Matthias Hillenbrand, Eric Markweg, Martin Hoffmann, Stefan Sinzinger:

Integrated hybrid GRIN lenses

Zuerst erschienen in: DGaO-Proceedings. - Erlangen-Nürnberg: Dt. Gesellschaft für angewandte Optik, ISSN 1614-8436. - Bd. 113.2012, P5, insg. 1 S. URN: urn:nbn:de:0287-2012-P005-2

Design Principle: Independent wavefront in two perpendicular directionscontrol

Direction 1: Perpendicular to the substrate

· GRIN element, variation of the refractive index during the layer deposition process

· Description of the refractive index profile:

Direction 2: Parallel to the substrate

· Etching process with perpendicular, optical quality side walls

· Element shape determined by 2D-profile of the lithographic mask

www.tu-ilmenau.de

Technische Universität Ilmenau®IMN MacroNano

Fachgebiet Technische Optik

Matthias Hillenbrand

Telefon: +49 3677 69-1276

Fax: +49 3677 69-1281

matthias.hillenbrand@tu-ilmenau.de

www.tu-ilmenau.de/optik

ReferencesThe authors would like to thank the German Federal Ministry of Education and Research and the Thuringian Ministry for Education, Science, and Culture for the financial support through the projects “Kompetenzdreieck Optische Mikrosysteme-KD OptiMi” (FKZ: 16SV3700) and “Graduate Research School on Optical Microsystems Technology (FZK: PE 104-1-1).

Acknowledgements

Macro ®NanoM. Hillenbrand, E. Markweg, M. Hoffmann, S. SinzingerIMN MacroNano , Technische Universität Ilmenau

®

Integrated Hybrid GRIN Lenses

Advantages· low cost by mass production (semiconductor technologies)· high reliability· high precision in geometric dimensions and positions (defined by lithography mask)· can be combined with integrated photonic elements on the same substrate· high refractive index range

Exemplary applications· efficient coupling structures between integrated optics and free space· beam shaping for integrated laser diodes

Challenges · 2D structuring for 3D functionality· High transmittance

Achievable parameters· Maximum height of the structures dependent on deposition

time; structures with 30µm GRIN layer height realized· Realized minimum feature size: 2 µm (DOE period)· Possible refractive index range: 1,47-1,85

[1] J.-i. Shimada, O. Ohguchi, R. Sawada: Gradient-index microlens formed by ion-beam sputtering, Applied Optics 31 No. 25, 5230 (1992)[2] D.R. Beltrami, J.D. Love, A. Durandet et al: Planar graded-index pecvd lens, Electronic Letters 32

No. 6, 549 (1996)

Wafer-level optics

sensor 1

sensor 2

single-

mode fiber

measure

beam

mirror

thermooptical

modulator

GRIN-

lense

mirror

Concept and prototype of a wafer-level interferometer for displacement measurements

variableGRIN-profile

Variety of diffractiveand refractive shapes

depostion of a ICPCVD film(SiO2/SiON)

electro-patterning of nickelstructured by UV-lithography

fluorine-based ICPRIE deep etching

separation and testingof the optical elements

Technology and experimental results

Design

Fabrication using semiconductor technologies

Design process· Raytracing-based optimisation· Simultaneous variaton of the refractive or

diffractive shape and the GRIN-profile· Merit function based on the wavefront

aberration of the output beam

refractive index

vert

ical p

osi

tio

n

Cylindrical Acylindrical Diffractive

Experimental setup for laser beam collimation

Beam profile at 15mm distance from the lens

collimated uncollimated

1/e^2 gaussian beam radius behind the GRIN lens

1/e

^2

beam

rad

ius

in m

m

distance from lens in mm

1,480

1,490

1,500

1,510

1,520

1,530

1,540

-10 -5 0 5 10

optimised refractive index profile

realised refractive index profile

stepped index profile of the produced elements

vertical position in µm

refr

act

ive in

dex

0

5

10

15

20

25

30

1,460

1,510

1,560

1,610

1,660

1,710

1,760

-5 5 15 25 35 45 55 65 75 85 95

refractive index of silicon oxynitride (500 W; 10 mTorr; SiH4 : 6sccm; 380 °C; gasratio N2O+N2= 100sccm)

gasratio vs refractive index at 380°C

deposition rate

gas ratio N2O

(N2 + N2O = 100 sccm)

refr

act

ive in

dex

dep

osi

tio

n r

ate

in

nm

/min

sensor 11

DGaO-Proceedings 2012 - http://www.dgao-proceedings.de - ISSN: 1614-8436 - urn:nbn:de:0287-2012-P005-2