6.13.24
Nik Papageorgiou
EPFL/Yang Liu CC-BY-SA 4.0
Scientists at EPFL have successfully miniaturized a powerful erbium-based fiber laser on a silicon-nitride photonic chip. Since typical erbium-based fiber lasers are large and difficult to scale down, the breakthrough promises major advances in optical communications and sensing technologies.
Lasers have revolutionized the world since the 60’s and are now indispensable in modern applications, from cutting-edge surgery and precise manufacturing to data transmission across optical fibers.
But as the need for laser-based applications grows, so do challenges. For example, there is a growing market for fiber lasers, which are currently used in industrial cutting, welding, and marking applications.
Fiber lasers use an optical fiber doped with rare-earth elements (erbium, ytterbium, neodymium etc) as their optical gain source (the part that produces the laser’s light). They emit high-quality beams, they have high power output, and they are efficient, low-maintenance, durable, and they are typically smaller than gas lasers. Fiber lasers are also the ‘gold standard’ for low phase noise, meaning that their beams remain stable over time.
But despite all that, there is a growing demand for miniaturizing fiber lasers on a chip-scale level. Erbium-based fiber lasers are especially interesting, as they meet all the requirements for maintaining a laser’s high coherence and stability. But miniaturizing them has been met by challenges in maintaining their performance at small scales.
Now, scientists led by Dr Yang Liu and Professor Tobias Kippenberg at EPFL have built the first ever chip-integrated erbium-doped waveguide laser that approaches the performance with fiber-based lasers, combining wide wavelength tunability with the practicality of chip-scale photonic integration. The breakthrough is published in Nature Photonics.
Building a chip-scale laser
The researchers developed their chip-scale erbium laser using a state-of-the-art fabrication process. They began by constructing a meter-long, on-chip optical cavity (a set of mirrors that provide optical feedback) based on ultralow-loss silicon nitride photonic integrated circuit.
“We were able to design the laser cavity to be meter-scale in length despite the compact chip size, thanks to the integration of these microring resonators that effectively extend the optical path without physically enlarging the device,” says Dr. Liu.
The team then implanted the circuit with high-concentration erbium ions to selectively create the active gain medium necessary for lasing. Finally, they integrated the citcuit with a III-V semiconductor pump laser to excite the erbium ions to enable them to emit light and produce the laser beam.
To refine the laser’s performance and achieve precise wavelength control, the researchers engineered an innovative intra-cavity design featuring microring-based Vernier filters, a type of optical filter that can select specific frequencies of light.
The filters allow for dynamic tuning of the laser’s wavelength over a broad range, making it versatile and usable in various applications. This design supports stable, single-mode lasing with an impressively narrow intrinsic linewidth of just 50 Hz.
It also allows for significant side mode suppression – the laser’s ability to emit light at a single, consistent frequency while minimizing the intensity of other frequencies (‘side modes’). This ensures “clean” and stable output across the light spectrum for high-precision applications.
Power, precision, stability, and low noise
The chip-scale erbium-based fiber laser features output power exceeding 10 mW and a side mode suppression ratio greater than 70 dB, outperforming many conventional systems.
It also has a very narrow linewidth, which means the light it emits is very pure and steady, which is important for coherent applications such as sensing, gyroscopes, LiDAR, and optical frequency metrology.
The microring-based Vernier filter gives the laser broad wavelength tunability across 40 nm within the C- and L-bands (ranges of wavelengths used in telecommunications), surpassing legacy fiber lasers in both tuning and low spectral spurs metrics (“spurs” are unwanted frequencies), while remaining compatible with current semiconductor manufacturing processes.
Next-generation lasers
Miniaturizing and integrating erbium fiber lasers into chip-scale devices can reduce their overall costs, making them accessible for portable and highly integrated systems across telecommunications, medical diagnostics, and consumer electronics.
It can also scale down optical technologies in various other applications, such as LiDAR, microwave photonics, optical frequency synthesis, and free-space communications.
“The application areas of such a new class of erbium-doped integrated lasers are virtually unlimited,” says Liu.
See the full article here .
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The Swiss Federal Institute of Technology in Lausanne [EPFL-École Polytechnique Fédérale de Lausanne] (CH) is a research institute and university in Lausanne, Switzerland, that specializes in natural sciences and engineering. It is one of the two Swiss Federal Institutes of Technology, and it has three main missions: education, research and technology transfer.
The QS World University Rankings ranks EPFL(CH) very high, whereas Times Higher Education World University Rankings ranks EPFL(CH) as one of the world’s best schools for Engineering and Technology.
EPFL(CH) is located in the French-speaking part of Switzerland; the sister institution in the German-speaking part of Switzerland is The Swiss Federal Institute of Technology ETH Zürich [Eidgenössische Technische Hochschule Zürich] (CH). Associated with several specialized research institutes, the two universities form The Domain of the Swiss Federal Institutes of Technology (ETH Domain) [ETH-Bereich; Domaine des Écoles Polytechniques Fédérales] (CH) which is directly dependent on the Federal Department of Economic Affairs, Education and Research. In connection with research and teaching activities, EPFL(CH) operates a nuclear reactor CROCUS; a Tokamak Fusion reactor; a Blue Gene/Q Supercomputer; and P3 bio-hazard facilities.
ETH Zürich, EPFL (Swiss Federal Institute of Technology in Lausanne) [École Polytechnique Fédérale de Lausanne](CH), and four associated research institutes form The Domain of the Swiss Federal Institutes of Technology (ETH Domain) [ETH-Bereich; Domaine des Écoles polytechniques fédérales] (CH) with the aim of collaborating on scientific projects.
The roots of modern-day EPFL(CH) can be traced back to the foundation of a private school under the name École Spéciale de Lausanne in 1853 at the initiative of Lois Rivier, a graduate of the École Centrale Paris (FR) and John Gay the then professor and rector of the Académie de Lausanne. At its inception it had only 11 students and the offices were located at Rue du Valentin in Lausanne. In 1869, it became the technical department of the public Académie de Lausanne. When the Académie was reorganized and acquired the status of a university in 1890, the technical faculty changed its name to École d’Ingénieurs de l’Université de Lausanne. In 1946, it was renamed the École polytechnique de l’Université de Lausanne (EPUL). In 1969, the EPUL was separated from the rest of the University of Lausanne and became a federal institute under its current name. EPFL(CH), like ETH Zürich (CH), and it is thus directly controlled by the Swiss federal government. In contrast, all other universities in Switzerland are controlled by their respective cantonal governments. EPFL(CH) has started to develop into the field of life sciences. It absorbed the Swiss Institute for Experimental Cancer Research (ISREC) in 2008.
In 1946, there were 360 students. In 1969, EPFL(CH) had 1,400 students and 55 professors. In the past two decades the university has grown rapidly and over 14,000 people study or work on campus, about 10,000 of these being Bachelor, Master or PhD students. The environment at modern day EPFL(CH) is highly international with the school attracting students and researchers from all over the world. More than 125 countries are represented on the campus and the university has two official languages, French and English.
Organization
EPFL is organized into eight schools, themselves formed of institutes that group research units (laboratories or chairs) around common themes:
School of Basic Sciences
Institute of Mathematics
Institute of Chemical Sciences and Engineering
Institute of Physics
European Centre of Atomic and Molecular Computations
Bernoulli Center
Biomedical Imaging Research Center
Interdisciplinary Center for Electron Microscopy
MPG-EPFL Centre for Molecular Nanosciences and Technology
Swiss Plasma Center
Laboratory of Astrophysics
School of Engineering
Institute of Electrical Engineering
Institute of Mechanical Engineering
Institute of Materials
Institute of Microengineering
Institute of Bioengineering
School of Architecture, Civil and Environmental Engineering
Institute of Architecture
Civil Engineering Institute
Institute of Urban and Regional Sciences
Environmental Engineering Institute
School of Computer and Communication Sciences
Algorithms & Theoretical Computer Science
Artificial Intelligence & Machine Learning
Computational Biology
Computer Architecture & Integrated Systems
Data Management & Information Retrieval
Graphics & Vision
Human-Computer Interaction
Information & Communication Theory
Networking
Programming Languages & Formal Methods
Security & Cryptography
Signal & Image Processing
Systems
School of Life Sciences
Bachelor-Master Teaching Section in Life Sciences and Technologies
Brain Mind Institute
Institute of Bioengineering
Swiss Institute for Experimental Cancer Research
Global Health Institute
Ten Technology Platforms & Core Facilities (PTECH)
Center for Phenogenomics
NCCR Synaptic Bases of Mental Diseases
College of Management of Technology
Swiss Finance Institute at EPFL
Section of Management of Technology and Entrepreneurship
Institute of Technology and Public Policy
Institute of Management of Technology and Entrepreneurship
Section of Financial Engineering
College of Humanities
Human and social sciences teaching program
EPFL Middle East
Section of Energy Management and Sustainability
In addition to the eight schools there are seven closely related institutions
Swiss Cancer Centre
Center for Biomedical Imaging (CIBM)
Centre for Advanced Modelling Science (CADMOS)
École Cantonale d’art de Lausanne (ECAL)
Campus Biotech
Wyss Center for Bio- and Neuro-engineering
Swiss National Supercomputing Centre
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