Hiring Institution
Université de Limoges (UniLim)

PhD-Awarding Institutions
Université de Limoges (UniLim)
Macquarie University (MQ)

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Option 1

High brightness light sources for mid-infrared spectroscopy

The middle-wave infrared (mid-IR) spectral region is also known as the molecular fingerprint region since most molecules produce characteristic vibrational signatures between 3 and 12 µm. Combined with the fact that the Earth’s atmosphere exhibits two windows of relatively high transparency from 3 to 5 µm and from 8 to 12 µm, the mid-IR spectral region attracts a great deal of attention for high-resolution molecular spectroscopy and remote monitoring of atmospheric pollutants [Dumas2020]. Highly sensitive biological and chemical sensors for homeland security and industrial and environmental monitoring as well as advanced astronomy applications such as planet hunting are examples of emerging applications of high brightness light sources covering the mid-IR.

In this context, we developed a Watt-level mid-IR fiber supercontinuum source pumped by an ultrafast thulium-doped fiber oscillator emitting at 2 µm and demonstrated its suitability for high-resolution spectromicroscopy [Borondics2018]. This new type of bench-top, optical fiber-based laser source can be used for high spatial resolution infrared micro-spectroscopy and chemical imaging rivaling, and in some regard even surpassing, the performances achieved at large-scale synchrotron facilities [https://optics.org/news/9/3/43]. However, the spectral coverage was limited to 4.3 μm due to the nonlinear medium used. Growing efforts from various research communities are deployed to reach deeper into the mid-IR by means of (i) truly mid-IR transparent nonlinear media and (ii) longer wavelength pump sources. Along this line, continuous efforts have been made in the photonics groups at the universities of Limoges and Macquarie to develop several pulsed pump sources optimized to a variety of nonlinear mid-IR waveguides. For example, we have developed an ultrafast 3 µm source to exacerbate supercontinuum generation in engineered chalcogenide microwires up to 12 µm [Hudson2017]. We have also developed a mid-IR supercontinuum source by pumping off-the-shelf chalcogenide fibers by means of an in-house built 4.5 µm ultrafast fiber laser [Tiliouine2022]. Very recently, we demonstrated for the first time to our knowledge efficient mid-IR supercontinuum generation via exacerbation of second-order nonlinearities in Gallium arsenide (GaAs) waveguides by means of a picosecond laser at 2.7 µm [Granger2023]. In this research project, we plan to improve the performance of the experimental configurations studied recently in order to demonstrate the potential of the sources for spectroscopic studies further in the mid-IR (5-12 µm).

Research methodology

Our research methodology is a mix between numerical and experimental studies. We develop numerical models to predict the propagation of light pulses in various realistic nonlinear media under various input conditions. From the numerical study, we deduce the parameters for the seed laser and nonlinear medium most appropriate to a specific application. Then we fabricate and characterize the seed laser and test the nonlinear media. These nonlinear media are either commercially available or designed and manufactured with the help of collaborators. Companies like Le Verre Fluoré, SelenOptics and Coractive provide mid-IR transparent fibers. Thales Research and Technology provide us with GaAs waveguides. In a feedback loop, we refine the characteristics of the laser seeders in terms of wavelength, pulse duration, energy, and repetition rate to the nonlinear media available. We can also laser post-process the nonlinear media to modify their characteristics and ensure a better match with the characteristics of the source. Finally, we refine the numerical models with the new experimental knowledge generated. This research methodology will be deployed in the three topics below.

Objectives

The goal will be to design, manufacture, characterize and implement a high repetition rate source of picosecond pulses in the mid-IR. This kind of laser source is necessary to exacerbate parametric mixing in nonlinear media since the detrimental effect of pulse walk-off is avoided with long picosecond pump pulses. The seed laser source will be a commercial laser source emitting 1.5 ps low energy pulses at 1.97 µm. The wavelength will be first converted towards the mid-infrared in a cascade of nonlinear fluoride optical fibers. Then, the pulse energy will be amplified in nonlinear fiber amplifier. Great attention will be paid to tailor the pulse temporal profile in the amplifier to reach long picosecond pulses. Then, the mid-IR source will be used to exacerbate nonlinearities in e.g. chalcogenide or semi-conductor waveguides. Finally, spectroscopic studies with the broadband laser source will be carried out (e.g. trace gas spectroscopy).

Option 2

Design and fabrication of fiber laser oscillators and amplifiers for mid-infrared spectroscopy

The middle-wave infrared (mid-IR) spectral region is also known as the molecular fingerprint region since most molecules produce characteristic vibrational signatures between 3 and 12 µm. Combined with the fact that the Earth’s atmosphere exhibits two windows of relatively high transparency from 3 to 5 µm and from 8 to 12 µm, the mid-IR spectral region attracts a great deal of attention for high-resolution molecular spectroscopy and remote monitoring of atmospheric pollutants [Dumas2020]. Highly sensitive biological and chemical sensors for homeland security and industrial and environmental monitoring as well as advanced astronomy applications such as planet hunting are examples of emerging applications of high brightness light sources covering the mid-IR.

In this context, we developed a Watt-level mid-IR fiber supercontinuum source pumped by an ultrafast thulium-doped fiber oscillator emitting at 2 µm and demonstrated its suitability for high-resolution spectromicroscopy [Borondics2018]. This new type of bench-top, optical fiber-based laser source can be used for high spatial resolution infrared micro-spectroscopy and chemical imaging rivaling, and in some regard even surpassing, the performances achieved at large-scale synchrotron facilities [https://optics.org/news/9/3/43]. However, the spectral coverage was limited to 4.3 μm due to the nonlinear medium used. Growing efforts from various research communities are deployed to reach deeper into the mid-IR by means of (i) truly mid-IR transparent nonlinear media and (ii) longer wavelength pump sources. Along this line, continuous efforts have been made in the photonics groups at the universities of Limoges and Macquarie to develop several pulsed pump sources optimized to a variety of nonlinear mid-IR waveguides. For example, we have developed an ultrafast 3 µm source to exacerbate supercontinuum generation in engineered chalcogenide microwires up to 12 µm [Hudson2017]. We have also developed a mid-IR supercontinuum source by pumping off-the-shelf chalcogenide fibers by means of an in-house built 4.5 µm ultrafast fiber laser [Tiliouine2022]. Very recently, we demonstrated for the first time to our knowledge efficient mid-IR supercontinuum generation via exacerbation of second-order nonlinearities in Gallium arsenide (GaAs) waveguides by means of a picosecond laser at 2.7 µm [Granger2023]. In this research project, we plan to improve the performance of the experimental configurations studied recently in order to demonstrate the potential of the sources for spectroscopic studies further in the mid-IR (5-12 µm).

Research methodology

Our research methodology is a mix between numerical and experimental studies. We develop numerical models to predict the propagation of light pulses in various realistic nonlinear media under various input conditions. From the numerical study, we deduce the parameters for the seed laser and nonlinear medium most appropriate to a specific application. Then we fabricate and characterize the seed laser and test the nonlinear media. These nonlinear media are either commercially available or designed and manufactured with the help of collaborators. Companies like Le Verre Fluoré, SelenOptics and Coractive provide mid-IR transparent fibers. Thales Research and Technology provide us with GaAs waveguides. In a feedback loop, we refine the characteristics of the laser seeders in terms of wavelength, pulse duration, energy, and repetition rate to the nonlinear media available. We can also laser post-process the nonlinear media to modify their characteristics and ensure a better match with the characteristics of the source. Finally, we refine the numerical models with the new experimental knowledge generated. This research methodology will be deployed in the three topics below.

Objectives

Very recently, we have demonstrated the fabrication of thermally stable high numerical aperture integrated waveguides and couplers for the mid-infrared spectral region [Fernandez2022]. Based on these devices, the goal will be to develop the first fully integrated figure-8 laser operating in the 2.7-3.5 µm range, delivering transform-limited femtosecond or picosecond pulses that will subsequently be amplified in an all-fiber amplifier stage. The generated optical pulses will subsequently be spectrally broadened in a suitable highly nonlinear medium, for example chalcogenide nanowires or GaAs waveguides. Finally, spectroscopic studies with the broadband laser source will be carried out (e.g. trace gas spectroscopy).

Option 3

Few-cycle fiber-based light sources in the mid-infrared

The middle-wave infrared (mid-IR) spectral region is also known as the molecular fingerprint region since most molecules produce characteristic vibrational signatures between 3 and 12 µm. Combined with the fact that the Earth’s atmosphere exhibits two windows of relatively high transparency from 3 to 5 µm and from 8 to 12 µm, the mid-IR spectral region attracts a great deal of attention for high-resolution molecular spectroscopy and remote monitoring of atmospheric pollutants [Dumas2020]. Highly sensitive biological and chemical sensors for homeland security and industrial and environmental monitoring as well as advanced astronomy applications such as planet hunting are examples of emerging applications of high brightness light sources covering the mid-IR.

In this context, we developed a Watt-level mid-IR fiber supercontinuum source pumped by an ultrafast thulium-doped fiber oscillator emitting at 2 µm and demonstrated its suitability for high-resolution spectromicroscopy [Borondics2018]. This new type of bench-top, optical fiber-based laser source can be used for high spatial resolution infrared micro-spectroscopy and chemical imaging rivaling, and in some regard even surpassing, the performances achieved at large-scale synchrotron facilities [https://optics.org/news/9/3/43]. However, the spectral coverage was limited to 4.3 μm due to the nonlinear medium used. Growing efforts from various research communities are deployed to reach deeper into the mid-IR by means of (i) truly mid-IR transparent nonlinear media and (ii) longer wavelength pump sources. Along this line, continuous efforts have been made in the photonics groups at the universities of Limoges and Macquarie to develop several pulsed pump sources optimized to a variety of nonlinear mid-IR waveguides. For example, we have developed an ultrafast 3 µm source to exacerbate supercontinuum generation in engineered chalcogenide microwires up to 12 µm [Hudson2017]. We have also developed a mid-IR supercontinuum source by pumping off-the-shelf chalcogenide fibers by means of an in-house built 4.5 µm ultrafast fiber laser [Tiliouine2022]. Very recently, we demonstrated for the first time to our knowledge efficient mid-IR supercontinuum generation via exacerbation of second-order nonlinearities in Gallium arsenide (GaAs) waveguides by means of a picosecond laser at 2.7 µm [Granger2023]. In this research project, we plan to improve the performance of the experimental configurations studied recently in order to demonstrate the potential of the sources for spectroscopic studies further in the mid-IR (5-12 µm).

Research methodology

Our research methodology is a mix between numerical and experimental studies. We develop numerical models to predict the propagation of light pulses in various realistic nonlinear media under various input conditions. From the numerical study, we deduce the parameters for the seed laser and nonlinear medium most appropriate to a specific application. Then we fabricate and characterize the seed laser and test the nonlinear media. These nonlinear media are either commercially available or designed and manufactured with the help of collaborators. Companies like Le Verre Fluoré, SelenOptics and Coractive provide mid-IR transparent fibers. Thales Research and Technology provide us with GaAs waveguides. In a feedback loop, we refine the characteristics of the laser seeders in terms of wavelength, pulse duration, energy, and repetition rate to the nonlinear media available. We can also laser post-process the nonlinear media to modify their characteristics and ensure a better match with the characteristics of the source. Finally, we refine the numerical models with the new experimental knowledge generated. This research methodology will be deployed in the three topics below.

Objectives

We plan to propose few cycles laser sources in the mid-infrared from 3 to 4 µm with enough energy per pulse to trigger high-harmonic generation in semi-conductors. The seed laser source will be a commercial laser source emitting 1.5 ps low energy pulses at 1.97 µm. The wavelength will be first converted towards the mid-infrared in a cascade of nonlinear fluoride optical fibers. Then, the pulse energy will be amplified in nonlinear fiber amplifiers made in rare-earth doped fluoride fibers (e.g. Er3+, Dy3+, Ho3+ depending on the wavelength of the seed). Great attention will be paid to nonlinearly compress the pulse inside the amplifier. Pulse durations of about 30-40 fs (3 to 4 cycles of the electric field) are expected with this technique with potential to decrease to sub-two cycle durations by further self-compression in passive nonlinear devices. Such ultrashort pulses with high energy (tens of nanojoules) are well suited to high-harmonics generation in solid materials such as semi-conductors [Franz2019]. Application to quantum microscopy are foreseen.

Sebastien Février
Alexander Fuerbach

Photonics, optical fibers, fiber lasers, nonlinear fiber optics