Reflective surfaces for the apertures of PPG optical components in PPG systems is disclosed. In a PPG system or device, the addition of reflective surfaces around, under, or near the apertures of the optical components can enhance the amount of light received by the light detector. As a result, the measured PPG signal strength can be higher and more accurate compared to the same PPG device without reflective surfaces. The reflective surfaces can reflect and/or recycle light that is incident upon the reflective surfaces back into the skin for eventual capture of the light by the light detectors. In some examples, the reflective surfaces can be diffuse or specular reflectors and/or can be configured to selectively reflect one or more wavelengths of light. In some examples, the back crystal and/or component mounting plane of the PPG system can be made of the same material as the reflective surfaces.
