Transverse mode control by a self-imaging process in a multimode fibre laser using a single-mode feedback loop

• Published in: Journal of optics. A, Pure and applied optics Vol. 10; no. 11; pp. 115303 - 115303 (6)
• Main Authors: Shalaby, B M, Kermene, V, Pagnoux, D, Barthelemy, A
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.11.2008; Institute of Physics
• Subjects: Beam characteristics: profile, intensity, and power; spatial pattern formation; Exact sciences and technology; Fiber lasers; Fundamental areas of phenomenology (including applications); Laser optical systems: design and operation; Lasers; Optics; Physics; Optical fibers; Beam profiles; Multimode laser; Multimode fibers; Transverse mode; beam control; Single mode fiber; Mode control; Digital simulation; Self imaging; multimodal fibre laser; large mode area fibre; Ring resonator; Feedback; Intensity distribution; unidirectional ring cavity; Fiber lasers
• ISSN: 1464-4258; 1741-3567
• DOI: 10.1088/1464-4258/10/11/115303

We propose new laser architecture to improve the spatial emission of a multimode fibre amplifier (MMFA) by using a self-imaging process. Interference between the different modes of the MMFA is filtered by a single-mode fibre section which serves as feedback in a unidirectional ring cavity. The laser self-adjusts its frequency to ensure self-imaging between opposite faces of the multimode fibre. The laser output pattern and longitudinal modes depend on the single-mode fibres' end face position with respect to the MMFA centre axis. As a proof of principle we report experimental results which are in good agreement with numerical simulations.