Abstract

With the aim of reducing surface reflections and increasing the diffraction efficiency we investigated the superposition of subwavelength phase gratings onto blazed phase gratings. With direct-write electron-beam lithography bare blazed gratings and blazed gratings carrying subwavelength gratings were fabricated and their optical performances compared. For TE polarization the subwavelength-carrying gratings showed a maximum diffraction efficiency of 90.6%, whereas the corresponding maximum value for the bare grating was 86.3%. The experiment was simulated with rigorous diffraction theory.

© 2000 Optical Society of America

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References

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  1. R. C. Enger, S. K. Case, “Optical elements with ultrahigh spatial-frequency surface corrugations,” Appl. Opt. 22, 3220–3228 (1983).
    [CrossRef] [PubMed]
  2. D. H. Raguin, G. M. Morris, “Structured surfaces mimic coating performance,” Laser Focus World, (April1997), pp. 113–117.
  3. Y. Kanamori, M. Sasaki, K. Hane, “Broadband antireflection gratings fabricated upon silicon substrates,” Opt. Lett. 24, 1422–1424 (1999).
    [CrossRef]
  4. P. Lalanne, G. M. Morris, “Antireflection behaviour of silicon subwavelength periodic structures for visable light,” Nanotechnology 8, 53–56 (1997).
    [CrossRef]
  5. M. T. Gale, “Replication,” in Micro-Optics: Elements, Systems and Applications, H. P. Herzig, ed. (Taylor & Francis, London, 1997), pp. 153–177.
  6. K. M. Baker, “Highly corrected close-packed microlens arrays and moth-eye structuring on curved surfaces,” Appl. Opt. 38, 352–356 (1999).
    [CrossRef]
  7. Conventionally, TE polarization refers to the case in which the electric field vector of the incident light is parallel to the grating grooves. For TM polarization the magnetic field vector of the incident light is parallel to the grating grooves.
  8. C. Heine, “Thin film coated submicron gratings: theory, design, fabrication and application,” Ph.D. dissertation (Institut de Microtechnique, Université de Neuchâtel, Neuchâtel, Switzerland, 1996).
  9. R. H. Morf, “Exponentially convergent and numerically efficient solution of Maxwell’s equations for lamellar gratings,” J. Opt. Soc. Am. A 12, 1043–1056 (1995).
    [CrossRef]
  10. M. Kuittinen, J. Turunen, P. Vahimaa, “Subwavelength-structured elements,” in Diffractive Optics for Industrial and Commercial Applications, J. Turunen, F. Wyrowski, eds. (Akademie, Berlin, 1997), pp. 303–323.

1999 (2)

1997 (2)

P. Lalanne, G. M. Morris, “Antireflection behaviour of silicon subwavelength periodic structures for visable light,” Nanotechnology 8, 53–56 (1997).
[CrossRef]

D. H. Raguin, G. M. Morris, “Structured surfaces mimic coating performance,” Laser Focus World, (April1997), pp. 113–117.

1995 (1)

1983 (1)

Baker, K. M.

Case, S. K.

Enger, R. C.

Gale, M. T.

M. T. Gale, “Replication,” in Micro-Optics: Elements, Systems and Applications, H. P. Herzig, ed. (Taylor & Francis, London, 1997), pp. 153–177.

Hane, K.

Heine, C.

C. Heine, “Thin film coated submicron gratings: theory, design, fabrication and application,” Ph.D. dissertation (Institut de Microtechnique, Université de Neuchâtel, Neuchâtel, Switzerland, 1996).

Kanamori, Y.

Kuittinen, M.

M. Kuittinen, J. Turunen, P. Vahimaa, “Subwavelength-structured elements,” in Diffractive Optics for Industrial and Commercial Applications, J. Turunen, F. Wyrowski, eds. (Akademie, Berlin, 1997), pp. 303–323.

Lalanne, P.

P. Lalanne, G. M. Morris, “Antireflection behaviour of silicon subwavelength periodic structures for visable light,” Nanotechnology 8, 53–56 (1997).
[CrossRef]

Morf, R. H.

Morris, G. M.

P. Lalanne, G. M. Morris, “Antireflection behaviour of silicon subwavelength periodic structures for visable light,” Nanotechnology 8, 53–56 (1997).
[CrossRef]

D. H. Raguin, G. M. Morris, “Structured surfaces mimic coating performance,” Laser Focus World, (April1997), pp. 113–117.

Raguin, D. H.

D. H. Raguin, G. M. Morris, “Structured surfaces mimic coating performance,” Laser Focus World, (April1997), pp. 113–117.

Sasaki, M.

Turunen, J.

M. Kuittinen, J. Turunen, P. Vahimaa, “Subwavelength-structured elements,” in Diffractive Optics for Industrial and Commercial Applications, J. Turunen, F. Wyrowski, eds. (Akademie, Berlin, 1997), pp. 303–323.

Vahimaa, P.

M. Kuittinen, J. Turunen, P. Vahimaa, “Subwavelength-structured elements,” in Diffractive Optics for Industrial and Commercial Applications, J. Turunen, F. Wyrowski, eds. (Akademie, Berlin, 1997), pp. 303–323.

Appl. Opt. (2)

J. Opt. Soc. Am. A (1)

Laser Focus World (1)

D. H. Raguin, G. M. Morris, “Structured surfaces mimic coating performance,” Laser Focus World, (April1997), pp. 113–117.

Nanotechnology (1)

P. Lalanne, G. M. Morris, “Antireflection behaviour of silicon subwavelength periodic structures for visable light,” Nanotechnology 8, 53–56 (1997).
[CrossRef]

Opt. Lett. (1)

Other (4)

M. T. Gale, “Replication,” in Micro-Optics: Elements, Systems and Applications, H. P. Herzig, ed. (Taylor & Francis, London, 1997), pp. 153–177.

M. Kuittinen, J. Turunen, P. Vahimaa, “Subwavelength-structured elements,” in Diffractive Optics for Industrial and Commercial Applications, J. Turunen, F. Wyrowski, eds. (Akademie, Berlin, 1997), pp. 303–323.

Conventionally, TE polarization refers to the case in which the electric field vector of the incident light is parallel to the grating grooves. For TM polarization the magnetic field vector of the incident light is parallel to the grating grooves.

C. Heine, “Thin film coated submicron gratings: theory, design, fabrication and application,” Ph.D. dissertation (Institut de Microtechnique, Université de Neuchâtel, Neuchâtel, Switzerland, 1996).

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Figures (7)

Fig. 1
Fig. 1

Experimental setup for transmittance and reflectivity measurements. P, rotable polarizer; S2, single-sided AR-coated reference quartz plate; D1 and D2, p-i-n detectors; S1, measurement sample; A1, aperture for diffraction order selection; A2, aperture for selection of reflected beam; L, lens; I/V, current to voltage. Only A1, A2, and S1 were moved during the measurements.

Fig. 2
Fig. 2

Measured transmittance through pure subwavelength-grating-structured area as a function of development time. Backside of the quartz substrate, AR coated. Subwavelength grating period, 300 nm. Duty cycle, 50%. Wavelength of probing laser beam, 633 nm. Polarization, TE and TM.

Fig. 3
Fig. 3

Measured transmitted power fraction in the first diffraction order as a function of development time after second exposure. Total development time after first exposure, 240 s. Solid curves, subwavelength-structured blazed grating (TE and TM polarization). Dotted curves, pure blazed grating (TE and TM polarization). Backside of the quartz substrate, AR coated. Subwavelength grating period, 300 nm. Duty cycle, 50%. Blazed grating period, 16 µm. Wavelength of probing laser beam, 633 nm.

Fig. 4
Fig. 4

Transmittance through pure subwavelength-grating-structured area as a function of relief depth, calculated with rigorous diffraction theory. Both sinusoidal (solid curves) and binary profile (dotted curves) shown. Subwavelength grating period, 300 nm. Duty cycle of binary grating, 50%. Optical wavelength, 633 nm. Polarization, TE and TM.

Fig. 5
Fig. 5

Calculated transmitted power fraction in the first diffraction order for a bare blazed grating (dotted curve) and a blazed grating with superimposed AR structure (solid curve) as a function of grating depth. The AR grating depth scales linearly with the blazed grating depth. For a blazed grating depth of 1.17 µm the AR grating depth is 140 nm. Subwavelength grating period, 300 nm. Blazed grating period, 16 µm. Optical wavelength, 633 nm. Polarization, TE.

Fig. 6
Fig. 6

Photograph of substrate with two AR-only-structured square areas (top) and AR-structured blazed grating and pure blazed grating (bottom). The reflected light is that of an overcast (broadband) sky. The reduced reflectivity of the AR-structured areas is clearly observable.

Fig. 7
Fig. 7

SEM picture of AR-only-subwavelength structured area. Grating period, 300 nm.

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