In-line light sensor

An integrated optical waveguide having an in-line light sensor integrally formed therewith, comprising:

• a first part of the waveguide leading to a photodiode portion thereof;
• a second part of the waveguide leading away from the photodiode portion, the material from which said first and second parts of the waveguide are formed having an energy band gap the magnitude of which corresponds to absorption of photons of a first wavelength, the photodiode portion comprising one or more regions of light absorbing material within the waveguide arranged to absorb a minor proportion of light of one or more selected wavelengths transmitted along the waveguide (so a major proportion of the light passes through to the second part of the waveguide) to thereby generate free charge carriers within the photodiode portion of the waveguide, the photodiode portion being modified to introduce deep band gap levels therein so as to provide at least partial absorption of photons of a selected wavelength or wavelength band greater than said first wavelength;
• and detecting means for detecting the presence of said free charge carriers.

An integrated optical waveguide having an in-line light sensor integrally formed thereon with the light sensor comprising a p-i-n diode formed in a semiconductor substrate having an energy band gap the magnitude of which corresponds to absorptions of photons of a first wavelength, the photodiode comprising a substantially intrinsic region in said semiconductor substrate between p- and n-doped regions, the intrinsic region being modified to introduce deep band gap levels therein so as to provide at least partial absorption of photons of an optical signal of a selected wavelength or wavelength band greater than said first wavelength and thus generate an electrical signal across the p-i-n diode indicative of said optical signal, said photodiode being provided within a resonant cavity.