Compact, diamond-cooled and stabilised semiconductor disk lasers for quantum technology

Start date: September 2017
Duration: 4 years, including 1 year integrated MSc

Important information: This project is part of the EPSRC Centre for Doctoral Training in Diamond Science and Technology (http://www2.warwick.ac.uk/fac/sci/dst/about_dstcdt) and includes a specially-designed one year MSc course at the University of Warwick and two mini-projects with collaborators during the summer of 2018; one at the University of Bath and one at the Fraunhofer Centre for Applied Photonics.

Background: Semiconductor disk lasers (SDLs) consist of an optically-pumped multi-quantum well active mirror in an external laser cavity. This format of semiconductor laser has a number of advantageous characteristics including power scaling with high beam quality, easy access to high intracavity power, and wavelength flexibility. Following the development of diamond-cooled AlGaInP-based red SDLs at the IoP, we are able to implement intracavity frequency doubling to reach ultraviolet wavelengths [1]. SDLs are unique among semiconductor lasers in that they have very high finesse external cavities with high power and therefore their intrinsic linewidth is very narrow. They also have very low intensity and frequency noise compared to other lasers so long as the photon lifetime exceeds the carrier lifetime; however, this means that the external cavity must be a few cm long and therefore subject to environmental noise. Linewidths of a few kHz are usually achieved via active stabilisation to an external reference, most often a Fabry Perot (see e.g. [1]). We have recently reported a 689nm SDL with linewidth of 5kHz for strontium atom cooling applications and demonstrated tuning with picometre precision via an intracavity diamond heatspreader acting as a variable etalon [2]. A broad range of compact ultra-narrow linewidth lasers, at novel wavelengths, are required for quantum technology; specifically metrology (based on optical clocks) where we aim to apply short wavelength (visible – ultraviolet) SDLs in collaboration with UK leaders in quantum science.

Project objective: In this project the student will develop narrow linewidth, diamond-cooled and stabilised SDL systems suitable for application in quantum technology. This work will take full advantage of the properties of diamond: enabling high power operation and providing thermal and mechanical stability. The research may include but is not limited to: design and optimisation of semiconductor gain structures, semiconductor processing, diamond processing, laser cavity engineering, optics and nonlinear optics, active stabilisation techniques and atom optics demonstrations with our collaborators. We will target novel results that will be published in the best journals in the field.

Research environment: This studentship will benefit from and contribute to a wider project supported by the EPSRC UK Quantum Technology Hub for Sensors and Metrology (www.quantumsensors.org), which involves multiple academic and industry partners. Dr Hastie leads the ‘Special Lasers’ workpackage of the Hub, developing narrow linewidth lasers at novel wavelengths for the optical clock systems of the other partners. We have an existing collaboration with the group of Hub Director Prof Kai Bongs at the University of Birmingham, using these lasers for cooling strontium. Dr Hastie is also the academic partner in an Innovate UK project in collaboration with the Fraunhofer Centre for Applied Photonics and M Squared Lasers Ltd to support the translation of the group’s laser technology to industry.

Institute of Photonics: The Institute of Photonics (IoP), established in 1996, is a commercially-oriented research unit, part of the Department of Physics, University of Strathclyde. The Institute’s key objective is to bridge the gap between academic research and industrial applications and development in the area of photonics. The offices, laboratories, and cleanrooms of the IoP are located in Strathclyde’s new Technology & Innovation Centre in Glasgow City Centre.

1] David Paboeuf, Peter J. Schlosser, and Jennifer E. Hastie, “Frequency stabilization of an ultraviolet semiconductor disk laser,” Optics Letters 38, p1736 (2013).
[2] David Paboeuf and Jennifer E. Hastie, “Tunable narrow linewidth AlGaInP semiconductor disk laser for Sr atom cooling applications,” Applied Optics 55, 4980 (2016).