  Fiber dosimeters have recently drawn much interest for measuring in vivo and
in real time the dose of medical radiations. This paper presents the first
miniaturized fiber dosimeter integrated at the end of a narrow 125-micron outer
diameter optical fiber. Miniaturization is rendered possible by exploiting the
concept of a leaky wave optical antenna for interfacing the scintillators and
the fiber, and by taking advantage of the low propagation loss of narrow silica
fibers and high detection yield of single-pixel photon counters. Upon
irradiation at 6 MV, our fiber probe led to a linear detection response with a
signal-to-noise ratio as high as 190 in air. Although implemented with
inorganic scintillators and fiber, our fiber probe induces an intensity
contrast in the impinging radiation lower than 0.9% over an area of 0.153 mm2.
Our nano-optically driven approach opens the route for ultra-compact fiber
dosimeters of negligible footprint in the radiotherapeutic processes, even with
non-water equivalent fibers and scintillators. A large panel of therapies
relying on ionizing radiations (photons or charged particles) may take benefit
of this nano-optically-driven technology.
