In some examples, an apparatus comprises: a first photodiode to sense a first component of light associated with a first wavelength, and a second photodiode configured to sense a second component of the light associated with a second wavelength, the first component and the second component being associated with, respectively, a first wavelength and a second wavelength. The apparatus further comprises a first optical structure and a second optical structure positioned over, respectively, the first photodiode and the second photodiode. The first optical structure is configured to increase a propagation path of the first component of the light within the first photodiode and has a first optical property based on the first wavelength. The second optical structure is configured to increase a propagation path of the second component of the light within the second photodiode, and has a second optical property based on the second wavelength.