Au SiO2 + Au mirror reflection coefficient (%) 78.5% >90.5% Current (mA) 1.5 3 6 9 SUMMARY Full divergence without microlenses (°) 18 22.6 28 38 attenuation a along track (cm-1) 0.169 0.067 We present an optical microsystem aimed to be integrated into a nanomechanical biosensor for functional genomic analysis. The operation principle is based on a nanometre resolution optical measurement of a cantilever deflection caused by a surface stress when the target nucleic acid molecule hybridises to the nucleic acid probe already immobilized on the active side of the cantilever. The resulting deflection, of the order of some nanometres, is measured by the means of an optical system, in which a laser beam reflected off the back of the cantilever is guided to a position sensitive photo-detector. We report in this paper on the design, fabrication and test of the optical head, a key element of the optical coupling system, which enables detection of the presence of target nucleic acid on the cantilever by amplifying the measured laser beam displacement. Z X transmitted intensity (%) 4.8% 28.6% Full divergence with microlenses (°) 4 5.7 6.36 7.62 Y Improvement factor 4.5 3.9 4.4 4.98 Lens array Silicon block VCSEL Global view of the optical system Flip chip machine positioning (3) array gluing (2) array positioning (1) gripping lens array Divergence measured 4.5cm far away from the device 13° • Results : • Compactness of the system : 2cm long final coupler • System providing needed amplification as far as adjustment margin Integrated optical coupling element for functional genomic analysis biosensor C.Vergnenègre, T.Camps,V.Bardinal, C.Bringer, C.Fontaine, A.Muñoz-Yagüe LAAS-CNRS - 7, avenue du Colonel Roche - 31077 Toulouse Cedex 4 Tel : 05 61 33 78 01, Fax : 05 61 33 69 36, E-mail : firstname.lastname@example.org OVERVIEW OF THE SYSTEM 20 cantilever array to be tested by an optical non invasive method • Cantilever deflection very small • Position detector sensibility : 0.1mm 14° FWHM laser source divergence VCSEL collimation is mandatory Development of an optical coupling element Measurement Beam Amplification VCSEL Collimation Most suited microlenses design (Zemax software) Lenses received, specified and mounted : A coupling element has been developed which ensures the amplification of the cantilever deflection angle, while preventing neighboring beams to overlap each other. The optical coupler is interlocked with the VCSEL laser sources head and the adjustment of the light spot on the PSD is made by tilting the micofluidic head. • Z positioning : 263,5 +/- 1.5 µm • X & Y positioning tolerance : relative variation (of RMS spot radius) ε < 3% for a ±10µm positioning error Photo for 10º incidence angle The optical coupler increases the beam path, thereby amplifies the laser beam shift on the photodetector surface from few nanometers to several micrometers in order to make it detectable. TESTS on multimode VCSEL : AlOx=9.5µm, 1/e2 = 18º gap(VCSEL-lens) = 220µm instead of 263µm The minimum track between the cantilever and the detector needed to detect the smallest cantilever deflection is around 15cm(1). (1) C.Vergnenègre et al., Integrated optical coupling element for functional genomic analysis biosensor, Proceedings of the SPIE, vol.5249, pp.648-656, 2003 Measurement of absorption and reflection coefficients : Data obtained with an incident angle of 10º (total track = 303mm) TESTS on singlemode VCSEL: AlOx=3.5µm, 1/e2 = 18° WITHOUT LENS WITH LENS gap(VCSEL-lens) = 250µm instead of 263µm 1.5° • Results : • Divergence reduction by a factor 8.5 despite a very constraining vertical positioning • Fabrication of 2 array support types Final support Test support This work is granted by the European project IST-2001-37239. We would like to thank the project partners participating to this proposal : University of Southampton (UK), CNB-CSIC and CNM-CSIC (Spain), and Genetrix, SL (Spain).