PhD position in Effects of Higher Order Modes on Optical Fiber Amplifiers and Lasers

DTU Electro

The Fiber Optics, Devices and Nonlinear Effects group at DTU Electro at the Technical University of Denmark is seeking a candidate for a PhD to explore the effect of higher order modes in optical fiber amplifiers and lasers. You will participate in an international team in an EU-funded Doctoral Network project called HOMTech. The project consists of 10 Ph.d. students at 6 universities and one company in 5 different EU countries. All, 10 Ph.d. projects are within the overall theme of higher order modes in optical fibers for application in telecommunication, optical sensing, and imaging. This Ph.D. project will take place at DTU Electro in close collaboration with OFS Denmark ( Apart from the time at DTU there will be secondments of minimum 3 months at OFS in Denmark and Chalmers University of Technology in Sweden. There will also be common meetings with the other 9 Ph.D. students in the doctoral network, including 5 training schools.

You will become part of a team at DTU with expertise in characterization, application and design of optical fibers supporting higher order modes. The activities within the project will benefit from synergies with other projects in the group as well as with other activities at the department. OFS Denmark is a world leading manufacturer of rare earth doped amplifier fibers as well as other specialty fibers and advanced transmission fibers. OFS will provide guidance and various fibers available for the project. The main supervisor will be Professor Karsten Rottwitt, Dr. Lars Grüner-Nielsen, DTU Electro, and Dr. Poul Kristensen, OFS Denmark will be co-supervisors.

Responsibilities and tasks
Optical amplifier and lasers are based on use of a short length (typically 1-10 meter) of a fiber doped with a rare earth material such as Erbium, Ytterbium or Thulium. The preferred rare earth material depends on the wavelength range where amplification is needed. Current doped fiber designs are strongly restricted by the general requirement to the fiber to guide only one mode at both the pump and signal wavelengths. The possibility to loosen this requirement and allow for guidance of one or more higher order modes at the pump wavelength and maybe even at the signal wavelength would open for new doped fiber designs with much improved properties. However, the effect of allowing higher order modes to be guided in the amplifier fiber is not well understood. Based on theoretical modeling and experimental investigations, this project aims at getting a deeper understanding on possible decremental effects of higher order modes and means to counteract these effects. The project will among others consist of the following:

  • Characterize higher order mode content and properties in rare earth doped fibers.
  • Characterize effect of higher order modes in rare earth doped fibers in amplifier and laser applications. For example, effect on power conversion efficiency gain and noise properties.
  • Modeling of effect of higher order modes and rare earth doped fibers and lasers.
  • Design of improved rare earth doped fibers.

HOMTech PhD student

Candidates must have a two-year master's degree (120 ECTS points) or a similar degree with an academic level equivalent to a two-year master's degree in photonics, electro, applied physics or similar.

Further obligations: The doctoral candidate (DC) is expected to travel to network partners under two secondments for a typical total duration of 3-5 months. Additionally, the DC is expected to participate in outreach activities including, but not limited to, YouTube videos, social media updates, participation in public events and campaigns, as well as dissemination to popular press. Furthermore, due to the mobility rules of the Marie Skłodowska-Curie program, the applicant must not have resided or carried out their main activity (work, studies, etc.) in Denmark for more than 12 months in the 36 months immediately before their recruitment date.

Approval and Enrolment
The scholarship for the PhD degree is subject to academic approval, and the candidate will be enrolled in one of the general degree programmes at DTU. For information about our enrolment requirements and the general planning of the PhD study programme, please see DTU's rules for the PhD education.

We offer
DTU is a leading technical university globally recognized for the excellence of its research, education, innovation and scientific advice. We offer a rewarding and challenging job in an international environment. We strive for academic excellence in an environment characterized by collegial respect and academic freedom tempered by responsibility.

Salary and appointment terms
The salary and appointment terms are consistent with the current rules for PhD degree students. The appointment will be based on the collective agreement with the Danish Confederation of Professional Associations. The allowance will be agreed upon with the relevant union. The period of employment is 3 years. Start for the grant: March 1, 2023.

You can read more about career paths at DTU here.

The yearly salary before tax will comprise a living allowance of €53,856and a mobility allowance of €7,200. An additional allowance of €6,000 may be payable but is dependent on individual family circumstances. The workplace is DTU Electro at the DTU Lyngby campus.

Further information
Further information may be obtained from Prof. Karsten Rottwitt (

You can read more about DTU Electro at

If you are applying from abroad, you may find useful information on working in Denmark and at DTU at DTU – Moving to Denmark. Furthermore, you have the option of joining our monthly free seminar “PhD relocation to Denmark and startup “Zoom” seminar” for all questions regarding the practical matters of moving to Denmark and working as a PhD at DTU.

Application procedure
Your complete online application must be submitted no later than 1 December 2022 (Danish time)Applications must be submitted as one PDF file containing all materials to be given consideration. To apply, please open the link "Apply online", fill out the online application form, and attach all your materials in English in one PDF file. The file must include:

  • A letter motivating the application (cover letter)
  • Curriculum vitae
  • Grade transcripts and BSc/MSc diploma (in English) including official description of grading scale

You may apply prior to ob­tai­ning your master's degree but cannot begin before having received it.

Applications received after the deadline will not be considered.

All interested candidates irrespective of age, gender, race, disability, religion or ethnic background are encouraged to apply.

The recruitment is taking place following the European Code of Conduct for Recruitment of Researchers, which all candidates are encouraged to study.

Selection process: HOMTech is open to researchers regardless of gender, religion, ethnicity, disability, sexual orientation, political views, language, age and nationality.  Applications from highly qualified applicants from outside the EU will thus be equally considered to other applicants. The integration of refugees is an EU priority and we will ensure equal opportunities to the researchers whose scientific careers have been interrupted. To ensure a gender balance in the project and work towards the Commission’s own policies on narrowing the gap between the genders in research, should two applicants be found to be equally qualified the preference will be given to the one that will balance the gender distribution in the entire Network. After the deadline, all submitted applications will be checked against the defined admissibility and eligibility criteria (e.g. submitted electronically, readable, complete, in English, including grades and references), and applicants will be informed by email within two work weeks on the outcome. The following interviews and selection process will be carried out by a temporary Selection Committee constituted by the Coordinator (when possible) and the supervisors. Evaluation criteria include: Scientific background, capacity for creativity and independent thinking and leadership, mentoring and presentation abilities.

Protection of personal data: The personal data of the applicants will be handled in compliance with applicable EU and national law on data protection (GDPR).

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DTU develops technology for people. With our international elite research and study programmes, we are helping to create a better world and to solve the global challenges formulated in the UN’s 17 Sustainable Development Goals. Hans Christian Ørsted founded DTU in 1829 with a clear mission to develop and create value using science and engineering to benefit society. That mission lives on today. DTU has 13,400 students and 5,800 employees. We work in an international atmosphere and have an inclusive, evolving, and informal working environment. DTU has campuses in all parts of Denmark and in Greenland, and we collaborate with the best universities around the world.