Comparison between infrared luminosity, L_IR, and radio luminosity at 150 MHz and 1400 MHz. Left: L_IR versus the radio luminosity at 150 MHz. L_IR and L_150 MHz are in units of solar luminosity. Measurements for median LOFAR radio-undetected quasars (RUQs, fuchsia and cyan squares), median LOFAR radio-detected quasars (RDQs, red and turquoise stars), RDQs detected by SPIRE at 250 μm (maroon stars), RUQs detected by SPIRE at 250 μm (yellow circles), and RUQs undetected by SPIRE at 250 μm (green circles) are shown. Upper limits are indicated by arrows in either L_IR or L_150 MHz. For median quasars, the increasing symbol size indicates an the increment in redshift or M₁₄₅₀ absolute luminosity. The dashed line is the far-infrared radio correlation (FIRC) at L_150 MHz derived by Calistro-Rivera et al. (2017). The gray shaded region indicates the spread of the FIRC scaled by a factor of ±2. The text indicates the median redshift of the first and last redshift bins of the stacking according to redshift. Right: Same as the right panel, but for the radio luminosity at 1400 MHz, L_1400 MHz. Measurements for RUQs detected by WSRT, but undetected by SPIRE at 250 μm (purple circles); and RUQs detected by both SPIRE and WSRT at 250 μm and 1400 MHz (blue circles), respectively are also displayed.