Achieving the control of light fields in a manner similar in sophistication to the control of electromagnetic fields in the microwave and radiofrequency regimes has been a major challenge in optical physics research. We manipulated the phase and amplitude of five discrete harmonics spanning the blue to mid-infrared frequencies to produce instantaneous optical fields in the shape of square, sawtooth, and subcycle sine and cosine pulses at a repetition rate of 125 terahertz. Furthermore, we developed an all-optical shaper-assisted linear cross-correlation technique to retrieve these fields and thereby verified their shapes and confirmed the critical role of carrier-envelope phase in Fourier synthesis of optical waveforms.
All solid‐state pulsed lasers (ASSPLs) play a significant role in the fields of medical, military, industry, and scientific research. Passive Q‐switching and mode‐locking are two of the most effective techniques for generating ASSPLs, in which a saturable absorber (SA) is the key element that has great impact on laser output parameters. Recently, 2D layered materials have been widely studied due to their intriguing properties. Their advantages of ultrafast dynamic processing, excellent nonlinear optical response, broadband operation, and easy fabrication and integration with lasers, enable them to be excellent SAs. Herein, the recent progress of ASSPLs with 2D layered material‐based SAs is reviewed, including a brief introduction of the fundamental characteristics, fabrication methods, characterization techniques of ultrafast dynamics, and nonlinear optical properties of 2D materials, design criteria of passively Q‐switched and mode‐locked bulk lasers, and their applications in ASSPLs. Finally, the potential developments and perspectives on 2D material‐based ASSPLs are also highlighted.
Mechanically
triturated n- and p-type Bi2Te3 nanoparticles,
the nanoscale topological insulators (TIs), are employed
as nonlinear saturable absorbers to passively mode-lock the erbium-doped
fiber lasers (EDFLs) for sub-400 fs pulse generations. A novel method
is proposed to enable the control on the self-amplitude modulation
(SAM) of TI by adjusting its dopant type. The dopant type of TI only
shifts the Fermi level without changing its energy bandgap, that the
n- and p-type Bi2Te3 nanoparticles have shown
the broadband saturable absorption at 800 and 1570 nm. In addition,
both the complicated pulse shortening procedure and the competition
between hybrid mode-locking mechanisms in the Bi2Te3 nanoparticle mode-locked EDFL system have been elucidated.
The p-type Bi2Te3 with its lower effective Fermi
level results in more capacity for excited carriers than the n-type
Bi2Te3, which shortens the pulse width by enlarging
the SAM depth. However, the strong self-phase modulation occurs with
reduced linear loss and highly nonsaturated absorption, which dominates
the pulse shortening mechanism in the passively mode-locked EDFL to
deliver comparable pulse widths of 400 and 385 fs with n- and p-type
Bi2Te3 nanoparticles, respectively. The first-
and second-order Kelly sidebands under soliton mode-locking regime
are also observed at offset frequencies of 1.31 and 1.94 THz, respectively.
We comprehensively investigated the concentration effect of dispersed single-walled carbon nanotubes (SWCNTs) in polymer films for being a saturable absorber (SA) to stabilize the mode locking performance of the erbium-doped fiber laser (EDFL) pulse through the diagnosis of its nonlinear properties of SA. The measured modulation depth was from 1 to 4.5% as the thickness increased 18 to 265 microm. The full-width half-maximum (FWHM) of the stable mode-locked EDFL (MLEDFL) pulse decreased from 3.43 to 2.02 ps as the concentrations of SWCNTs SA increased 0.125 to 0.5 wt%. At constant concentration of 0.125 wt%, the similar pulse shortening effect of the MLEDFL was also observed when the FWHM decreased from 3.43 to 1.85 ps as the thickness of SWCNTs SA increased 8 to 100 microm. With an erbium-doped fiber length of 80 cm, the shortest pulse width of 1.85 ps were achieved at 1.56 microm with a repetition rate of 11.1 MHz and 0.2 mW of the output power under an output coupling ratio of 5%. An in-depth study on the stable mode-locked pulse formation employing SWCNTs SA, it is possible to fabricate the SWCNT films for use in high performance MLEDFL and utilization of many other low-cost nanodevices.
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