An illumination device (200-c;200-d) includes a light source (210-c;210-d) configured to emit, during operation, light with a prevalent direction of propagation different from a direction of an optical axis (102-c) of the illumination device; and an optical coupler (220-c;220-d) including a transparent material, the optical coupler having an input aperture, an exit aperture (225-c,225-d) and a first side surface (224-c;224-d) and a second side surface (226-c;226-d) arranged between the input aperture and the exit aperture (225-c;225-d), the exit aperture being centered on the optical axis of the illumination device. The optical coupler (220-c;220-d) receives the emitted light through the input aperture from the light source. Further, the first side surface and the second side surface redirect the received light via total internal reflection (TIR) to the exit aperture. Additionally, the redirected light is issued through the exit aperture.