Etalon, a wavelength monitor/locker using the etalon and associated methods

A wavelength monitor comprising:

• a first substrate being optically transparent and having first and second opposing parallel faces;
• at least two photodetectors;
• a splitting element which creates at least two light beams from an input beam;
• a directing element which directs each of said at least two light beams onto a respective photodetector;
• and
• an etalon in the path of at least one of said at least two photodetectors, the etalon and the first substrate being secured together,
• wherein said splitting element and said directing element are on at least one of said first and second opposing parallel faces of the first substrate and parallel faces of any structure secured to at least one of said first substrate and said etalon.

A wavelength locker comprising:

• a divider creating at least a first beam and a second beam from an input beam from a light source;
• a first photodetector receiving the monitor beam;
• a second photodetector receiving the reference beam;
• an etalon in a path between the divider and the monitor photodetector;
• an optics block having an optical element thereon;
• and
• a connector supplying outputs of the monitor photodetector and the reference photodetector to a wavelength controller of the light source, wherein the etalon, the divider and the optical element are formed on surfaces that are parallel to one another.