Nanographene-Based Saturable Absorbers for Ultrafast Fiber Lasers

Hsin-Hui Kuo,Shuo-Fu Hong

doi:10.1155/2014/631928

Abstract

The generation of femtosecond pulse laser in the erbium-doped fiber laser system is presented by integrating of the nanographene-based saturable absorbers (SAs). A simplified method of dispersed nanographene-based SAs side-polished fiber device with controllable polished length and depth was also developed. The dependence of geometry of a graphene-deposited side-polished fiber device on optical nonlinear characteristics and on the performance of the MLFL was screened. We found that the 10 mm polished length with 1.68 dB insertion loss had the highest modulation depth (MD) of 1.2%. A stable MLFL with graphene-based SAs employing the optimized side-polished fiber device showed a pulse width, a 3 dB bandwidth, a time-bandwidth product (TBP), a repetition rate, and pulse energy of 523 fs, 5.4 nm, 0.347, 16.7 MHz, and 0.18 nJ, respectively, at fundamental soliton-like operation. The femtosecond pulse laser is achieved by evanescent field coupling through graphene-deposited side-polished fiber devices in the laser cavity. This study demonstrates that the polished depth is the key fabrication geometric parameter affecting the overall optical performance and better results exist within the certain polished range.

Highlights

Ultrafast lasers are interesting to researchers in diverse fields including ultrafast spectroscopy, optical coherence tomography, frequency comb generation, and material processing [1, 2]
The trace shows the smooth absorption feature from 400 to 2000 nm due to its zero-gap linear band structure, as theoretically expected [11, 12]. It is different from the carbon nanotube that has specific absorption peaks originated from the energy band gap
The optical nonlinear properties of mica-dispersed graphenedeposited side-polished fiber devices with the different polished lengths and polished depths indicated by the insertion losses were investigated

Summary

Introduction

Ultrafast lasers are interesting to researchers in diverse fields including ultrafast spectroscopy, optical coherence tomography, frequency comb generation, and material processing [1, 2]. The first passively mode-locked fiber laser (MLFL) based on SWCNT-SA was reported in 2003 [10]. Graphenebased SAs were recently reported for passively mode-locked lasers [13, 14] in the generation of femtosecond-scaled pulses [15, 16]. The optical properties of mica-dispersed graphene-deposited side-polished fiber devices and the performance of a MLFL output are demonstrated. A stable MLFL with graphene-based SAs employing the optimized side-polished fiber device showed a pulse width of 523 fs, a 3 dB bandwidth of 5.4 nm, and a time-bandwidth product of 0.347. This study of the graphenedeposited side-polished fiber device with controllable polished length and depth could provide an effective approach for the femtosecond pulse generation in the fiber laser and the polished depth of a side-polished fiber device has the stronger effect on the optical nonlinearities and the laser performance

Experimental Details

Results and Discussion

Conclusion