**6. References**


Although fabrication errors on these structures will redistribute the energy among diffraction orders and increase the efficiency of central order, the total energy remains the same. It is also noted that the choice of fabrication method introduce different errors. For example, EBL tends to have variations in exposure dosage which has excess etch depth and shape errors. But it can provide very fine width and vertical shape walls and hence it can support high density structure. Conversely, chemical etching technique can provide very sharp side walls and accurate etch depth with carful timing. But, it never supports high density structure as the linewidth it can sustain is in order of um. The users must to balance

This project is supported by GRF (No. 112710) of the Research Grant Council in Hong Kong.

[2] C. B. Burckhardt (1966). Diffraction of a plane wave at a sinusoidally stratified dielectric

[3] M. G. Moharam & T. K. Gaylord (1982). Diffraction Analysis of Dielectric Surface Relief

[4] H. Dammann & K. Gortler (1971). High-efficiency in line multiple imaging by means of

Gratings. *Journal of the Optical Society of America,* Vol. 72, pp.1385-1392, ISSN 0030-

multiple phase holograms. *Optics Communications,* Vol.3, pp.312-315, ISSN 0030-

[1] E. Hecht (2002). *Optics*, Addison Wesley, ISBN 0-80-538566-5, US

grating. *J. Opt. Soc. Am.* Vol. 56 pp.1502–1509, ISSN 0030-3941

Fig. 26. Duty Cycle against efficiency.

**5. Acknowledgement** 

**6. References** 

3941

4018

between the cost and performance requirements.


**7** 

*Japan* 

Close to wavelength

λ

*m*

2 )( <sup>2</sup> <sup>2</sup> <sup>−</sup> <sup>=</sup>

(wavelength order)

(depending on material)

*mr <sup>f</sup> <sup>m</sup>*

λ

**Fabrication of Binary Diffractive Lens on Optical** 

Two types of lenses can focus light: an optical lens using refraction phenomenon and a diffractive lens using diffraction phenomena. Table 1 shows the characteristics of each lens. The focal length of the diffractive lens is controlled by the structures of the lens, as mentioned in detail in Section 2.2. This suggests that the focal length of the diffractive lens is independent of refractive index and curvature. Thus, application of diffractive lenses to UV

Principle Refraction Diffraction

Thin structure Possible

Difficult Possible Controlling light

Difficult

Table 1. Comparison of characters between refractive lens and diffractive lens

<sup>−</sup> )1(2 <sup>=</sup> *<sup>n</sup> <sup>R</sup> <sup>f</sup>*

*n, R* (depending on material) *rm* Control of *f* (m=1,2,・・・)

**1. Introduction**

Focal length *f* 

Short wavelength light such as UV and

X-ray

distribution

Structure

optical elements or thin optical elements is possible.

**Films by Electron Beam Lithography** 

*The Center of Ultimate Technology on nano-Electronics, Mie University* 

Refractive lens Diffractive lens

Difficult Possible

Radius of curvature *R* Radius *r*<sup>m</sup>

Atsushi Motogaito and Kazumasa Hiramatsu *Graduate School of Engineering, Mie University* 

