Wideband tunable Q-switched fiber laser using graphene as a saturable absorber

Abstract

An ultra-wide wavelength tuning range, which covers three different band regions consisting of the S-, C-, and L-bands, is proposed and demonstrated for a graphene-based Q-switched erbium-doped fiber laser using a tunable bandpass filter as the wavelength tuning and filtering mechanism. A 3 m length of erbium-doped fiber is used as the gain medium in a ring laser cavity configuration, with absorption coefficients of between 11 and 13 dB m À1 at 980 nm and about 18 dB m À1 at 1550 nm. The tuning range of the Q-switching pulses covers a wide wavelength range of 58 nm, which spans from 1512.5 nm to 1570.5 nm. In addition, the lasing and Q-switching thresholds are considerably low, with respective values of $11.0 mW and $18.4 mW. A repetition rate of 55.3 kHz is obtained at the maximum pump power of 100.4 mW, together with pulse width and pulse energy of 1.6 μs and 25.8 nJ, respectively.

Tunable Q-Switched Fiber Laser Based on a Graphene Saturable Absorber Without Additional Tuning Element

“…According to the type of Q-factor switching, Q-switched fiber lasers can be classified as either passive or active. Compared to the actively Q-switched fiber lasers, which need additional external switching electronics, passively Q-switched fiber lasers have attracted more attention owing to their advantages of compactness, low cost, and simple configurations [3]- [5]. The saturable absorber (SA) is a key element for the passively Q-switched fiber laser, as it is quite important for the Q-switching output perfor-mance.…”

“…There are several reports on tunable Q-switched fiber lasers using graphene SAs [2]- [5], [21]. In 2011, a tunable Q-switched fiber laser was realized using a graphene-film SA and tunable filter that covered a tunable wavelength range of 32 nm [4].…”

“…In 2013, Ahmad et al reported a graphene tunable Q-switched fiber laser based on a tunable fiber Bragg grating, which provided a tunable range of 10 nm [2]. All the reported graphene tunable Q-switched fiber lasers need additional tuning elements such as a tunable bandpass filter [3]- [5], [21] or tunable fiber Bragg grating [2], which increase the complexity of the laser system. Compared to the graphene-film SA used in the reported tunable Q-switched fiber laser, graphene SAs based on tapered fibers provide advantages of a high damage threshold, large interaction length, and simplicity to modularize and package [22].…”