Polarized surface brightness profiles along the major axis (top) and minor axis (bottom) of the HD 135344B disk. The position angle of the axis (measured east of north) is shown in the top left and right, and the colors indicate different filters. Data points show the mean Q_φ surface brightness and the error bars show 1σ uncertainties determined from the corresponding U_φ image. We have rejected bins in which the mean Q_φ count rate is negative as well as lower limit error bars that correspond to negative flux values. We note that the error bars do not include the uncertainty from the photometric calibration. The dotted lines show 1σ and 5σ background levels in the Q_φJ-band image at large separation from the star.