Contacts: Yazhou Wang (yazwang@fotonik.dtu.dk), Abubakar Adamu (abisa@fotonik.dtu.dk), Callum Smith (caros@fotonik.dtu.dk) and Christos Markos, chmar@fotonik.dtu.dk .
Raman Line Generation
Anti-resonant hollow-core fiber based on the mature silica technology can exhibit very low loss in the mid-infrared region, and thus provides a promising way to guide mid-infrared optical waves. When the hollow core fiber is filled with Raman active gas (hydrogen), it is expected to greatly expand the laser wavelength with Raman Stokes frequency-shift effect. This project aims to achieve high performance nanosecond pulsed Raman laser at 4.2µm by pumping the hydrogen-filled anti-resonant hollow-core fiber with a 1532 nm fiber laser, which, with advantages of compact structure and high efficiency, is desirable for detection of CO2 emission in ships, cars, and so on. The student will build the Raman generation system based on hydrogen-filled anti-resonant hollow-core fiber, and study and optimize and performance of the laser, including gas pressure, fiber length, pump pulse parameters, etc. If time permits, the student will also characterize the relative intensity noise (RIN) of the generated Raman lines.
Ammonia Monitoring
Ammonia emission has significant contribution to environmental pollution. Therefore the detection and real-time monitoring of ammonia with high sensitivity and selectivity is extremely important, especially in livestock farms, where large amounts of ammonia is liberated to the atmosphere. Gas filled hollow-core fibers provide excellent medium for confinement of both light and gas, making them ideal for gas absorption spectroscopy. In this project, the student will have the opportunity to perform experiments in gas detection of ammonia molecules, based on absorption spectroscopy inside a novel hollow-core fiber. The student will learn about supercontinuum light sources –which will be used as the light source, and the basic guiding mechanisms associated such optical fibers. The project will aim to develop an all-fiber system for the detection of ammonia, the student will experimentally detect ammonia and if time permits, characterize the sensitivity of sensing system by diluting gas concentration with a mass flow controller.
Pulse Compression
Lasers can be manipulated to periodically emit short bursts of radiation. This pulsed operation has been exploited in numerous applications, where pulse parameters such as pulse duration, pulse energy and repetition rate are tailored to maximise the efficacy of the process. The minimum pulse duration that can be directly emitted from a laser is limited by the laser material itself. It is often desirable to shorten the pulse duration of a laser to suit a specific application, i.e. material processing or high-field physics. One way to achieve this is through nonlinear pulse compression. This process utilises nonlinear processes to spectrally broaden the laser pulse, before applying controlled dispersion to temporally compress the pulse. The student will build a nonlinear pulse compression system based on a gas-filled hollow core fiber. The student will learn about nonlinear effects, dispersion, pulse propagation and measurement and free-space optics.