Large-Scale Fabrication of Boron Nitride Nanosheets and Their Utilization in Polymeric Composites with Improved Thermal and Mechanical Properties

The ultrafast relaxation and recombination dynamics of photogenerated electrons and holes in epitaxial graphene are studied using optical-pump Terahertz-probe spectroscopy. The conductivity in graphene at Terahertz frequencies depends on the carrier concentration as well as the carrier distribution in energy. Time-resolved studies of the conductivity can therefore be used to probe the dynamics associated with carrier intraband relaxation and interband recombination. We report the electron-hole recombination times in epitaxial graphene for the first time. Our results show that carrier cooling occurs on sub-picosecond time scales and that interband recombination times are carrier density dependent.

Ultrafast Optical-Pump Terahertz-Probe Spectroscopy of the Carrier Relaxation and Recombination Dynamics in Epitaxial Graphene

There has been an enormous infusion of new ideas in the field of solar cells over the last 15 years; discourse on energy transfer has gotten much richer, and nanostructures and nanomaterials have revolutionized the possibilities for new technological developments. However, solar energy cannot become ubiquitous in the world's power markets unless it can become economically competitive with legacy generation methods such as fossil fuels. The new edition of Dr. Stephen Fonash's definitive text points the way toward greater efficiency and cheaper production by adding coverage of cutting-edge topics in plasmonics, multi-exiton generation processes, nanostructures and nanomaterials such as quantum dots. This book's new structure improves readability by shifting many detailed equations to appendices, and balances the first edition's semiconductor coverage with an emphasis on thin-films. Further, it now demonstrates physical principles with simulations in the well-known AMPS computer code developed by the author. This classic text is now updated with new advances in nanomaterials and thin films that point the way to cheaper, more efficient solar energy production and, many of the detailed equations from the first edition have been shifted to appendices in order to improve readability. It carries important theoretical points are now accompanied by concrete demonstrations via included simulations created with the well-known AMPS computer code.

太阳电池器件物理 = Solar cell device physics

Manuscript received April 14, 1983; revised June 24, 1983. N. B. Abraham is with the Department of Physics, BrynMawr College, Bryn Mawr, PA 19010. P. Mandel is with the Service de Chimie Physique 11, Universite Libre de Bruselles, Brussels, Belgium. L. W. Casperson is with the Department of Electrical Engineering and Applied Science: University of California, Los Angeles, CA 90024. Editor’s Note: A similar correction by Dr. F. Holigner and Prof. Dr. H. Weber of the Universitat Kaiserslautern was received on May 4, 1983. tions can be expressed as BR = y + p P (3a j

Principles of lasers

We propose and demonstrate 1, 1.5, and 2 μm passively Q-switched fiber lasers by exploiting a few-layer Molybdenum sulfide (MoS2) polymer composite as broadband saturable absorber (SA), respectively. The few-layer MoS2 nanosheets are prepared by the liquid-phase exfoliation method, and are composited with polyvinyl alcohol (PVA). The PVA-MoS2 film is sandwiched between two fiber ferrules to form the fiber-compatible SA. The few-layer MoS2 not only shows good transparency from ultraviolet to mid-infrared spectral region, but also possesses the nonlinear saturable absorption. The modulation depth and saturation optical intensity of the PVA-MoS2 film are measured to be 1.6% and 13 MW/cm2 at 1566 nm by the balanced twin-detector technique, respectively. By further inserting the filmy PVA-MoS2 SA into the cavities of Yb-, Er- and Tm-doped fiber lasers, we achieve stable Q-switching operations at 1.06, 1.56, and 2.03 μm, respectively. The output characteristics of the Q-switched pulses at the three wavelengths have been investigated, respectively. The MoS2-based Q-switching enables the large pulse energy of ∼1 μJ with a pulse width of 1.76 μs. This is, to the best of our knowledge, the first demonstration of MoS2-based Q-switched fiber lasers in a wide wavelength range (from 1 to 2 μm). Our results experimentally confirm that the new-type 2-D material, few-layer MoS2, is a promising broadband SA to Q-switch fiber lasers covering all major wavelengths from near- to mid-infrared region.

1-, 1.5-, and 2-μm Fiber Lasers Q-Switched by a Broadband Few-Layer MoS 2 Saturable Absorber

A linear cavity Brillouin fiber laser (BFL) is proposed and demonstrated for multi-wavelength operation. The BFL uses a single mode fiber (SMF) as a non-linear gain medium and an optical circulator to generate a linear cavity resonator. Two couplers are used to inject the Brillouin Pump (BP) and tap the BFL output respectively. The effect of the coupler ratio on the BFL performance is studied by keeping constant the ratio of the first coupler and varying the ratio of the second coupler. 11 simultaneous lines with a line spacing of 0.8 nm are obtained at a BP of 11.7 dBm and a coupler ratio of 95:5. The laser output is stable at room temperature with 5 lines obtained at above – 30 dBm, and has the largest signal to noise ratio observed at the remaining lines. The proposed BFL has the advantage of being able to operate at any wavelength and is only dependent on the available BP wavelength.

http://iopscience.iop.org/article/10.1002/lapl.200710134/pdf

A linear cavity Brillouin fiber laser with multiple wavelengths output

A compact Q-switched thulium-doped fiber laser (TDFL) operating near the 2.0- μm region is proposed and demonstrated. The proposed laser uses a 2-m-long thulium-doped fiber with a core absorption of 27 dB/m at 793 nm as the active medium and a graphene oxide (GO)-based saturable absorber (SA) as the Q-switching element. The SA is fabricated by optically depositing GO particles dissolved in distilled water onto the face of a fiber ferrule, which is then used to assemble the SA. The proposed TDFL is capable of generating pulses with a maximum repetition rate of 16.0 kHz and pulsewidths as narrow as 9.8 μs, as well as having maximum average output power and pulse energy of 0.3 mW and 18.8 nJ, respectively. The combination of the easily fabricated GO-based SA, together with the TDFL's ability to operate in the eye-safe region of 2.0 μm, gives the proposed Q-switched TDFL a high potential for a multitude of real-world applications, including range-finding, medicine, and spectroscopy.

2.0- $\mu\hbox{m}$ Q-Switched Thulium-Doped Fiber Laser With Graphene Oxide Saturable Absorber

Bidirectional multiwavelength Brillouin fiber laser (BFL) generation is demonstrated using a 25 km long single-mode fiber as a Brillouin gain medium in a ring cavity. Odd-order Brillouin Stokes waves appear in the backward direction whereas Brillouin pump and the even Stokes orders are in the forward direction with the line spacing 0.16 nm (∼20 GHz) between each two consecutive waves in forward and backward directions. In addition, by a combination of the backward and forward outputs, we have a higher number comb generation of a multiwavelength BFL with the line spacing 0.08 nm (∼10 GHz). The proposed configuration can work at any wavelength which is a benefit to the others.

https://iopscience.iop.org/article/10.1088/1464-4258/10/5/055101/pdf

Bidirectional multiwavelength Brillouin fiber laser generation in a ring cavity

A high sensitivity pressure sensor design without a polymer transducer is demonstrated in this paper. The sensor uses a thin metal diaphragm as a pressure transducer instead of a polymer. The sensor is tested to a maximum pressure of 100 psi and has a sensitivity of 0.0115 nm/psi, which matches the calculated sensitivity of 0.0127 nm/psi. The sensor is provides accurate measurement of the pressure and shows good repeatability in its readings. The sensor is also tested at the flow loop of the University of Tulsa, and shows a good match with the pressure readings of the flow loop.

K. Thambiratnam

Papers

A linear cavity Brillouin fiber laser with multiple wavelengths output

2.0- $\mu\hbox{m}$ Q-Switched Thulium-Doped Fiber Laser With Graphene Oxide Saturable Absorber

Bidirectional multiwavelength Brillouin fiber laser generation in a ring cavity

High Sensitivity Fiber Bragg Grating Pressure Sensor Using Thin Metal Diaphragm

Mode-locking in Er-doped fiber laser with reduced graphene oxide on a side-polished fiber as saturable absorber