DD222586A1 - METHOD FOR THE PRODUCTION OF OPTICALLY INHOMOID MEDIA - Google Patents

Abstract

The invention relates to a process for the preparation of optically inhomogeneous media for planar coupling and Verzweigerstrukturen in conjunction with optical waveguide step index fibers in multi-mode operation. According to the invention, this object is achieved by ion exchange with a glass of the composition Na 2 O: 18.5 to 33.3 mol% B 2 O 3: 0 to 14.8 mol% SiO 2: 63.2 to 66.7 mol% a molten salt of the composition (NaNO3) 1y (TlNO3) y with 0.1 y 0.15 or (NaNO3) 0.6 (Na2SO4) 0.25 (TlNO3) 0.15 is carried out at temperatures between 450 and 560 C. The replacement times are up to 55 h. The refractive index gradients produced according to the invention achieve the following parameters: 0.03 Dn 0.05 and Dx 200 mm. The invention finds application in scientific instrumentation and the industries of information processing and transmission.

Description

Process for the preparation of optically inhomogeneous media

Application of the invention

The invention relates to a method for the production of optically inhomogeneous media which are suitable for use in optical components. Such components are used in assemblies of integrated optics and in optically coupled computer systems and in optical fiber communication systems (optical information transmission) and in optical sensor components intended",

Characteristic of the known technical solutions

Optically inhomogeneous media, the use in planar Koppelbzw. Due to the geometrical dimensions of these fibers, branching structures for step index fibers in muItimoden operation should have refractive index gradients which extend over depths of ^ X> 200 / μm with / \ n > + 0.03 (Δη = η - n _ra ; n_s refractive index of the substrate glass). The optical length of the fibers requires that the substrate glass has a refractive index in the range 1.50 <n <1.55. For refractive index profiles of this type with / 3n> 0, which are produced by ion exchange with molten salts at T <Tg or T near Tg (Tg = Transformations temperature of the SubstratglasJ while maintaining the dimensional stability of the glass body and maintaining the high transparency, are so far none sufficient described economic production method.

 , · ·. , , 2

Only from the journal Jap. Journ. Appl. Phys. (vol 20, No. 4s April 1981, p.L 296) it is known that on a BK7 glass after a considerable time of 165 h after a considerable time of 165 h at high temperatures (up to 600 ^° C.) after a Na, K / Tl exchange. Diffusion depths up to 400 / do should be achievable; in which explicitly no statements are made about the change in refractive index · The methods described in the Auslegeschriften DE-AS 1913358 and DB-AS 1933 124 for the generation of refractive index profiles by ion exchange in glass rods are not suitable for the production of coupling or Ver branch elements, since these Glasses already contain appreciable amounts of TIpO and PbO, whereby the refractive index of the substrate glass is already above 1.58 · Furthermore, the refractive index drops according to these methods from the axis of the glass body towards the surface, ie Δη <0.

Object of the invention

The aim of the invention is to provide a method for producing optically inhomogeneous media for coupling and / or branching of lchtwellenleitenden step index fibers for multi-floor operation available. This method should be characterized by minimal technological effort ·

Explanation of the essence of the invention,

The object of the invention is to produce by a suitable method in hydrolysis-stabilized glasses a sufficient for the optical waveguide in multimode operation refractive index gradient · According to the invention the object is achieved in that on a glass of the composition

Na ₂ O: 18.5 to 33.3 mole% B ₂ O ₃ : O to 14.8 mole # SiO ₂ : 63.2 to 66.7 mole%

an ion exchange with a molten salt of the composition (HaHOo) ₁ - (TlIO ^ V. with 0.1 * = y <0.15 in the temperature range from 450 to 510 ⁰ C is made, the exchange times to

According to the invention can be replaced by Na ₂ SO ₄ in the molten salt at exchange temperatures greater than 5TO ⁰ C, a portion of the NaNO ^, so that a melt of the composition (NaN0 ₃ ) ₀ 5 (Na ₂ SO ^) ₀ (^ 1 ^ 03) 0 15 ^applies. The replacement times are up to 55 h.

Surprisingly, in some alkali borosilicate glasses according to this invention both a high resistance to hydrolysis and in conjunction with a Na / T! ion exchange in reasonable times diffusion depth AX ^ OO / can be realized so that - taking into account the refractive index change achieved + 0.03 · <Δη <· + 0.05 - a use for planar coupling and branching structures in conjunction with light-conducting * Hengel * * step index fibers in multi-mode operation is possible. According to the invention, the borosilicate glasses are subjected to the following treatment. ,

- Preheat at a heating rate R ^ * 5 - 10 K / min

- ion exchange with. a molten salt of the composition (NaNO ^) ₁ (TINO3) with 0.1 <y <c0.15 at temperatures in the range 450 to 510 ⁰ C in times up to 32 h or with a molten salt of the composition

(NaNO ₃ ) o _s 6 ^(Na 2 ^{S <} Vo 25 ^ ^T1HO 3 ^ O 15 ^{at Tem} P ^eratl * ^r e ⁿ up to 560 ⁰ in times up to 55 h.

- Cooling at a cooling rate R ^. «5 K / min

-3 χ wash with distilled water and wash with alcohol 3 times.

embodiments

The essence of the invention will be explained in more detail by the following examples

Table 1 shows the glasses 1 to 4 used in the process (previous composition, consumption of H / 100 HCl according to ¹ SQtL 14809 for determining the hydrolysis class, transformation temperature).

Table 2 'contains the inventive Ausführungsbeisp'iele] to V to the process. The diffusion depth AX ₁ Q 1 corresponds to the depth at which the refractive index change relative to the substrate glass is only 10 % of the change in the refractive index in the glass surface. The indication of the refractive index change Δη refers to the glass surface (maximum change).

Table 1 Glass

Concentration data in mole percent 1 2

Consumption ml "

33.3 31.6 25.9 O 5.2 7.4 66.7 63.2 66.7 350-400 65 9.5 465 470 485

18.5 14.8 66.7

2,0 560

Table 2 Example

II III

IV

Glass of molten salt

Exchange temperature exchange time / h * '

/ ⁰ O

», 9 M.

490

19

460

+ 0.05

(T1NO ₃ ) _O> .

450 19 28

+ 0.05 0.9> 0.1

485

30

260

+ 0.03

>, 85> t15

510

32

220

+ 0.04

^; 3'0.6 (Na ₂ SO ₄ ) _{Oi 25}

3 0.15 560

55 240

+ 0.03.

Claims (2)

invention claim 1. A process for the production of optically inhomogeneous media, characterized in that on a glass of the composition Na ₂ O: 18.5 to 33.3 mol% B ₂ O ₃ : 0 to 14.8 mol% SiO ₂ s 63.2 to 66.7 mol% an ion exchange with a molten salt of the composition (NaNO ₃ V ₁ (TlNO ₃ ) with 0.1 <y <0.15 in the temperature range 450 to 510 ⁰ C vorj
be up to 32 hours. range 450 to 510 ⁰ C, with the replacement 2. The method according to item 1, characterized in that in the molten salt at exchange temperatures between 510 and 560 ⁰ C, a portion of the NaNO is replaced by Na ₃ SO ₄ , wherein a melt of the composition ₃₀ ^ ₂₄ ) ₀ 2J ₅ (TlNO ^) _{0 15} is used and the replacement times are up to 55 h »