Free-space combining of laser beam radiation

A diode laser beam combining apparatus for producing a high combined beam power density in the far field at reduced levels of power consumption and heat dissipation, comprising:

• an array of semiconductor laser emitters arranged in a collinear manner with respect to each other and having an emitter pitch;
• a cylindrical lens for collimating emitter beams generated by the array of laser emitters in a direction perpendicular to a junction plane of the laser emitters, said cylindrical lens having a focal length between 0.7 mm and 2.5 mm;
• a micro-optic array configured to perform rotational transformation of the collimated emitter beams, said micro-optic array having a lateral spacing in a direction parallel to the junction plane of the laser emitters that matches the emitter pitch;
• and
• a long focal length cylindrical lens for collimating emitter beams in the direction perpendicular to the junction plane after passing through the micro-optic array, wherein the long focal length cylindrical lens has a focal length fSA selected in accordance with the following equation:
• f
• SA
• =
• w
• SA
• θ
• SA
• where θSA is a far-field divergence angle in a slow axis direction, and wSA is an aperture width of individual emitters in the slow axis direction.

A diode laser beam combining apparatus for producing a high combined beam power density in the far field at reduced levels of power consumption and heat dissipation, comprising:

• an array of semiconductor laser emitters arranged in a collinear manner with respect to each other and having an emitter pitch between 0.7 mm and 2.5 mm;
• a cylindrical lens for collimating emitter beams generated by the array of laser emitters in a direction perpendicular to a junction plane of the laser emitters, the cylindrical lens having a focal length fFA;
• a micro-optic array configured to perform rotational transformation of the collimated emitter beams, said micro-optic array having a lateral spacing in a direction parallel to the junction plane of the laser emitters that matches the emitter pitch;
• a long focal length cylindrical lens for collimating emitter beams in the direction perpendicular to the junction plane after passing through the micro-optic array, the long focal length cylindrical lens having a focal length fSA;
• wherein a ratio of the focal length fSA of the long focal length cylindrical lens to the focal length fFA of the cylindrical lens is selected in accordance with the equation:
• f
• SA
• f
• FA
• =
• w
• SA
• λ
• 2
• ⁢
• tan
• ⁡
• (
• θ
• FA
• )
• +
• h
• S
• +
• h
• M
• where wSA is a width of an individual emitter aperture in a slow axis direction, hS is a diode bar smile value, hM represents optics misalignments, λ is a wavelength of propagating radiation, and θFA represents a far-field divergence angle in a fast axis direction.

A diode laser beam combining apparatus for producing a required far field aspect ratio

• output beam, comprising:
• an array of semiconductor laser emitters arranged in a collinear manner with respect to each other and having an emitter pitch;
• a cylindrical lens for collimating emitter beams generated by the array of laser emitters in a direction perpendicular to a junction plane of the laser emitters;
• a micro-optic array configured to perform rotational transformation of the collimated emitter beams, said micro-optic array having a lateral spacing in a direction parallel to the junction plane of the laser emitters that matches the emitter pitch;
• and
• a long focal length cylindrical lens for collimating emitter beams in the direction perpendicular to the junction plane after passing through the micro-optic array, where the required far field aspect ratio of the output beam is achieved by selection of the focal lengths fFA and fSA of the cylindrical lens and the long focal length cylindrical lens wherein a square-shaped output far field distribution is achieved by selecting the focal lengths fFA and fSA of the collimating cylindrical lenses to satisfy the following relation:
• f
• FA
• f
• SA
• =
• w
• SA
• λ
• 2
• ⁢
• tan
• ⁡
• (
• θ
• FA
• )
• +
• h
• S
• +
• h
• M
• where WSA is the width of the individual emitter apertures in the slow axis direction, λ is the wavelength of the laser radiation, and θFA is the far field beam divergence in the fast axis direction, hS is the diode bar smile value, and hM represents optics misalignments such as those caused by post-bonding shifts.