Recently, black phosphorus (BP) has joined the two-dimensional material family as a promising candidate for photonic applications due to its moderate bandgap, high carrier mobility, and compatibility with a diverse range of substrates. Photodetectors are probably the most explored BP photonic devices, however, their unique potential compared with other layered materials in the mid-infrared wavelength range has not been revealed. Here, we demonstrate BP mid-infrared detectors at 3.39 μm with high internal gain, resulting in an external responsivity of 82 A/W. Noise measurements show that such BP photodetectors are capable of sensing mid-infrared light in the picowatt range. Moreover, the high photoresponse remains effective at kilohertz modulation frequencies, because of the fast carrier dynamics arising from BP’s moderate bandgap. The high photoresponse at mid-infrared wavelengths and the large dynamic bandwidth, together with its unique polarization dependent response induced by low crystalline symmetry,...

Black Phosphorus Mid-Infrared Photodetectors with High Gain

Silicon germanium (SiGe) has moved from being a research material to accounting for a small but significant percentage of manufactured semiconductor devices. This percentage is predicted to increase substantially as SiGe begins to be used in complementary metal oxide semiconductor (CMOS) technology in the future to substantially improve performance. It is the development of Si/SiGe heterostructures which has enabled band structure and strain engineering allowing Si/SiGe to be used in many different ways to improve conventional microelectronic device performance along with allowing new concepts to be explored. This paper presents a review of the material properties, growth techniques, band structure and the main electronic devices of the Si/SiGe heterostructure system. In particular, the important device technologies in mainstream microelectronics of the SiGe heterostructure bipolar transistor (HBT) and strained-Si CMOS will be reviewed before future device and optoelectronics concepts are explored.

https://iopscience.iop.org/article/10.1088/0268-1242/19/10/R02/pdf

Si/SiGe heterostructures: from material and physics to devices and circuits

Terahertz fields and applications

We provide an overview of recent developments of quantum cascade lasers (QCLs), from the mid-infrared (mid-IR) to the far-IR (THz) range, with a special focus on their metrological-grade applications in a number of fields. A special emphasis on the physics of the QCLs allows underlining peculiar effects and device features recently unveiled that pave the way to novel demanding photonics applications.

https://iopscience.iop.org/article/10.1088/0957-0233/25/1/012001/pdf

Quantum cascade lasers: a versatile source for precise measurements in the mid/far-infrared range

We combine photonic and electronic band structure engineering to create a surface-emitting quantum cascade microcavity laser. A high-index contrast two-dimensional photonic crystal is used to form a micro-resonator that simultaneously provides feedback for laser action and diffracts light vertically from the surface of the semiconductor surface. A top metallic contact allows electrical current injection and provides vertical optical confinement through a bound surface plasmon wave. The miniaturization and tailorable emission properties of this design are potentially important for sensing applications, while electrical pumping can allow new studies of photonic crystal and surface plasmon structures in nonlinear and near-field optics.

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Quantum cascade surface-emitting photonic crystal laser.

Following an introduction to the history of the invention of the quantum cascade (QC) laser and of the band-structure engineering advances that have led to laser action over most of the mid-infrared (IR) and part of the far-IR spectrum, the paper provides a comprehensive review of recent developments that will likely enable important advances in areas such as optical communications, ultrahigh resolution spectroscopy and applications to ultrahigh sensitivity gas-sensing systems We discuss the experimental observation of the remarkably different frequency response of QC lasers compared to diode lasers, ie, the absence of relaxation oscillations, their high-speed digital modulation, and results on mid-IR optical wireless communication links, which demonstrate the possibility of reliably transmitting complex multimedia data streams Ultrashort pulse generation by gain switching and active and passive modelocking is subsequently discussed Recent data on the linewidth of free-running QC lasers (/spl sim/150 kHz) and their frequency stabilization down to 10 kHz are presented Experiments on the relative frequency stability (/spl sim/5 Hz) of two QC lasers locked to optical cavities are discussed Finally, developments in metallic waveguides with surface plasmon modes, which have enabled extension of the operating wavelength to the far IR are reported

Quantum cascade lasers: ultrahigh-speed operation, optical wireless communication, narrow linewidth, and far-infrared emission

Quantum cascade distributed feedback (QC-DFB) lasers based on a heterogeneous-cascade two-wavelength active waveguide core and a multisectioned cavity featuring two different Bragg gratings are demonstrated. Optimised lasers display singlemode emission at /spl lambda//spl sim/5.0 and 7.5 /spl mu/m simultaneously and a tunability on both modes equal to single-wavelength QC-DFB lasers.

A.M. Sergent

Papers

Quantum cascade lasers: ultrahigh-speed operation, optical wireless communication, narrow linewidth, and far-infrared emission

Simultaneously at two wavelengths (5.0 and 7.5 [micro sign]m) singlemode and tunable quantum cascade distributed feedback lasers