Research

ULTRAVIOLET FREQUENCY COMB SPECTROSCOPY OF NOBLE GASES FOR QUANTUM SENSING

Atomic magnetometers are quantum sensors that measure magnetic fields by detecting the effect of these fields on spin-polarized atoms (i.e., atoms with aligned electronic or nuclear spin). Applications of atomic magnetometers include tests of fundamental physics, nuclear magnetic resonance spectroscopy (for chemical analysis), and magnetic resonance imaging (MRI, e.g., for medical diagnosis or the study of porous materials). State-of-the-art atomic magnetometers are limited by a trade-off between the detection method’s robustness against noise and external interference (background) and spin relaxation time (the time it takes the spins to become misaligned). Optical spectroscopic detection is most resilient against noise and background, however it is limited to atomic species with relaxation times well below 1 minute. Optically inaccessible noble gas nuclear spins offer relaxation times reaching hundreds of hours. These could be accessed optically with the high-power ultraviolet frequency comb lasers that we are developing. These lasers could therefore open the way to magnetometric sensitivity that is orders of magnitude better than today’s state of the art capabilities. In the long term, we will apply these novel magnetometers to push the boundaries of tests of fundamental physics, including searches for axionic dark matter and quantum gravity.

Selected related publications:

• James Maldaner, Mitja Fridman, Saurya Das, and Gil Porat, Feasibility analysis of a proposed test of quantum gravity via novel optical magnetometry in xenon, Physical Review A 109, 032814 (2024). Preprint: arXiv:2402.17057.
  
• Mitja Fridman, James Maldaner, Gil Porat, and Saurya Das, Test of quantum gravity in optical magnetometers, The European Physical Journal Plus 140, 458 (2025).
  

DEVELOPMENT OF LOW-NOISE MODE-LOCKED FIBER LASERS

Low-noise mode-locked lasers are crucial for a wide range of emerging and established technologies, including quantum sensing and metrology, timing synchronization, and microscopy. Particulalry, mode-locked fiber lasers are compact and robust, making them attractive for applications. We study and advance the performance of such lasers, e.g., in terms of intensity noise, wavelength tunability, power scaling, etc.

Selected related publications:

• Saeid Ebrahimzadeh, Sakib Adnan, Yishen Li, Vito F. Pecile, Jakob Fellinger, Sarper Salman, Christoph M. Heyl, Ingmar Hartl, Oliver H. Heckl, and Gil Porat, Spectrally tunable phase-biased NALM mode-locked Yb:fiber laser with nJ-level pulse energy, Journal of Physics: Photonics 6, 02LT01 (2024).
• Saeid Ebrahimzadeh, James Maldaner, Sakib Adnan, Campbell Rea, Yishen Li, and Gil Porat, Mechanism of intensity noise suppression in Yb-doped phase-biased mode-locked NALM lasers, Optics Express 33, 33786 (2025).
  

NOVEL NONLINEAR OPTICS METHODS OF FREQUENCY CONVERSION AND NOISE SUPPRESSION

Applications of laser light, such as spectroscopy, sensing, and imaging, require laser sources at different frequencies and with different properties, such as power, bandwidth, pulse duration, etc. Across many spectral ranges, light produced by direct laser action is not available or does not have the properties needed for certain applications. A case in point is the deep ultraviolet frequency comb laser light needed for the noble gas spectroscopy and quantum magnetic sensor that we are developing (see above). We are developing nonlinear optics methods for efficient frequency conversion that transfers the excellecent properties of mature laser sources (mostly in the near-infrared) to other frequency regimes, particularly deep ultravilolet and THz. Particularly, we utilize adiabatic frequency conversion to achieve efficient and broadband frequency conversion. This approach is based on using slow spatial variation along a medium that interacts with laser light, rather than a medium with fixed or periodically-alternating properties. Adiabatic nonlinear optics defeats long-standing trade-offs between efficiency and robustness. We are also developing nonlinear optical methods for suppressing laser noise and pulse-to-pulse energy fluctuations, as noise reduction directly translates to improved perfomance in many laser applications, including quantum sensing.


Selected related publications:

• Yongyao Li, Ofir Yesharim, Inbar Hurvitz, Aviv Karnieli, Shenhe Fu, Gil Porat, and Ady Arie, Adiabatic geometric phase in fully nonlinear three-wave mixing, Physical Review A 101, 033807 (2020).
  
• Peleg Margules, Jeffrey Moses, Haim Suchowski, and Gil Porat, Ultrafast Adiabatic Frequency Conversion, Journal of Physics: Photonics 3, 022011 (2021).
  
• Yishen Li, Farzaneh Seddighi, and Gil Porat, Broadband suppression of laser intensity noise based on second-harmonic generation, Physical Review Applied 22, 014026 (2024).