Methods, apparatuses, and systems associated with a sample testing device are provided. For example, an example sample testing device may include a substrate layer defining a bottom surface of the sample testing device, as well as a waveguide disposed on the substrate layer and includes at least one reference channel and at least one sample channel.

A chip-scale, reusable sensor can detect aromatic hydrocarbons, such as benzene, toluene, ethylbenzene, and xylenes (BTEX), rapidly in water without sample preparation. The device is capable of real-time, continuous monitoring for BTEX solutes, which diffuse into a film, such as a polymer, on the sensors surface. In operation, BTEX analytes concentrate in the film, causing an increase in refractive index, which modulates evanescent coupling into the chips integrated photodetector array. Integration of the photodetector array simplifies system instrumentation and permits incorporation of an on-chip photocurrent reference region in the immediate vicinity of the sensing region, reducing drift due to temperature fluctuations. In some examples, the chip responds linearly for BTEX concentrations between 1 ppm and 30 ppm, with a limit of detection of 359 ppb, 249 ppb, and 103 ppb for benzene, toluene, and xylene in water, respectively.

A chip-scale, reusable sensor can detect aromatic hydrocarbons, such as benzene, toluene, ethylbenzene, and xylenes (BTEX), rapidly in water without sample preparation. The device is capable of real-time, continuous monitoring for BTEX solutes, which diffuse into a film, such as a polymer, on the sensors surface. In operation, BTEX analytes concentrate in the film, causing an increase in refractive index, which modulates evanescent coupling into the chips integrated photodetector array. Integration of the photodetector array simplifies system instrumentation and permits incorporation of an on-chip photocurrent reference region in the immediate vicinity of the sensing region, reducing drift due to temperature fluctuations. In some examples, the chip responds linearly for BTEX concentrations between 1 ppm and 30 ppm, with a limit of detection of 359 ppb, 249 ppb, and 103 ppb for benzene, toluene, and xylene in water, respectively.

A chip-scale, reusable sensor can detect aromatic hydrocarbons, such as benzene, toluene, ethylbenzene, and xylenes (BTEX), rapidly in water without sample preparation. The device is capable of real-time, continuous monitoring for BTEX solutes, which diffuse into a film, such as a polymer, on the sensors surface. In operation, BTEX analytes concentrate in the film, causing an increase in refractive index, which modulates evanescent coupling into the chips integrated photodetector array. Integration of the photodetector array simplifies system instrumentation and permits incorporation of an on-chip photocurrent reference region in the immediate vicinity of the sensing region, reducing drift due to temperature fluctuations. In some examples, the chip responds linearly for BTEX concentrations between 1 ppm and 30 ppm, with a limit of detection of 359 ppb, 249 ppb, and 103 ppb for benzene, toluene, and xylene in water, respectively.

A method and apparatus for improving contrast in prism coupling measurements of waveguide mode spectra, wherein the measured waveguide sample has a surface region of rapidly decreasing index, characterized with normalized slope $.Math.\frac{}{n}\frac{n}{z}.Math.>0.0004.$ An opaque light-blocking element is placed in the portion of the light beam closest to the plane of the contact between prism and measured sample, on the input side, output side or both sides of the prism. The light blocking element prevents light from the light source to reach a portion of the length of the prism-sample coupling interface along the optical path, prevents light reflected from a portion of the aforementioned length to reach the detector, or both when input and output light-blocking elements are used.

Methods, apparatuses, and systems associated with a sample testing device are provided. For example, an example sample testing device may include a substrate layer defining a bottom surface of the sample testing device, as well as a waveguide disposed on the substrate layer and includes at least one reference channel and at least one sample channel.

Methods, apparatuses, and systems associated with a sample testing device are provided. For example, an example sample testing device may include a substrate layer defining a bottom surface of the sample testing device, as well as a waveguide disposed on the substrate layer and includes at least one reference channel and at least one sample channel.

Methods, apparatuses, and systems associated with a sample testing device are provided. For example, an example sample testing device may include a substrate layer defining a bottom surface of the sample testing device, as well as a waveguide disposed on the substrate layer and includes at least one reference channel and at least one sample channel.

Methods, apparatuses, and systems associated with a sample testing device are provided. For example, an example sample testing device may include a substrate layer defining a bottom surface of the sample testing device, as well as a waveguide disposed on the substrate layer and includes at least one reference channel and at least one sample channel.