Compact, stable and efficient all-fibre gas cells using hollow-core photonic crystal fibres

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Abstract
Gas-phase lasers small enough to fit in a credit card or hand-held laser pointer could soon become a reality. A hollow-core photonic crystal fibre based gas cell has been developed, containing a tenth of a microlitre of hydrogen in a 5-metre-long cell. Laser light can be easily launched into this cell, and its practicality has been demonstrated by using it in a compact Raman laser. Acetylene-filled cells proved their worth in a compact all-optical fibre system for laser frequency stabilization. Gas-phase materials are used in a variety of laser-based applications—for example, in high-precision frequency measurement1,2, quantum optics and nonlinear optics3,4. Their full potential has however not been realized because of the lack of a suitable technology for creating gas cells that can guide light over long lengths in a single transverse mode while still offering a high level of integration in a practical and compact set-up or device. As a result, solid-phase materials are still often favoured, even when their performance compares unfavourably with gas-phase systems. Here we report the development of all-fibre gas cells that meet these challenges. Our structures are based on gas-filled hollow-core photonic crystal fibres, in which we have recently demonstrated substantially enhanced stimulated Raman scattering5,6, and which exhibit high performance, excellent long-term pressure stability and ease of use. To illustrate the practical potential of these structures, we report two different devices: a hydrogen-filled cell for efficient generation of rotational Raman scattering using only quasi-continuous-wave laser pulses; and acetylene-filled cells, which we use for absolute frequency-locking of diode lasers with very high signal-to-noise ratios. The stable performance of these compact gas-phase devices could permit, for example, gas-phase laser devices incorporated in a ‘credit card’ or even in a laser pointer.