DE3921512C1 - Coupling piece for powerful laser pulses - has ceramic sleeve surrounding end section of glass optical fibre but leasing projecting piece - Google Patents

Abstract

The coupling piece is designed for feeding powerful laser pulses into glass fibre optical conductors, in particular for a laser lithotripter. A ceramic sleeve (K) is provided for enclosing the start of the fibre. This sleeve is fitted directly on the coat or cover or on the core of the fibre (F) and only the glass fibre core or the glass fibre core with cover projects out of the sleeve. The length of this projection amounts to 0.1 mm to 10 mm. USE/ADVANTAGE - Higher power can be connected without damaging the fibre. Suitable for medical use.

Description

The invention relates to a coupling piece for high-energy Laser pulses according to the preamble of claim 1.

In laser lithotripsy with transfer of energy in a glass fiber (light guide) are high light outputs in to couple the fiber. The light generated by the laser is via a coupling optics (converging lens) into the glass fiber headed. When coupling high performance of pulsed lasers in the glass fiber can on the connector, which holds the fiber, due to a laser-induced breakthrough the high field strength in the focus area of the coupling optics arise. Because of this laser-induced breakthrough a plasma can be generated which destroys the Fiber can result. Because of this effect, the laser power that can be coupled into the fiber is limited.

From DE-OS 34 44 824 is a coupling piece for the intracorporeal laser radiation known in which the light is focused on a flat fiber optic start.

Fig. 2 of the reference shows one possibility at which Exit side of the glass fiber to remove the sheath a bit, to avoid damage.

The object of the invention is to propose a coupling piece,  with the high laser powers without damage the fiber can be coupled.

This object is achieved according to the invention by a coupling piece with the features of claim 1. Embodiments of the invention are the subject of subclaims.

According to the invention, the ceramic sleeve can be connected the threshold with a fiber protrusion of up to 1 cm shifted upwards for the creation of a plasma will. This means that the laser power that can be coupled in is not more limited by the plasma formation at the connector.

In order to obtain the highest possible coupling efficiency, the coupling-in fiber end must be as close as possible behind bring the focus of the coupling optics. It poses the following problem:

In many cases it is not possible to use 100% of the laser radiation - for example due to physical parameters or mechanical tolerances - to couple into the fiber. The part of the radiation that is not coupled in goes past the fiber and causing a plasma at the connector, which is the connector itself, but especially the fiber and the fiber end, destroyed.

According to the invention, this is prevented by two devices:

• - The front part of the fiber connector consists of Ceramics. Ceramic has an essential insulator higher plasma threshold than a conductor such as Example metal.
• - Due to the fiber protrusion, the energy density of the radiation not coupled into the connector is so low that there is no plasma on the connector.
  In some cases, for example, if a large part of the laser radiation passes the input end of the fiber due to mechanical tolerances or physical parameters, it is advantageous to prepare this part on the input side, i.e. in the area of the protrusion, so that only the bare core the fiber survives.
  In the plug, however, the fiber must again be surrounded by a suitable sheath material, such as, for example, 1st sheath or adhesive, which limits the radiation emitted by the fiber. This prevents overheating in the connector, which could result in fiber destruction.

Should, for example due to adjustment errors, the Plugs come into the focus area and therefore come on Plasma will appear on the ceramic sleeve, the fiber will not damaged by splashing metal. This is in addition to the increased coupling power into the glass fiber as Another advantage of the ceramic sleeve.

Virtually all ceramics can be used for the sleeve. Tests with white Macor showed good results.

For example, the following fibers can be used:

• a) Step index fibers:
  • - All-glass fiber, fiber structure:
    Quartz core, 1st quartz jacket, 2nd polymer or jacket
  • - HCS (Hard Clad Silica), fiber structure:
    Quartz core, 1st polymer shell
• b) gradient fibers.

Preferred dimensions: diameter of the fiber from 100 µm to 1000 µm.
Length of the overhang from 0.1 mm to 10 mm.
Sleeve diameter mainly SMA standard, other diameters also possible.

The invention is illustrated by three figures.

Show it

Fig. 1 and 2, two Einkoppelstücke according to the invention,

Fig. 3 shows schematically the coupling of laser light into a glass fiber with the coupling piece according to the invention.

Fig. 1 shows the connector ST which surrounds the glass fiber F. According to the invention, the glass fiber F is surrounded at the front by a ceramic sleeve K and protrudes a little from this ceramic sleeve K. In this version, laser light is introduced on the right side of the coupling piece.

Fig. 2 shows a further embodiment in which the ceramic sleeve K , which connects to the connector ST , is sharpened. The overhang of the glass fiber F can again be seen.

Fig. 3 shows the use of a coupling piece, again consisting of the connector ST , the ceramic sleeve K and the protruding end of the glass fiber F , when coupling in laser energy. The light comes from the right, is focused on the start of the glass fiber F by a coupling optics, shown here by a converging lens. The coupling piece then guides the light onto the commercially available glass fiber (indicated on the left).

The fiber can be clamped or glued in the coupling piece. The fiber and connector are also available sterile.

Claims (2)

1. Coupling piece for high-energy laser pulses in a glass fiber (F) , in particular for a laser lithotripter, characterized in that a ceramic sleeve (K) surrounding the beginning of the fiber is provided, which is applied directly to the glass fiber cladding or the glass fiber core, and that only the glass fiber core or the glass fiber core with the jacket protrudes from the ceramic sleeve (K) . 2. Coupling piece according to claim 1, wherein the length the protrusion is between 0.1 and 10 mm.