Optical path rotating device used with linear array laser diode and laser apparatus applied therewith

• US 5,513,201 A
• Filed: 04/28/1994
• Issued: 04/30/1996
• Est. Priority Date: 04/30/1993
• Status: Expired due to Term

• Current Assignee: Nippon Steel Corporation
• Original Assignee: Nippon Steel Corporation
• Inventors: Daimon, Masahiro, Kobayashi, Tetsurou, Yamaguchi, Satoshi, Chiba, Koichi, Saito, Yoshimasa
• Primary Examiner(s): Davie, James W.
• Application Number:
  US08/235,455
• Time in Patent Office: 733 Days
• Field of Search: 372/50, 372/69, 372/70, 372/75, 385/33, 385/34, 359/619, 359/629
• US Class Current: 372/75
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0057 in the form of a laser diode array, e.g. laser diode bar semiconductor laser arrays with beam combining arrangement H01S5/4012
• CPC Class Codes: G02B 27/0944 Diffractive optical elements, e.g. gratings, holograms gratings per se G02B5/18; holograms used as optical elements per se G02B5/32
• CPC Class Codes: G02B 27/0961 Lens arrays lens arrays per se G02B3/0006
• CPC Class Codes: G02B 27/0966 Cylindrical lenses cylindrical lenses per se G02B3/06
• CPC Class Codes: G02B 27/0972 Prisms prisms per se G02B5/04
• CPC Class Codes: G02B 6/4206 Optical features G02B6/4207, G02B6/421 take precedence
• CPC Class Codes: G02B 6/425 Optical features semiconductor laser arrays H01S5/40; hybrid LED arrays H01L25/0753; monolithic LED arrays H01L27/153
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 5/005 Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/4025 Array arrangements, e.g. constituted by discrete laser diodes or laser bar H01S5/42 takes precedence

Abstract

An optical path rotating device, disposed in front of a linear array laser diode having a plurality of long and narrow and linearly arranged emitters for emitting a group of laser beams in the form of a dotted line, the optical path rotating device being able to convert the laser beams from the emitters into laser beams lined up in the form of ladder rungs by receiving the group of laser beams collimated by being refracted in a direction substantially perpendicular to the direction of the dotted line, rotating the positions of the laser beams from the emitters substantially for a right angle, and emitting the laser beams, and a laser apparatus, which uses the optical path rotating device, for collimating the substantially rung-shaped laser beams into two directions independently, bringing the laser means into focus, thus increasing the density of the laser energy at the focus.

Claims

1. A semiconductor laser apparatus comprising:

a linear array laser diode, having a plurality of laser-beam-emitting emitters having emitter faces arranged to extend linearly in a first direction for emitting a group of laser beams in a form of a dotted line;

a first condenser, disposed in front of said linear array laser diode, for collimating said group of laser beams by refracting them to a direction substantially perpendicular to said first direction;

an optical path rotating device, disposed in front of said first condenser, having arranged in parallel a plurality of optical elements for bending substantially at a right angle an axis of a cross section of at least a laser beam, for receiving the group of laser beams collimated in said second direction, and emitting the group of laser beams substantially in the form of ladder rungs lined up in said first direction by rotating the axis of the cross section of the laser beams for each of said optical elements;

a second condenser for collimating said group of laser beams substantially in the form of ladder rungs by refracting the beams to a direction substantially perpendicular to said first direction; and

a third condenser for bringing the group of laser beams emitted from said second condenser into focus.

2. A semiconductor laser apparatus according to claim 1, further comprising an optical fiber having an end face at a face of said focus.

3. A semiconductor laser apparatus according to claim 1, wherein said first and second condensers are respectively cylindrical lenses.

4. An optical path rotating device comprising a plurality of optical elements, each including a light receiving part for receiving an incident beam, the cross section of which is perpendicular to an optical axis and which has a first axis;

an optical system for rotating substantially by a right angle the first axis of said cross section of the beam; and

a light emitting part for emitting an emerging beam having passed through said optical system, wherein the light receiving parts and the light emitting parts of the optical elements are arranged so as to be adjacent to one another in the same planes, respectively and in such a way that said optical elements correspond to the emitting faces of a linear array laser diode.

5. An optical path rotating device according to claim 4, wherein said optical elements are arranged at the same pitches as the pitches of the emitters of the linear array laser diode.

6. An optical path rotating device according to claim 4, wherein said optical elements are disposed to correspond to a plurality of emitters of the linear array laser diode.

7. An optical path rotating device according to claim 4, wherein each said optical element has a first reflecting face on which the incident beam having said first axis and reflected by said light receiving part is incident, and a second reflecting face for emitting the emerging beam having said first axis rotated substantially by a right angle by reflecting the incident beam emitted from the first reflecting face.

8. An optical path rotating device according to claim 7, wherein each said optical element has the optical axis of the incident beam, the light receiving part, first and second reflecting faces, and emitting parts formed in such a way as to satisfy the following relations:

space="preserve" listing-type="equation">(N·

A).sup.2 +(M·

A).sup.2 -2(N·

A)(M·

A)(N·

M)=(1-cosθ

)/2

space="preserve" listing-type="equation">(N·

Ap).sup.2 +(M·

Ap).sup.2 -2(N·

Ap)(M·

Ap)(N·

M)=1/2

where A is a unit direction vector representing the optical axis of said incident beam, Ap is a unit direction vector representing the direction of the first axis in the incident beam, C is a unit direction vector representing the optical axis of the emerging beam, Cp is a unit direction vector representing the direction of the rotated first axis in the emerging beam, θ

is an angle formed by A and C, N is a unit direction vector representing the normal to the first reflecting face, and M is a unit direction vector representing the normal to the second reflecting face.

9. An optical path rotating device according to claim 7, wherein in each said optical element, the angle θ

formed by the optical axis of the incident beam and the optical axis of the emerging beam is substantially 90 degrees, the normal to the first reflecting face lies in a plane defined by the direction of the optical axis of the incident beam and the direction of the first axis, an angle formed by said normal and incident beam is an acute angle, and the second reflecting face is parallel to said incident beam and the normal to the second reflecting face is inclined at substantially 45 degrees to the first axis.

10. An optical path rotating device according to claim 9, wherein said acute angle is 45 degrees.

11. An optical path rotating device according to claim 9, wherein said first and second reflecting faces intersect to form an angle of 60 degrees.

12. An optical path rotating device according to claim 7, further comprising a third reflecting face for receiving the incident beam from said second reflecting face, bending the optical axis thereof substantially to a right angle, and making the direction of the optical axis of the emerging beam from the optical path rotating device substantially parallel with the optical axis of the incident beam.

13. An optical path rotating device according to claim 7, wherein a plurality of pairs of reflecting faces are arranged side by side with each other, each said pair of reflecting faces comprising the first reflecting face intersecting a first plane at right angles and also intersecting a second plane at an included angle of 45 degrees and the second reflecting face intersecting said second plane at right angles and also intersecting said first plane at an included angle of 45 degrees at a place where said two planes intersect in a solid body having said first and second plane intersecting at right angles.

14. An optical path rotating device according to claim 13, wherein a right angle prism is placed against said first plane of the optical path rotating device in claim 13.

15. An optical path rotating device according to claim 7, wherein each said optical element is a prism made of a transparent body and having a face of incidence as a light receiving part, a face of emergence as a light emitting part, and a plurality of internal reflecting faces disposed so that said first axis of the cross section of said beam is rotated by a right angle.

16. An optical path rotating device according to claim 15, wherein said first reflecting face is vertical and inclined at substantially 45 degrees to the face of incidence, and said second reflecting face is perpendicular to the face of incidence and inclined at substantially 45 degrees to a horizontal plane.

17. An optical path rotating device according to claim 16, wherein each said optical element is a triangular pyramid prism in a shape of a triangular pyramid having an isosceles right triangle, an apex of an acute angle of said isosceles right triangle, through which apex a perpendicular to a plane including said isosceles right triangle passes, wherein a length of said perpendicular is equal to a length of each of two equal sides of said isosceles right triangle.

18. An optical path rotating device according to claim 17, wherein each said optical element is in a shape that the face of incidence of a right angle prism is joined to the face of an isosceles right angle of said triangular pyramid prism, which does not face the corresponding semiconductor laser stripe.

19. An optical path rotating device according to claim 16, wherein each said optical element is a triangular pyramid frustum prism in a shape that has as a lower bottom a face formed by a right-angled triangle, three sides of which triangle are not equal in a triangular pyramid having a isosceles right triangle and an apex of an acute angle of said isosceles right triangle, through which apex a perpendicular to a plane including said isosceles right triangle passes and as an upper bottom a cross section obtainable by cutting said triangular frustum of pyramid along a plane parallel with said isosceles right triangle, wherein a face formed by a bilaterally symmetric isosceles trapezoid of said optical element is placed against a stripe of the linear array semiconductor laser, with a result that said optical elements are arranged in an array.

20. An optical path rotating device according to claim 19, wherein said optical element is formed such that a right angle prism is provided such that a face formed by a trapezoid having a right angle at an apex angle not facing the semiconductor laser stripe of said triangular pyramid frustum prism is joined to the face of incidence.

21. An optical path rotating device according to claim 12, wherein said optical element is an oblique prism having a face of incidence as the light-receiving part and a face of emergence as a light-emitting part parallel with the face of incidence, and a transparent body as an optical system in which said first reflecting face is vertical and inclined at substantially 45 degrees to said face of incidence to reflect a horizontally incident beam to a substantially horizontal direction and at right angles, said second reflecting face is perpendicular to said face of incidence and inclined at substantially 45 degrees to a horizontal plane to reflect the beam reflected by the first reflecting face to a substantially vertical direction, and the third reflecting face horizontally intersects said face of incidence and is inclined at substantially 45 degrees to a horizontal plane to reflect the beam reflected by the second reflecting face to a direction substantially vertical.

22. An optical path rotating device according to claim 21, wherein said optical element has an intersection angle of 60 degrees between the first reflecting face and the second reflecting face, between the second reflecting face and the third reflecting face, and between the third reflecting face and the first reflecting face, respectively.

23. An optical path rotating device according to claim 22, wherein said optical element is an oblique prism formed by parallel translation of an arbitrary line segment extending on a diagonal drawn from an apex of a cube and passing through the center of the cube, and wherein the oblique prism is formed by moving one end of said line segment first on diagonal of a square in one face of the cube, then moving that end of the line segment for a specified length on the side thereof, further moving in parallel with the diagonal on which that end of the line segment has moved, and finally moving that end of the line segment until it returns the starting point.

24. An optical path rotating device according to claim 22, wherein said optical element is an oblique prism formed by moving in parallel translation a trapezoid enclosed by two adjacent sides of a square as one face of the cube, a straight line parallel with one of the two sides, and a diagonal of the square, and wherein the oblique prism is formed by moving an apex having an acute angle of the trapezoid is moved for a specified length on the diagonal passing through the center of the cube.

25. An optical path rotating device according to claim 22, wherein said optical path rotating device has first and second planes which are mutually parallel, a third plane intersecting said first plane at an included angle of 135 degrees, and a cyclically corrugated face like a washboard having peak lines and bottom lines occurring alternately at angles of 60 degrees in a direction intersecting said first plane at an angle of tan^-1 (1/√

2), and a fourth face having peak lines and bottom lines in parallel with said third plane, and wherein said first plane is used as the face of incidence, said second plane is used as the face of emergence, out of the bend-faces constituting a fourth face, one-side bend-faces intersecting said first plane at an included angle of 45 degrees are used as first reflecting faces, and the other-side bend-faces are used as second reflecting faces, and said third plane is used as a third reflecting face.

26. An optical path rotating device according to claim 15, wherein said prism is a dove prism with a trapezoidal cross section.

27. An optical path rotating device according to claim 7, wherein said optical element includes two triangular pyramid prisms bonded together so as to be symmetric with respect to the axis, each prism is in a shape of a triangular pyramid including an isosceles right triangle, and an apex of an acute angle of said triangle in a plane including said triangle, through which apex a perpendicular to a plane including said isosceles right triangle passes, wherein a point of said perpendicular which makes the perpendicular equal to each of two equal sides of said isosceles right triangle is used as the apex.

28. An optical path rotating device according to claim 27, wherein a transparent prism having a cross section of a right triangle is joined to the face of emergence of said triangular pyramid prism as the face of emergence of said optical element.

29. An optical path rotating device according to claim 7, wherein said optical element is a space defined by the reflecting faces, including the first reflecting face which is vertical and inclined at substantially 45 degrees to the incident beam and the second reflecting face which is parallel with the incident beam and inclined at substantially 45 degrees to a horizontal plane.

30. An optical path rotating device according to claim 12, wherein said optical element is a space defined by the reflecting faces, including the first reflecting face which is vertical and inclined at substantially 45 degrees to the incident beam, the second reflecting face which is parallel with the incident beam and inclined at substantially 45 degrees to a horizontal plane, and a third reflecting face parallel with an intersection between the first reflecting line and second reflecting line.

31. An optical path rotating device according to claim 7, wherein said optical element is formed by cutting out from a cube a triangular pyramid having as an apex the point of the perpendicular to the apex of the acute angle of the isosceles right triangle in a plane including said isosceles right triangle in the case where the length of the perpendicular is equal to each of the equal sides of the isosceles right triangle.

32. An optical path rotating device according to claim 7, wherein said optical element is in the shape obtained by cutting a part including an apex having an acute angle of the upper bottom of a prism, which has the upper and lower bottoms in the shape of a paralleled in which one opposite angle is 45 degrees, at a plane inclined 45 degrees to a horizontal plane and parallel with a normal to a front side face.

33. An optical path rotating device according to claim 7, wherein along the edge formed by an upper face and a front face in a prism having an upper face and a front face intersecting said upper face at right angles, recessed portions formed by a vertical face intersecting the front face at 45 degrees and a face perpendicular to the front face and intersecting the upper face at 45 degrees are arranged side by side with each other at pitches corresponding to the emitters of the linear array semiconductor laser and the recessed portions are mirror-finished.

34. An optical path rotating device according to claim 12, wherein along an edge formed by an upper face and a front face in a prism having said upper face and the front face intersecting the upper face at right angles, recessed portions formed by a vertical face intersecting the front face at 45 degrees and a face perpendicular to the front face and intersecting the upper face at 45 degrees are arranged side by side with each other at pitches corresponding to the emitters of the linear array semiconductor laser, and a right angle prism is joined to the upper face.

35. An optical path rotating device according to claim 12, wherein in a flat plate having a specified thickness, recessed portions are formed, which have vertical first faces produced at pitches corresponding to the emitters of the linear array semiconductor laser and intersecting the front face at 45 degrees, second faces perpendicular to the front face and intersecting a horizontal plane at 45 degrees, a third face parallel with edges formed by intersections of said first and second faces, a fourth face connecting the first face at the end with the third face, and a fifth face connecting the second face at the end with the third face, and wherein the recessed portions are mirror-finished.

36. An optical path rotating device according to claim 4, wherein said optical element is a linearly-distributed refractive index lens element made of optical glass in which a refractive index is highest at the center plane and gradually decreases as we move towards the side faces, and wherein said center plane is inclined at substantially 45 degrees to a horizontal plane.

37. An optical path rotating device according to claim 4, wherein said optical element is a linearly-distributed refractive index lens element made of optical glass having two mutually parallel side faces, in which the refractive index is highest at one side face and gradually decreases as we move towards the other side face, and wherein said side faces are inclined at substantially 45 degrees to a horizontal plane.

38. An optical path rotating device according to claim 4, wherein a plurality of semi-cylindrically-distributed refractive index lens elements, 45-degree-inclined, are arranged side by side with each other linearly on either side of the optical glass body in a manner that said corresponding lens elements on the opposite sides are paired and correspond to the emitter faces of the linear array laser diode, and wherein the refractive index in said lens elements is highest at the center of the semi-circle and gradually decreases as we move towards the outer side.

39. An optical path rotating device according to claim 4, wherein said optical elements are pairs of bowed cylindrical lenses, the axes of which are inclined 45 degrees, arranged face to face with each other across a specified distance.

40. An optical path rotating device according to claim 4, wherein said optical elements are cylindrical lenses having bowed lens portions at opposite ends across side faces, and wherein said optical elements are joined together each inclined at 45 degrees to the incident beam.

41. An optical path rotating device according to claim 4, wherein a plurality of cylindrical surfaces, inclined substantially 45 degrees in the same direction, are formed on the face of incidence and the face of emergence of optical glass prism with a rectangular cross section, and wherein the incident beams incident on the respective cylindrical surfaces are rotated substantially by 90 degrees and emerge from the faces of emergence.

42. An optical path rotating device according to claim 4, wherein in arranging the optical element, each pair of optical elements, in which power varies only in a direction perpendicular to the center axis by diffraction, is placed facing each other with the center axis inclined substantially at 45 degrees.

43. An optical path rotating device according to claim 42, wherein said optical element is a set of binary optic elements, in each of which a number of grooves are formed along the center axis with depths varying symmetrically with respect to the center axis inclined substantially at 45 degrees in a direction perpendicular to the center axis.

44. An optical path rotating device according to claim 42, wherein said optical element is a set of bowed linear Fresnel lenses of the same cross section, each of which is formed so that power varies along the substantially-45-degree-inclined center axis and only in a direction perpendicular to the center axis.

45. An optical path rotating device according to claim 44, wherein said Fresnel lens is a laminar type Fresnel zone plate.

46. An optical path rotating device according to claim 44, wherein said Fresnel lens is a mask type Fresnel zone plate.

47. An optical path rotating device according to claim 42, wherein a plurality of optical elements are arranged side by side to correspond to the active layer stripes of the linear array laser diode, each optical element having the face of incidence and the face of emergence parallel with the face of incidence and the axis of the face of incidence inclined at 45 degrees to horizontal, and wherein a plurality of optical elements symmetric with the optical elements at the face of incidence are arranged side by side to correspond to the optical elements of the face of incidence.

48. An optical path rotating device according to claim 4, further comprising a transparent flat plate on which said linearly-arranged optical elements are fixed.

49. A composite of a condenser and an optical path rotating device for use with a linear array laser diode, said composite comprising a face of incidence for receiving an incident beam having a cross section which is perpendicular to the optical axis and which includes a first axis;

an optical system for rotating the first axis of said cross section substantially by a right angle;

a plurality of optical elements having faces of emergence for emitting the emerging beams that have passed through said optical system; and

a cylindrical lens having a flat face of incidence and a bow-shaped face of emergence, wherein the faces of emergence of said optical elements are arranged linearly and fixed such that the faces of emergence are adjacent to the face of incidence of the cylindrical lens, and correspond to the emitting faces of the linear array laser diodes.

50. A composite of a condenser and an optical path rotating device for use with linear array diode, said device comprising:

a face of incidence for receiving an incident beam having a cross section which is perpendicular to the optical axis and which includes a first axis;

an optical system for rotating the first axis of said cross section substantially by a right angle;

a plurality of optical elements having faces of emergence for emitting the emerging beams that have passed through said optical system; and

a cylindrical lens having a flat face of incidence and a bow-shaped face of emergence, wherein

the faces of incidence of said optical elements are arranged linearly and fixed such that said faces of incidence are adjacent to said face of emergence of the cylindrical lens, and correspond to the emitting faces of the linear array laser diode.

51. A semiconductor-laser-pumped solid state laser apparatus comprising:

a linear array laser diode, having a plurality of laser-beam-emitting emitters having emitter faces arranged to extend linearly in a first direction, for emitting a group of laser beams in the form of a dotted line;

a first condenser, disposed in front of said linear array laser diode, for collimating said group of laser beams by refracting them to a second direction perpendicular to said first direction;

an optical path rotating device, disposed in front of said first condenser, and having a plurality of optical elements arranged in parallel for bending the axis of a cross section of at least one laser beam substantially to a right angle, for receiving the group of laser beams collimated in said second direction, rotating the axes of the cross sections of the laser beams, and emitting the group of laser beams substantially in the form of ladder rungs lined up in said first direction;

a second condenser for collimating the group of laser beams substantially in the form of ladder rungs to a direction substantially perpendicular to said first direction;

a third condenser for bringing the group of laser beams emitted from said second condenser into focus; and

a solid state laser element having a pumping-light-receiving face to which said focus is adjusted.

52. A semiconductor-laser-pumped solid state laser apparatus comprising:

a linear array laser diode, having a plurality of laser-beam-emitting emitters having emitter faces arranged to extend linearly in said first direction, for emitting a group of laser beams in the form of a dotted line;

a first condenser, disposed in front of said linear array laser diode, for collimating the group of laser beams by refracting them to a second direction perpendicular to said first direction;

an optical path rotating device, disposed in front of said first condenser, and having a plurality of optical elements arranged in parallel for bending the axis of a cross section of at least one laser beam substantially to a right angle, for receiving the group of laser beams collimated in said second direction, rotating the axes of the cross sections of the laser beams, and emitting the group of laser beams substantially in the form of ladder rungs lined up in said first direction;

a second condenser for collimating the group of laser beams substantially in the form of ladder rungs to a direction substantially perpendicular to said first direction;

a third condenser for bringing the group of laser beams emitted from said second condenser into focus;

an optical fiber for transmitting light of the group of the laser beams focused into said first focus;

a collimator for collimating the light emitted from said optical fiber to converge the light to a second focus; and

a solid state laser element having a pumping-light-receiving face to which said focus is adjusted.

53. A semiconductor-laser-pumped solid state laser apparatus comprising:

a first linear array laser diode, having a plurality of laser-beam-emitting emitters having emitter faces arranged to extend linearly in said first direction, for emitting a group of laser beams in the form of a dotted line;

a first condenser, disposed in front of said linear array laser diode, for collimating the group of laser beams by refracting them to a second direction perpendicular to said first direction;

an optical path rotating device, disposed in front of said first condenser, and having a plurality of optical elements arranged in parallel for bending the axis of a cross section of at least one laser beam substantially to a right angle, for receiving the group of laser beams collimated in said second direction, rotating the axes of the cross sections of the laser beams, and emitting the group of laser beams substantially in the form of ladder rungs lined up in said first direction;

a second condenser for collimating the group of laser beams substantially in the form of ladder rungs to a direction substantially perpendicular to said first direction;

a second linear array laser diode, having a plurality of laser-beam-emitting emitters having emitter faces arranged to extend linearly in said third direction, for emitting a group of laser beams in the form of a dotted line;

a third condenser, disposed in front of said second linear array laser diode, for collimating the group of laser beams by refracting them to a fourth direction perpendicular to said third direction;

a second optical path rotating device, disposed in front of said third condenser,

and having a plurality of optical element s arranged in parallel for bending the axis of a cross section of at least one laser beam substantially for a right angle, for receiving the group of laser beans collimated in said fourth direction, rotating the axes of the cross sections of the laser beams, and emitting the group of laser beams substantially in the form of ladder rungs lined up in said third direction;

a fourth condenser for collimating the group of laser beams substantially in the form of ladder rungs to a direction substantially perpendicular to said first direction;

a polarization beam splitter having a first face of incidence for receiving a group of laser beams emitted from said second condenser, a second face of incidence for receiving a group of laser beams emitted from a fourth condenser, and a face of emergence for emitting a group of laser beans, wherein

the group of laser beams received on the first face of incidence and having a first polarization direction are made to travel straight, a group of laser beams having a second polarization direction intersecting the first polarization direction and emitted from the fourth condenser are received on the second face of incidence and refracted to a direction of traveling towards the face of emergence, and as a result, both groups of laser beams are emitted from the face of emergence;

a fifth condenser for bringing the group of laser beams emitted from said polarization beam splitter into focus; and

a solid-state laser element having a pumping-light-receiving face to which said focus is adjusted.

54. A semiconductor-laser-pumped solid state laser apparatus according to claim 53, further comprising a halfwave plate to cause a polarization direction of a group of laser beams emitted from said third condenser to intersect the polarization direction of said group of laser beams.