[Paper Review] Black phosphorus as a new broadband saturable absorber for infrared passively Q-switched fiber lasers

Tian Jiang, Ke Yin+3 more|arXiv (Cornell University)|Apr 28, 2015

Advanced Fiber Laser Technologies28 references26 citations

TL;DR

This paper demonstrates black phosphorus (BP) as a broadband saturable absorber for infrared fiber lasers, enabling passively Q-switched operation at 1550 nm and 2 μm. By integrating bulk BP onto a side-polished fiber, the authors achieve tunable sub-microsecond pulses (9.35–31 μs) and a 103 nm tuning range (1832–1935 nm), marking the first experimental verification of BP's broadband saturable absorption in ultrafast fiber lasers.

ABSTRACT

Black phosphorus (BP) with its enticing electric and optical properties is intensely researched in the field of optoelectronics. In this paper, Q-switched pulses at 1550 nm and 2 um wavelengths are obtained by inserting bulk-structured BP based saturable absorber (SA) into an erbium-doped fiber laser (EDFL) and an thulium/holmium-doped fiber laser (THDFL), respectively. The BP-SA was prepared by depositing powered BP material on to the flat side of a side-polished single mode fiber. Q-switched 1550 nm pulses with width tuned from 9.35 to 31 us were obtained for the EDFL. For the THDFL, over 100 nm wavelength range could be achieved from 1832 to 1935 nm by adjusting the pump power. To the best of our knowledge, these results demonstrated the broadband saturable absorption property of BP and for the first time verified that BP as a new two-dimensional material for applications in saturable absorption devices.

Motivation & Objective

• To explore black phosphorus as a novel two-dimensional material for saturable absorption in fiber lasers.
• To address the need for broadband, tunable saturable absorbers in infrared fiber laser systems.
• To demonstrate the feasibility of BP-based saturable absorbers in both erbium-doped and thulium/holmium-doped fiber lasers.
• To evaluate the performance of bulk-structured BP in generating passively Q-switched pulses across multiple infrared wavelengths.

Proposed method

• Bulk black phosphorus was mechanically exfoliated and deposited onto the flat side of a side-polished single-mode fiber to fabricate a saturable absorber (SA).
• The BP-SA was integrated into an erbium-doped fiber laser (EDFL) and a thulium/holmium-doped fiber laser (THDFL) for Q-switching experiments.
• Pulse characteristics were measured by varying pump power, enabling tuning of pulse width and wavelength in both laser systems.
• The saturable absorption mechanism was analyzed based on the nonlinear optical response of BP under high-intensity excitation.
• Spectral and temporal measurements were performed using an optical spectrum analyzer and an electrical sampling oscilloscope.
• The broadband nature of BP was confirmed by observing tunable lasing across a wide range of wavelengths in the THDFL.

Experimental results

Research questions

• RQ1 Can black phosphorus function as an effective saturable absorber in infrared fiber lasers?
• RQ2 What is the bandwidth and tunability of Q-switched pulses generated using BP-based saturable absorbers?
• RQ3 How does the performance of BP compare to other 2D materials in the context of broadband infrared Q-switching?
• RQ4 Can BP-based saturable absorbers support stable, passively Q-switched operation at both 1550 nm and 2 μm?
• RQ5 What is the range of pulse width and wavelength tuning achievable with BP-SA in different fiber laser configurations?

Key findings

• Q-switched pulses with full width at half maximum (FWHM) of 9.35 μs were achieved in the erbium-doped fiber laser (EDFL) at 1550 nm.
• Pulse width in the EDFL was tunable over a range of 9.35 to 31 μs by adjusting the pump power.
• In the thulium/holmium-doped fiber laser (THDFL), a broadband tuning range of 103 nm was demonstrated, from 1832 to 1935 nm.
• The BP-based saturable absorber enabled stable, passively Q-switched operation in both EDFL and THDFL configurations.
• The results represent the first experimental verification of black phosphorus as a broadband saturable absorber in ultrafast fiber lasers.
• The study confirms the potential of black phosphorus as a promising alternative to existing 2D materials in infrared saturable absorption applications.