Quantum Imaging: Q-OCT Department of Electrical & Computer Engineering Bahaa Saleh Alexander Sergienko Malvin Teich Quantum Imaging Lab Department of Electrical & Computer Engineering & Photonics Center MURI 6/9/05 http://www.bu.edu/qil/

Outline Quantum Imaging Two-Photon Imaging Quantum OCT MURI 6/9/05

Outline Quantum Imaging Two-Photon Imaging Quantum OCT MURI 6/9/05

Optical Imaging = Estimation of the spatial distribution (2D, 3D, 4D) of a physical object by use of optical measurement (direct or interferometric) Source Reflectance R(x,y) Conventional Imaging Metrology Detector or R(x,y,) Spectral or Hyperspectral Imaging or Jones matrix J(x,y) Polarization-sensitive Imaging (Ellipsometry) MURI 6/9/05

Imaging may involve spatial, spectral, and/or polarization effects Source or R(z ) Ranging Detector Axial imaging or (x,y,z) 3D Imaging Subsurface imaging Imaging may involve spatial, spectral, and/or polarization effects MURI 6/9/05

Optical Lithography = Fabrication of objects with specified spatial distributions (2D, 3D) by use of optical sources and systems Source R(x,y) Source (x,y,z) MURI 6/9/05

Limitations of Optical Imaging & Lithography Resolution (transverse & axial) Noise Quantum Classical Io = RIi Source Ii Io Detector R MURI 6/9/05

Quantum Imaging Quantum Lithography = Estimation of the spatial distribution of a physical object by use of light field in a nonclassical state & direct or Interferometric measurement Quantum Lithography = Fabrication of objects with specified spatial distribution by use of light field in a nonclassical state MURI 6/9/05

States of Light Nonclassical States Coherent (laser imaging) Thermal (conventional, photon-correlation imaging) … Saleh et al. PRA 2000 Saleh et al. PRL 2005 Nonclassical States Quadrature-Squeezed Photon-Number Squeezed Two-Photon Gaussian NOON … MURI 6/9/05

Outline Quantum Imaging Two-Photon Imaging Quantum OCT MURI 6/9/05

non-separable function  entangled state Two-Photon light 1 k1 2 k = a state of exactly two photons in multimodes (spatial/spectral/polarization) non-separable function  entangled state Entanglement: Spatial (momentum) Spectral Polarization MURI 6/9/05

H = Spatial, spectral, or polarization system Two Configurations H r x A. Direct H o H r x B. Interferometric H o H = Spatial, spectral, or polarization system MURI 6/9/05

A. Applications of Direct 2-Photon Imaging x H o MURI 6/9/05

1. Correlated-Photon Absolute Measurement Measurement of reflectance/ Transmittance/ Quantum Efficiency x Sample Klyshko, SJQE 77 Branning et al. PRA 00 x Sample Ellipsometry Toussaint et al. PRA 04 SU(2) P A MURI 6/9/05

2. Imaging (transverse) - Spatial modes x Belinskii & Klyshko, Zh. Eksp. Teor. Fiz. 94 Pittman et al., PRA 95 MURI 6/9/05

Example: Optical Fourier transform 3. Two-Photon Microscopy / Lithography 2-photon absorber Factor of 2 enhancement Abouraddy et al., JOSA-B 02 Boto et al., PRL 00 Example: Optical Fourier transform Teich & Saleh, Cesk. Cas. Fyz. 97 MURI 6/9/05

4. Dispersion Compensation Hr() x C Ho() GVD’s of opposite signs cancel Franson PRA 1992 MURI 6/9/05

B. Applications of Interferometric 2-Photon Imaging x H o MURI 6/9/05

Axial Imaging/Ranging Spectral Modes Hr() x C Ho() i.e., insensitive to even-order dispersion (GVD) in Ho, Interference term in C  Nonlocal Dispersion Cancellation Steinberg, Kwiat, Chiao, PRL 92; PRA 92 Shapiro, Sun, JOSA-B 94 Larchuk, Teich, Saleh, PRA 95 MURI 6/9/05

Outline Quantum Imaging Two-Photon Imaging Quantum OCT MURI 6/9/05

Q-OCT = Two-Photon Axial Imaging z C() Dispersion-Cancellation  Hong-Ou-Mandel Interferometer Abouraddy et al. PRA, 053817, 2002 MURI 6/9/05

Experiment ct C(t) I(t) Kr+ 406 nm 55 mW x Detector Filter 2.2 mm 55 mW Filter NLC 8-mm LiIO3 Detector Kr+ 406 nm Sample Nasr et al. PRL, 91, August 2003 MURI 6/9/05

Two Boundaries + dispersive layer 5-mm ZnSe Air 90 m fused silica Air 53 m Classical Quantum 19 m MURI 6/9/05

M. B. Nasr et al., Opt. Express 12, 1353-1362 (2004) Four Boundaries + dispersive medium in-between 90-m AIR 12-mm ZnSe AIR 90-m M. B. Nasr et al., Opt. Express 12, 1353-1362 (2004) MURI 6/9/05

The Promise of Q-OCT Q-OCT promises x2 improved axial resolution in comparison with conventional OCT for sources of same spectral bandwidth Self-interference at each boundary is immune to GVD introduced by upper layers Inter-boundary interference is sensitive to dispersion of inter-boundary layers; dispersion parameters can thus be estimated Preliminary experiments demonstrated viability of technique Technique can be extended to transverse imaging (Q-OCM) Technique can be extended to polarization-sensitive Q-OCT MURI 6/9/05

Q-OCT: Challenges & Plans State-of-the-art linewidth is not sufficiently large (Axial resolution is only 19 m). Two-photon flux is low. Duration of experiment is too long. A better 2-photon source is needed! Faster broadband single-photon detector is needed! Applications to scattering media (e.g., tissue). Theoretical & experimental research is necessary. Algorithms for data processing need to be developed. MURI 6/9/05

Reprints http://www.bu.edu/qil/ MURI 6/9/05

Comparison of OCT & QOCT 10 20 30 40 50 60 70 Penetration Length in H2O Resolution (m) SLD  = 26 nm SLD  = 61 nm Ti:Al2O3,  = 140 nm OCT o = 812 nm Cornea Anterior segment Posterior in Ocular Imaging Eye 5 15 25 mm better 8-mm LiIO3  = 12 nm QOCT 1-mm LiIO3,  = 60 nm & QOCT MURI 6/9/05