Solitons are stable localized wave packets that can propagate long distance in dispersive media without changing their shapes. As particle-like nonlinear localized waves, solitons have been investigated in different physical systems. Owing to potential applications in optical communication and optical signal processing systems, optical solitons have attracted intense interest in the past three decades. To experimentally study the formation and dynamics of temporal optical solitons, fiber lasers are considered as a wonderful nonlinear system. During the last decade, several kinds of theoretically predicted solitons were observed experimentally in fiber lasers. In this review, we present a detailed overview of the experimentally verified optical solitons in fiber lasers, including bright solitons, dark solitons, vector solitons, dissipative solitons, dispersion-managed solitons, polarization domain wall solitons, and so on. An outlook for the development on the solitons in fiber lasers is also provided and discussed.

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Recent progress of study on optical solitons in fiber lasers

In this work, we demonstrate that the performance of c-Si/ZnO heterojunction ultrathin-film solar cells (SCs) is enhanced by an integrated structure of c-Si trapezoidal pyramids on the top of a c-Si active layer and Al pyramids in the active layer on the Al back electrode. The top c-Si trapezoidal pyramid (TTP) increases the absorption of short wavelengths by lengthening the propagation distance of incident light and coupling the incident light into photonic modes in the active layer. The bottom Al pyramid (BP) improves the overall optical absorption performance especially for the long wavelength band by forming the surface plasmon resonance (SPR) mode in the active layer. As a result, the average absorption in the entire wavelength range (300-1400 nm) reaches 93.16%. The optimized short-circuit current density (Jsc) and photoelectric conversion efficiency (PCE) of ultra-thin film c-Si/ZnO SCs are 41.94 mA cm-2 and 18.97%, respectively. Moreover, the effect of different illumination angles on the optical absorption of the SCs was explored. The SCs have good absorption when the incident angles are in the range from 0 degrees to 60 degrees. Furthermore, the underlying mechanism for the enhancement of photon absorption in the SCs was discussed through careful analysis of the electric field intensity profile at different wavelengths. It was found that the electric field tends to concentrate around the bottom pyramids and top trapezoidal pyramids even for the long-wave band, which results in an excellent light-trapping performance.

Realization of 18.97% theoretical efficiency of 0.9 μm thick c-Si/ZnO heterojunction ultrathin-film solar cells via surface plasmon resonance enhancement.

We report the use of black silicon (bSi) as a growth platform for III–V nanowires (NWs), which enables low reflectance over a broad wavelength range as well as fabrication of optoelectronic devices by metalorganic vapor phase epitaxy. In addition, a new isolated growth regime is reported for self-catalyzed InAs NWs at record-low temperatures of 280 °C–365 °C, where consistently rectangular [-211]-oriented NWs are obtained. The bSi substrate is shown to support the growth of additionally GaAs and InP NWs, as well as heterostructured NWs. As seed particles, both ex-situ deposited Au nanoparticles and in-situ deposited In droplets are shown feasible. Particularly the InAs NWs with low band gap energy are used to extend low-reflectivity wavelength region into infrared, where the bSi alone remains transparent. Finally, a fabricated prototype device confirms the potential of III–V NWs combined with bSi for optoelectronic devices. Our results highlight the promise of III–V NWs on bSi for enhancing optoelectronic device performance on the low-cost Si substrates, and we believe that the new low-temperature NW growth regime advances the understanding and capabilities of NW growth.

/pdf/iii-v-nanowires-on-black-silicon-and-low-temperature-growth-4anb60hjtx.pdf

III–V nanowires on black silicon and low-temperature growth of self-catalyzed rectangular InAs NWs

Fabrication and characteristics of black silicon for solar cell applications: An overview

High power diode-pumped continuous wave (CW) and Q-switch operation of Tm,Ho:YVO4 laser is reported. Using two Tm,Ho:YVO4 rods in a single cavity, up to 20.2 W of CW output lasing at 2054.7 nm was obtained under cryogenic temperature of 77 K with an optical to optical conversion efficiency of 32.9%. For Q-switch operation, up to 19.4 W of output was obtained under 15 kHz pulse repetition frequency (PRF) with a minimum pulse width of 24.2 ns. In addition, different pulse repetition frequencies of Q-switch operation with 10.0 kHz, 12.5 kHz and 15.0 kHz were investigated comparatively.

http://iopscience.iop.org/article/10.1002/lapl.201010074/pdf

High power diode‐pumped continuous wave and Q‐switch operation of Tm,Ho:YVO4 laser

Broadband antireflection of silicon has been realized by combining black silicon, surface passivation and surface plasmons. Black silicon, fabricated by Ag assisted chemical etching, was employed here to reduce the reflection of incident light with wavelengths below 1100 nm. Due to the increased bandgap caused by the quantum confinement effect and enhanced backward-scattering in our black silicon, light trapping was diminished at the wavelengths above 1100 nm. Ag nanoparticles were deposited on black silicon to obtain the lowest reflectivity at the wavelengths above 1100 nm. Compared with traditionally textured multicrystalline silicon, the average reflectivity of passivated black multicrystalline silicon patterned with 5 nm mass thickness of Ag was decreased to 5.7% in the wavelength range from 300 nm to 1100 nm and was reduced by 20.2% in the wavelength range from 1100 nm to 1400 nm. The surface plasmon effect of the Ag nanoparticles on the black silicon was also demonstrated by surface enhanced Raman scattering, which was observed in the Ag nanoparticle patterned black silicon after being immersed in rhodamine 6g.

Broadband antireflection on the silicon surface realized by Ag nanoparticle-patterned black silicon

We design a low-timing-jitter, repetition-rate-tunable, stretched-pulse passively mode-locked fiber laser by using a nonlinear amplifying loop mirror (NALM), a semiconductor saturable absorber mirror (SESAM), and a tunable optical delay line in the laser configuration. Low-timing-jitter optical pulses are stably produced when a SESAM and a 0.16 m dispersion compensation fiber are employed in the laser cavity. By inserting a tunable optical delay line between NALM and SESAM, the variable repetition-rate operation of a self-starting, passively mode-locked fiber laser is successfully demonstrated over a range from 49.65 to 50.47 MHz. The experimental results show that the newly designed fiber laser can maintain the mode locking at the pumping power of 160 mW to stably generate periodic optical pulses with width less than 170 fs and timing jitter lower than 75 fs in the 1.55 mu m wavelength region, when the fundamental repetition rate of the laser is continuously tuned between 49.65 and 50.47 MHz. Moreover, this fiber laser has a feature of turn-key operation with high repeatability of its fundamental repetition rate in practice.

https://iopscience.iop.org/article/10.1088/2040-8978/12/9/095204/pdf

Low-timing-jitter, stretched-pulse passively mode-locked fiber laser with tunable repetition rate and high operation stability

An asynchronous optical sampling scheme based on four-wave mixing (FWM) in highly nonlinear fiber (HNLF) is experimentally demonstrated. Based on this scheme, 10-GHz input pulse train with 1.8-ps pulse width is successfully sampled in 100-m HNLF. A single pulse at 10 GHz with 2.3-ps pulse width is rebuilt by using a 50-MHz frequency tunable free-running fiber laser as the sampling pulse source (SPS). 40-GHz pulse train is used as the input signal. The rebuilt waveforms, together with the low-jitter eye diagram, are also presented.

Ultrashort optical pulse monitoring using asynchronous optical sampling technique in highly nonlinear fiber

Diode side pumped and acousto-optical (AO) Q-switched Tm, Ho, LuLiF laser at 2 μm wavelength obtained in a ring resonator is reported in this paper. The three LDAs were placed 120° apart around the laser rod of ∅4 × 20 mm dimension. A ring resonator has been used for its At free run mode, four different output loss ouplers has been tried. When the output loss is 20%, 103 mJ per pulse at 1 Hz pulse repetition frequency has been obtained with the optical to optical energy conversion efficiency of 3.17%. At the Q-switched mode, the laser pulse energy is 30 mJ with the pulse width of 417 ns. The optical to optical energy conversion efficiency is 0.93%. The slope efficiency is 6.36 and 2.90% under the two running mode, respectively.

Diode-side-pumped AO Q-switched Tm, Ho:LuLiF laser

The present invention provides a method for generating an ultrashort pulse of an externally injection gain switch laser. The ultrashort optical pulse sequence signal which is generated by the gain switch laser and has multiple longitudinal mode spectral property is transmitted to an optical amplifier for amplifying. An optical spectrum component signal selector screens out a narrow optical spectrum component signal which is outputted by the optical amplifier and is in the spontaneous radiation ASE noise frequency band and has a central wavelength same to a longitudinal mode in the gain switch laser. One route of narrow optical spectrum component signal outputted by the optical spectrum component signal selector is taken as external seed light and is re-injected to the gain switch laser through the optical spectrum component signal feedback loop to reinforce the oscillation of the single longitudinal mode selected in the gain switch laser cavity and form an external light injection locking. The other route outputted by the optical spectrum component signal selector is the required ultrashort optical pulse sequence. The invention settles the problems of fixed repetition frequency, limited application range, complex structure, large volume and high cost in the background art, and the invention also has a function of turnable wavelength.

Yuanshan Liu

Papers

Broadband antireflection on the silicon surface realized by Ag nanoparticle-patterned black silicon

Low-timing-jitter, stretched-pulse passively mode-locked fiber laser with tunable repetition rate and high operation stability

Ultrashort optical pulse monitoring using asynchronous optical sampling technique in highly nonlinear fiber

Diode-side-pumped AO Q-switched Tm, Ho:LuLiF laser

Method for generating ultra-short pulse of outer injection type gain switch laser