  The upper power limit of linear response of light trap detectors was recently
measured [2,3]. We have completed this measurement with test of traps with bias
voltage at several visible wavelengths using silicon photodiodes Hamamatsu
S1337 1010 and made a brief test of S5227 1010. Bias extends the linearity
limit by factor of more than 10 for very narrow beams and more than 30 for wide
beams [5]. No irreversible changes were detected even for the highest
irradiance of 33 W/cm2 at 406nm. Here we present measurement of minimal bias
voltage necessary for 99%, 99.8% and 99.95% linearity for several beam sizes.
