Laser Sources for Frequency-Domain Optical Coherence Tomography FD-OCT Photonic Sensing Workshop SWISSLaser.Net Biel, 17. 9. 2009 Ch. Meier 1/ 20 SWISSLASER.NET Ch. Meier 17.09.09
Content 1. duction 2. FD-OCT basic principles, spectrometer / swept source based FD-OCT 3. Laser sources for OCT 4. Conclusion and Outlook es Source 2/ 20 SWISSLASER.NET Ch. Meier 17.09.09
nce erforman Pe Some application Ophthalmology Anterior segment Retina imaging Drexler W., Fujimoto J. Science Direct 2007 Dispers sion Cardio-vascular application Grulkowski., Optic Express, march 2009 3/ 20 LightLab 2008 SWISSLASER.NET Ch. Meier 17.09.09
Some application Dentistry Pe erforman nce Dispers sion Security and Identification 0.35 mm From Lantis Tooth, Enamel - Dentin, BFH OptoLab, 2009 Epidermis Papilla layer Internal Fingerprint BFH OptoLab, 2009 Dermis B-scan of Fingerprint, 4/ 20 BFH OptoLab, 2009 SWISSLASER.NET Ch. Meier 17.09.09
Tomographic Methods in Medicine Source es MRI, PET CT Name Speed Hazard CT - +++ MRI - - PET - +++ UST ++ - ODT - - PAT + - OCT +++ - 5/ 20 SWISSLASER.NET Ch. Meier 17.09.09
OCT Similar to ultrasonic tomography Depth profiles are constructed by measuring the time delay of backscattered or backreflected light Cross sectional images are obtained by scanning in x and y direction es Source From: W. Drexler, J.Fujimoto, Springer 2008 6/ 20 SWISSLASER.NET Ch. Meier 17.09.09
FD-OCT, basic principles i Broadband source coupled to SM fiber Source S(λ) Spectrometer Reference arm z 0 z 1 sample z es Source 7/ 20 SWISSLASER.NET Ch. Meier 17.09.09
FD-OCT, basic principles i Source S(λ) Spectrometer z 0 z 1 z es Source 8/ 20 SWISSLASER.NET Ch. Meier 17.09.09
FD-OCT, basic principles i Interferences due to optical path difference Source S(λ) Spectrometer z 0 z 1 z Source es Frequency enc in k-space is proportional to OPD Reflectivity profile is obtained by a Fourier transformation 9/ 20 SWISSLASER.NET Ch. Meier 17.09.09
Source es Axial resolution = coherence length 10 / 20 SWISSLASER.NET Ch. Meier 17.09.09
FD OCT, swept source Narrow band Laser Large wavelenth tuning range Source S(λ) Detector z 0 z 1 z Source es Time encoded Fourier domain signal ty a.u. Intensit time a.u 11 / 20 SWISSLASER.NET Ch. Meier 17.09.09
OCT Sources, needs Spectrometer based SeFD OCT Swept Source TeFD OCT Spectrum 800nm, 1000nm, 1300nm 800nm, 1000nm, 1300nm Hemoglobin and water have low absorption in near infrared Source es 12 / 20 SWISSLASER.NET Ch. Meier 17.09.09
OCT Sources, needs Spectrometer based SeFD OCT Swept Source TeFD OCT Spectrum 800nm, 1000nm, 1300nm 800nm, 1000nm, 1300nm Resolutiuon Broad spectrum (up to 200nm ) High scanning range Measuring range High spectrometer resolution Narrow laser spectrum A-scan rate Fast line camera Fast scanning swept source Source es pixel up to 140 khz λ FDML laser up to 200 khz λ 13 / 20 SWISSLASER.NET Ch. Meier 17.09.09
Sources for Spectrometer based FD-OCT high resolution broad bandwidth or low temporal coherence Interferometry plane wave or high spatial coherence Source es Super Luminescend Diode SLD or SLED Center wavelength 840 nm 1310 nm Bandwidth 30 100 nm Fs Laser (Ti:S) Center wavelength 820 nm Bandwidth 120 240 nm 14 / 20 SWISSLASER.NET Ch. Meier 17.09.09
Swept sources Source es Wall plug Systems available 16 khz 20 khz ~ 125 nm sweep range ~30 k 15 / 20 Goldberg, OpticsExpress 2009 SWISSLASER.NET Ch. Meier 17.09.09
Integratete swept source: SG-DBR (sampled grating) Driving current es Source From: Judson + Small size (3 mm chip length) - complicated driving sceme + Low cost - wide laser line width (10MHz) + Wavelength can be engineered - Moderate output power (10 mw). + 5 ns frequency switching time 16 / 20 SWISSLASER.NET Ch. Meier 17.09.09
FDML Laser (Fourier Domain Mode Locking) SOA Broadband semiconductor optical amplifier FFP Fabry-Perrot tunable filter OI Optical Isolators FC Fiber coupler FDL Fiber delay line es Source up to 200 khz sweep rate Gora, 17. Aug. 2009, OpticsExpress 17 / 20 SWISSLASER.NET Ch. Meier 17.09.09 λ
FDML es Source Gora, M.; Wojtkowski, M. OpticExpress, Aug. 2009 18 / 20 SWISSLASER.NET Ch. Meier 17.09.09
OCT summary Modern OCT Systems are based on Fourier/Frequency Domain (FD-OCT) Static broadband source and Spectrometer > Se FD-OCT Swept source and single detector -> Te FD-OCT OCT need high speed, scan rates > 100kHz are demonstrated Source es Movies or high resolution 3D images without motion artefacts are feasible 19 / 20 SWISSLASER.NET Ch. Meier 17.09.09
OptoLab in Biel Different projects in the field of OCT are running Places for master student available Source es Master Thesis in the field of OCT are possible, for Biomedical Master and MSE Laser + Photonics Partial financing is possible Thank you for your attention 20 / 20 SWISSLASER.NET Ch. Meier 17.09.09