DD222290A1 - METHOD FOR THE PRODUCTION OF OPTICALLY INHOMOID MEDIA - Google Patents

Abstract

The invention relates to a method for producing optically inhomogeneous media for planar coupling and Verzweigerstrukturen in conjunction with optical waveguide gradient fibers in multi-mode operation. The optically inhomogeneous media have refractive index gradients (0.05 Dn 0.09 and Dx 40 mm) and are used in optical components. According to the invention, the object is achieved by bringing a glass of KF3 into contact with a salt melt (NaNO 3) 1-y (TINO 3) y (0.1-0.2) at temperatures between 440 and 520 ° C. The replacement times are up to 40 h. The invention finds application in the scientific Geraetebau as well as in the industries of information processing and -Uebertragung.

Description

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Title of the invention Process for the preparation of optically inhomogeneous media

Application of the invention

The invention relates to a process for the preparation of optically inhomogeneous media, which find use in optical components. They are suitable for use in assemblies of optical information transmission (optical message transmission, autoinitiation technology, computer systems) and in optical sensor components.

Characteristic of the known technical solutions Ion exchange processes in glasses for the generation of refractive index changes are known. The highest refractive index changes were achieved on the basis of the Na / Ag or Na / Tl Austausohes in suitable molten salts. However, optically inhomogeneous media having an Ag concentration gradient show a marked tendency for reduced transmission due to colloidal silver discoloration, especially at high levels of exchange. On the other hand, optically inhomogeneous media whose refractive index gradient is caused by a Tl concentration gradient do not have this disadvantage. Due to the much larger ionic radius of thallium ⁽¹ V ₁ + - '1 ^ & r "= 0.96 + .S), however, the ion exchange rate substantially less than in the case of exchange with silver with r = + 1.26 Ä, so that at most in extreme

Ag

Uneconomic diffusion times larger diffusion depths are achievable. Under certain conditions are so far probably well

- 2 Br eclizalLl changes of Δη = 0.04 achievable, but without the diffusion depths Δχ exceed a few microns (Δη = η -η; η: refractive index of the substrate glass).

So

For the application of optically inhomogeneous media in components for coupling or branching of optical waveguide gradient fibers into multimode operation, however, both with regard to the refractive index change Δη and with respect to the diffusion coefficient

low A s sufficiently high values required. Achieving this requirement is in principle made more difficult by the fact that the glasses must continue to have a sufficiently high resistance to hydrolysis during the photolithographic treatment. This requirement is generally associated with a slight mobility of the alkaloids, which in turn only allows your diffusion depth. In the laid-open specifications DB-OS 2309788 and DE-OS 2332736 the replacement depths of thallium are additionally applied electric fields to increase * Thereby the ¥ erte Δ η = 0.02; Δσ = 5 - 10 Vizm or Δη. = 0.03; Δ ^Σ - 5 - 15 / Um achieved. The experimental effort in such a ^ -Schmelzen arrangement is considerable. Due to the toxicity of Tl-containing molten salts is also pay attention to fully enclosed as possible apparatus, which is difficult in the considered process by electrical and mechanical feedthroughs.

Of articles in the magazine "Appl. Lett 2J_. Phys., 12 (1972) 584 and 32y ^{12 (1} 978) 997) is known, 'that the Na / Tl exchange for the purpose of optical ¥ elle line in an optical Bo ^ rosilikatglas in which soda-lime glass Corning 1802 leads to the following values: ^ n = 0 »003 and £ χ = 100 / um or ^ n = 0,0 ^ 5 and 4

around.

Object of the Invention

The aim of the invention is, on the basis of a commercially available optical glass, to develop a process for the production of optically inhomogeneous media, which is characterized by a minimal technological effort and which is used for the production of optical Eopplern or branching fiber optic gradient fibers for the multimode Operation is suitable.

Presentation of the invention of the invention

The object of the invention is to produce a refractive index gradient sufficient for the optical waveguide in cult mode operation by a suitable method in a glass of optical quality which is stable against hydrolysis.

According to the invention the object is achieved in that on a Kronflintglas KF 3 of the composition 70-72 Gew.-Ji

15 - 16 3 Wt. -5b Na ₂ O the composition 5 - 6 Wt. - ^c / o PbO 5 Wt. - £ ZnO 1 - 2 Wt. - # Al ₂ O ο, Wt. - As ₂ O ₃ an ion exchange with a molten salt

) _1. (TINO ,,), with 0,, 1 <y <0.2, in the temperature range between 44O and 520 C. The replacement times are up to kO h.

Surprising nieise was found that the ion exchange, the glass EP 3 with the NaJJO "-TlNO" melt, a high refractive index change over a sufficient depth can be achieved, so that a use in optical components for coupling and branching of optical waveguide gradient fibers is possible , The refractive index change of the optically inhomogeneous media produced by the process according to the invention is / in3> 0.05 at diffusion depths Ax 40äum, With an Ms to 0.2 molar proportions T ^ -NO "increased content of thallium are refractive index changes to ^ n = 0, 09 reachable.

According to the invention, the glass KF 3 is subjected to the following treatment:

- Preheat at the heating rate R-_ = 10 - 20 K / min

- Ion exchange with a molten salt

with 0.1 <-y «= 0.2

at temperatures in the range of 44θ to 520 ⁰ C over times up to 40 h

Cooling with the cooling rate IL, = 5 K / min

- several times, washing with distilled water

After ion exchange, no fine-optical aftertreatment of the glass surface is required. · -

·,. .

embodiments

The invention will be explained below in the following embodiments. ^x .

Fig ^! , 1 shows the sample form and the sample processing

''. '"' (Pig. 2 shows the refractive index gradients

1. Sin, piece of KF3 glass (Tg = 460 ° C, ^ ₆ ^ = 1.5105, dimensions:

/ 20 3: 20 χ 10 mm) is ground and polished on one side (1 in Fig. 1). At 440 ⁰ C, the ion exchange in contact

with a molten salt (iiaN0 _o ) _ _o (TlN0 ")". (F = 300 ° C). 3 0.9 3 0.1 ρ

performed. The replacement time is 40 h. After washing off the salt residues, the 4 edge pieces are removed, exposing the core (2 in FIG. 1) so as to grind and polish surfaces 2 opposite thereto plane-parallel (3 in FIG. 1). FIG. 2 a shows the refractive index profile resulting from η "" measurements according to the κ KB method with Δη = 0.053 and Δ:

2. A piece of KF3 glass - processed as in Example 1 - is at 480 ⁰ C for 40 h in contact with a molten salt (NaNO ^) _no (TINO «) -. The refractive index profile is recorded in Fig. 2b, which is obtained from measurements of the values of η "or by measuring the mode interference, resulting in the following values n n = 0.053" and x x 90 90 / μm.

3 "A piece of KF3 glass - machined as in the example

1 - is at 480 ⁰ C 4Ö h in contact with a molten salt (NaHCO ^) _n 5, _(no TlNOj (P "= 275 ° C brought> 2c assigned -.... By measurements and calculations in accordance with Embodiment

2 - the refractive index difference / \ n = 0.09 and the diffusion depth Ax &

x & 95 /

4, A piece of KF3 glass - processed as in Embodiment 1 - at 520 C ion exchange with a molten salt (NaMK) _{n ο} (Τ1Ν0ο) _{η Λ} subjected. After 7 h, the refractive index profile indicated in Fig. 2d with a refractive index change of An = 0.055 "and a diffusion depth of Ax £ Z9Q / um is reached.

Claims (2)

¹ sentence Process for the production of optically, inhomogeneous media, characterized in that KF3 of the composition 70 - 72 Gew.-Ja 15 - 1 6 wt. - ^C J> ₂ Ja ₂ O , 5-6% by weight of PbO 5 parts by weight ZnO 1 - 2 wt .- ^ Al ₂ O. 0.3% by weight of As ₂ O an ion exchange with a molten salt (NaNOw) _n ο (TlNOo) ₀ * in the temperature range between khO and 520 C is carried out, wherein the replacement times are up to 40 h. 2. The method according to item 1, characterized in that the molten salt has up to au to thallium. melt a content increased to 0.2 moles T1NO " 1-page drawings