Method and apparatus for coupling radiation from a stack of diode-laser bars into a single-core optical fiber

A method of coupling laser-radiation into an optical fiber, comprising the steps of:

• (i) providing a plurality of diode-laser bars, each of said diode-laser bars including at least first and second spaced-apart diode-laser emitters emitting respectively first and second beams of laser-radiation;
• (ii) optically combining said first and second laser-radiation beams from each of said diode-laser bars to form a plurality of third laser-radiation beams, each of said third laser-radiation beams including co-propagating ones of said first and second laser-radiation beams from a corresponding diode-laser bar;
• and
• (iii) focusing said third laser-radiation beams into an entrance face of the optical fiber wherein said first and second laser-radiation beams are plane-polarized in a first orientation, and step (ii) includes (a) providing a composite prism including a parallelepiped prism and a triangular prism with a face of said parallelepiped prism optically bonded to a face of said triangular prism, a face of the parallelepiped prism parallel to the bonded face thereof providing a mirror having a high reflectivity for said laser-radiation in said first polarization orientation, one of said bonded faces being optically coated such that said bonded faces provide a second mirror, spaced apart from and parallel to said first mirror, and having a high reflectivity for said laser-radiation in said first polarization orientation and a high transmissivity for said laser-radiation in a second polarization orientation perpendicular to said first polarization orientation;
• (b) rotating the polarization orientation of said second laser-radiation beam from said first orientation to said second orientation and transmitting said polarization-rotated, second laser-radiation beam through said second mirror;
• and (c) reflecting said first laser-radiation beam sequentially from said first and second mirrors such that said sequentially-reflected first laser-radiation beam co-propagates with said transmitted, polarization-rotated second laser-radiation beam.

A method of coupling laser-radiation into an optical fiber, comprising the steps of:

• (i) providing a plurality of diode-laser bars, each of said diode-laser bars including at least first and second spaced-apart diode-laser emitters emitting respectively first and second beams of laser-radiation;
• (ii) optically combining said first and second laser-radiation beams from each of said diode-laser bars to form a plurality of third laser-radiation beams, each of said third laser-radiation beams including co-propagating ones of said first and second laser-radiation beams from a corresponding diode-laser bar;
• and
• (iii) focusing said third laser-radiation beams into an entrance face of the optical fiber wherein said first and second laser-radiation beams are plane-polarized in a first orientation, and step (ii) includes (a) providing a composite prism including a parallelepiped prism and a triangular prism with a face of said parallelepiped prism optically bonded to a face of said triangular prism, a face of the parallelepiped prism parallel to the bonded face thereof providing a mirror having a high reflectivity for said laser-radiation in said first polarization orientation, one of said bonded faces being optically coated such that said bonded faces provide a second mirror, spaced apart from and parallel to said first mirror, and having a high reflectivity for said laser-radiation in a second polarization orientation perpendicular to said first polarization orientation and a high transmissivity for said laser-radiation in said first polarization orientation;
• (b) transmitting said second laser-radiation beam through said second mirror;
• and (c) rotating the polarization orientation of said first laser-radiation beam from said first orientation to said second orientation and reflecting said polarization-rotated first laser-radiation beam sequentially from said first and second mirrors such that said sequentially-reflected, polarization-rotated first laser-radiation beam co-propagates with said transmitted second laser-radiation beam.

A method of coupling laser-radiation into an optical fiber, comprising the steps of:

• (i) providing a plurality N of diode-laser bars where N is an integer greater than zero, each of said diode-laser bars including at least first and second diode-laser emitters emitting respectively first and second beams of laser-radiation from an emitting-aperture having a height and a width, with said apertures aligned in the width direction thereof and spaced apart center-to-center by a distance S, said laser-radiation beams diverging in fast and slow axes perpendicular to each other and mutually perpendicular to the direction of emission with said slow axis being parallel to the width direction of said emitters, and said emitted laser-radiation beams being plane-polarized in a first polarization orientation perpendicular to said slow-axis;
• (ii) arranging said diode-laser bars parallel to each other and one above the other in said fast-axis direction such that emitters in adjacent bars have a fast-axis spacing therebetween;
• (iii) collimating said first and second laser-radiation beams from each of said diode-laser bars;
• (iv) providing first and second mirrors arranged parallel to each other and spaced apart and being inclined to said emission direction of said laser-radiation beams, said first and second mirrors being highly reflective for said laser-radiation polarized in said first orientation and said second mirror being highly transmissive for said laser-radiation polarized in a second orientation perpendicular to said first orientation;
• (v) rotating the polarization plane of each said fast-axis collimated second laser-radiation beams from said first orientation to said second orientation;
• (vi) transmitting said fast-axis collimated, polarization-rotated, second laser-radiation beams through said second mirror and sequentially reflecting each of said collimated first laser-radiation beams from said first and second mirrors such that N combined laser-radiation beams are formed, each of said combined laser-radiation beams including co-propagating ones of said fast-axis collimated first and said fast-axis collimated, polarization-rotated second laser-radiation beams from a corresponding diode-laser bar;
• and
• (viii) focusing said N combined laser-radiation beams into an entrance face of the optical fiber.

A method of coupling laser-radiation into an optical fiber, comprising the steps of:

• (i) providing a plurality N of diode-laser bars where N is an integer greater than zero, each of said diode-laser bars including at least first and second diode-laser emitters emitting respectively first and second beams of laser-radiation from an emitting-aperture having a height and a width, with said apertures aligned in the width direction thereof and spaced apart center-to-center by a distance S, said laser-radiation beams diverging in fast and slow axes perpendicular to each other and mutually perpendicular to the direction of emission with said slow axis being parallel to the width direction of said emitters, and said emitted laser-radiation beams being plane-polarized in a first polarization orientation perpendicular to said slow-axis;
• (ii) arranging said diode-laser bars parallel to each other and one above the other in said fast-axis direction such that emitters in adjacent bars have a fast-axis spacing therebetween;
• (iii) collimating said first and second laser-radiation beams from each of said diode-laser bars;
• (iv) providing first and second mirrors arranged parallel to each other and spaced apart and being inclined to said emission direction of said laser-radiation beams, said first and second mirrors being highly reflective for said laser-radiation polarized in said first orientation and said second mirror being highly transmissive for said laser-radiation polarized in a second orientation perpendicular to said first orientation;
• (v) rotating the polarization plane of each said fast-axis collimated second laser-radiation beams from said first orientation to said second orientation;
• (vi) transmitting said fast-axis collimated first laser-radiation beams through said second mirror and sequentially reflecting each of said collimated, polarization-rotated second laser-radiation beams from said first and second mirrors such that N combined laser-radiation beams are formed, each of said combined laser-radiation beams including co-propagating ones of said fast-axis collimated first and said fast-axis collimated, polarization-rotated second laser-radiation beams from a corresponding diode-laser bar;
• and
• (viii) focusing said N combined laser-radiation beams into an entrance face of the optical fiber.

Optical apparatus comprising:

• a diode-laser array including first and second emitters, each thereof having a height and a width, said emitters being spaced apart in the width direction and arranged to emit laser-radiation in first and second beams thereof, said laser-radiation beams propagating parallel to each other in a direction generally along a propagation direction, and each of said first and second laser-radiation beams diverging in fast and slow axes, said fast axis, said slow axis, and said propagation direction being mutually perpendicular, said slow axis being parallel to the width direction of said emitters, and each of said laser-radiation beams being plane-polarized in a first orientation perpendicular to said slow axis;
• a cylindrical lens in front of said diode-laser array arranged to collimate said first and second laser-radiation beams in said fast axis thereof;
• first and second mirrors inclined to said propagation axis and parallel to each other, each thereof being highly reflective for said laser-radiation plane-polarized in said first orientation, and said second mirror being highly transmissive for said laser-radiation plane-polarized in a second orientation perpendicular to said first orientation;
• a polarization-rotating device arranged to rotate the polarization orientation of said fast-axis collimated second laser-radiation beam from said first orientation to said second orientation;
• said first and second mirrors and said polarization rotating device being arranged such that said fast-axis collimated, polarization-rotated second laser-radiation beam is transmitted through said second mirror and said fast-axis collimated, first laser-radiation beam is reflected sequentially by said first and second mirrors such that said sequentially-reflected fast-axis collimated, first laser-radiation beam and said transmitted, fast-axis collimated, polarization-rotated second laser-radiation beam are combined and propagate in the same direction.

Optical apparatus comprising:

• a diode-laser array including first and second emitters, each thereof having a height and a width, said emitters being spaced apart in the width direction and arranged to emit laser-radiation in first and second beams thereof, said laser-radiation beams propagating parallel to each other in a direction generally along a propagation direction, and each of said first and second laser-radiation beams diverging in fast and slow axes, said fast axis, said slow axis, and said propagation direction being mutually perpendicular, said slow axis being parallel to the width direction of said emitters, and each of said laser-radiation beams being plane-polarized in a first orientation parallel to said slow axis;
• a cylindrical lens in front of said diode-laser array arranged to collimate said first and second laser-radiation beams in said fast axis thereof;
• first and second mirrors inclined to said propagation axis and parallel to each other, each thereof being highly reflective for said laser-radiation plane-polarized in a second orientation perpendicular to said first orientation, and said second mirror being highly transmissive for said laser-radiation plane-polarized in said first orientation;
• a polarization-rotating device arranged to rotate the polarization orientation of said fast-axis collimated second laser-radiation beam from said first orientation to said second orientation;
• said first and second mirrors and said polarization rotating device being arranged such that said fast-axis collimated first laser-radiation beam is transmitted through said second mirror, and said fast-axis collimated, polarization-rotated second laser-radiation beam is reflected sequentially by said first and second mirrors such that said transmitted, fast-axis collimated first laser-radiation beam and said sequentially-reflected fast-axis collimated, polarization-rotated second laser-radiation beam are combined and propagate in the same direction.

Optical apparatus comprising:

• a number N of elongated diode-laser bars where N is an integer greater than zero, each thereof including first and second emitters each of said emitters having a height and a width, said emitters being spaced apart in the width direction and arranged to emit laser-radiation in first and second beams thereof, said laser-radiation beams propagating parallel to each other in a direction generally along a propagation direction, and each of said first and second laser-radiation beams diverging in fast and slow axes, said fast axis, said slow axis, and said propagation direction being mutually perpendicular, said slow axis being parallel to the width direction of said emitters, each of said laser-radiation beams being plane-polarized in a first orientation perpendicular to said slow axis, and said diode-laser bars arranged spaced apart and parallel, one above the other in the fast-axis direction;
• a number N of cylindrical lenses, one located in front of each diode-laser bar and arranged to collimate said first and second laser-radiation beams in said fast axis thereof;
• first and second mirrors inclined to said propagation axis and parallel to each other, each thereof being highly reflective for the laser-radiation plane-polarized in said first orientation, and said second mirror being highly transmissive for radiation plane-polarized in a second orientation perpendicular to said first orientation;
• a polarization rotating device arranged to rotate the polarization orientation of said fast-axis collimated second laser-radiation beams from said first orientation to said second orientation;
• said first and second mirrors and said polarization rotating device being arranged such that said fast-axis collimated, polarization-rotated second laser-radiation beams are transmitted through said second mirror, and said fast-axis collimated, first laser-radiation beams are reflected sequentially by said first and second mirrors such that corresponding ones of said sequentially-reflected fast-axis collimated, first laser-radiation beams and said transmitted, fast-axis collimated, polarization-rotated second laser-radiation beams are combined and propagate in the same direction as N combined beams.

Optical apparatus comprising:

• a number N of elongated diode-laser bars where N is an integer greater than zero, each thereof including first and second emitters each of said emitters having a height and a width, said emitters being spaced apart in the width direction and arranged to emit laser-radiation in first and second beams thereof, said laser-radiation beams propagating parallel to each other in a direction generally along a propagation direction, and each of said first and second laser-radiation beams diverging in fast and slow axes, said fast axis, said slow axis, and said propagation direction being mutually perpendicular, said slow axis being parallel to the width direction of said emitters, each of said laser-radiation beams being plane-polarized in a first orientation parallel to said slow axis, and said diode-laser bars arranged spaced apart and parallel, one above the other in the fast-axis direction;
• a number N of cylindrical lenses, one located in front of each diode-laser bar and arranged to collimate said first and second laser-radiation beams in said fast axis thereof;
• first and second mirrors inclined to said propagation axis and parallel to each other, each thereof being highly reflective for the laser-radiation plane-polarized in a said second orientation perpendicular to said first orientation, and said second mirror being highly transmissive for radiation plane-polarized in said first orientation;
• a polarization rotating device arranged to rotate the polarization orientation of said fast-axis collimated second laser-radiation beams from said first orientation to said second orientation;
• said first and second mirrors and said polarization rotating device being arranged such that said fast-axis collimated first laser-radiation beams are transmitted through said second mirror, and said fast-axis collimated, polarization-rotated second laser-radiation beams are reflected sequentially by said first and second mirrors such that corresponding ones of said fast-axis collimated, transmitted first laser-radiation beams and said fast-axis collimated, polarization-rotated, sequentially-reflected second laser-radiation beams are combined and propagate in the same direction as N combined beams.

Optical apparatus, comprising:

• a number N of elongated diode-laser bars where N is an integer greater than zero, each thereof including first and second emitters, each of said emitters having a height and a width, said emitters being spaced apart in the width direction and arranged to emit laser-radiation in first and second beams thereof, said laser-radiation beams propagating parallel to each other in a direction generally along a propagation direction, and each of said first and second laser-radiation beams diverging in fast and slow axes, said fast axis, said slow axis, and said propagation direction being mutually perpendicular, said slow axis being parallel to the width direction of said emitters, each of said laser-radiation beams being plane-polarized in a first orientation perpendicular to said slow axis, and said diode-laser bars arranged spaced apart and parallel, one above the other in the fast-axis direction;
• a number N of cylindrical lenses, one located in front of each diode-laser bar and arranged to collimate said first and second laser-radiation beams in said fast axis thereof;
• a number N of alignment plates, one in front of each diode-laser bar, each thereof being selectively rotatable about the fast axis direction for displacing the beam-path of said collimated first and second laser-radiation beams in the slow axis direction;
• first and second mirrors inclined to said propagation axis and parallel to each other, each thereof being highly reflective for the laser-radiation plane-polarized in said first orientation, and said second mirror being highly transmissive for radiation plane-polarized in a second orientation perpendicular to said first orientation, said first and second mirrors being incorporated in a composite prism, said composite prism including a parallelepiped prism and an isosceles-triangle prism with one face of the parallelepiped prism providing said first mirror and with an opposite face of the parallelepiped prism being bonded to an isosceles face of the triangular prism, with one of the bonded prism faces being optically coated, thereby providing said second mirror;
• a polarization-rotating device arranged to rotate the polarization orientation of said fast-axis collimated second laser-radiation beams from said first orientation to said second orientation;
• and
• said first and second mirrors and said polarization-rotating device being arranged such that said fast-axis collimated, polarization-rotated second laser-radiation beams are transmitted through said second mirror, and said fast-axis collimated, first laser-radiation beams are reflected sequentially by said first and second mirrors such that corresponding ones of said sequentially-reflected, fast-axis collimated, first laser-radiation beams and said transmitted, fast-axis collimated, polarization-rotated second laser-radiation beams are combined to form N combined beams propagating parallel to each other, one or more of said alignment plates being selectively rotated such that said combined beams are aligned one-above the other in the fast-axis direction.

Optical apparatus comprising:

• a number N of elongated diode-laser bars where N is an integer greater than zero, each thereof including first and second emitters each of said emitters having a height and a width, said emitters being spaced apart in the width direction and arranged to emit laser-radiation in first and second beams thereof, said laser-radiation beams propagating parallel to each other in a direction generally along a propagation direction, and each of said first and second laser-radiation beams diverging in fast and slow axes, said fast axis, said slow axis, and said propagation direction being mutually perpendicular, said slow axis being parallel to the width direction of said emitters, each of said laser-radiation beams being plane-polarized in a first orientation perpendicular to said slow axis, and said diode-laser bars arranged spaced apart and parallel, one above the other with corresponding emitters thereof aligned one above the other in the fast-axis direction;
• a number N of cylindrical lenses, one located in front of each diode-laser bar and arranged to collimate said first and second laser-radiation beams in said fast axis thereof;
• first and second mirrors inclined to said propagation axis and parallel to each other, each thereof being highly reflective for the laser-radiation plane-polarized in said first orientation, and said second mirror being highly transmissive for radiation plane-polarized in a second orientation perpendicular to said first orientation;
• a polarization rotating device arranged to rotate the polarization orientation of said fast-axis collimated second laser-radiation beams from said first orientation to said second orientation;
• said first and second mirrors and said polarization rotating device being arranged such that said fast-axis collimated, polarization-rotated second laser-radiation beams are transmitted through said second mirror, and said fast-axis collimated, first laser-radiation beams are reflected sequentially by said first and second mirrors such that corresponding ones of said sequentially-reflected, fast-axis collimated, first laser-radiation beams and said transmitted, fast-axis collimated, polarization-rotated second laser-radiation beams are combined and propagate in the same direction as N combined beams propagating parallel to each other and aligned one above the other in the fast axis direction.

Optical apparatus comprising:

• a diode-laser bar including first and second clusters of spaced apart emitters each emitter having a width and each cluster having a width, said clusters of emitters being spaced apart center-to-center in the width direction by at least two cluster widths, and said emitters in said clusters thereof being spaced apart by less than two emitter widths, said first and second clusters of emitters arranged to emit laser-radiation in respectively first and second beams thereof, said laser-radiation beams propagating parallel to each other in a direction generally along a propagation direction, and each of said first and second laser-radiation beams diverging in fast and slow axes, said fast axis, said slow axis, and said propagation direction being mutually perpendicular, said slow axis being parallel to the width direction of said emitters, and each of said laser-radiation beams being plane-polarized in a first orientation perpendicular to said slow axis;
• a cylindrical lens in front of said diode-laser bar arranged to collimate said first and second laser-radiation beams in said fast axis thereof;
• first and second mirrors inclined to said propagation axis and parallel to each other, each thereof being highly reflective for the laser-radiation plane-polarized in said first orientation, and said second mirror being highly transmissive for radiation plane-polarized in a second orientation perpendicular to said first orientation;
• a polarization-rotating device arranged to rotate the polarization orientation of said fast-axis collimated second laser-radiation beam from said first orientation to said second orientation;
• said first and second mirrors and said polarization-rotating device being arranged such that said fast-axis collimated, polarization-rotated second laser-radiation beam is transmitted through said second mirror and said fast-axis collimated, first laser-radiation beam is reflected sequentially by said first and second mirrors such that said sequentially-reflected, fast-axis collimated, first laser-radiation beam and said transmitted, fast-axis collimated, polarization-rotated second laser-radiation beam are combined and propagate in the same direction.

Optical apparatus comprising:

• a diode-laser bar including first and second clusters of spaced apart emitters each emitter having a width and each cluster having a width, said clusters of emitters being spaced apart center-to-center in the width direction by at least two cluster widths, and said emitters in said clusters thereof being spaced apart by less than two emitter widths, said first and second clusters of emitters arranged to emit laser-radiation in respectively first and second beams thereof, said laser-radiation beams propagating parallel to each other in a direction generally along a propagation direction, and each of said first and second laser-radiation beams diverging in fast and slow axes, said fast axis, said slow axis, and said propagation direction being mutually perpendicular, said slow axis being parallel to the width direction of said emitters, and each of said laser-radiation beams being plane-polarized in a first orientation parallel to said slow axis;
• a cylindrical lens in front of said diode-laser bar arranged to collimate said first and second laser-radiation beams in said fast axis thereof;
• first and second mirrors inclined to said propagation axis and parallel to each other, each thereof being highly reflective for the laser-radiation plane-polarized in a second orientation perpendicular to said first orientation, and said second mirror being highly transmissive for radiation plane-polarized in said first orientation;
• a polarization-rotating device arranged to rotate the polarization orientation of said fast-axis collimated second laser-radiation beam from said first orientation to said second orientation;
• said first and second mirrors and said polarization-rotating device being arranged such that said fast-axis collimated first laser-radiation beam is transmitted through said second mirror and said fast-axis collimated, polarization-rotated second laser-radiation beam is reflected sequentially by said first and second mirrors such that said fast-axis collimated, first laser-radiation beam and said transmitted, fast-axis collimated, polarization-rotated, sequentially-reflected second laser-radiation beam are combined and propagate in the same direction.

A method of coupling laser-radiation into an optical fiber, comprising the steps of:

• (i) providing a plurality of diode-laser bars, each of said diode-laser bars including at least first and second spaced-apart diode-laser emitters emitting respectively first and second beams of laser-radiation;
• (ii) optically combining said first and second laser-radiation beams from each of said diode-laser bars to form a plurality of third laser-radiation beams, each of said third laser-radiation beams including co-propagating ones of said first and second laser-radiation beams from a corresponding diode-laser bar;
• and
• (iii) focusing said third laser-radiation beams into an entrance face of the optical fiber wherein each of said first and second emitters includes a cluster of spaced-apart sub-emitters, each of said sub-emitters having a sub-emitter width and said clusters of emitters each having a cluster width, and wherein said clusters of emitters are spaced apart by two or more cluster widths, and said sub-emitters are spaced-apart by less than two sub-emitter widths.

A method of coupling laser-radiation into an optical fiber, comprising the steps of:

• (i) providing a plurality of diode-laser bars, each of said diode-laser bars including at least first and second spaced-apart diode-laser emitters emitting respectively first and second beams of laser-radiation;
• (ii) optically combining said first and second laser-radiation beams from each of said diode-laser bars to form a plurality of third laser-radiation beams, each of said third laser-radiation beams including co-propagating ones of said first and second laser-radiation beams from a corresponding diode-laser bar;
• and
• (iii) focusing said third laser-radiation beams into an entrance face of the optical fiber wherein said first and second laser-radiation beams are plane-polarized in a first orientation, and step (ii) includes providing a first mirror having a high reflectivity for said laser-radiation in said first polarization orientation;
• providing a second mirror spaced apart from and parallel to said first mirror and having a high reflectivity for said laser-radiation in said first polarization orientation and a high transmissivity for said laser-radiation in a second polarization orientation perpendicular to said first polarization orientation;
• rotating the polarization orientation of said second laser-radiation beam from said first orientation to said second orientation;
• transmitting said polarization-rotated second laser-radiation beam through said second mirror;
• and reflecting said first laser-radiation beam sequentially from said first and second mirrors such that said sequentially-reflected first laser-radiation beam co-propagates with said transmitted, polarization-rotated second laser-radiation beam.

A method of coupling laser-radiation into an optical fiber, comprising the steps of:

• (i) providing a plurality of diode-laser bars, each of said diode-laser bars including at least first and second spaced-apart diode-laser emitters emitting respectively first and second beams of laser-radiation;
• (ii) optically combining said first and second laser-radiation beams from each of said diode-laser bars to form a plurality of third laser-radiation beams, each of said third laser-radiation beams including co-propagating ones of said first and second laser-radiation beams from a corresponding diode-laser bar;
• and
• (iii) focusing said third laser-radiation beams into an entrance face of the optical fiber wherein said first and second laser-radiation beams are plane-polarized in a first orientation, and step (ii) includes providing a first mirror having a high reflectivity for said laser-radiation in said first polarization orientation;
• providing a second mirror spaced apart from and parallel to said first mirror and having a high reflectivity for said laser-radiation in a second polarization orientation perpendicular to said first polarization orientation and a high transmissivity for said laser-radiation in said first polarization orientation;
• transmitting said second laser-radiation beam through said second mirror;
• rotating the polarization orientation of said first laser-radiation beam from said first orientation to said second orientation and reflecting said polarization-rotated first laser-radiation beam sequentially from said first and second mirrors such that said sequentially-reflected, polarization-rotated first laser-radiation beam co-propagates with said transmitted second laser-radiation beam.

An apparatus for combining the radiation from first and second laser beams each having the same initial polarization state comprising:

• a parallelepiped prism having first and second opposed faces;
• a triangular prism, with said first face of said parallelepiped prism defining a first mirror and with an opposite face of said parallelepiped prism being bonded to a face of the triangular prism, with one of the bonded prism faces being optically coated, thereby defining a second mirror, each mirror being highly reflective for laser radiation in a first polarization state and with said second mirror being highly transmissive for laser radiation in a second polarization state perpendicular to said first polarization state;
• and
• a polarization-rotating device for rotating the polarization state of one of the laser beams and being aligned in front of either the parallelepiped prism or the triangular prism whereby in use, radiation from one of the laser beams reflects off both the first and second mirrors and radiation from the second laser beam is transmitted through the second mirror.