techniques, development of excellent nonlinear optical elements is desired. The nonlinear optical element is generally a waveguide type nonlinear optical element in which a waveguide made of a nonlinear optical material film is formed on a substrate, and the nonlinear optical material includes an inorganic nonlinear optical material and an organic nonlinear optical material. An optical material may be used. At this time, while the inorganic nonlinear optical material causes a nonlinear phenomenon due to lattice vibration,
On the other hand, the organic nonlinear optical material has a high third-order nonlinear optical characteristic such as a nonlinear optical response because it causes a nonlinear phenomenon by conjugation of π electrons, and has a high characteristic as a waveguide. Also,
Organic nonlinear optical materials have various structures. Therefore, there are high expectations for the development of excellent organic nonlinear optical materials.

Further, in the above organic nonlinear optical material, when molecules of the material form an aggregate (association body), exciton interaction works between the molecules, and the transition dipole moment increases as compared with the monomer. However, it is said that the nonlinear optical susceptibility is improved and the nonlinear optical characteristic is improved (Shunsuke Kobayashi, Proceedings of the 3rd Symposium on Optoelectronic Materials, Next Generation Industrial Fundamental Technology, P85 (1992)). Is expected to develop excellent organic nonlinear optical materials.

However, the above phenomenon has been confirmed only in a solution or a polymer dispersion system. For example, pseudo isocyanine dye (hereinafter referred to as PIC).
Is highly ordered J in a water-ethylene glycol mixed solution at a concentration of 10 ⁻³ M and a temperature of 230 K or less.
Forming an aggregate, the third-order nonlinear optical susceptibility χ ⁽³⁾ = 2.8 × 10 ^-8 under the conditions of a temperature of 77 K and a wavelength of 570.7 nm.
Indicates esu. However, it is very difficult to form a non-linear optical element by forming an organic non-linear optical material film on a substrate as described above using an aggregate of liquid organic non-linear optical material molecules as described above. . Further, it is not practical because it exhibits high nonlinearity only at an extremely low temperature of 77 K, and a high concentration of 10 ⁻³ M is required for formation.

A method of microcrystallizing the above PIC by utilizing the salting-out effect to form a J-aggregate has also been reported (Hachiro Nakanishi, Proceedings of the 3rd Symposium on Optoelectronic Materials, Next Generation Industrial Fundamental Technology, P47). (1992)). In this case, the forming conditions are a concentration of 10 ⁻⁵ M and room temperature, which is more practical than the above-mentioned examples, but it is difficult to form an organic nonlinear optical material film on the substrate.

[0006]

Therefore, the present invention has been proposed in view of the conventional circumstances, and an organic material having a large third-order nonlinear optical susceptibility and a high third-order nonlinear optical characteristic such as nonlinear optical response. An object of the present invention is to provide a non-linear optical material and an organic non-linear optical element in which a waveguide is formed by the organic non-linear optical material film. Further, it is possible to reduce the thickness of the organic nonlinear optical material, form an aggregate of the organic nonlinear optical material molecules, and further increase the third-order nonlinear optical susceptibility of the organic nonlinear optical material. It is an object of the present invention to provide a method for manufacturing an organic nonlinear optical element that can further improve the characteristics.

[0007]

In order to achieve the above-mentioned object, the present invention provides an organic nonlinear optical element in which an organic nonlinear optical material film is laminated on a substrate, wherein the organic nonlinear optical material film is It is characterized by being a laminated film in which a plurality of monomolecular layers containing the cyanine dye shown in 2 are laminated.

[0008]

[Chemical 2]

Further, the present inventors have found that the above-mentioned cyanine dye has a relatively high molecular assembling property, and thus can be formed into a thin film by the Langmuir-Blodgett method (hereinafter referred to as the LB method). The LB method is a method of expanding and compressing thin film forming material molecules at the air-water interface, and copying this onto the substrate. Further, on the air-water interface, it is very easy to control the orientation of the thin film forming molecules. Therefore, if the above-mentioned cyanine dye is thinned by the LB method, a highly ordered cyanine dye molecule aggregate can be formed on the substrate.

That is, in the method for producing an organic nonlinear optical element of the present invention, the cyanine dye molecules in the organic nonlinear optical material film of the organic nonlinear optical element are mixed by using the LB method. It is characterized by being manufactured so as to form a united body.

[0011]

According to the present invention, in the organic nonlinear optical element in which the organic nonlinear optical material film is laminated on the substrate, the organic nonlinear optical material film has a plurality of monolayers containing the cyanine dye shown in the chemical formula 2 above. It is a laminated film that is laminated,
Since the third-order nonlinear optical susceptibility of the cyanine dye is large, the third-order nonlinear optical characteristics such as the nonlinear optical response of the organic nonlinear optical material film that serves as a waveguide are improved.

Further, according to the method for producing an organic nonlinear optical element of the present invention, since the organic nonlinear optical material film of the above organic nonlinear optical element is produced by the LB method, the cyanine dye can be thinned. Furthermore, since the cyanine dye molecules in the organic nonlinear optical material film are formed so as to form an aggregate, the third-order nonlinear optical susceptibility increases, and the radiation transition probability increases in the organic nonlinear optical material film. ,
The rate of radiation deactivation from the excited state is increased, and an organic nonlinear optical material film having higher nonlinear optical response is formed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings. In this embodiment, R ₁ of the cyanine dye as shown in Chemical formula 3 as the organic nonlinear optical material is C ₆ H ₅ , R ₂ is Cl, and R
₃ and C ₂ H _5, X ^- a I ^- and the 3,3'-diethyl-9-phenyl-5,5'-dichloro-2,2'-shear carbocyanine iodide (hereinafter, referred to as Cy. ) Was used to fabricate an organic nonlinear optical element using the organic nonlinear optical material film as a waveguide, and its characteristics were investigated.

[0014]

[Chemical 3]

In order to form the organic nonlinear optical element of this embodiment, the thin film of Cy was formed on the substrate by the LB method. First, Cy and arachidic acid (C ₁₉ H ₃₉ COOH) were dissolved in chloroform at a molar ratio of 2: 1 to give a concentration of 1.0 mg.
/ Ml of developing solution was prepared. Then, using ultrapure water as the lower layer liquid, 250 μl of the developing solution was dropped on the water surface. Further, a glass substrate or a quartz substrate is used as the substrate (a quartz substrate is used in this embodiment), the substrate surface is subjected to a hydrophobic treatment with a silane coupling agent (octadecyltrichlorosilane), and then a thin film is accumulated on the substrate. Formed. At this time, since the substrate surface is made hydrophobic,
The cumulative formation starts when the substrate is lowered. Therefore, the substrate was moved up and down at a vertical speed of 3 to 10 mm / min to form a thin film. An LB film production apparatus manufactured by Lauda Co. was used, and the computer performed all the controls such as the vertical movement of the substrate. As a result, the Y-type LB film made of Cy was favorably accumulated on the substrate.

Next, L formed cumulatively as described above
The orientation state of Cy molecules in the B film was investigated. That is, the ultraviolet / visible light absorption spectrum of the LB film was measured. The results are shown in Fig. 1. In the figure, the horizontal axis represents wavelength and the vertical axis represents absorbed light intensity. In addition, in FIG. 1, the above result is shown by a solid line, and for comparison, the spectrum of a methanol solution of Cy at a concentration of 10 ⁻⁶ M is shown by a broken line in the figure. As can be seen from the result of FIG. 1, in the methanol solution of Cy shown by the broken line in the figure, Cy exists as a monomer and its maximum absorption wavelength is about 565 nm. On the other hand, in the LB film shown by the solid line in the figure, the maximum absorption wavelength is 670 nm, which is shifted to the longer wavelength side than the Cy monomer. That is, L
It was confirmed that a J-aggregate, which is a highly-ordered molecular association, was formed in the B film. The 670 nm absorption in the LB film is the J band resulting from the J aggregate. Therefore, in the LB film, it is expected that the third-order nonlinear optical susceptibility is increased and the nonlinear optical response is further improved.

Therefore, the third-order nonlinear optical susceptibility χ ⁽³⁾ of the LB film was evaluated. That is, as a measurement sample, a 16-layered LB film (Y-type 32 molecular layer) was prepared on both surfaces of a quartz substrate, and this was evaluated by the THG maker fringe method.

The THG maker fringe method measuring device is shown in FIG. 2. The THG maker fringe method measuring device is a Q switch Nd; YAG laser light source 1, THG crystal 2, optical parametric oscillator (OPO) 3, plural mirrors. 4, an optical system including a lens 6, a sample 7, a filter 8, a spectroscope 9, a detector including a photomultiplier tube 10, a photodetector 5, a boxcar integrator 11, and a computing unit including a personal computer 12. .

The maker fringe method is a typical method for measuring the nonlinear optical susceptibility, and the second harmonic (SHG), the second harmonic (SHG), or the second harmonic (SHG) generated when the sample 7 is irradiated with laser light from the laser light source 1 The intensity of the third harmonic (THG) is measured, and the thickness of the sample 7 is effectively changed by rotating the sample 7, and the interference pattern of the fringe caused by the SHG light or the THG light is measured. It has a feature that it can be applied even when phase matching cannot be achieved.

When the third-order nonlinear optical susceptibility χ ⁽³⁾ of the LB film is evaluated, the incident light wavelength on the sample 7 is set to 1.82 μm, and the incident light A is applied to the sample as shown in FIG. 7 is made incident in a direction having an incident angle θ as shown in the figure with respect to the vertical movement direction C of the substrate (that is, the polarization direction B is parallel to the vertical movement direction C of the substrate), and the sample The measurement was carried out by rotating 7 in the direction of arrow D in the figure. The results are shown in Fig. 4. In the figure, the horizontal axis represents the incident angle and the vertical axis represents the third harmonic intensity. In the figure, X ₁ shows the result of the LB film on the substrate, and X ₂ in the figure shows the result of only the substrate. Both showed nonlinear optical characteristics. At this time, the third-order nonlinear optical susceptibility χ ⁽³⁾ _LB of the LB film obtained by the THG maker fringe method can be expressed by the equation 1. (Note that Equation 1 is based on T. Kobayashi ed., “No.
nlinear Optics of Organic
It is a modification based on the calculation formula of Kuboji and others shown in "and Semiconductors".)

[0021]

[Equation 1]

Using Equation 1, the third-order nonlinear optical susceptibility of the substrate
χ⁽³⁾ Of LB film of Cy compared with ⁽³⁾ I asked for
5 x 10^-12 you can get a high value of esu
It was Therefore, the actual implementation using the LB film of Cy as a waveguide
The organic nonlinear optical element of the embodiment may have sufficient characteristics.
confirmed. Note that such third-order nonlinear optical susceptibility χ
⁽³⁾ Of the present embodiment using a LB film with high conductivity as a waveguide
In a non-linear optical element, for example, a laser diode
It is possible to operate with light with low power
Power consumption can be reduced.

The organic nonlinear optical element of the present embodiment as described above is used as an optical control optical switch element (Mach-Sender type all-optical switch) having an optical coupling type waveguide as shown in FIG. 5, for example. it can.

The above-mentioned optically controlled optical switch element is one in which an organic nonlinear optical material film 14 is formed on a substrate 13,
A waveguide 20, which is a convex portion having a predetermined shape, is formed on one main surface 14a of the organic nonlinear optical material film 14, and one end of the waveguide 20 receives the signal light and the control light entrance 15. Is a bifurcated shape, and the signal light entrance 15 and the control light entrance 16 are joined to each other at the central portion.
And has a shape in which the other end is divided into a first light emission port 18 and a second light emission port 19 again. In the light control optical switch element, the arrow L ₁
In the state where the signal light indicated by (1) is incident from the signal light incident port 15, the control light indicated by the arrow L ₂ in the figure is incident from the control light incident port 16 and the organic light forming the waveguide 20 is formed by the control light L _2. By changing the refractive index of the nonlinear optical material,
The emission port of the signal light L ₁ can be switched to the first light emission port 18 or the second light emission port 19. Such an optical control optical switching element has very good switching characteristics and is useful for an optical processing circuit such as an optical computer.

By the way, in order to manufacture the above-mentioned optically controlled optical switch with the organic nonlinear optical element of this embodiment, C is formed on the substrate.
After the LB film of y is formed, the LB film may be processed into a predetermined waveguide shape by using a pattern forming technique by etching after resist treatment.

The organic nonlinear optical element of this embodiment can be used as an optical bistable element in addition to the above-mentioned optical control optical switch, and can be used in optical electronics systems such as optical communication, optical disks, and optical information processing. It enables further improvement of technology.

[0027]

As is apparent from the above description, according to the present invention, in the organic nonlinear optical element in which the organic nonlinear optical material film is laminated on the substrate, the organic nonlinear optical material film is represented by the following chemical formula 4. The above-mentioned cyanine dye is a laminated film in which a plurality of monomolecular layers containing the cyanine dye are laminated. Since the third-order nonlinear optical susceptibility of the cyanine dye is large, the nonlinear optical response of the organic nonlinear optical material film serving as a waveguide is shown. 3 of sex
The second-order nonlinear optical characteristic is improved, and the characteristic of the organic nonlinear optical element is improved.

[0028]

[Chemical 4]

Further, in the method for manufacturing an organic nonlinear optical element of the present invention, since the organic nonlinear optical material film of the organic nonlinear optical element as described above is manufactured by the LB method, the cyanine dye can be thinned. In addition, since the cyanine dye in the organic nonlinear optical material film is formed so as to form an aggregate, the third-order nonlinear optical susceptibility increases, and in the organic nonlinear optical material film, the radiation transition probability increases, The rate of radiation deactivation from the excited state is increased, and an organic nonlinear optical material film having higher nonlinear optical response is formed. Since the organic non-linear optical element manufactured by the present invention has high third-order non-linear optical characteristics, it can be operated by light with low power consumption, and power consumption can be reduced.

Furthermore, the organic nonlinear optical element of the present invention comprises
Since it has good characteristics, it enables further improvement of the technology of optoelectronic systems such as optical communication, optical disks, and optical information processing, and its industrial value is very high.

[Brief description of drawings]

FIG. 1 is a diagram showing an ultraviolet / visible light absorption spectrum of an LB film of Cy and a methanol solution of Cy.

FIG. 2 is a schematic diagram showing a THG maker fringe method measuring device.

FIG. 3 is a schematic diagram showing a relationship between a sample, an incident angle of incident light, and a polarization direction.

FIG. 4 is a third view of the LB film on the substrate and the incident angle of the substrate.
It is a figure which shows the next harmonic intensity.

FIG. 5 is a perspective view showing a Mach-Sender type all-optical switch.

[Explanation of symbols]

13 ... Substrate 14 ... Organic nonlinear optical material film 14a ... One main surface 15: Signal light entrance 16 ... Control light entrance 17 ... Joining part 18 ... First light output port 19 ... Second light exit port 20 ... Waveguide

Continuation of front page (56) Reference JP-A-2-225334 (JP, A) JP-A-2-281047 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1 / 35

Claims (2)

(57) [Claims] 1. An organic nonlinear optical element comprising an organic nonlinear optical material film laminated on a substrate, wherein the organic nonlinear optical material film is formed by laminating a plurality of monomolecular layers containing a cyanine dye represented by the following chemical formula 1. An organic nonlinear optical element characterized by being a laminated film. [Chemical 1] 2. The organic non-linear optical material film of the organic non-linear optical element according to claim 1 is produced by a Langmuir-Blodgett method so that cyanine dye molecules in the organic non-linear optical material film form an aggregate. A method of manufacturing an organic nonlinear optical element, which is characterized by the above.