TY - JOUR
T1 - Diffractive optical elements using the sub-wavelength scale pillar array structure
AU - Hakamata, Masakatsu
AU - Tsuda, Hiroyuki
PY - 2004/9/13
Y1 - 2004/9/13
N2 - We propose the diffractive optical element using the sub-wavelength scale pillar array structure. The equivalent microscopic refractive index can be controlled by changing pillar width and the pillar lattice constant. Advantages of using the sub-wavelength scale structure to manipulate the equivalent index in such a manner are that the optical functional elements can be fabricated by a single-etch-step process, and that the anisotropic optical characteristics can be realized using isotropic materials. In this paper, we have designed and fabricated the Fresnel lens with sub-wavelength structure on the Si substrate. The equivalent refractive index, neff, as a function of the pillar width and the lattice constant was calculated by the EMT (Effective Medium Theory). The width of pillar at the n-th lattice point, an, was determined by neff and required the local optical length of the target diffractive optical element. The design wavelength, λ, was set at 1.6 μm, the lattice constant, Λ, was 0.45 μm, the pillar height, h, was 1.21 μm, and the refractive index of Si, nsi, was 3.48, respectively. These parameter values satisfied the sub-wavelength condition of λ > nsi Λ. The Fresnel lens with a focal length of 20 mm and the effective diameter of 1.8mm was designed and fabricated.
AB - We propose the diffractive optical element using the sub-wavelength scale pillar array structure. The equivalent microscopic refractive index can be controlled by changing pillar width and the pillar lattice constant. Advantages of using the sub-wavelength scale structure to manipulate the equivalent index in such a manner are that the optical functional elements can be fabricated by a single-etch-step process, and that the anisotropic optical characteristics can be realized using isotropic materials. In this paper, we have designed and fabricated the Fresnel lens with sub-wavelength structure on the Si substrate. The equivalent refractive index, neff, as a function of the pillar width and the lattice constant was calculated by the EMT (Effective Medium Theory). The width of pillar at the n-th lattice point, an, was determined by neff and required the local optical length of the target diffractive optical element. The design wavelength, λ, was set at 1.6 μm, the lattice constant, Λ, was 0.45 μm, the pillar height, h, was 1.21 μm, and the refractive index of Si, nsi, was 3.48, respectively. These parameter values satisfied the sub-wavelength condition of λ > nsi Λ. The Fresnel lens with a focal length of 20 mm and the effective diameter of 1.8mm was designed and fabricated.
KW - Diffractive optical element
KW - Effective medium theory
KW - Fresnel lens
KW - Sub-wavelength structure
UR - http://www.scopus.com/inward/record.url?scp=4344644965&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=4344644965&partnerID=8YFLogxK
U2 - 10.1117/12.529304
DO - 10.1117/12.529304
M3 - Conference article
AN - SCOPUS:4344644965
VL - 5360
SP - 411
EP - 418
JO - Proceedings of SPIE - The International Society for Optical Engineering
JF - Proceedings of SPIE - The International Society for Optical Engineering
SN - 0277-786X
T2 - Photonic Crystal Materials and Devices II
Y2 - 26 January 2004 through 29 January 2004
ER -