Non-linear optical device

Details Non-linear optical device Non-linear optical device

1992-12-17

1994-10-04

Tucker, Philip

Compositions

Light transmission modifying compositions

252587, 359328, F21V 900

Patent

active

053523881

DESCRIPTION:

BRIEF SUMMARY
This invention relates to non-linear optical (NLO) devices incorporating second harmonic generator materials which produce a second harmonic generation (SHG) of optical wavelength electromagnetic radiation, in particular laser radiation.
It is known that various organic and inorganic compounds possess the ability to double the frequency of laser light passing through them. This ability is known as second harmonic generation (SHG) and is particularly significant because it provides the ability to produce laser light of higher energy than that provided by the initial laser light source.
Known inorganic compounds which possess SHG properties include alpha-silica, potassium dihydrogenphosphate (KDP), zinc blende wurtzite, and gadolinium and terbidium molybdates. Known organic compounds which possess SHG properties include urea, cadmium-thiourea complexes, L-argininium dihydrogen phosphate monohydrate (LAP), some siloxane and silicone polymeric liquid crystals, stilbene-containing liquid crystals, some silver containing emulsions, dipotassium tartrate hemihydrate, potassium sodium tartrate tetrahydrate, compounds having large secondary molecular susceptibilities (beta-values) such as 4-(N-pyrrolidino)-3-(N-ethanamido)-nitrobenzene (PAN) and 4-(dimethylamino)-3-(N-ethanamido)-nitrobenzene (DAN), and blends of large beta-value compounds with polypeptides as disclosed in European Patent Application Number EP-0338702-A1.
Within the field of known SHG materials, crystalline materials form an important class because many can be grown from solution into large, transparent single crystals of good optical quality. However, ideally a crystalline SHG material must possess a combination of desirable properties to be practically useful for incorporation in an NLO device. Amongst the most important of these properties are:
(1) High solubility in organic and/or aqueous media in order to promote a reasonable rate of crystal growth from solution.
(2) Good crystal growth properties.
(3) High thermal stability, in particular high melting point, to facilitate the (normally high temperature) incorporation of the materials into NLO devices and to provide adequate resistance to thermal damage in the presence of laser radiation.
(4) Good mechanical strength.
(5) lack of colour, in order to promote high optical transmissivity at all optical wavelengths and low heat absorption of laser energy.
(6) Absence of hygroscopy.
(7) Ability to form hydrate-free crystals, since prolonged heating of a hydrated crystalline material by laser radiation may promote the liberation of water vapour and so degrade the structure of the material from within.
(8) High SHG response chracteristics.
(9) Low cost of production.
Very few crystalline materials possess a sufficient number of these properties to render them useful in practical NLO devices. The principle disadvantage of known crystalline inorganic compounds exhibiting SHG response is their generally low threshold to optical damage which leaves them vulnerable to damage by laser light. The principle disadvantages of known crystalline organic compounds exhibiting SHG response is their generally high cost of production, and their generally poor crystal strength and high volatility which results in mechanical damage and dissipation of the materials. Any material damage results in a reduction of power in the light emitted from NLO devices employing the material, and also results in the material absorbing excessive amounts of heat which can cause further damage to the material. For example, although KDP and LAP are currently widely used in NLO devices, KDP is hygroscopic, and LAP is both hydrated and possesses a melting point of only 140.degree. C., and neither exhibits an SHG response of high magnitude.
It is an object of the present invention to provide materials for use in NLO devices which are capable of providing an SHG response whereby the aforementioned disadvantages are reduced to more acceptable levels. It is a further object of the present invention to provide effective SHG responsive materials w

REFERENCES:
patent: 5196147 (1993-03-01), Taketani et al.

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