Wavelength reference apparatus and method

A laser apparatus, comprising:

• (a) a gain medium having a first facet to emit a first light beam;
• (b) a first wavelength reference element positioned in association with said first light beam having a first free spectral range and having a plurality of first transmission peaks within a wavelength range of interest;
• (c) a second wavelength reference element positioned in association with said first light beam having a second free spectral range and having a plurality of second transmission peaks within said wavelength range of interest, said second free spectral range different from said first free spectral range, said first and second wavelength reference elements configured to define a single joint transmission peak within said wavelength range of interest;
• and
• (d) a detector positioned in association with said first light beam after said first and second wavelength reference elements.

A method of operation, comprising:

• (a) directing a portion of a light beam emitted by a gain medium through first and second wavelength reference elements;
• (b) generating a first plurality of transmission peaks within a gain bandwidth of said gain medium with said first wavelength reference element;
• (c) generating a second plurality of transmission peaks within said gain bandwidth with said second wavelength reference element;
• (d) generating only one joint transmission peak within said gain bandwidth by aligning one of said first plurality of transmission peaks with one of said second plurality of transmission peaks;
• and
• (b) measuring optical power of said portion of said light beam after directing said portion of said light beam through said first and second wavelength selection elements.