A. Melnyk

Design and fabrication of a planar PDMS transmission grating microspectrometer.

We describe the monolithic integration of microfluidic channels, optical waveguides, a collimating lens and a curved focusing transmission grating in a single PDMS-based microsystem. All optical and fluidic components of the device were simultaneously formed in a single layer of high refractive index (n~1.43) PDMS by soft lithography. Outer layers of lower-index (n~1.41) PDMS were subsequently added to provide optical and fluidic confinement. Here, we focus on the design and characterization of the microspectrometer part, which employs a novel self-focusing strategy based on cylindrical facets, and exhibits resolution <10 nm in the visible wavelength range. The dispersive behavior of the grating was analyzed both experimentally and using numerical simulations, and the results are in good agreement with simplified analytical predictions.

Wavelength interrogation of fiber Bragg grating sensors using tapered hollow Bragg waveguides.

We describe an integrated system for wavelength interrogation, which uses tapered hollow Bragg waveguides coupled to an image sensor. Spectral shifts are extracted from the wavelength dependence of the light radiated at mode cutoff. Wavelength shifts as small as ~10  pm were resolved by employing a simple peak detection algorithm. Si/SiO₂-based cladding mirrors enable a potential operational range of several hundred nanometers in the 1550 nm wavelength region for a taper length of ~1  mm. Interrogation of a strain-tuned grating was accomplished using a broadband amplified spontaneous emission (ASE) source, and potential for single-chip interrogation of multiplexed sensor arrays is demonstrated.

Visible-band dispersion by a tapered air-core Bragg waveguide

We describe out-coupling of visible band light from a tapered hollow waveguide with TiO(2)/SiO(2) Bragg cladding mirrors. The mirrors exhibit an omnidirectional band for TE-polarized modes in the ~490 to 570 nm wavelength range, resulting in near-vertical radiation at mode cutoff positions. Since cutoff is wavelength-dependent, white light is spatially dispersed by the taper. Resolution on the order of 2 nm is predicted and corroborated by experimental results. These tapers can potentially form the basis for compact micro-spectrometers in lab-on-a-chip and optofluidic micro-systems.

Tunable open-access microcavities for on-chip cavity quantum electrodynamics

We report on the development of on-chip microcavities and show their potential as a platform for cavity quantum electrodynamics experiments. Microcavity arrays were formed by the controlled buckling of SiO2/Ta2O5 Bragg mirrors and exhibit a reflectance-limited finesse of 3500 and mode volumes as small as 35λ3. We show that the cavity resonance can be thermally tuned into alignment with the D2 transition of 87Rb and outline two methods for providing atom access to the cavity. Owing to their small mode volume and high finesse, these cavities exhibit single-atom cooperativities as high as C1=65. A unique feature of the buckled-dome architecture is that the strong-coupling parameter g0/κ is nearly independent of the cavity size. Furthermore, strong coupling should be achievable with only modest improvements in mirror reflectance, suggesting that these monolithic devices could provide a robust and scalable solution to the engineering of light-matter interfaces.We report on the development of on-chip microcavities and show their potential as a platform for cavity quantum electrodynamics experiments. Microcavity arrays were formed by the controlled buckling of SiO2/Ta2O5 Bragg mirrors, and exhibit a reflectance-limited finesse of 3500 and mode volumes as small as 35lambda^3. We show that the cavity resonance can be thermally tuned into alignment with the D2 transition of 87Rb, and outline two methods for providing atom access to the cavity. Owing to their small mode volume and high finesse, these cavities exhibit single-atom cooperativities as high as C1 = 65. A unique feature of the buckled-dome architecture is that the strong-coupling parameter g0/kappa is nearly independent of the cavity size. Furthermore, strong coupling should be achievable with only modest improvements in mirror reflectance, suggesting that these monolithic devices could provide a robust and scalable solution to the engineering of light-matter interfaces.

Air gap resonant tunneling bandpass filter and polarizer.

We describe a bandpass filter based on resonant tunneling through an air layer in the frustrated total internal reflection regime, and show that the concept of induced transmission can be applied to the design of thin film matching stacks. Experimental results are reported for Si/SiO2-based devices exhibiting a polarization-dependent passband, with bandwidth on the order of 10 nm in the 1550 nm wavelength range, peak transmittance on the order of 80%, and optical density greater than 5 over most of the near infrared region.

Visible range hollow waveguides by guided buckling of Ta 2 O 5 /SiO 2 multilayers

Hollow waveguides operating near 550 nm wavelength were fabricated by guided formation of delamination buckles within Ta2O5/SiO2 multilayers. Fabrication of straight and curved waveguides is described, along with preliminary light guiding results.

Tapered air-core Bragg waveguides for spectrally resolved fluorescence detection on a chip

We describe a micro-spectrometer based on a tapered channel Bragg waveguide, and show that it is well-suited to spectrally resolved fluorescence detection in optofluidic micro-systems. Experimental results for small-volume emitters (fluorescent beads) are reported.

Tapered air-core Bragg waveguide spectrometers for lab-on-a-chip applications

Lab-on-a-chip and optofluidic micro-systems often rely on bulky off-chip optical components such as lenses and spectrometers for detection. There is a growing demand for compact microspectrometers that can be integrated on-chip, to increase portability and potentially reduce the cost and complexity of these systems. We have previously reported chip-scale microspectrometers based on tapered air-core Bragg waveguides with omnidirectional Bragg claddings. Here, we describe the integration of these air-core waveguide spectrometers with microfluidics, including results for a prototype sensing system based on spectrally-resolved fluorescence detection.