(1985)Previous research on the Ettingshausen effect is limited to the interpretation of temperature differences which appear in a specimen vertical to the electric current j and the magnetic field BZ. The temperature difference then generally is regarded in connection with a constant temperature gradient ATEtt/b which is given by the relation is large compared g Simultaneous to the Ettingshausen effect a c a r r i e r concentration profile, with enriched and depleted areas, appears in an intrinsic semiconductor specimen with finite surface recombination velocities. This is the well known magnetoconcentration effect /1 to 3/, which does not cause just only resistance variations, but also luminescence phenomena /4/.The spatially depending non-equilibrium concentration, given by this effect, gives rise to a disturbance of the "Ettingshausen effect". In contrast t o the equilibrium conditions, where c a r r i e r generation and recombination, respectively, occurs just on the side surfaces, the non-equilibrium concentrations produce heat sinks and sources by c a r r i e r generation and recombination in the bulk. Under these conditions the Ettingshausen effect is also 1) Postfach 3329, D-3300 Braunschweig, FRG.

The stabilization of C0,-laser radiation (or other high power radiation in the spectral region of about 5 to 50 pm wavelength) can be realized by the free carrier absorption of intrinsic semiconductors. This effect is due to the increasing free carrier concentration with increasing temperature. In this way the free carrier absorption reduces the transmitted radiation-flux density if the input power of radiation rises and therefore we have a corresponding increasing temperature. This "stabilization filter" works without any outer control mechanism as a passive optical device. The paper states the theoretical background of the control characteristic as well as the experimental parameters for the realized example. At a laser power of about 7 W the output power is typically 1.2 W with a stabilization factor of 1 : 30 and a time constant of about 1.0 s. Semiconductors as i-germanium and i-InSb, respectively, are used as filter materials.Die Stabilisierung von C0,-Laserstrahlung (oder anderer entsprechend intensiver Strahlung im Spektralbereich von etwa 5 bis 50 pm Wellenlange) kann erreicht werden durch Ausnutzung der Absorption freier Ladungstrager von eigenleitenden Halbleitern. Dies gelingt aufgrund der mit der Temperatur ansteigenden Tragerkonzentration. Auf diese Weise reduziert die Absorption der freien Ladungstrager die transmittierte StrahIungsfluBdichte, wenn die einfallende Strahlungsleistung und damit die Temperatur ansteigt. Dieses ,,Stabilisierungsfilter" arbeitet ohne jeden auaeren Regelmechanismus als passives optisches Bauelement. Die Arbeit stellt den theoretischen Hintergrund der Regelcharakteristik dar und gibt die experimentellen Parameter eines realisierten Beispiels an. Bei einer Laserleistung von etwa 7 W betrug die Ausgangsleistung typisch 1,2 W bei einem Stabilisierungsfaktor von 1 : 30 und einer Zeitkonstanten von etwa 1,0 s. Als Halbleiter fanden sowohl i-Germanium als auch i-InSb Verwendung.') Pockelsstr. 4, W-3300 Braunschweig, FRG. ' ) The first publication of the results was an oral presentation at DPG Spring-Meeting, Miinster [9].

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