The polarization electric field provided by ferroelectric materials can achieve precise control of the carrier concentration in van der Waals semiconductors, providing a more flexible, convenient, and efficient new approach for improving the performance and intelligent application of photodetectors. The UV-midinfrared photodetector with a sandwich structure of BP/MoS2$\text{BP/MoS}_2$/CIPS, leverages the spontaneous polarization and Cu+$\text{Cu}<^>+$ ion migration within CIPS to modify the electric dipole moment at the interface between BP and MoS2$\text{MoS}_2$. This modification induces changes in the built-in electric field between BP and MoS2$\text{MoS}_2$, facilitating carrier separation and migration, thereby suppressing dark current and enhancing detectivity. Through gate voltage control, the device achieves an order-of-magnitude improvement in photocurrent, which demonstrates high specific blackbody detectivity, reaching up to 1.17 x1010$\times \ 10<^>{10}$ cm in the infrared region. Furthermore, high-resolution images of letters are achieved by the BP/MoS2$\text{BP/MoS}_2$/CIPS-based ferroelectric photodetectors. The devices achieve accurate image recognition by applying deep learning techniques. This work not only highlights the potential of CIPS-based device for high-sensitivity and broadband detection but also offers a new approach to neuromorphic computing applications.

In the context of infrared photodetectors, the performances of infrared materials determine the photoresponse performance of devices. Bismuth telluride (Bi2Te3), as a topological insulator, is considered a strong competitor in the field of infrared photodetectors. In this study, polycrystalline Bi2Te3 thin films were prepared using pulsed laser deposition at different growth temperatures. The crystallization of Bi2Te3 films commenced at 150 °C, and with an increase in the preparation temperature, the crystal quality improved, reaching its peaks at 250 °C. Infrared performance of polycrystalline Bi2Te3 thin films were measured at low temperature, featuring a high responsivity of 56.98 mA/W and outstanding detectivity of 1.82 × 109 Jones, surpassing that of other two-dimensional materials. In a low-temperature environment, amorphous Bi2Te3 films are more prone to reaching photocurrent saturation compared to their crystalline counterparts. The generation of saturable photocurrent can be attributed to the effect of defect and disorder. Simultaneously, the presence of lattice defects enhances the photoresponse of the films. Essentially, these founding will pave the way to investigate of Bi2Te3 thin films for applications in infrared photodetectors.

Wireless communication technology is indispensable in our daily lives, but it also results in serious electromagnetic radiation pollution. Hence, developing smart electromagnetic interference shielding materials with adjustable electromagnetic wave (EMW) responses holds significant promise for future electromagnetic shielding devices. In this study, we propose an electromagnetic shielding switch (ESS) characterized by tunable electromagnetic shielding performance achieved by fabricating a three-dimensional (3D) carbon nanotube-based spacer fabric (CNT-SF) and modifying CNT-SF with chemical vapor deposition (CCNT-SF). The CCNT-SF displays direction-dependent electrical conductivity by manipulating the warp and weft density, measuring 128 S/m transversely and 447 S/m vertically. This characteristic allows the CCNT-SF to transmit or shield EMW by adjusting the angle of EMW incidence through fabric rotation, resulting in anisotropic electromagnetic shielding performance (33 dB transversely and 87 dB vertically). This feature enables switchable shielding with an on/off ratio of 2.64. Furthermore, the unique 3D structure confers excellent mechanical properties on the fabric, with compressive strength reaching 120 kPa. As a flexible, lightweight, and mechanically robust ESS, the CCNT-SF holds promising prospects for mitigating the challenges of increasingly severe and intricate electromagnetic environments.

Tungsten is an important material constituting the first wall of the Experimental Advanced Superconducting Tokamak due to its excellent corrosion resistance. The temperature distribution of the first wall during the discharge process are the key to ensuring the safe and stable operation of the EAST. Therefore, it is necessary to explore the dependence of material emissivity on temperature and wavelength for improving temperature measurement accuracy. This work quantitatively explores the normal spectral emissivity of tungsten within the 3 μm to 5 μm in the temperature range between 100°C and 500°C based on the Fourier transform infrared spectrometer. The dependence of emissivity on wavelength and temperature are experimentally analyzed, and the possible functional relationship between the emissivity of tungsten and the surface temperature and the wavelength are established respectively. This work could lay the foundation for the application of multi-wavelength thermometry on temperature measurement of the first wall of the EAST.

Two-dimensional (2D) materials have attracted extensive attention for use in fiber lasers for pulse generation due to their unique nonlinear optical properties. While 2D materials with tunable band gaps hold promise as versatile saturable absorber materials, their L-band (long-band) pulse generation capability remains challenging. Metal phosphorus trichalcogenides (MPX3) have recently attracted the attention of researchers and shown potential for sub-band gap saturable absorption in the L-band due to their high diversity of chemical components and band structural complexity. Herein, high-quality MnPSe3 is synthesized and exhibits broad-band linear and nonlinear absorption with the modulation depth and saturation intensity of 5.4% and 0.295 MW/cm2, respectively. Moreover, a stable passive pulse generation in the L-band is demonstrated in a fiber laser. The wavelengths of the passively pulsed laser at different pump powers are recorded, featuring a fixed central wavelength located at around 1602 nm with a maximum output power of 19.54 mW. This research promotes the realization of L-band pulsed lasers based on 2D materials, inspiring further exploration of the unique properties of the MPX3 family.

Based on the saturable absorption properties of narrow band gap semiconductor PbSe,saturable absorber devices are achieved by physical vapor deposition using pure PbSe powder as the precursor and transferred by optical fiber probe. And pulse fiber lasers with different wavelengths are built. By using a simple ring cavity in near infrared,the stable mode-locked output is realized with almost unchanged devices in the range of near-infrared 1 similar to 2 mu m, and the central wavelengths are 1060.46 nm, 1563.24 nm and 1908.34 nm respectively, the fundamental frequencies are 0.593 MHz, 13.59 MHz and 10.25 MHz separately, and the pulse widths are 30.53 ns, 4.26 ns and 1 ns respectively. This result expands the applications of the new nanocrystalline material lead selenide compound, provides a solution for the wavelength regulation of pulsed fiber laser, and satisfies the application requirements of multi-wavelength tunable laser in biomedical, monitoring and other places.

The all-fiber high-power linearly polarized single-frequency fiber laser based on the polarization-maintaining tapered Yb-doped fiber (T-YDF) is systematically studied. As a result, a 300 W-level stable output with linear polarization and nearly diffraction-limited beam quality is demonstrated. In particular, the overall properties of the transverse mode instability (MI) effect in such a single-frequency laser system are discussed in detail for the first time, to the best of our knowledge, including temporal, frequency, polarization, and spatial domains. Furthermore, the beam pointing error taking the MI effect into account is investigated. Theoretical analyses covering both stimulated Brillouin scattering and the MI effects reveal the great potential of the T-YDF for further power scaling as well.

Stable bright/dark switchable mode-locked nanosecond pulse fiber laser incorporating black phosphorus (BP) was demonstrated in the Yb-doped fiber ring cavity for the first time, to the best of our knowledge. The high-quality BP saturable absorber (SA) was fabricated by the modified electrochemical delamination exfoliation process. The states between bright and dark pulse could be switched by simply adjusting the infra-cavity polarization states, and close agreement with the cubic Ginzburg-Landau equation (CGLE) models is present.

As a member of the metal phosphorus trichalcogenide family, MPS3 is widely used in nonlinear optics and devices, which can be regarded as a significant benefit for the excellent photonic and optoelectronic properties. In this work, the MnPS3 nanosheet is prepared by the chemical vapor transport method and the MnPS3 saturable absorber is demonstrated by modifying mechanical exfoliation. To the best of our knowledge, the dual-wavelength self-starting mode-locking erbium-doped fiber laser with MnPS3 saturable absorber is demonstrated for the first time. The dual wavelength mode-locked laser with a pulse repetition rate of 5.102 MHz at 1565.19 nm and 1565.63 nm is proposed. Its maximum output power at the dual-wavelength is 27.2 MW. The mode-locked laser can self-start and stably run for more than 280 h.

Due to the characteristics of easy processing, tunable energy band, and excellent nonlinear optical properties, various novel two-dimensional (2D) materials have been synthesized and employed in ultrafast fiber laser generation. In this work, we demonstrated a stable passively mode-locked operation based on MnPS3 nanosheets as saturable absorber (SA). It is worth mentioning that we have continuously measured the performances of the laser ring cavity for seven days and the results indicated that the mode-locked laser is stable and self-starting. Meanwhile, the maximum output power was 27 mW with the fundamental frequency repetition of 5.102 MHz. These results not only supply other choice of SAs in pulse generation, but also provide a guidance to extend other possible applications of MPT3 family for the nonlinear optics.

This chapter contains sections titled: Development History of Thermoelectric Materials Principles of Thermoelectric Materials Properties of Thermoelectric Materials Methods to Improve Thermoelectric Performance Outlook

A free-standing black phosphorus saturable absorber (BP-SA) fabricated by a modified electrochemical delamination strategy exfoliation process was inserted inside a Er-doped ring laser cavity. Based on the saturable absorber of BP, a stable pulse laser could be achieved. When the pump power increased to 30 mW, the pulse laser began to initiate. The maximum output power was 4.8 mW. And the repetition rate could vary from 23.24 kHz to 69.65 kHz. The obtained minimum pulse duration is 1.67 mu s. These demonstrations indicate that BP could apply in pulse laser field and benefit industrial community in the future.

A black arsenic-phosphorus saturable absorber (SA) was fabricated and experimentally applied for a passively Q-switched Er-doped fiber laser for the first time to the best of our knowledge. The high-quality black arsenic-phosphorus crystals were synthesized by the mineralizer-assisted chemical vapor transport (CVT) method, and the fewer-layer black arsenic-phosphorus thin film nanosheet SA was performed by a unique electrochemical delamination exfoliation procedure. Meanwhile, a stable passively Q-switched pulse was proposed based on the SA modified Er-doped ring fiber cavity, which had the repetition rate of 38.47 kHz, corresponding to a minimum pulse width of 5.26 mu s, and a corresponding output power as high as 3.68 mW was obtained. The results suggest that black arsenic-phosphorus is a good choice to make practical two-dimensional saturable absorbers for potential ultrafast photonic applications due to its designable bandgap value and excellent optical characteristics. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

As a preferable material in the field of photo-detection and catalysis, the characteristics of FePS 3 in broad wavelength range have been proven by many experimental studies. However, FePS 3 has not been used as a saturable absorber（SA）in fiber lasers yet. We propose and demonstrate the generation of a single wavelength and dual-wavelength based on an Er-doped fiber laser（EDFL） at 1.5 μm by using an innovative FePS 3 saturable absorber for the first time. The result shows that a stable passively Q-switched pulse can be generated, which demonstrates that the new two-dimensional（2D） material FePS 3 served as SA provides a valid method to realize passively Q-switched laser. In addition, we achieve the output of the dual-wavelength pulse by properly rotating the polarization controller. To the best of our knowledge, the dual-wavelength pulse EDFL could be applied in biomedicine, spectroscopy, and sensing research.

Since early 2014, black phosphorus (BP), a rising star among post-graphene, has been exploited to generate ultrashort pulses in fiber lasers. BP has a large direct bandgap range from 0.3 eV (bulk, corresponding to 4.13 μm) to 2 eV (monolayer, corresponding to 620 nm), which enables ultrashort pulse generation from near-infrared to visible waveband. In our progresses, an ultra-stable (more than 100 days) pulse fiber laser based on real BP-SA was demonstrated, which exhibited various interesting ultrafast phenomenon in 1 μm region. Our results extended the application of BP in the spatial and temporal domains.

In the past decade, two-dimensional (2D) materials have attracted increasing attention due to their energy band structure, optical properties and excellent performance in ultrafast photonics and nonlinear optics. As a kind of new 2D ternary layered material, NiPS3 can exhibit more novel electrical, optical and magnetic properties compared with those unary and binary 2D layered materials because of higher chemical diversity and structural complexity. In this work, we demonstrated a passively Q-switched operation based on few-layer NiPS3 as a saturable absorber (SA) in an erbium-doped fiber (EDF) laser. And the Q-switched output was achieved when the pump power at 40 similar to 105 mW. To our best of knowledge, it is the first time to utilize the NiPS3 as a SA in pulse laser generation.

Two-dimensional transition metal dichalcogenides（TMDs） provide fertile ground to study the interplay between dimensionality and electronic properties because they exhibit a variety of electronic phases, such as semiconducting, superconducting, charge density waves（CDW） states, and other unconventional physical properties. Compared with other classical TMDs, such as Mott insulator 1T–TaS 2 or superconducting 2H–NbSe 2 , bulk 2H–TaSe 2 has been a canonical system and a touchstone for modeling the CDW measurement with a less complex phase diagram. In contrast to ordinary semiconductors that have only single-particle excitations, CDW can have collective excitation and carry current in a collective fashion. However, manipulating this collective condensation of these intriguing systems for device applications has not been explored. Here, the CDW-induced collective driven of non-equilibrium carriers in a field-effect transistor has been demonstrated for the sensitive photodetection at the highly-pursuit terahertz band. We show that the 2H–TaSe 2 -based photodetector exhibits a fast photoresponse, as short as 14 μs, and a responsivity of over 27 V/W at room temperature. The fast response time, relative high responsivity and ease of fabrication of these devices yields a new prospect of exploring CDW condensate in TMDs with the aim of overcoming the existing limitations for a variety of practical applications at THz spectral range.

The quantum behavior of carriers in solid is the foundation of modern electronic and optoelectronic technology, but it is still facing huge challenges within inherited single‐particle quantum processes working at the millimeter wave/terahertz (THz) band. Here, a straightforward strategy for the direct detection of millimeter wave/THz photons in a sub‐wavelength metal‐TaSe 2 ‐metal structure under strong interaction with a localized field of surface plasmon is proposed. By breaking the inversion symmetry under the perturbations of electric field and atomic reconstruction from van der Waals integration, the nonequilibrium electronic states under a radiant field can be manipulated in a collective fashion, leading to a large photocurrent responsivity over 40 A W −1 and noise equivalent power less than 1 pW Hz −1/2 even at room temperature. A more than 40‐fold enhancement in responsivity is achieved when transitioning from the normal phase to the CDW phase. The findings shed fresh light on the understanding of the delicate balance in the charge‐ordered phase, and facilitate the exploitation of a correlated electron system for optoelectronic applications in fields of security, remote sensing, and imaging.

Black phosphorus (BP) ranks among the most promising saturable absorber materials for ultrafast pulse generations at 2 μm. However, the easy-to-degrade characteristic of BP seriously limits the long-term operation of ultrafast fiber lasers and hence becomes a bottleneck for its relevant practical applications. In this paper, a modified electrochemical delamination exfoliation process was explored to produce high-performance, large-size, and oxidation-resistant BP nanosheets, where BP nanosheets in high yield with evenly coated tetra-n-butyl-ammonium organics by precisely controlling the intercalation chemistry can be obtained. A mode-locked Tm/Ho co-doped fiber laser with high temporal stability and long-term operation capability was demonstrated based on the innovatively fabricated BP saturable absorber. The self-starting mode-locking operation featuring a high signal-to-noise ratio of 58 dB and long-term stability has been verified for at least 3 weeks, which indicates the successful passivation of the employed synthesis method. These results fully indicated that passivated BP is an efficient candidate in a 2 μm range ultrafast photonic field, which will promote the ultrafast optical application of BP and also other infrared photonic and photoelectronic devices.

In recent years, metal chalcogenide nanomaterials have received much attention in the field of ultrafast lasers due to their unique band-gap characteristic and excellent optical properties. In this work, two-dimensional (2D) indium monosulfide (InS) nanosheets were synthesized through a modified liquid-phase exfoliation method. In addition, a film-type InS-polyvinyl alcohol (PVA) saturable absorber (SA) was prepared as an optical modulator to generate ultrashort pulses. The nonlinear properties of the InS-PVA SA were systematically investigated. The modulation depth and saturation intensity of the InS-SA were 5.7% and 6.79 MW/cm(2), respectively. By employing this InS-PVA SA, a stable, passively mode-locked Yb-doped fiber laser was demonstrated. At the fundamental frequency, the laser operated at 1.02 MHz, with a pulse width of 486.7 ps, and the maximum output power was 1.91 mW. By adjusting the polarization states in the cavity, harmonic mode-locked phenomena were also observed. To our knowledge, this is the first time an ultrashort pulse output based on InS has been achieved. The experimental findings indicate that InS is a viable candidate in the field of ultrafast lasers due to its excellent saturable absorption characteristics, which thereby promotes the ultrafast optical applications of InX (X = S, Se, and Te) and expands the category of new SAs.