Peter T. Rakich

The advent of high quality factor (Q) microphotonic-resonators has led to the demonstration of high-fidelity optical sensors of many physical phenomena (e.g. mechanical, chemical, and biological sensing) often with far better sensitivity than traditional techniques. Microphotonic-resonators also offer potential advantages as uncooled thermal detectors including significantly better noise performance, smaller pixel size, and faster response times than current thermal detectors. In particular, microphotonic thermal detectors do not suffer from Johnson noise in the sensor, offer far greater responsivity, and greater thermal isolation as they do not require metallic leads to the sensing element. Such advantages make the prospect of a microphotonic thermal imager highly attractive. Here, we introduce the microphotonic thermal detection technique, present the theoretical basis for the approach, discuss our progress on the development of this technology and consider future directions for thermal microphotonic imaging. Already we have demonstrated viability of device fabrication with the successful demonstration of a 20{micro}m pixel, and a scalable readout technique. Further, to date, we have achieved internal noise performance (NEP{sub Internal} < 1pW/{radical}Hz) in a 20{micro}m pixel thereby exceeding the noise performance of the best microbolometers while simultaneously demonstrating a thermal time constant ({tau} = 2ms) that is five times faster. Inmore » all, this results in an internal detectivity of D*{sub internal} = 2 x 10{sup 9}cm {center_dot} {radical}Hz/W, while roughly a factor of four better than the best uncooled commercial microbolometers, future demonstrations should enable another order of magnitude in sensitivity. While much work remains to achieve the level of maturity required for a deployable technology, already, microphotonic thermal detection has demonstrated considerable potential. « less

Evanescent field perturbation of an integrated microring resonator is examined as a means of achieving high-fidelity reversible tuning of photonic microcavities over large wavelength ranges. A 1.7% wavelength tuning is achieved through the use of a novel silica fiber probe that provides access to the evanescent field of an air-clad high-index-contrast ring resonator. As the microring is perturbed, the probe–ring distance is found through simultaneous nanometric distance calibration and force measurements. Experimental results agree well with theoretical tuning. Possible microelectromechanical systems implementation of this effect is discussed, as well as avenues for improvement of the tuning range.

Diffraction, a fundamental process in wave physics, leads to spreading of the optical beams as they propagate. However, new photonic crystal (PhC) meta-materials can be nano-engineered to generate extreme anisotropy, resulting in apparent propagation of light without diffraction. This surprising phenomenon, called supercollimation, effectively freezes the spatial width of a light beam inside a PhC, observed over a few isotropic diffraction-lengths^1,2,3,4,5,6. However, using such experiments to predict the behaviour for longer propagation lengths is difficult, as a tiny error in a measured width can extrapolate to order unity uncertainty in the width at distances over hundreds of diffraction-lengths. Here, supercollimation is demonstrated in a macroscopic PhC system over centimetre-scale distances, retaining spatial width confinement without the need for waveguides or nonlinearities. Through quantitative studies of the beam evolution in a two-dimensional PhC, we find that supercollimation possesses unexpected but inherent robustness with respect to short-scale disorder such as fabrication roughness, enabling supercollimation over 600 isotropic diffraction-lengths. The effects of disorder are identified through experiments and understood through rigorous simulations. In addition, a supercollimation steering capability is proposed.

The use of ultra-broadband supercontinuum generated by an all-fiber system to characterize high-index contrast photonic circuits over the wavelength range 1.2–2.0 µm is demonstrated. Efficient, broadband waveguide coupling techniques and sensitive normalized detection enable rapid and high-resolution measurements of nano-scale one-dimensional photonic crystal microcavities. Experimental mappings of bandgaps and cavity mode resonances with a wavelength resolution of 0.1 nm compare well with computer simulations.