This monograph, written by an outstanding expert in time resolved spectroscopy of semiconductors, presents the most striking recent advances in the field of ultrafast spectroscopy of semiconductors and their nanostructures. The book contains 8 chapters with in total 1160 references and 186 figures, preface and subject index. It begins with an introductory chapter on basic concepts of semiconductor physics and ultrafast spectroscopic techniques. The following five chapters are arranged in the order of occurrence of events in a homogeneous semiconductor following photoexcitation by an ultrashort pulse. These events comprise four temporally-overlapping regimes:

Ultrafast Spectroscopy of Semiconductors and Semiconductor Nanostructures

Semiconductor science and technology (S T) is a very active branch in the field of natural science, and is also a typical example embodying the development of advanced S T. The Nobel prize for physics is a prize of the highest honour in the world, and there are certain relationships between this award and semiconductor S T. We explore and analyze these inherent relationships which have practical importance for our understanding of the development of semiconductor S T and for predicting its future.

Semiconductor science and technology, and Nobel physics prizes

This paper reviews the recent progress of quantum-dot semiconductor optical amplifiers developed as ultrawideband polarization-insensitive high-power amplifiers, high-speed signal regenerators, and wideband wavelength converters. A semiconductor optical amplifier having a gain of > 25 dB, noise figure of < 5 dB, and 3-dB saturation output power of > 20 dBm, over the record widest bandwidth of 90 nm among all kinds of optical amplifiers, and also having a penalty-free output power of 23 dBm, the record highest among all the semiconductor optical amplifiers, was realized by using quantum dots. By utilizing isotropically shaped quantum dots, the TM gain, which is absent in the standard Stranski-Krastanow QDs, has been drastically enhanced, and nearly polarization-insensitive SOAs have been realized for the first time. With an ultrafast gain response unique to quantum dots, an optical regenerator having receiver-sensitivity improving capability of 4 dB at a BER of 10-9 and operating speed of > 40 Gb/s has been successfully realized with an SOA chip. This performance achieved together with simplicity of structure suggests a potential for low-cost realization of regenerative transmission systems.

Quantum-Dot Semiconductor Optical Amplifiers

Narrow linewidth lasers have many applications, such as higher order coherent communications, optical sensing, and metrology. While semiconductor lasers are typically unsuitable for such applications due to relatively low coherence, recent advances in heterogeneous integration of III-V with silicon have shown that this is no longer true. In this tutorial, we discuss in-depth techniques that are used to drastically reduce the linewidth of a laser. The heterogeneous silicon-III/V platform can fully utilize these techniques, and fully integrated lasers with Lorentzian linewidth on the order of 100 Hz and tuning range of 120 nm are shown.

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Tutorial on narrow linewidth tunable semiconductor lasers using Si/III-V heterogeneous integration

We report a simple and inexpensive way for the preparation of highly transparent ZnO thin films and their application as active layer in UV ray sensor devices. ZnO thin films were deposited on glass substrates by thermal evaporation of pure ZnO powder. The as-deposited films were then annealed at different temperatures (100, 200, 300 and 400 °C) for various time durations (5, 15, 25 and 35 min) to make optically transparent in the visible region. The films annealed at 300 °C for 15 min show very good visible transparency and other material properties. These films were used as the active material for Ag/ZnO/Ag UV sensor devices. The sensor devices are photo conductive type and only sensitive in the UV region of the electromagnetic spectrum. Maximum photo-current gain of the UV sensor device is ∼2. Possible sensing mechanism has been discussed.

Preparation of transparent ZnO thin films and their application in UV sensor devices

In this work, we study and investigate the thermally effects on the compact continuous wave (CW) distributed feedback
(DFB) laser as a tuning method using an external platinum μ-heater film in a vertical and lateral configurations. A low
injection current into platinum heater produces the variation temperature inside the active and grating regions to shift the
lasing wavelength. The frequency is continuously tuned up to 3 THz at operation wavelength of 937 nm, by controlling
the temperature of the laser to achieve sub-millimetre (sub-mmW) and terahertz (THz) signals generation by
photomixing.

Thermally Tunable DFB Dual Mode Laser Diode by an External Platinum Thin-Film Heater for THz Generation

An InP-based quantum dot (QD) laser with InAs QDs emitting around 1.3 μm wavelength was realized. In comparison to C-band QD lasers, a modified growth process enhancing the nucleation of smaller QDs was developed, which allows the emission at the desired wavelength and preserves a high dot density. The influence of growth parameters on the formation of homogenous QDs was investigated. Broad area and ridge waveguide lasers were processed and first material and device results will be presented. A high internal quantum efficiency of 0.8 and a record value in the modal gain of more than 90 cm−1 for a laser with 6 QD layers were obtained, which relates to 15 cm−1 per QD layer. Temperature dependent laser characteristics show best T0 values up to 250 K between 20 and 70 °C.

High-gain InP-based quantum dot lasers emitting at 1.3 μm

We demonstrate an optically pumped vertical external-cavity surface-emitting laser (VECSEL) based on quantum dots (QDs) with a high optical gain. The photoluminescence (PL) emission of the QDs at the operating wavelength of 1030 nm has been optimized towards a high integrated intensity by using a dot density in the range of 1011 cm−2 and a narrow PL linewidth of around 30 meV due to an improved size homogeneity. Additionally, post-growth rapid thermal annealing at 650 °C for 45 s was found to reduce the non-radiative recombination centers and further improve the output power efficiency. During this study, the number of QD layers, the heat sink temperature and the heat spreader material were analyzed. The best results with a record slope-efficiency of 35% and a maximum continuous-wave output power of 5.7 W could be achieved with an RTA treated QD based VECSEL containing 24 QD layers in the gain section. The laser was processed with a solder-based flip-chip bonding technique on a diamond heat sink and temperature stabilized at 4 °C. Furthermore, an excellent symmetric beam profile with M2 = 1.12 was achieved.

Quantum-Dot Based Vertical External-Cavity Surface-Emitting Lasers With High Efficiency

InP-based quantum dot (QD) laser devices emitting at 1.3 µm were realized by incorporating a GaAs nucleation layer underneath the InAs QD layers. A good carrier confinement while retaining the waveguiding properties is achieved by embedding the QDs in In0.528Al0.371Ga0.101As. Length dependent P-I characteristics yielded static parameters, which were comparable to static parameters obtained for InP-based lasers emitting at 1.55 µm. Additionally, temperature dependent measurements were conducted and evaluated. The lasers show ground mode lasing up to high operation temperatures with good temperature stability of the threshold current density and external quantum efficiency. 

Emission characteristics and temperature stability of InP-based quantum-dot lasers emitting at 1.3 µm

A review will be given on the latest development of highspeed directly modulated 1.55 μm lasers based on high model gain quantum dot material. Static and dynamic properties of short cavity lasers will be presented exhibiting data rates well beyond 20 GBit/s. The impact of structural and operational parameters will be discussed and compared with a simulation model, which includes the complex carrier dynamics in quantum dot laser materials.

Vitalii Sichkovskyi

Papers

Thermally Tunable DFB Dual Mode Laser Diode by an External Platinum Thin-Film Heater for THz Generation

High-gain InP-based quantum dot lasers emitting at 1.3 μm

Quantum-Dot Based Vertical External-Cavity Surface-Emitting Lasers With High Efficiency

Emission characteristics and temperature stability of InP-based quantum-dot lasers emitting at 1.3 µm

New class of 1.55 μm quantum dot lasers for future high data rate optical communication