A technique called optical coherence tomography (OCT) has been developed for noninvasive cross-sectional imaging in biological systems. OCT uses low-coherence interferometry to produce a two-dimensional image of optical scattering from internal tissue microstructures in a way that is analogous to ultrasonic pulse-echo imaging. OCT has longitudinal and lateral spatial resolutions of a few micrometers and can detect reflected signals as small as approximately 10(-10) of the incident optical power. Tomographic imaging is demonstrated in vitro in the peripapillary area of the retina and in the coronary artery, two clinically relevant examples that are representative of transparent and turbid media, respectively.

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Optical coherence tomography

Fundamentals of Plasmonics.- Electromagnetics of Metals.- Surface Plasmon Polaritons at Metal / Insulator Interfaces.- Excitation of Surface Plasmon Polaritons at Planar Interfaces.- Imaging Surface Plasmon Polariton Propagation.- Localized Surface Plasmons.- Electromagnetic Surface Modes at Low Frequencies.- Applications.- Plasmon Waveguides.- Transmission of Radiation Through Apertures and Films.- Enhancement of Emissive Processes and Nonlinearities.- Spectroscopy and Sensing.- Metamaterials and Imaging with Surface Plasmon Polaritons.- Concluding Remarks.

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Plasmonics: Fundamentals and Applications

Using self-resonant coils in a strongly coupled regime, we experimentally demonstrated efficient nonradiative power transfer over distances up to 8 times the radius of the coils We were able to transfer 60 watts with ∼40% efficiency over distances in excess of 2 meters We present a quantitative model describing the power transfer, which matches the experimental results to within 5% We discuss the practical applicability of this system and suggest directions for further study

http://science.sciencemag.org/content/sci/317/5834/83.full.pdf

Wireless Power Transfer via Strongly Coupled Magnetic Resonances

Microcavity physics and design will be reviewed. Following an overview of applications in quantum optics, communications and biosensing, recent advances in ultra-high-Q research will be presented.

Optical microcavities

Extremely narrow optical resonances in cold atoms or single trapped ions can be measured with high resolution. A laser locked to such a narrow optical resonance could serve as a highly stable oscillator for an all-optical atomic clock. However, until recently there was no reliable clockwork mechanism that could count optical frequencies of hundreds of terahertz. Techniques using femtosecond-laser frequency combs, developed within the past few years, have solved this problem. The ability to count optical oscillations of more than 1015 cycles per second facilitates high-precision optical spectroscopy, and has led to the construction of an all-optical atomic clock that is expected eventually to outperform today's state-of-the-art caesium clocks.

Optical frequency metrology

Microring resonators side coupled to signal waveguides provide compact, narrow band, and large free spectral range optical channel dropping filters. Higher order filters with improved passband characteristics and larger out-of-band signal rejection are realized through the coupling of multiple rings. The analysis of these devices is approached by the novel method of coupling of modes in time. The response of filters comprised of an arbitrarily large dumber of resonators may be written down by inspection, as a continued fraction. This approach simplifies both the analysis and filter synthesis aspects of these devices.

Microring resonator channel dropping filters

Waves and fields in optoelectronics

The evolution of the theory of mode-locking over the last three and a half decades is reviewed and some of the salient experiments are discussed in the context of the theory. The paper ends with two-cycle pulses of a mode-locked Ti:sapphire laser.

Mode-locking of lasers

In an optical-communications system using soliton pulse transmission, periodic amplification is needed to maintain the energy of the solitons. We show that amplifier noise causes a soliton's group velocity to undergo a random-walk process. The resultant timing errors at the receiver limit the system's product of length times bit rate, in one example, to about 24 000 GHz-km.

Random walk of coherently amplified solitons in optical fiber transmission

This paper reviews recent progress on ultrashort pulse generation with erbium-doped fiber ring lasers. The passive mode-locking technique of polarization additive pulse mode-locking (P-APM) is used to generate stable, self- starting, sub-500 fs pulses at the fundamental repetition rate from a unidirectional fiber ring laser operating in the soliton regime. Saturation of the APM, spectral sideband genera- tion, and intracavity filtering are discussed. Harmonic mode- locking of fiber ring lasers with soliton pulse compression is addressed, and stability regions for the solitons are mapped and compared with theoretical predictions. The stretched- pulse laser, which incorporates segments of positive- and negative-dispersion fiber into the P-APM fiber ring, gen- erates shorter (sub-100 fs) pulses with broader bandwidths (> 65 nm) and higher pulse energies (up to 2: 7n J). We dis- cuss optimization of the net dispersion of the stretched-pulse laser, use of the APM rejection port as the laser output port, and frequency doubling for amplifier seed applications. We also review the analytical theory of the stretched-pulse laser as well as discuss the excellent noise characteristics of both the soliton and stretched-pulse lasers.

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Hermann A. Haus

Papers

Microring resonator channel dropping filters

Waves and fields in optoelectronics

Mode-locking of lasers

Random walk of coherently amplified solitons in optical fiber transmission

Ultrashort-pulse fiber ring lasers