The good optical transmission of hollow-core photonic crystal fiber and their relative low insertion loss in conventional fiber network gave rise to a new type of all-fiber gas-phase devices. These range from Raman converters as laser sources, compact frequency standard devices for laser frequency control to electromagnetically-induced transparency and saturable absorption for quantum optical devices. Here I report on the performance of these devices and their prospects.
IntroductionGas-phase materials have many compelling laser-related applications, for example in high precision frequency measurement[1,2], quantum optics and nonlinear optics [3,4]. Their potential has however not been realized because of the lack of a suitable technology for creating gas cells that guide light in a single transverse mode over long interaction lengths while still offering a high level of integration in a practical and compact set-up or device. This has meant that solid-phase materials are commonly favored in practice, even when their performance is second-best compared to gasphase materials. Here, we report what we believe to be the first all-fiber gas cell which meets these challenges. The novel gas-cell exhibits excellent long-term pressure stability, ultra-high performance, and ease of use. To illustrate the huge potential of this development, we report four different devices: (i) a hydrogen-filled cell for efficient generation of rotational Raman scattering using only quasi-CW laser pulses, (ii) acetylene-filled cells used for absolute frequency locking of diode lasers with a very high signal-to-noise ratio, (iii) an acetylene cell for electromagnetically induced transparency generation and (iv) an acetylene cell for saturable absorption generation. The stable performance of these ultra-compact gas-phase devices makes it feasible for the first time to envisage extremely compact gas-laser devices. Figure 1 shows photographs of such gas cells. They consist of a gas filled hollow-core photonic crystal fibre (HC-PCF) spliced to a conventional optical fibre. The details of the assembly is described in [5]