An overview of the most recent developments and improvements to the low-loss TriPleX Si 3 N 4 waveguide technology is presented in this paper. The TriPleX platform provides a suite of waveguide geometries (box, double stripe, symmetric single stripe, and asymmetric double stripe) that can be combined to design complex functional circuits, but more important are manufactured in a single monolithic process flow to create a compact photonic integrated circuit. All functionalities of the integrated circuit are constructed using standard basic building blocks, namely straight and bent waveguides, splitters/combiners and couplers, spot size converters, and phase tuning elements. The basic functionalities that have been realized are: ring resonators and Mach-Zehnder interferometer filters, tunable delay elements, and waveguide switches. Combination of these basic functionalities evolves into more complex functions such as higher order filters, beamforming networks,

We present a high power, widely tunable, continuous wave external cavity quantum cascade laser designed for infrared vibrational spectroscopy of molecules exhibiting broadband and single line absorption features. The laser source exhibits single mode operation with a tunability up to 303 cm−1 (∼24% of the center wavelength) at 8 μm, with a maximum optical output power of 200 mW. In combination with off-axis integrated output spectroscopy, trace-gas detection of broadband absorption gases such as acetone was performed and a noise equivalent absorption sensitivity of 3.7 × 10−8 cm−1 Hz−1/2 was obtained.

Optical methods based on quantum cascade lasers (QCLs) are becoming popular in many life science applications. We report on two trace gas detection schemes based on continuous wave QCLs for on-line detection of nitric oxide (NO) at the sub-part-per-billion level by volume (ppbv, 1 : 10 −9 ), using wavelength modulation spectroscopy (WMS) and Faraday rotation spectroscopy (FRS) at 1894 cm −1 and 1875.73 cm −1 , respectively. Several technical incremental steps are discussed to further improve the sensitivity of these methods. Examples are included to demonstrate the merits of WMS-based sensor: direct monitoring of NO concentrations in exhaled breath, and from plants under pathogen attack. A simple hand-held breath sampling device that allows single breath collection at various exhalation flows (15, 50, 100 and 300 mL/s, respectively) is developed for off-line measurements and validated in combination with the WMS-based sensor. Additionally, the capability of plants to remove environmental NO is presented.

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