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The World of Micro-Optics

Hans Peter Ilcrzig,

lnstitute of Microtcchnology, University of Ncuch;Rtel, Riic A.-L. Breguet 2, CH-2000 Ncuchitel, Switzerland

Micro-optical cleincnts arc optical componcnts with structures in the sub-inro and sub-p iangc, which are fabricated hy a variety of high-resolution lithographic arid optical processes. Micro- optics incliides ii.cc-spacc optics, intcgratcd optics, semiconductor light sotirccs a r ~ d detectors. This ovcrvicw coriceidi’ates on fiee-spacc micro-optics wherc the light propagates in 3D.

Data Tor arbitrary phase profiles can he transformccl into efficient optical elements (Figs. 3 ~ 6 ) . These elements al’c inacle of rigid materials, such as glass arid fiiscd silica, or they are rcplicatetl at low cost into plastic and epoxy inaterials. Micro-optical clerncnts are used in various applications, rangiug from illumination to medicine. Sonic examples arc presentcd in the following.

Illumination light pipes transform a quasi-point source (like an LEU) into an arlificial extended light sourcc (Fig.2).

Beam-shaping is the most general task that an optical element can perform. It iricliides the collimation of highpower laser diodc arrays, spaceinvariant diffiiscrs atid the conversion of- an incident beam into an arbitrary intensity distribution.

Chemical niicrocliips mid miniaturized analytical systems (pTAS) are of increasing intercst in livc sciences. Usually, a coniplex arrangement of lasers, detectors, filters, optics, and high precision mechanical stages is required for illurninatioii and optical detection. Microlens arrays offer ii large potential to reducc the size and to siniplify the architecture of analytical systems 141. Figure 7 shows a photograph of microlenses made in photoresist. The lenses are rlepositcd directly onto a glass chip that contains thc fluidic microchannels.

Miniaturized spectrornetcrs can be realized based 011 optical MEMX technology. Recently, a compact Fourier transform spectroinetcr (PTS) has hcen realized in silicon [SI. Thc I:TS is a Michelson iuterferometcr with one scanning mirror (39 pin displacement). The iesolution of the FTS was better than 10 nm (at 633 tim). P’igure 8 prcscnts the electroslatic actuator, the 75 p m x 500 pm movable mirror, the combs, and the springs.

l’oday, micro-optics is a small but iiicrcasing inarket including applications in lele- communications (optical interconnccts, WDM, fiber couplers), medicine (alignment, vision correction, imaging), electronic devices (optical scanners, copy tnachincs, CCU cameras, CI) & DVL) drives and players, cinn corders, pagcrs), automotive (lighting) and defcnsc. SO %I or thc elcments ;ire made in quarkiglass and SO‘% arc replicated in plastic. In future the plastic elcmcnts will dominate the inarket.

1I.P. Hcrzig, cd., Micro-Optics: Eicrnents, Systcms, and Applications, (l’aylor 8z h n c i s , London, 1097). J. Tumnen, F. Wyrowski, ctls., 1)iffr;ictivc Optics for Industrid arid Commercial Applications, (Akaclemie Verlag, Berlin, 1997). S. Sinzinger, J. Jahiis, “Microoptics” (Wiley-VCH, Weinlicim, 1999). J.-Ch. IZoulct, K. Viilkel, M.P. I-lerzig, E. Veq~oorte, N.V. (le Rooij, I{. IXiiidlikcr, “Microlens systems for fluorescerice dctectioii in chcniical microsystems”, submitted for publ. in Opt. Eiigin. 0. Manzardo, H.P. Heizig, C. Marxer, N.F. dc Rooij, “Miniaturized time-scanning Fourier transrorm spectrometer based on silicon tcclinology”, Opt. Lett. 24, 1705- 1707 (1999).

0-7803-5947-W00/$10.0~2000 IEEE 639

Fig. 1 Amplitude distribution of E-field Fig. 2 Non-scqucritial ray-tracing within a light propagating through blazed grating. p i p ,

Fig. 3 Spherical lenses (diametcr 3 pin). Fig. 4 Interferometrically Iccordcd crossed grating beriod A = I pin).

Fig. 5 Grating on top o f a microlens Fig. 6 Arbitrary surface produced by gray- (A = 1 p). tone lithography.

Fig. 7 Photoresist inicrolenses deposited Pig. 8 Scanning electron microscopy directly onto a chip containing microchariiiels

[41' photograph of a miniatiuized spectrometw

based on silicon technology [Si.

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