JPH02201320A - Organic nonlinear optical materials and their manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding organic nonlinear optical materials made of condensed polycyclic hydrocarbons, the present invention aims to effectively utilize two-dimensional excitons (exciton) formed at crystal interfaces of such materials. A plurality of layers of an organic nonlinear optical material made of condensed polycyclic hydrocarbons are laminated with intermediate layers interposed therebetween.

[Industrial application field]

The present invention relates to an organic nonlinear optical material, and more particularly, to an organic nonlinear optical material made of a condensed polycyclic hydrocarbon such as anthracene, naphthacene, etc., and a method for producing the same.

The nonlinear optical material according to the present invention can be advantageously used, for example, as a material for optical-optical devices.

[Conventional technology]

As is well known, nonlinear optical materials are materials that exhibit a second-order or third-order nonlinear optical effect when a voltage is applied or under a strong electric field of laser light, and from the viewpoint of phenomena, they can also be used for optical frequency conversion, optical switching, optical amplification, etc. Because it performs many element functions, it is attracting attention as a key material in fields such as optical communications and optical combiners. Conventional typical nonlinear optical materials are inorganic materials, such as KDP, LiNbO3, KNbO
, , LiTaD+ and the like are known. Since around 1983, development and research on organic nonlinear optical materials has been actively conducted. This is because it has been discovered that organic nonlinear optical materials exhibit characteristics superior to inorganic materials. Specifically, when looking at second-order nonlinear optical constants, for example, at the molecular level, 1iNb03 etc. This is because many crystals have been found to have constants that are two or more orders of magnitude larger than those of known inorganic crystals. Representative organic nonlinear optical materials include MNA, DAN, MNMA, NPP, and others.

Incidentally, recently, the usefulness of anthracene crystals as nonlinear optical crystals has attracted attention. For example, Sakae Hanamura-1 “Nonlinear optical crystal J, Oplus B N (1103°7
7-85 (June 1988), anthracene crystals form three-dimensional van der Waalska crystals, but two-dimensional excitons are formed in the planes of the first and second layers at the interface. In addition, the lifetimes of these excitons are less than 2 ps (first layer) and ~15 ps (second layer), respectively, and the third-order nonlinear polarizability χ( 3) is reported to be on the order of -1 esu.

[Problem to be solved by the invention]

However, anthracene crystal exists in the form of a bulk crystal, so when it is used as a nonlinear optical material, the response is rate-limited by 980 ps, which is the emission lifetime of bulk excitons, and two-dimensional excitons cannot be used effectively. comes out.

Therefore, an object of the present invention is to effectively utilize two-dimensional excitons (exciton) formed at the crystal interface of a nonlinear optical material made of a condensed polycyclic hydrocarbon such as anthracene.

[Means to solve the problem]

According to the present invention, the above object can be achieved by an organic nonlinear optical material characterized in that a plurality of layers of organic nonlinear optical materials each made of a condensed polycyclic hydrocarbon are laminated with an intermediate layer interposed therebetween. can.

In the present invention, the layers of the nonlinear optical material and the intermediate layer are alternately laminated to form a laminate, and in this case, the thickness of the nonlinear optical material layer is preferably calculated in terms of molecules of the material. It is within 5 molecular layers. The thickness of this layer is generally several ~
Several tens of people, preferably about 5 to 208 people. In addition to anthracene, suitable nonlinear optical substances include those capable of forming molecular crystals similar to anthracene, such as naphthacene, naphthalene, and other hydrocarbons. Monocyclic hydrocarbons such as -4-nitroaniline and the like can also be used advantageously.

The intermediate layer to be interposed between the nonlinear optical material layers is
It can be formed from a variety of materials, as long as it does not adversely affect the intended purpose, and its thickness can vary depending on the desired result.

Suitable materials for the intermediate layer include, for example, polymethyl methacrylate (PMM8), a-3iOx,
a-3i, -, Nx0y, ^RJ*, phthalocyanine, layered compound (MoS, etc.), TiOx
MgF, polyvinyl alcohol (PVA), etc.
A wide variety of inorganic and organic insulators and semiconductors can be mentioned. If anthracene or the like is not used as a nonlinear optical material, these materials may be used in the intermediate layer.

Furthermore, according to the present invention, in producing the described organic nonlinear optical material, the nonlinear optical material or its precursor is caused to fly onto the substrate to form a layer of the organic nonlinear optical material, and an intermediate layer is formed. There is also provided a method for producing an organic nonlinear optical material, which is characterized by alternately repeating the steps of flying a substance or a precursor thereof onto a substrate to form an intermediate layer. Here, the term "precursor" refers to a substance that can ultimately lead to an organic nonlinear optical material and an intermediate layer material as a result of some reaction.

The substrate to which the organic nonlinear optical material of the present invention is to be deposited can be formed by selecting any material commonly used in this technical field. Suitable substrate materials include, for example, quartz, glass, alkali halide crystals, mica, layered compounds (such as MoS2), and others.

Lamination of organic nonlinear optical materials can be performed using various film formation methods. As an appropriate film forming method, for example, MBE (molecular
beam epitaxy) or MBD (mo
regular beam position),
Examples include the LB method. Above all, the method of folding organic MBE (or MBD) or organic MBE (or MBD) and inorganic MBE (or MBD) is most suitable.

[For production]

In the organic nonlinear optical material according to the present invention, the organic nonlinear material is stacked in layers, and each layer is set to a thickness of one to several molecular layers, so the organic nonlinear material in each layer has a bulk. There are no excitons, so only two-dimensional excitons are formed.

〔Example〕

FIG. 1 is a sectional view showing a preferred example of the organic nonlinear optical material according to the present invention.

In the case of the illustrated nonlinear optical material, on the quartz substrate 1,
Nonlinear optical material layer made of anthracene (film thickness approximately 1OA)
) 2 and PMMA (film thickness approx. 10 layers) 3
are layered. With such a layer configuration, there is actually no bulk exciton in the anthracene of the nonlinear optical material layer 2, and therefore the response speed is 15 ps or less,
A characteristic of z'' = 1 esu is obtained. Although not shown, a buffer layer such as PVA, polyimide, etc. may be provided between the substrate 1 and the nonlinear optical material layer 2, if necessary.

The nonlinear optical material shown in FIG. 1 can be formed using, for example, an organic thin film forming apparatus as schematically shown in FIG. 2. The illustrated device is an MBE device,
It has a vacuum bell jar 20 as a reaction chamber. The substrate 10 in the vacuum belljar 20 is a quartz substrate, supported by a substrate holder 8, and cooled to a predetermined temperature by a cooling liquid or gas 9 passing through the holder.

Note that the cooling medium used here may be liquid nitrogen, alconium, etc. in addition to cooling water. A heater 6 is also used to adjust the temperature of the substrate. As shown in the figure, an electrode 14 is formed on the substrate 8 in advance, and another electrode (here, the grid 7) is arranged on the front surface of the substrate 8.

Advantageously, the grid 7 is a porous structure, a mesh structure or the like.

Anthracene for forming a nonlinear optical material layer is K
The cells (Knudsen cells H5, 16, and 17) are evaporated onto the substrate while being controlled by the shutter 5. After forming the first nonlinear optical material layer, the first intermediate layer is formed. Gasified sources from gas cylinders, ampoules, etc. outside the Belljar 20 (here, MMA
Monomer) is introduced into a bell jar (not shown).

In this way, the MMA monomer is made to fly onto the substrate and the substrate is irradiated with light to produce an intermediate layer. As light, light 12 from a light source 11, for example visible light or ultraviolet light, can be used. 13 is a window.

The light source 11 can also be placed inside the vacuum bell jar 20 if necessary. The monomers were K cell 15°16 and 1
7 and store it in either cell temperature and shutter 5.
It may be evaporated while adjusting.

Further, the light irradiation is performed constantly, simultaneously with the monomer flying onto the substrate, or intermittently.

Furthermore, the monomer flying and light irradiation may be performed alternately, and by doing so, the polymerization reaction may be carried out more completely.

〔Effect of the invention〕

According to the present invention, a nonlinear optical material layer (thickness: 1 molecule layer to
Since the interfacial layer (several molecular layers) and the intermediate layer were alternately laminated, the characteristics of the first to nth interfacial layers were clearly produced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a preferred example of the organic nonlinear optical material according to the present invention, and FIG. 2 is a schematic diagram of an organic thin film manufacturing apparatus used to manufacture the organic nonlinear optical material shown in FIG. It is an illustration. In the figure, 1 is a substrate, 2 is a nonlinear optical material layer, and 3 is an intermediate layer.

Claims (1)

[Scope of Claims] 1. An organic nonlinear optical material characterized in that a plurality of layers of organic nonlinear optical substances each made of a condensed polycyclic hydrocarbon are laminated with an intermediate layer interposed therebetween. 2. In producing the organic nonlinear optical material according to claim 1, a nonlinear optical material or its precursor is flown onto a substrate to form a layer of the organic nonlinear optical material, and a material forming an intermediate layer. Alternatively, a method for producing an organic nonlinear optical material characterized by alternately repeating the process of flying the precursor onto a substrate to form an intermediate layer.