Tunable is committed to making the world’s most versatile optical gas analyzer, capable of detecting multiple gases simultaneously. The sensor principle is based two core components: a novel tunable Fabry-Perot optical filter and a highly sensitive optical microphone, both made using micro- and nano fabrication techniques. The innovative technology enables the detection and quantification of several gases with high accuracy and high sensitivity.
Most gases have a unique “optical fingerprint” as shown in Figure 1, detectable as a characteristic absorption spectrum in the infrared region of the electromagnetic spectrum. Therefore, infrared transmission spectroscopy is an excellent tool for gas analysis by allowing detection of gas molecules directly, as opposed to indirectly as in sensors based on chemical reactions. The Tunable analyzers carry out infrared transmission spectroscopy by scanning the wavelength of light from a broadband infrared source with a tunable filter. The working principle is shown in Figure 2. When the wavelength of the light overlaps with the absorption spectrum of a gas, energy is absorbed, and the light intensity is attenuated. The amount of attenuation depends on the gas concentration. The light intensity can be measured with a detector that converts light to an electrical signal. Just like a radio can scan to find radio stations, our tunable filter can scan to find gases. The detector signal combined with a sophisticated algorithm determines the type of gas present as well as its concentration.
The key component of our gas analyzers is the tunable Fabry-Perot filter. The filter consists of two closely spaced, parallel mirrors that form a resonant cavity for light. At a certain mirror spacing, some wavelengths interfere constructively and are transmitted, while others interfere destructively and are reflected. The device therefore acts as a filter that only transmits certain wavelengths. By controlling the gap precisely, the wavelength can be tuned continuously.
Our filter is electronically tunable over a wide wavelength range and can be programmed to measure various gases identifiable with their characteristic “optical fingerprints”.
While transmission spectroscopy can be a very powerful technique, high sensitivity will require a long absorption path. In other words, there is a limit to how small you can make a transmission analyzer without compromising on performance. For applications requiring a miniaturized device, we have therefor developed a photo-acoustic spectrometer. In this analyzer we also make use of the fact that many gases absorb infrared light, but instead of measuring the attenuation of transmitted light, we measure the change in pressure resulting from the absorption. This technique is superior with respect to sensitivity per analyzer size.
Photo-acoustic spectroscopy is a fascinating technique illustrated in figure3. Simply put, we tickle the molecules with infrared light and make them hum: As the optical filter scans its peak wavelength in and out of the absorbing spectral range of a target gas, the temperature will oscillate, and in turn result in a periodic change in pressure also known as a sound. This century old technique has been miniaturized by Tunable through the power of an optical microphone fabricated using nano-technology. With our photo-acoustic spectrometer we have created a highly compact, yet sensitive gas analyzer, that fits inside the palm of your hand.
All human senses, except the sense of smell, have been artificially improved, digitalized, and miniaturized.
Our Tunable nose can detect multiple gases in one small package with the potential of matching a dog’s highly developed factory sense. Tunable has a ground-breaking technology replicating the sense of smell.