Q-switched fibre laser using 21 cm Bismuth-erbium doped fibre and graphene oxide as saturable absorber

Abstract

A compact, Q-switched fibre laser is proposed and demonstrated using a compact Bismuth-based erbium doped fibre (Bi-EDF) together with a Graphene Oxide (GO) Saturable Absorber (SA). The 21cm long Bi-EDF has an erbium dopant concentration of 6300ppm with absorption rates of about 83 and 133dB/m at 1480 and 1530nm. The SA is fabricated from graphene flakes dissolved in water, forming a GO film that is sandwiched between two FC/PC connectors. The Q-switched Bi-EDF laser has an Amplified Spontaneous Emission (ASE) spectrum of 120nm, stretching from 1490 to 1610nm and a Q-switching threshold power of about 65mW. At the maximum pump power of 118mW, the pulses are generated with an average output power and pulse energy of 0.11mW and 4.3nJ, with a repetition rate and pulse width of 27.2kHz and 7.7μs. The output can be tuned over the amplified spontaneous emission spectrum with an average peak power of about −16.8dBm, and observation under a radio frequency spectrum analyser shows a highly stable output at 21.8kHz. The proposed Bi-EDF laser will have substantial uses in applications requiring short and stable pulses such as rangefinding and sensing.