Abstract
Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm3+:ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.
Highlights
Mode-locking are the two main techniques for pulse generation in fiber lasers[13]
Mode-locking is a technique requiring balance of the intracavity dispersion and nonlinearity, and which induces a fixed-phase resulting in a single pulse with typical durations ranging from ps down to fs, and a repetition rate corresponding to the cavity round-trip time
We combine the use of a single gain medium—Tm3+:ZBLAN fiber—and a common graphene saturable absorber (SA) to support ultrabroad dual-band operation and demonstrate (1) a Tm3+:ZBLAN fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm and a synchronized repetition rate from 20 kHz to 40.5 kHz and (2) a synchronous mode-locked Tm3+:ZBLAN fiber linear laser with full-width at half maximum (FWHM) pulse widths of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, and a repetition rate of 12.3 MHz
Summary
Mode-locking are the two main techniques for pulse generation in fiber lasers[13]. Q-switching is a modulation process of the quality factor Q of the laser cavity to produce high intensity pulses with typical durations ranging from μs to ns. Compared to other SAs such as doped bulk crystals, semiconductor SA mirrors, single wall carbon nanotubes, etc., graphene has distinctive advantages such as low saturation intensity, ultra-broadband operating wavelength range, high optical damage threshold, and ease of fabrication[15]. Sotor et al.[19,20] demonstrated a mode-locked fiber laser (without and with synchronization) operating simultaneously at 1565 nm with Er-doped silica fiber and 1944 nm with Tm-doped silica fiber using a common graphene SA In all of these demonstrations, two separate gain media are employed, which often leads to increased complexity in implementation and laser design. We simplify the implementation of ultra-broadband dual-band sources using a single gain medium and one common graphene SA to achieve synchronized Q-switched and mode-locked operation. The pulsed sources are expected to provide enhanced functionality and capabilities in a number of applications from sensing to communications to instrumentation
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