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Research

Gas-filled hollow-core fiber lasers

Fiber lasers and amplifiers underpin a vast range of modern technologies, from high-speed internet and laser eye surgery to precision manufacturing in the automotive and electronics industries. Yet, conventional silica-based fiber lasers are constrained by the intrinsic transmission window of silica glass (~300–2200 nm), limiting their utility for applications that demand light outside this spectral band. Hollow-core fiber (HCF) technology is now transforming this landscape. By guiding light in an air- or gas-filled core rather than solid glass, HCFs dramatically extend the accessible spectral range and provide a platform for exploiting strong light–matter interactions in gases. This enables robust, fiber-integrated laser systems to generate novel wavelengths and ultrafast dynamics far beyond the reach of traditional silica fibers.

(PhD student James Drake aligning a laser into a gas-filled HCF)
(left) An interferometric view of an HCF (fabricated at CREOL by Prof. Amezcua Correa’s group), (middle) A 3D image of the same HCF generated using the interferometry data, and (right) a height map of the end-face.
(top) The emission attenuation spectrum of silica glass (red line) with the emission cross-section of various rare-earth laser emitters including ytterbium (Yb), erbium (Er), thulium (Tm), and holmium (Ho). (bottom) The attenuation spectrum of a CREOL-built HCF (black line) with the emission wavelengths from a 1060 nm pump laser (green) and the resulting Raman shifted wavelength using a methane-filled HCF (blue) and a hydrogen-filled HCF (purple).

Programmable Frequency Comb Emitters

Optical frequency combs have become indispensable tools across science and technology, providing precisely spaced spectral lines that serve as rulers for frequency measurement (Nobel Prize in 2005), high-capacity carriers for data transmission, and broadband sources for ultrafast spectroscopy and imaging. Traditionally, frequency comb generation has relied on mode-locked lasers or nonlinear microresonators, both of which have limitations in terms of flexibility and spectral control. Our group is pursuing a novel approach to comb emission by harnessing cascaded four-wave mixing (CFWM) in optical fibers, where the nonlinear interaction redistributes energy into a broad set of evenly spaced spectral lines. The key innovation is our use of a programmable spatial light modulator (SLM) for dispersion control within a 4f pulse-shaping configuration. This allows us to actively shape the phase landscape that governs the nonlinear evolution, enabling tunable comb spectra with potentially fully selectable power spectral density (PSD) profiles. By embedding this reconfigurable control into a fiber-based architecture, we are developing a uniquely versatile platform for comb sources that can be optimized in real time for applications ranging from precision metrology and optical communications to ultrafast science and astronomy.

Comb spectra from our programmable comb generator. Using a genetic algorithm to optimize the dispersion profile to control cascaded four-wave mixing, we can generate as few as 10 comb lines (blue) to as many as 167 comb lines (red). Future work aims to employ machine learning to allow for arbitrary spectral profiles of the comb lines.