CE24 - Micro et nanotechnologies pour le traitement de l’information et la communication

Electron-Pumped UV Laser – UVLASE

Electron-Pumped UV Laser (UVLASE)

Design and development of an electron-beam-pumped ultraviolet laser based on AlGaN heterostructures

UVLASE: Targets

There is a huge demand for lasers in the deep UV field for applications such as Lidar remote sensing, non-line-of-sight (NLOS) communications, biochemistry, 3D printing, etc. This spectral range is currently covered by gas lasers or frequency conversion based lasers, which are bulky, inefficient and operate at a fixed wavelength. Laser diodes would be a very promising alternative, but their implementation remains problematic because of the difficulty in obtaining highly conductive p-AlGaN layers. In this UVLASE project, we will develop a new compact UV laser technology based on the excitation of AlGaN nanostructures by a beam of high energy electrons delivered by a carbon nanotube cathode. We are aiming for quasi-continuous UV sources, cooled by a Peltier module, emitting at 350 nm and 265 nm, with an output power > 50 mW. This choice of wavelengths should allow a direct comparison with the existing UV technology based on Nd-YAG laser. However, thanks to UVLASE's electronic pumping, the laser wavelength could be adjusted to each specific application over the entire 350-250 nm range, without significant degradation in performance.

The UVLASE project brings together the know-how and experience of the Interdisciplinary Research Institute of Grenoble (CEA-IRIG) and the Néel Institute (CNRS, Grenoble) in the design, growth and characterization of AlGaN heterostructures, and those of the University Claude Bernard Lyon I in the manufacture of ultra-bright electron source with carbon nanotube cathodes. The synergy generated by the interaction between the three partners should lead to a significant advance in the field of UV solid state lasers.

We have completed the design and development of AlGaN/GaN heterostructures constituting the active element of electron-beam pumped UV lasers. Our aim is to fabricate a ridge laser operating at relatively low acceleration voltages (7-10 kV). This should allow producing efficient devices that provide medium power in quasi-cw operation with reduced x-ray emission, to compete with Nd-YAG lasers. The result of Monte Carlo simulations of the electron penetration depth imposed a design with the active region close the surface (depth around 130 nm). We adapted the waveguide and electronic design to this requirement. The structures were synthesized by plasma-assisted molecular beam epitaxy on bulk GaN substrates, and their structural quality was validated using transmission electron microscopy and X-ray diffraction. Mirror facets were fabricated by cleaving, without distributed Bragg reflector. Gain was measured using the variable stripe length (VSL) method with an ArF excimer laser (193 nm). The threshold power density under optical pumping with an Nd-YAG laser (266 nm) was estimated around 27 kW/cm2 and 92 kW/cm2 for devices emitting at 365 and 355 nm. Characterization of various laser cavities with different length clearly indicate the dominant source of loses are mirror losses and not internal losses, even for 1.5-mm-long cavities. These samples should allow lasing using electron pumping as specified in the project (10 kV, 20 A/cm2)

There are reasons to expect further improvement:
* lower lasing threshold should be achieved by reducing the number of quantum wells.
* Imlementing a GRINSCH architecture should improve the carrier collection.
* Etching a ridge should improve the lateral confinement.
* Using a high-reflective coating for the mirrors should reduce mirror loses.

PUBLICATIONS

1. “Electrical and Optical Properties of Heavily Ge-Doped AlGaN”, R. Blasco, A. Ajay, E. Robin, C. Bougerol, K. Lorenz, L. C. Alves, I. Mouton, L. Amichi, A. Grenier, and E. Monroy, J. Phys. D: Appl. Phys. 52, 125101 (2019) (DOI: 10.1088/1361-6463/aafec2)

2. “Correlated electro-optical and structural study of electrically tunable nanowire quantum dot emitters”, M Spies, A Ajay, E Monroy, B Gayral, MI Den Hertog, Nano Letters 20, 314 (2020) (DOI: 10.1021/acs.nanolett.9b03858)

3. “Assessment of AlGaN/AlN superlattices on GaN nanowires as active region of electron-pumped ultraviolet sources”, I Dimkou, A Harikumar, F Donatini, J Lähnemann, MI den Hertog, C Bougerol, E Bellet-Amalric, N Mollard, A Ajay, G Ledoux, ST Purcell, and E Monroy, Nanotechnol. 31, 204001 (2020) (DOI: 10.1088/1361-6528/ab704d)

4. “Internal quantum efficiency of AlGaN/AlN quantum dot superlattices for electron-pumped ultraviolet sources”, A. Harikumar, F. Donatini, C. Bougerol, E. Bellet-Amalric, Q.-M. Thai, C. Dujardin, I. Dimkou, S. T. Purcell, and E. Monroy, Nanotechnology (2020) (DOI: 10.1088/1361-6528/aba86c)

5. “Design of AlGaN/AlN Dot-in-a-wire Heterostructures for Electron-Pumped UV Emitters”, I Dimkou, A Harikumar, A Ajay, F Donatini, E Bellet-Amalric, A Grenier, Martien I den Hertog, Stephen T Purcell, and E. Monroy, physica status solidi (a) 217, 1900714 (2020) (DOI: 10.1002/pssa.201900714)
BOOK CHAPTERS

1. Book Chapter. “Electromechanical self-oscillations of CNT field emitter”, A. Ayari, P. Vincent, S. Perisanu, P. Poncharal, & S. T. Purcell. Book Title: «Nanostructured Carbon Electron Emitters and its Applications« Editor Y. Saito. Pan Stanford Publishing. To appear.

2. Book Chapter. “Edge field emission from single layer graphene”, S. T. Purcell, P. Vincent, S. Perisanu, A. Ayari, & P. Poncharal. Book Title: «Nanostructured Carbon Electron Emitters and its Applications« Editor Y. Saito. Pan Stanford Publishing. To appear.

There is a strong demand for deep-UV lasers for applications such as Lidar remote detection, non-line-of sight communication, chem-bio sensing, 3D printing, etc. This spectral range is currently covered by gas lasers or lasers based on frequency conversion, which are bulky, inefficient, and inflexible in wavelength. Laser diodes should provide an alternative solution, but their implementation is held back by the difficulties to fabricate highly-conductive p-AlGaN cladding layers. In this project, we will develop a new compact UV-laser technology based on the excitation of AlGaN nanostructures by a highly energetic electron beam from a carbon nanotube cathode. We target Peltier-cooled quasi-continuous-wave devices at 350 nm and 265 nm, with an average output power > 50 mW. The choice of wavelengths aims at a direct comparison with the Nd-YAG technology. However, the electron pumping principle of UVLASE allows selecting by design any lasing wavelength in the entire 350-250 nm range to match specific applications, without significant degradation of the efficiency. The UVLASE project brings together the know-how of the Insititut Nanoscience and Cryogénics (CEA, Grenoble) and Institut Néel (CNRS, Grenoble) in the design, growth and characterization of AlGaN heterostructures, and the experience of the University Claude Bernard Lyon I on the fabrication of high-current-density cathodes using carbon nanotubes. The synergy generated by the interaction between these two partners should lead to a breakthrough in the domain of solid-state UV lasers.

Project coordination

Eva MONROY (Photonique Electronique et Ingénierie Quantiques)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

PHELIQS Photonique Electronique et Ingénierie Quantiques
ILM INSTITUT LUMIERE MATIERE
INEEL Institut Néel - CNRS

Help of the ANR 571,362 euros
Beginning and duration of the scientific project: - 48 Months

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