A 147 fs mode-locked erbium-doped fiber laser with a carbon nanotubes saturable absorber in evanescent field

We demonstrate a high-repetition-rate Er-doped all fiber laser with nonlinear-polarization-rotation mode-locking. The highest repetition rate of the laser is 217 MHz. The fiber laser has a very simple and compact structure and can output a stable mode-locking pulse only by using one polarization-dependent isolator and a polarization controller. The pulse width, spectral width and signal-to-noise ratio are measured to be 69 fs, 56 nm and 76 dB respectively.

High-repetition-rate passively mode-locked erbium-doped all fiber laser

Dou¹,

Tian²,

Li³

et al. 2015

Repetition rate optimization of passively mode-locked fiber laser for high-speed linear optical sampling

Han¹,

Liu²,

Fu³

et al. 2015

Optical fiber communication systems are going to adopt the use of advanced modulation formats. It is thus important to develop measurement techniques and solutions capable of quantifying such signals. Linear optical sampling is an effective technique to characterize the quality of an advanced modulation format for high-speed optical signal with high fidelity, while the passively mode-locked fiber laser is an enabling module to implement the linear optical sampling. In this paper, we obtain a trade-off relationship between the repetition rate of passively mode-locked fiber laser and the linewidth of high-speed signal under test, after the introduction of operation principle for linear optical sampling. It is found that, for the quadrature phase shift keying (QPSK) signal, when the ratio of the linewidth of the signal under test to the repetition rate of passively mode-locked fiber laser is less than 1.5×10-3, the linear optical sampling-induced impairments can be ignored when there occurs phase noise. Therefore, the phase estimation can be successfully made by using the Viterbi-Viterbi algorithm applied to the block of samples corresponding to the modulation format phase states. Next, we use an optical sampling pulse with a repetition rate of 95.984 MHz, and carry out the optical linear sampling to a 28 Gbaud QPSK signal with a linewidth of 100 kHz. The error vector magnitude (EVM) has long been a commonly used parameter for quantifying the quality of advanced modulation signals. Using the standard coherent detection algorithm, we can successfully recover the constellation with the error vector magnitude (EVM) error less than 1%. Theoretical investigations agree well with the experimental characterization. Such a conclusion is helpful to optimize the design of passively mode-locked fiber laser for optical sampling application.

Research progress of low-dimensional semiconductor materials in field of nonlinear optics

Bai¹,

Yang²,

Wei³

et al. 2020

Since the first ruby laser was invented, researchers have focused their attention on how to achieve a strong laser light source, which cannot be produced by the ordinary light sources. Since then, the rich and colorful characteristics of nonlinear optical materials have been discovered, such as the saturation absorption, reverse saturation absorption and nonlinear refraction. They are applied to optoelectronic devices, optical switching devices and optical communication. At the same time, with the increase of the requirements for device integration performance in industrial production, ordinary three-dimensional devices are difficult to meet the production requirements, and the advent of low-dimensional semiconductor devices effectively solves this problem. Therefore, the combination of nonlinear optics and low-dimensional semiconductor materials is a general trend. The emergence of quantum dots, quantum wire lasers, and amplifiers confirms this. In this paper, we summarize the frontier work on nonlinear optics by selecting several special low-dimensional structures and several materials, providing some references for future research. However, due to the fact that the instability and low filling ratio of low-dimensional materials remain to be improved, further relevant research is still required.