Abstract
We propose and demonstrate a tunable single frequency fiber laser based on Fabry Pérot laser diode (FP-LD) injection locking. The single frequency operation principle is based on the fact that the output from a FP-LD injection locked by a multi-longitudinal-mode (MLM) light can have fewer longitudinal-modes number and narrower linewidth. By inserting a FP-LD in a fiber ring laser cavity, single frequency operation can be possibly achieved when stable laser oscillation established after many roundtrips through the FP-LD. Wavelength switchable single frequency lasing can be achieved by adjusting the tunable optical filter (TOF) in the cavity to coincide with different mode of the FP-LD. By adjustment of the drive current of the FP-LD, the lasing modes would shift and wavelength tunable operation can be obtained. In experiment, a wavelength tunable range of 32.4 nm has been obtained by adjustment of the drive current of the FP-LD and a tunable filter in the ring cavity. Each wavelength has a side-mode suppression ratio (SMSR) of at least 41 dB and a linewidth of about 13 kHz.
Highlights
Single frequency fiber laser has attracted much interest for its potential applications in optical communications [1], fiber sensing [2], and high-resolution spectroscopy [3] due to the advantage of its good coherence
We propose and demonstrate a tunable single frequency fiber laser based on Fabry Pérot laser diode (FP-LD) injection locking
The single frequency operation principle is based on the fact that the output from a FP-LD injection locked by a multi-longitudinal-mode (MLM) light can have fewer longitudinal-modes number and narrower linewidth
Summary
Single frequency fiber laser has attracted much interest for its potential applications in optical communications [1], fiber sensing [2], and high-resolution spectroscopy [3] due to the advantage of its good coherence. Different techniques have been proposed to realize single frequency oscillation in fiber lasers [4,5,6,7,8,9,10,11,12,13,14,15]. These include the utilization of short cavity to increase the longitudinal-mode spacing such as distributed feedback (DFB) and distributed Bragg reflector (DBR) fiber lasers [7,8], the introduction of a segment of un-pumped erbium doped fiber (EDF) which operates as an auto-tracking ultra-narrow-band filter [9,10,11], the insertion of sub-ring to form compound cavity to increase the longitudinal-mode spacing [12,13], and the utilization of narrow gain profile of stimulated Brillouin scattering [14,15]. Since the EDFL usually has a long cavity which would lead to a large number of densely spaced longitudinal modes, it is difficult to ensure stable single frequency operation even the FP-LD has narrowing effect
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