Research On The Design And Fabrication Technology Of A Varied Line-spacing Grating Lens

Owing to its compact size, miniature spectrometer is finding many applications in recentyears, such as on-line monitoring of pharmaceutics production processes as well as on-site foodquality inspection. Rearch on the miniature spectrometer will be of great significance.Varied line-spacing grating lens is a key element in a transmission-type miniaturespectrometer. It combines the functions of collimation, dispersion and focusing in a compact size,and hence, plays a crucial role to the quality of the miniature spectrometer.The varied line-spacing grating lens is characterized by that the grating pattern is fabricateddirectly onto the lens surface and that the grating is varied line-spacing. With the advancement ofMicro Opto-Electro-Mechanical Systems (MOEMS) technology, fabricating such variedline-spacing grating lens has become possible. This thesis presents the design and fabrication ofa varied line-spacing grating lens.The design consists of three steps. First, the design of a aried line-spacing grating lens ispresented. This design is based on the use of MOEMS technology, and has only two mediums.Second, based on the design and the Principle of Least Wave change, its optical path function isderived, which can be used to evaluate the aberration-reduction. Third, the optical pathdifference function is expressed as a power series. Each term in the power series corresponds to aparticular aberration. The design model is optimized using MATLAB. The optimizationobjective is to make the aberration as small as possible, based on which the pattern of variedline-spacing gating is obtained. The grating spacing varies from line to line, but the variation isrelatively low compared with the grating space. Third, we use ZEMAX to simulate the resultsof the single-wavelength optimization and the multi-wavelength optimization. The latter exhibitsbetter result throughout the450~650nm target wavelength range. The finest resolution is0.2nm and the overall resolution is within0.8nm, which meets the requirement.The fabrication of the variable gating lens is done using the thermal reflow method. Twolayers of spin coat and carefully controlled development can make micro lens with about1.1mmdiameter. Moreover, the influences of the contact angle, the development depth and the lensdiameter are also studied. In general, small contact angle can help to achieve better performance.The thesis also explored the possibilities to fabricate the variable grating using E-beamlithography and UV lithography. E-beam lithography can achieve very high accuracy with theline width reaching10nm. But it is difficult to fabricate patterns on curve surface and it requiresthe substrate being conductive. UV lithography can produce line widths on the order of micrometers and/or sub-micrometers. We have tried to spin coat on a glass lens and producegrating directly on the resist, but the result is not good. Some resist accumulate around the lens.