Optical behavior analogous to electromagnetically induced transparency and absorption is observed in experiments using coupled fused-silica microspheres. This behavior results from interference between coresonant whispering-gallery modes of the two spheres. Coupled-resonator-induced transparency and absorption are observed. Which effect is seen depends on the strength of coupling of incident light from a tapered fiber into the first sphere and on the strength of coupling between the two spheres. The observed effects can enhance microresonator performance in various applications.

Ultralow-threshold continuous-wave lasing is achieved at room temperature in a fused-silica microsphere that is coated with HgTe quantum dots (colloidal nanoparticles). The 830 nm pump input and HgTe microlaser output are efficiently coupled into and out of whispering-gallery modes by tapered fibers. Lasing occurs at wavelengths ranging from 1240 to 1780 nm, depending on the size and composition of the quantum dots (HgCdTe is also used). A linear fit to the data determines the lowest observed threshold pump power to be 0 ± 2 W.

Tunable diode laser absorption spectroscopy using microresonator whispering-gallery modes (WGMs) is demonstrated. WGMs are excited around the circumference of a cylindrical cavity 125 mum in diameter using an adiabatically tapered fiber. The microresonator is very conveniently tuned by stretching, enabling the locking of an individual WGM to the laser. As the laser is scanned in frequency over an atmospheric trace-gas absorption line, changes in the fiber throughput are recorded. The experimental results of cavity-enhanced detection using such a microresonator are centimeter effective absorption pathlengths in a volume of only a few hundred microns cubed. The measured effective absorption pathlengths are in good agreement with theory.

A new electro-optic waveguide platform, which provides unprecedented voltage control over optical phase delays (> 2mm), with very low loss (< 0.5 dB/cm) and rapid response time (sub millisecond), will be presented. This technology, developed by Vescent Photonics, is based upon a unique liquid-crystal waveguide geometry, which exploits the tremendous electro-optic response of liquid crystals while circumventing their historic limitations. The waveguide geometry provides nematic relaxation speeds in the 10's of microseconds and LC scattering losses that are reduced by orders of magnitude from bulk transmissive LC optics. The exceedingly large optical phase delays accessible with this technology enable the design and construction of a new class of previously unrealizable photonic devices. Examples include: 2-D analog non-mechanical beamsteerers, chip-scale widely tunable lasers, chip-scale Fourier transform spectrometer (< 5 nm resolution demonstrated), widely tunable micro-ring resonators, tunable lenses, ultra-low power (< 5 microWatts) optical switches, true optical time delay devices for phased array antennas, and many more. All of these devices may benefit from established manufacturing technologies and ultimately may be as inexpensive as a calculator display. Furthermore, this new integrated photonic architecture has applications in a wide array of commercial and defense markets including: remote sensing, micro-LADAR, OCT, FSO, laser illumination, phased array radar, etc. Performance attributes of several example devices and application data will be presented. In particular, we will present a non-mechanical beamsteerer that steers light in both the horizontal and vertical dimensions.

Frames from an IR video showing a 1550 nm beam scanned across a parking lot (above a seated person). ABSTRACTWe are presenting a novel electro-optic architecture for non-mechanical laser beam steering with a demonstrated 80 degrees of steering in a chip-scale package. To our knowledge this is the largest angular coverage ever achieved by non-mechanical means. Even higher angular deflections are possible with our architecture both in the plane of the waveguide and out of the waveguide plane. In the present paper we describe the steering in the plane of the waveguide leaving the out-of-plane scanning mechanism to be detailed in a subsequent publication. In order to realize this performance we exploit an entirely new electro-optic architecture. Specifically, we utilize liquid crystals (LCs), which have the largest known electro-optic response, as an active cladding layer in an LC-waveguide geometry. This architecture exploits the benefits of liquid crystals (large tunable index), while circumventing historic LC limitations. LC-waveguides provide unprecedented macroscopic (>1 mm) electro-optic phase delays. When combined with patterned electrodes, this provides a truly analog, "Snell's-law-type" beam-steerer. With only two control electrodes we have realized an 80 degree field of view for 1550 nm light. Furthermore, the waveguide geometry keeps the light from ever coming into contact with an ITO electrode, thereby permitting high optical power transmission. Finally, the beamsteering devices have sub-millisecond response times.

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