Broad band wire grid polarizing beam splitter for use in the visible wavelength region

• US 6,243,199 B1
• Filed: 09/07/1999
• Issued: 06/05/2001
• Est. Priority Date: 09/07/1999
• Status: Expired due to Term

• Current Assignee: Moxtek (Polatechno Co.,Ltd.)
• Original Assignee: Moxtek (Polatechno Co.,Ltd.)
• Inventors: Hansen, Douglas P., Perkins, Raymond T., Gardner, Eric
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): Juba, Jr., John
• Application Number:
  US09/390,833
• Time in Patent Office: 637 Days
• Field of Search: 359/483, 359/485, 359/486, 359/900
• US Class Current: 359/485.05
• CPC Class Codes: G02B 5/3058 comprising electrically conductive elements, e.g. wire grids, conductive particles
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A wire grid polarizing beam splitter has a generally parallel arrangement of thin, elongated elements which interact with electromagnetic waves of a source light beam to generally transmit or pass light of one polarization, and reflect light of the other polarization. The arrangement of elements has a throughput greater than approximately 50%, and an extinction greater than approximately 100. In addition, the arrangement of elements has a period less than approximately 0.21 μm, and a width to period ratio of between approximately 0.25 to 0.76. The elements have a thickness of between approximately 0.05 to 0.5 μm.

Claims

1. A broad band wire grid polarizing beam splitter for efficiently reflecting one polarization of visible light and transmitting another polarization, the beam splitter comprising:

a generally parallel arrangement of thin, elongated elements disposed in the visible light, the arrangement being configured and the elements being sized to interact with electromagnetic waves of the visible light to generally (i) transmit light having a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, and (ii) reflect light having a polarization oriented in the plane that includes at least one of the elements and the direction of the incident light beam; and

wherein the arrangement of elements has a throughput greater than approximately 50% over substantially the entire visible spectrum, the throughput being defined by the product of the fractional amount of one polarization of reflected light with respect to the total reflected light and the fractional amount of another polarization of transmitted light with respect to the total transmitted light; and

wherein the arrangement of elements has an extinction greater than approximately 50 in either reflection or transmission.

2. The beam splitter of claim 1, wherein the arrangement of elements reflects at least 67% of one polarization.

3. The beam splitter of claim 1, wherein the arrangement of elements transmits at least 67% of one polarization.

4. The beam splitter of claim 1, wherein the arrangement of elements is oriented at an incident angle between approximately 0 to 80 degrees.

5. The beam splitter of claim 1, wherein the arrangement of elements has a period less than approximately 0.21 μ

m.

6. The beam splitter of claim 1, wherein the elements have a thickness of between approximately 0.05 to 0.5 μ

m.

7. The beam splitter of claim 1, wherein the elements have a width to period ratio of between approximately 0.25 to 0.76.

8. The beam splitter of claim 1, wherein the elements each have a trapezoidal-shaped cross-section with a base, a top opposite the base, and opposite left and right sides;

and wherein the sides form an angle with respect to the base of between approximately 68 to 112 degrees.

9. The beam splitter of claim 1, wherein the elements each have a trapezoidal-shaped cross-section with a base, a top opposite the base, and opposite left and right sides;

and wherein the sides form different angles with respect to the base.

10. The beam splitter of claim 1, wherein the elements each have a rounded top.

11. The beam splitter of claim 1, wherein the elements each have a sinusoidal-shaped cross-section.

12. The beam splitter of claim 1, wherein the elements are formed of aluminum having optical constant n which is greater than approximately 50 percent of 0.618 at a wavelength of 450 nm, greater than approximately 50 percent of 0.958 at a wavelength of 550 nm, and greater than approximately 50 percent of 1.47 at a wavelength of 650 nm.

13. The beam splitter of claim 1, wherein the elements are formed of aluminum having optical constant k which is greater than approximately 50 percent of 5.47 at a wavelength of 450 nm, greater than approximately 50 percent of 6.69 at a wavelength of 550 nm, and greater than approximately 50 percent of 7.79 at a wavelength of 650 nm.

14. The beam splitter of claim 1, wherein the elements are formed of silver having optical constant n which is greater than approximately 80 percent of 0.144 at a wavelength of 459.2 nm, greater than approximately 80 percent of 0.120 at a wavelength of 563.6 nm, and greater than approximately 80 percent of 0.140 at a wavelength of 652.6 nm.

15. The beam splitter of claim 1, wherein the elements are formed of silver having optical constant k which is greater than approximately 80 percent of 2.56 at a wavelength of 459.2 nm, greater than approximately 80 percent of 3.45 at a wavelength of 563.6 nm, and greater than approximately 80 percent of 4.15 at a wavelength of 652.6 nm.

16. A broad band wire grid polarizing beam splitter for efficiently reflecting one polarization of visible light and transmitting another polarization, the beam splitter comprising:

a generally parallel arrangement of thin, elongated elements disposed in the visible light, the arrangement being configured and the elements being sized to interact with electromagnetic waves of the visible light to generally (i) transmit light having a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, and (ii) reflect light having a polarization oriented in the plane that includes at least one of the elements and the direction of the incident light beam; and

wherein the arrangement of elements has a throughput greater than approximately 50% over substantially the entire visible spectrum, the throughput being defined by the product of the fractional amount of one polarization of reflected light with respect to the total amount of reflected light and the fractional amount of another polarization of transmitted light with respect to the total amount of transmitted light;

wherein the arrangement of elements has an extinction greater than approximately 50; and

wherein the arrangement of elements has a period less than approximately 0.21 μ

m.

17. The beam splitter of claim 16, wherein the elements have a thickness of between approximately 0.05 to 0.5 μ

m.

18. The beam splitter of claim 16, wherein the elements have a width to period ratio of between approximately 0.25 to 0.76.

19. The beam splitter of claim 16, wherein the arrangement of elements reflects at least 67% of one polarization.

20. The beam splitter of claim 16, wherein the arrangement of elements transmits at least 67% of one polarization.

21. The beam splitter of claim 16, wherein the arrangement of elements are oriented at an incident angle between approximately 0 to 80 degrees.

22. The beam splitter of claim 16, wherein the elements each have a trapezoidal-shaped cross-section with a base, a top opposite the base, and opposite left and right sides;

and wherein the sides form an angle with respect to the base of between approximately 68 to 112 degrees.

23. The beam splitter of claim 16, wherein the elements each have a trapezoidal-shaped cross-section with a base, a top opposite the base, and opposite left and right sides;

and wherein the sides form different angles with respect to the base.

24. The beam splitter of claim 16, wherein the elements each have a rounded top.

25. The beam splitter of claim 16, wherein the elements each have a sinusoidal-shaped cross-section.

26. The beam splitter of claim 16, wherein the elements are formed of aluminum having optical constant n which is greater than approximately 50 percent of 0.618 at a wavelength of 450 nm, greater than approximately 50 percent of 0.958 at a wavelength of 550 nm, and greater than approximately 50 percent of 1.47 at a wavelength of 650 nm.

27. The beam splitter of claim 16, wherein the elements are formed of aluminum having optical constant k which is greater than approximately 50 percent of 5.47 at a wavelength of 450 nm, greater than approximately 50 percent of 6.69 at a wavelength of 550 nm, and greater than approximately 50 percent of 7.79 at a wavelength of 650 nm.

28. The beam splitter of claim 16, wherein the elements are formed of silver having optical constants n and k;

wherein n is greater than approximately 80 percent of 0.144 at a wavelength of 459.2 nm, greater than approximately 80 percent of 0.120 at a wavelength of 563.6 nm, and greater than approximately 80 percent of 0.140 at a wavelength of 652.6 nm; and

wherein k is greater than approximately 80 percent of 2.56 at a wavelength of 459.2 nm, greater than approximately 80 percent of 3.45 at a wavelength of 563.6 nm, and greater than approximately 80 percent of 4.15 at a wavelength of 652.6 nm.

29. A broad band wire grid polarizing beam splitter for efficiently reflecting one polarization of visible light and transmitting another polarization, the beam splitter comprising:

a light source for emitting a source light beam having a wavelength in a range between approximately 0.4 to 0.7 microns;

a generally parallel arrangement of thin, elongated elements disposed in the source light beam, the arrangement being configured and the elements being sized to interact with electromagnetic waves of the source light beam over substantially the entire visible spectrum to generally (i) transmit light having a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, and (ii) reflect light having a polarization oriented in the plane that includes at least one of the elements and the direction of the incident light beam; and

wherein the arrangement of elements has a period less than approximately 0.21 μ

m;

wherein the elements have a thickness of between approximately 0.05 to 0.5 μ

m; and

wherein the elements have a width to period ratio of between approximately 0.25 to 0.76.

30. The beam splitter of claim 29,

wherein the arrangement of elements has a throughput greater than approximately 50% over substantially the entire visible spectrum, the throughput being defined by the fractional amount of the percent of one polarization of reflected light with respect to the total amount of reflected light and the fractional amount of another polarization of transmitted light with respect to the total amount of transmitted light; and

wherein the arrangement of elements has an extinction greater than approximately 50.

31. The beam splitter of claim 29, wherein the arrangement of elements reflects at least 67% of one polarization.

32. The beam splitter of claim 29, wherein the arrangement of elements transmits at least 67% of one polarization.

33. The beam splitter of claim 29, wherein the arrangement of elements are oriented at an incident angle between approximately 0 to 80 degrees.

34. The beam splitter of claim 29, wherein the elements each have a trapezoidal-shaped cross-section with a base, a top opposite the base, and opposite left and right sides;

and wherein the sides form an angle with respect to the base of between approximately 68 to 112 degrees.

35. The beam splitter of claim 29, wherein the elements each have a trapezoidal-shaped cross-section with a base, a top opposite the base, and opposite left and right sides;

and wherein the sides form different angles with respect to the base.

36. The beam splitter of claim 29, wherein the elements each have a rounded top.

37. The beam splitter of claim 29, wherein the elements each have a sinusoidal-shaped cross-section.

38. The beam splitter of claim 29, wherein the elements are formed of aluminum having optical constants n and k;

wherein n is greater than approximately 50 percent of 0.618 at a wavelength of 450 nm, greater than approximately 50 percent of 0.958 at a wavelength of 550 nm, and greater than approximately 50 percent of 1.47 at a wavelength of 650 nm; and

wherein k is greater than approximately 50 percent of 5.47 at a wavelength of 450 nm, greater than approximately 50 percent of 6.69 at a wavelength of 550 nm, and greater than approximately 50 percent of 7.79 at a wavelength of 650 nm.

39. The beam splitter of claim 29, wherein the elements are formed of silver having optical constant n which is greater than approximately 80 percent of 0.144 at a wavelength of 459.2 nm, greater than approximately 80 percent of 0.120 at a wavelength of 563.6 nm, and greater than approximately 80 percent of 0.140 at a wavelength of 652.6 nm.

40. The beam splitter of claim 29, wherein the elements are formed of silver having optical constant k which is greater than approximately 80 percent of 2.56 at a wavelength of 459.2 nm, greater than approximately 80 percent of 3.45 at a wavelength of 563.6 nm, and greater than approximately 80 percent of 4.15 at a wavelength of 652.6 nm.

41. A method for designing a broad band wire grid polarizing beam splitter operable over a desired range of incidence angles and operable over substantially the entire visible spectrum and having a predetermined extinction, the method comprising:

determining the transmission efficiency for the predetermined upper and lower limits of the incidence angles at various element thicknesses using a lower limit of the visible spectrum;

selecting other parameters including at least the period and the width to period ratio;

determining the element thickness at which the transmission efficiency for the upper and lower limits of the incidence angles is the same;

determining the extinction for the determined element thickness at both the upper and lower limits of the incidence angles; and

repeating the above steps while varying at least one of the parameters until the predetermined extinction is reached.

42. The method of claim 41, further comprising:

determining the transmission efficiency for various different incidence angles within the desired range and for various wavelengths within the visible spectrum; and

repeating the above steps while varying at least one of the parameters until the transmission efficiency is at least 80% and generally similar over the visible spectrum.

43. A wire grid polarizing beam splitter, comprising:

a generally parallel arrangement of thin, elongated elements configured to be disposed in visible light, the arrangement being configured and the elements being sized to interact with electromagnetic waves of visible light to generally (i) transmit light having a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, and (ii) reflect light having a polarization oriented in the plane that includes at least one of the elements and the direction of the incident light beam; and

wherein the arrangement of elements has a throughput greater than approximately 50% defined by the product of the fractional amount of one polarization of reflected light with respect to the total reflected light and the fractional amount of another polarization of transmitted light with respect to the total transmitted light; and

wherein the arrangement of elements has an extinction greater than approximately 50 in either reflection or transmission; and

wherein at least some of the elements have a trapezoidal-shaped cross-section with a base, a top opposite the base, and opposite left and right sides; and

wherein the sides form different angles with respect to the base.

44. A wire grid polarizing beam splitter, comprising:

a generally parallel arrangement of thin, elongated elements configured to be disposed in visible light, the arrangement being configured and the elements being sized to interact with electromagnetic waves of visible light to generally (i) transmit light having a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, and (ii) reflect light having a polarization oriented in the plane that includes at least one of the elements and the direction of the incident light beam; and

wherein the arrangement of elements has a throughput greater than approximately 50% defined by the product of the fractional amount of one polarization of reflected light with respect to the total reflected light and the fractional amount of another polarization of transmitted light with respect to the total transmitted light; and

wherein the arrangement of elements has an extinction greater than approximately 50 in either reflection or transmission; and

wherein at least some of the elements have a rounded top.

45. A wire grid polarizing beam splitter, comprising:

a generally parallel arrangement of thin, elongated elements configured to be disposed in visible light, the arrangement being configured and the elements being sized to interact with electromagnetic waves of visible light to generally (i) transmit light having a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, and (ii) reflect light having a polarization oriented in the plane that includes at least one of the elements and the direction of the incident light beam; and

wherein the arrangement of elements has a throughput greater than approximately 50% defined by the product of the fractional amount of one polarization of reflected light with respect to the total reflected light and the fractional amount of another polarization of transmitted light with respect to the total transmitted light; and

wherein the arrangement of elements has an extinction greater than approximately 50 in either reflection or transmission; and

wherein at least some of the elements have a sinusoidal-shaped cross-section.

46. A wire grid polarizing beam splitter, comprising:

a generally parallel arrangement of thin, elongated elements configured to be disposed in visible light, the arrangement being configured and the elements being sized to interact with electromagnetic waves of visible light to generally (i) transmit light having a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, and (ii) reflect light having a polarization oriented in the plane that includes at least one of the elements and the direction of the incident light beam; and

wherein the arrangement of elements has a throughput greater than approximately 50% defined by the product of the fractional amount of one polarization of reflected light with respect to the total reflected light and the fractional amount of another polarization of transmitted light with respect to the total transmitted light; and

wherein the arrangement of elements has an extinction greater than approximately 50 in either reflection or transmission; and

wherein the elements are formed of silver having optical constant n which is greater than approximately 80 percent of 0.144 at a wavelength of 459.2 nm, greater than approximately 80 percent of 0.120 at a wavelength of 563.6 nm, and greater than approximately 80 percent of 0.140 at a wavelength of 652.6 nm; and

wherein the elements are formed of silver having optical constant k which is greater than approximately 80 percent of 2.56 at a wavelength of 459.2 nm, greater than approximately 80 percent of 3.45 at a wavelength of 563.6 nm, and greater than approximately 80 percent of 4.15 at a wavelength of 652.6 nm.