A monolithically integrated mode-locked semiconductor laser is proposed. The compound ring cavity is composed of a colliding pulse mode-locking (ML) subcavity and a passive Fabry-Perot feedback subcavity. These two 1.6 mm long subcavities are coupled by using on-chip reflectors at both ends, enabling harmonic mode locking. By changing DC-bias conditions, optical mode spacing from 50 to 450 GHz is experimentally demonstrated. Ultrafast pulses shorter than 0.3 ps emitted from this laser diode are shown in autocorrelation traces.
In this paper, we studied the optimal alignment and anti-alignment of O2 molecules by femtosecond laser pulse under different input energy. The results show that there is an energy limit in molecular alignment. The optimal molecular alignment and anti-alignment degree will never increase with the increase of laser energy when the input laser energy exceeds the energy limit. Besides, under the energy limit, the molecular optimal alignment (or anti-alignment) degree by using a shorter pulse duration (under 100 fs) will be about same when the input laser energy remained constant (different pulse …
Pancharatnam-Berry phase optical elements for wavefront shaping in the visible domain: switchable helical modes generation
本文报道了Pancharatnam-Berry位相光学元件的研制[Z.博姆宗湾Biener，V. Kleiner，and E. Hasman，Opt. Lett. \textbf{27}，1141（2002）]，用于基于图案化液晶技术在可见光谱域中工作的波前整形。该器件产生可见光的螺旋模式，通过控制输入圆偏振的旋向性，可以在相反的螺旋度之间进行电光切换。通过级联这种方法，可以实现多个波前螺旋度之间的快速切换，具有潜在的应用于多态光学信息编码。本文所提出的方法可以推广到其他偏振控制的波前整形器件，如可切换透镜、分束器和全息元件。
In this paper, we demonstrate a pulse energy-governed nonlinear self-switching of femtosecond pulses at wavelength of 1700 nm in a highly nonlinear high index contrast dual-core fibre. The fibre structure is composed of two microdimension cores and a solid cladding made of two thermally matched soft glasses developed in-house. A double switching behaviour under monotonic increase of the input pulse energy from 1 nJ to 3 nJ was observed at 35 mm fibre length in its anomalous dispersion region. A spatial intensity distribution measurement identified a switching contrast of 16.7 dB, and the regis…
In-line Dispersion Control of Femtosecond Laser Pulses by Multilayer Huygens' Metasurfaces
Friedrich-Schiller-University Jena（耶拿弗里德里希·席勒大学）；Australian National University（澳大利亚国立大学）；Fraunhofer Institute for Applied Optics and Precision Engineering IOF（弗劳恩霍夫应用光学和精密工程研究所）
We report an experiment to measure the femtosecond electric field of the signal emitted from an optical third-order nonlinear interaction in carbon dioxide molecules. Using degenerate four-wave mixing with femtosecond near infrared laser pulses in combination with the ultra-weak femtosecond pulse measurement technique of TADPOLE, we measure the nonlinear signal electric field in the time domain at different time delays between the interacting pulses. The chirp extracted from the temporal phase of the emitted nonlinear signal is found to sensitively depend on the electronic and rotational contr…
Raman-enhanced spectral compression of high-energy femtosecond laser pulses in molecular gases
Huazhong University of Science and Technology（华中科技大学）；Wuhan National Laboratory for Optoelectronics（武汉光电国家研究中心）；Cornell University（康奈尔大学）；Xi’an Institute of Applied Optics（西安应用光学研究所）
Inverse design of photonic surfaces on Inconel via multi-fidelity machine learning ensemble framework and high throughput femtosecond laser processing
Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；University of California at Berkeley（加州大学伯克利分校）；National Renewable Energy Laboratory（国家可再生能源实验室）；Boston University（波士顿大学）
Harmonics of femtosecond and continuous-wave radiation for precision spectroscopy: generation efficiency and spectral line shape
P.N. Lebedev Physical Institute of the Russian Academy of Sciences（俄罗斯科学院列别杰夫物理研究所）；Moscow Institute of Physics and Technology（莫斯科物理技术学院）；Russian Quantum Center（俄罗斯量子中心）
Tunable supercontinuum in multimode fiber via bending-induced dispersion modification
Massachusetts Institute of Technology（麻省理工学院）；Research Laboratory of Electronics, Massachusetts Institute of Technology（麻省理工学院电子研究实验室）；Department of Biology, Massachusetts Institute of Technology（麻省理工学院生物学系）；Beth Israel Deaconess Medical Center, Harvard Medical School（哈佛医学院贝斯以色列女执事医疗中心）
Compact chip-scale comb sources are of significant interest for many practical applications. Here, we experimentally study the generation of supercontinuum (SC) in an axially varying integrated waveguide. We show that the local tuning of the dispersion enables the continuous blue shift of dispersive waves thanks to their trapping by the strongly compressed pump pulse. This mechanism provides new insight into supercontinuum generation in a dispersion varying integrated waveguide. Pumped close to 2.2 $μ$m in the femtosecond regime and at a pulse energy of $\sim$ 4 pJ, the output spectrum extends…
