TWO NOVEL HCD-STRUCTURES FOR CuII-LASERS AND THEIR PERFORMANCE

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Submitted on 1 Jan 1979

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TWO NOVEL HCD-STRUCTURES FOR CuII-LASERS AND THEIR PERFORMANCE

H. Eichler, H. Koch, J. Paffenholz, J. Salk, G. Skrobol

To cite this version:

H. Eichler, H. Koch, J. Paffenholz, J. Salk, G. Skrobol. TWO NOVEL HCD-STRUCTURES FOR CuII-LASERS AND THEIR PERFORMANCE. Journal de Physique Colloques, 1979, 40 (C7), pp.C7- 379-C7-380. �10.1051/jphyscol:19797186�. �jpa-00219164�

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JOURNAL DE PHYSIQUE CoZZoque C7, suppZ6ment au n 0 7 , Tome 40, J u i Z Z e t 1979, page ~ 7 - 379

TWO NOVEL HCD-STRUCTURES FOR CUD-LASERS AND THEIR PERFORMANCE

H.J. Eichler, H.Koch, J. Paffenholz, J. Salk and G. Skrobol.

G p t i s c h e s I n s t i t u t TU B e r l i n , S e k r . p11 S t r . d . 17. J u n i 135, 1000 B e r l i n 12.

The major problems of sputtering hollow

cathode devices (HCD) for high continuous ^.- -. - . - - - -Anode -@.-

power operation of CuII-lasers /I/ are discharge instability and losses of Cu-vapour,

Cathode -

He-Ions and light quanta.

The following constructions (fig. 1 and 3)

were designed considering these criteria. 6 ^.node

-9-

The first design applies the type of HCD -Fig 1 -

introduced by White / 2 / . The advantages of

350-UiV1 200 -@[mwl

these cavity hollow cathodes (exceptionally high skability and r~~inimum losses) can .be used for CuII-laser operation by lining up the cavity hollow cathodes and connecting

300- them by a bore which constitutes the laser tube. Two anode rods are opposing the aper- tures of the cavity cathodes. Both anodes and the cathode arrangement are watercooled.

\

&- 100

1 CAI 250d

As this design is still in the development 10 20 10

ir.

^3b^{Flg 3}^Oo

¹

^/

...

²⁰^, ^11.¹ ³⁰^,

stage fig. 2 shows the discharge voltage

Cathodes

and the laser output+ vs. the discharge current I at a total pressure of 15 mb for

not optimized conditions. The parameters - Fig.3

are as follows:

laser bore diameter: 4 mm ^L _Anodes

laser bore length : 300 mm LOO-UIVI cavity aperture : 2 mm

cavity spacing : 7,5 nun

resonator: fully reflecting mirror and an

1 % transmittance mirror, both with radius I[Al

of 2 m.

He:Ar mixture of pressure ratio 20:1, total pressure: 15 mb.

120- Fig. 1 Cavity hollow cathode laser

Fig. 2 U ( 1 ) - and +(I)-characteristics of

the first design 80 -

Fig. 3 Cylindrical hollow cathode laser tube

'Fig. 4 U (1,p) - and +(1,p) -characteristics of the second design

I [A1

0 2 4 6 8 10 12 14 16 18 20

Fig 6

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797186

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. - - - - - - 7

/ 6

-

2 _Y

I CAI 115cm 200 -@cmw1

d Lmml d Crnml

pure He Fig'5

Fig. 5 U (I) - and (I) - dependence on the HCD geometry

Fig. 6 Efficiency vs. discharge current for different cathode bore diameters Fig. 7 Laser output power saturation

ILAl IIAI

Fia 6 Fla. 7 Fig. 6 shows the dependence of the effici-

The secona design consists of watercooled cylindrical hollow cathodes. High stabili- ty and minimization of losses were obtained with this structure by employing a small cathode-anode gap, that provides a restric- tion of the discharge to the laser bore only. Fig. 4 exhibits the dependences of discharge voltage U and laser multiline

(7 40-7 90 nm) output on the discharge current I and the total gas pressure p (He:Ar

= 20: 1 ) for an IICD-arrangement consisting of 4 cathodes with 5 mm bore diameter and 40 mm length. The U (I) -characteristics display the reverse branches of the indi- cated full U (I) -curve.

It is known, that the HCD-performance is strongly dependent on the cathode bore geometry. To our knowledge we have investiga- ted the geometry dependence of the laser- HCD-parameters for the first time quanti- tatively in this high current and pressure range. Fig. 5 reveals the influence of the hollow cathode bore geometry on the U ( 1 ) -

and the $(I) -characteristics (active length 160 mm) .

ency (e-g. laser output power divided by the product of discharge voltage and current) on the discharge current for different cathode bore diameters (8 cathodes of 20 mm length). We employed anodes of vari- ous bore lengths (2-6 mm) and bore dlame- ters, that were equal and up to 4 mm bigger than the cathode bore diameters, without any appreciable change in discharge voltage and laser output.

Finally we were able to observe for the first time saturation of the 7 8 0 ~ 8 nm laser line at high discharge currents. Vlith only one cathode segment of 30 rnrn length and 7 mm diameter it was possible to ob- tain 14 A discharge current without dama- ging the device. Fig. 7 shows measurements of the saturation of the IR-laser output for He:Ar mixtures with different pressure ratios.

References:

/I/ B.E. Warner et al, IEEE J. Quant.

Electr., Vol. QE-14, No. 8, 568 (1978) / 2 / A.D. White, J. Appl. Phys., &, ⁷¹¹

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