Tuning system for external cavity diode laser

In an external cavity tunable laser system having a laser, having a laser, a diffraction grating and a rotatable mirror positionable to reflect a beam diffracted by said diffraction grating at a selected angle, corresponding to the diffraction angle of a selected wavelength, back into said laser, the improvement comprising:

• a. pivot means for said mirror;
• b. the axis of rotation of said pivot means positioned at the line of intersection of the bisectors of the angles created by the normals to the plane of said mirror at three different angular positions of said mirror representing the diffraction angle from said grating of three different wavelengths;
• c. said normals passing through their corresponding mirror planes at the points of intersection between said mirror planes at said three different angular positions;
• d. said three different angular positions of said mirror corresponding to the angular position which reflects three different wavelengths within the tuning range of said laser and a lineal position representing an integral number of half wavelengths within said cavity at said three different wavelengths;
• and,
• e. one of said three different wavelengths is the nominal center wavelength of the system.

An external cavity tunable laser system comprising:

• a. a base member;
• b. diffraction grating means mounted on said base member;
• c. diode laser means mounted on said base member and having an output beam positioned to strike said grating at a grazing angle;
• d. mirror means for reflecting a diffracted beam from said grating back onto said grating and thence back into said laser;
• e. mirror mounting means providing for simultaneous lineal and rotational movement of said mirror about an axis of rotation corresponding to the line of intersection of the bisectors of the angles created by the normals to the plane of said mirror at three different positions of said mirror, said normals passing through their corresponding mirror planes at the points of intersection between said mirror planes at said three different angular positions, each of said three different angular positions of said mirror providing an integral number of half wavelengths within said cavity at a selected wavelength, calculated according to the general formula:
• Opl=Ph1+C,
• where:
• Opl=the optical length of the tuning cavity
• Phl=the physical length of the tuning cavity
• C=a correction for the wavelength-dependent indices of refraction of the optical elements of the system.