Dispersionless impedance-matched low-loss optical bottle resonator slow light delay line

A slow light miniature delay line with a breakthrough performance is proposed and demonstrated. This delay line has a shape of a strongly elongated bottle resonator with a nanoscale radius variation. It is shown that this resonator can perform a multi-nanosecond long dispersionless delay of light in a nanometer-order bandwidth with minimal losses. In excellent agreement with the developed theory, a 3 mm long 0.12 mm² footprint bottle resonator, which exhibits dispersionless 2.58 ns (3 bytes) delay of 100 ps pulses with 0.44 dB/ns intrinsic loss and 1.2 dB/ns full loss, is demonstrated experimentally.