By pumping an 11-cm-long step-index chalcogenide fiber with ∼330  fs pulses at 4.0 μm from an optical parametric amplifier, mid-infrared supercontinuum generation spanning from ∼1.8 to ∼10  μm within a dynamic range of ±15  dB has been demonstrated at a relatively low power threshold of ∼3000  W.

We reported diverse soliton operations in a thulium/holmium-doped fiber laser by taking advantage of a tapered fiber-based topological insulator (TI) Bi 2 Te 3 saturable absorber (SA). The SA had a nonsaturable loss of ∼53.5% and a modulation depth of 9.8%. Stable fundamentally mode-locked solitons at 1909.5 nm with distinct Kelly sidebands on the output spectrum, a pulse repetition rate of 21.5 MHz, and a measured pulse width of 1.26 ps were observed in the work. By increasing the pump power, both bunched solitons with soliton number up to 15 and harmonically mode-locked solitons with harmonic order up to 10 were obtained. To our knowledge, this is the first report of both bunched solitons and harmonically mode-locked solitons in a fiber laser at 2 μm region incorporated with TIs.

High-purity Ge-As-Se and Ge-As-S chalcogenide glasses were prepared by modified physical and chemical purification techniques. Using the purified glasses, step-index fibers with a small core (~5.5 lm) and large numerical aperture (~1.3) were fabricated. When a 13.5-cm-long fiber was pumped with 320 fs pulses at a repetition rate of 10.5 MHz at 4.1 lm, supercontinuum spanning from~1.8 to~9.8 lm with a dynamic range of ±10 dB and an average power of~3 mW was generated. P. Lucas-contributing editorManuscript No. 36278.

A passively Q-switched fiber laser near 2 μm is achieved with a semiconductor saturable absorber mirror (SESAM) as a saturable absorber. Stable Q-switched pulses are generated from an extremely compact setup with a central wavelength of 1958.2 nm. Under the bidirectional pump configuration, the repetition rate of the fiber laser can be widely tuned from 20 to 80 kHz by increasing the pump power at the same time the pulse width decreases from 1 μs to 490 ns. When the incident pump power is 1.3 W, the average output power, the pulse repetition rate, the pulse width, and the highest single pulse energy are 91 mW, 80 kHz, 490 ns, and 1.14 μJ, respectively. To further optimize the system configuration, the pulse width can be reduced to 362 ns when the cavity length is reduced.

Purpose -The purpose of this paper is to separate households into several types based on their features, and then to further investigate determinants of household fish consumption in China by figuring out consumption preference divergences between types of households under the effects of economic and socio-demographics factors. Design/methodology/approach -This paper first applies Multiple Correspondence Analysis to separate the modalities of variables and households according to their features, with health knowledge and time constraint of a spouse highlighted. Then, the transcribed principal information of both variables and households has been added into Marshallian demand function with fish price, income, child effect, and health status for identification of factors on household fish demand. The robust fixed effect and robust random effect GLS regression has been conducted.

Photonic integrated Raman lasers have extended the wavelength range of chip-scale laser sources and have enabled applications including molecular spectroscopy, environmental analysis, and biological detection. Yet, the performance is strongly determined by the pumping condition and Raman shift value of nonlinear medias, leaving challenges to have a widely and continuously tunable Raman laser (e.g., over 100 nm). Here, photonic engineered Raman lasers based on chip-integrated chalcogenide microresonators are demonstrated. The home-developed chalcogenide photonic platform is of high nonlinearity, wide transparency, and low loss. The strong and broadband material Raman response has promised rich dynamics of Raman lasing. Indeed, both single-mode Raman lasing and a broadband Raman-Kerr comb, which are found engineered by tuning the dispersion of the chalcogenide microresonator, are demonstrated. The single-mode Raman laser, together with its cascaded modes, supports a gap-free tuning range over 140 nm, while the threshold power is as low as 3.25 mW. The results may contribute to the understanding of Raman and Kerr nonlinear interactions in dissipative and nonlinear microresonators, and on application aspect, may pave a way to integrated and efficient laser sources that is desired in spectroscopic applications in the infrared.

An ordered chalcogenide fiber bundle with a high resolution for infrared imaging was fabricated using a stack-and-draw approach. The fiber bundle consisted of about 810,000 single fibers with an As2S3 glass core of 9 μm in diameter and a polyetherimide (PEI) polymer cladding of 10 μm in diameter. The As2S3/PEI fibers showed good transparency in the 1.5-6.5 μm spectral region. It presented a resolution of ∼45  lp/mm and a crosstalk of ∼2.5%. Fine thermal images of a hot soldering iron tip were delivered through the fiber bundle.

In order to remove band-pass filters while maintaining narrow-band photodetection, three feasible approaches have been proposed. The first is the synthesis of narrow-band absorption of photoactive materials such as organic molecular materials with highly selective absorption characteristics. [7,8] Another one is the design of optic microcavity to intentionally enhance light absorption at a particular wavelength. [9,10] The third is the construction of thick films or bulk single crystals to tailor surface-charge recombination. Here, only long-wavelength light could generate photoexcited charges due to high light penetration length, whereas the shortwavelength photogenerated charges are lost as heat through charge recombination during the travel to the electrodes. [11,12] Lead halide perovskites are currently under intensive investigation owning to the exceptional optoelectronic properties that make them suitable for important applications in solar cells, light-emitting diodes, and photodetectors. [13][14][15][16][17][18][19][20][21] In particular, it has been shown that the photodetectors based on halide perovskite films with thicknesses larger than 10 µm can generate a significant narrow-band photoresponse with tunable spectralThe positive bias in theory narrows down the depletion region and thus results in significant charge injection, which should be detrimental to charge generation and collection performance for traditional photodetectors. Here, instead, it is found that the external quantum efficiency (EQE) is increased by more than 50 times when the photodetector is positively biased. A positive bias of +6 V drives ion migration of Br − and Cs + towards the anode and cathode, respectively, leading to self-doping within bulk single crystals to form an advantageous p-i-n junction for better charge collection in the devices. Meanwhile, the injected holes are allowed to tunnel through the cesium lead bromide/fullerene interface to reach the cathode which also significantly contributes to the enhancement of EQE in the forward-biased devices. The positively-biased narrow-band (full width at half maxima (FWHM) = 16 nm) photodetectors exhibit a specific detectivity of 6.5 × 10 10 Jones at 550 nm, along with the −3 dB cutoff frequency of 2776 Hz. By manipulating charge injection and ion migration using interfacial engineering, a class of non-traditional, positively-biased, and highly narrow-band photodetectors is demonstrated, which offers an alternative design strategy for imaging, biosensing, automatic control, and optical communication.