Explore the vast range of titles available.

\"This reference book provides a fully integrated novel approach to the development of high power, single transverse mode, edge-emitting diode lasers by addressing the complementary topics of device engineering (Part 1), reliability engineering (Part 2) and device diagnostics (Part 3) in the same book in altogether nine comprehensive chapters, and thus closes the gap in the current book literature.Diode laser fundamentals are discussed, followed by an elaborate discussion of problem-oriented design guidelines and techniques, and by a systematic treatment of the origins of laser degradation and a thorough exploration of the engineering means to address for effective remedies and enhanced optical strength. The discussion covers also stability criteria of critical laser characteristics and key laser robustness factors. Clear design considerations are discussed in the context of reliability engineering concepts and models, along with typical programs for reliability tests and laser product qualifications. A final extended part of novel, advanced diagnostic methods covers in detail, for the first time in book literature, performance- and reliability-impacting factors such as temperature, stress and material instabilities.Further key features include: Furnishes comprehensive practical design guidelines by considering also reliability related effects and key laser robustness factors, and discusses basic laser fabrication and packaging issues. Discusses in detail diagnostic investigations of diode lasers, the fundamentals of the applied approaches and techniques, many of them pioneered by the author to be fit-for-purpose and novel in the application. Provides a systematic insight into laser degradation modes such as catastrophic optical damage, and covers a wide range of technologies to increase the optical strength of diode lasers. Discusses basic concepts and techniques of laser reliability engineering, and provides for the first time in a book details on a standard commercial program for testing the reliabity of high power diode laser. Semiconductor Laser Engineering, Reliability and Diagnostics reflects the extensive expertise of the author in the diode laser field both as a top scientific researcher as well as a key developer of highly reliable devices. It features two hundred figures and tables illustrating numerous aspects of diode laser engineering, fabrication, packaging, reliability, performance, diagnostics and applications, and an extensive list of references to all addressed technical topics at the end of each chapter. With invaluable practical advice, this novel reference book is suited to practising researchers in diode laser technologies, and to postgraduate engineering students. \"--

Single- and multi-quantum well (QW) structures of Ga(AsBi)/GaAs with up to 10% Bi were grown by molecular beam epitaxy (MBE) at 300–330°C substrate temperature. The photoluminesce measurements of QW structures demonstrated room temperature emission up to wavelengths of ∼1.43 μm. In the structures obtained using a combined growth approach – an active layer with three QWs with ∼6% Bi was grown by MBE, whereas (AlGa)As claddings were grown by the metal organic vapour phase epitaxy technique – room temperature lasing at 1060 nm was documented.

Laser pulses are essential in various scientific fields, yet existing laser diode drivers offer limited adjustability. This paper presents a digitally adjustable subnanosecond gain-switched laser diode driver, a first one with step sizes of the control being in the single-digit picosecond range. The proposed circuit differentially drives the laser diode (LD) using two high-current gate drivers whose relative delay is digitally adjusted by a dual programmable delay line. Pulse width is defined by the delay difference between the two channels, enabling fine control without the need for high-speed semiconductor switching. Experimental results demonstrate stable optical pulse generation with widths tunable from 350ps to 2.8ns in 9ps increments and repetition rates exceeding 150MHz. Timing jitter remains below 15ps, and amplitude variation is below 1% across the tested operating conditions. The proposed solution provides a compact, low-cost, and highly adjustable platform for applications that require precise timing and pulse-width control, such as time-resolved measurements, range finding, and nonlinear optical excitation.

In this paper, a novel symmetrical three-wavelength toggling archetype for measuring the concentration of gases using a tunable diode laser absorption spectroscopy (TDLAS) system is introduced and demonstrated. The system was operated at 1.5714 µm with a 2 kHz update rate, targeting an absorption line of gaseous CO2. Precompensated diode–current pulses are introduced to offset the inherent thermal time constants of the diode laser by orders of magnitude. Here, repetition rates matching that of contemporary methods can be achieved, while simultaneously providing a noteworthy wavelength stability of 0.6 pm for the three targeted wavelengths that are approximately 70 pm apart (142 pm maximum wavelength excursion). A 10 Hz current loop locks one of the wavelengths to a CO2 absorption peak, thus providing an absolute and stable wavelength reference. The flexibility in choosing the shape and repetition frequency of the current pulses makes this approach easily adaptable to other gases and/or absorption lines, since wavelength filters are avoided. The new method is benchmarked against a two-wavelength precompensated continuous-wave TDLAS technique, revealing a fourfold improvement in reproducibility with system restart over the span of 24 days, while outperforming other widespread spectroscopic techniques applied to comparable transmittance levels. The effect of the analytical model was further studied by thermally inducing baseline changes, showing a 7.9 ± 0.2 times weaker correlation between concentration and temperature with respect to the one observed using the two-wavelength TDLAS archetype. These results demonstrate the system’s suitability for sensitive applications.

Objectives The primary aim of this ex vivo study was to evaluate thermal damage and cutting efficiency of micro and super pulsed diode lasers. The secondary aim was to suggest a guideline to perform simple surgical excisions adequate for histopathological evaluation. Material and Methods Ten groups of 10 specimens of pig tongues were excised using a blade (G1), a micro pulsed (G2–G9), and a super pulsed diode (G10) lasers. Different output power, pulse duration, pulse interval, and duty cycle were tested. Quantitative measures of thermal damage and excision times were recorded. Statistical analysis was performed at a significance level of 5%. Results The control group (G1) presented no thermal damage. Within the laser groups (G2–G10), no statistically significant differences in depth of thermal damage (µm) were noted. G3 showed significantly less area of thermal damage (mm2) when compared with G7 and G9 (p < .05). The median excision time of the control group and super pulsed diode laser group were significantly lower (p < .001) than the micro pulsed diode laser groups. Conclusions The cutting efficiency of the super pulsed diode laser is comparable to traditional blade, and with appropriate parameters, these lasers can produce predictable surgical outcomes with less collateral damage.

Using the developed 2D numerical model of laser diodes, we study the effect of the cavity characteristics on the loss, and analyze the choice of the cavity parameters for efficient operation of the laser at ultrahigh pump currents. It is shown that at a fixed pump-current amplitude, a maximum output power is achieved for a combination of the optimal cavity parameters, namely, the cavity length L opt and the output mirror reflectivity R ARopt . It is found that the possibility of increasing the power by reducing the R AR coefficient is limited due to the formation of a local region of high optical loss and recombination loss currents near the cavity face with a high reflectivity.

A nanolaser is a key component for on-chip optical communications and computing systems. Here, we report on the low-threshold, continuous-wave operation of a subdiffraction nanolaser based on surface plasmon amplification by stimulated emission of radiation. The plasmonic nanocavity is formed between an atomically smooth epitaxial silver film and a single optically pumped nanorod consisting of an epitaxial gallium nitride shell and an indium gallium nitride core acting as gain medium. The atomic smoothness of the metallic film is crucial for reducing the modal volume and plasmonic losses. Bimodal lasing with similar pumping thresholds was experimentally observed, and polarization properties of the two modes were used to unambiguously identify them with theoretically predicted modes. The all-epitaxial approach opens a scalable platform for low-loss, active nanoplasmonics.

A broadband, compact, all-electrically driven mid-infrared frequency comb based on a quantum cascade laser widens the scope of application of combs in this frequency range beyond that of sources which depend on a chain of optical components. A mid-infrared frequency comb Optical frequency combs are light sources that produce a comb-like spectrum, with sharp equidistant frequency modes, and have many uses in metrology and spectroscopy applications. The mid-infrared regime is particularly important for molecular fingerprinting, but so far the comb sources in this wavelength regime are bulky and rely on a chain of optical components. For wide practical applications, an electrically injected, compact scheme is desired. Andreas Hugi et al . now demonstrate a mid-infrared frequency comb generator based on a semiconductor device, a continuous-wave quantum cascade laser. Optical frequency combs 1 act as rulers in the frequency domain and have opened new avenues in many fields such as fundamental time metrology, spectroscopy and frequency synthesis. In particular, spectroscopy by means of optical frequency combs has surpassed the precision and speed of Fourier spectrometers. Such a spectroscopy technique is especially relevant for the mid-infrared range, where the fundamental rotational–vibrational bands of most light molecules are found 2 . Most mid-infrared comb sources are based on down-conversion of near-infrared, mode-locked, ultrafast lasers using nonlinear crystals 3 . Their use in frequency comb spectroscopy applications has resulted in an unequalled combination of spectral coverage, resolution and sensitivity 4 , 5 , 6 , 7 . Another means of comb generation is pumping an ultrahigh-quality factor microresonator with a continuous-wave laser 8 , 9 , 10 . However, these combs depend on a chain of optical components, which limits their use. Therefore, to widen the spectroscopic applications of such mid-infrared combs, a more direct and compact generation scheme, using electrical injection, is preferable. Here we present a compact, broadband, semiconductor frequency comb generator that operates in the mid-infrared. We demonstrate that the modes of a continuous-wave, free-running, broadband quantum cascade laser 11 are phase-locked. Combining mode proliferation based on four-wave mixing with gain provided by the quantum cascade laser leads to a phase relation similar to that of a frequency-modulated laser. The comb centre carrier wavelength is 7 micrometres. We identify a narrow drive current range with intermode beat linewidths narrower than 10 hertz. We find comb bandwidths of 4.4 per cent with an intermode stability of less than or equal to 200 hertz. The intermode beat can be varied over a frequency range of 65 kilohertz by radio-frequency injection. The large gain bandwidth and independent control over the carrier frequency offset and the mode spacing open the way to broadband, compact, all-solid-state mid-infrared spectrometers.

The dynamic characteristics of a discrete mode laser diode fabricated in the InGaAs/InP multiple quantum well material system and emitting single mode at λ ≃ 2.0 μm are reported. Results are presented on the electro-optical bandwidth, direct modulation and gain switched performance.

Most light-emitting devices based on quantum-confined structures are commonly utilized as electrically injected devices. However, the electric-field-dependent energy band gap induced by the quantum confinement Stark effect (QCSE) usually hinders the realization of frequency-stable laser devices. This is because the change in the energy band gap, which also means the corresponding change in the photon energy, will result in an electric-field-dependent frequency. Here, we propose a novel approach to mitigate this electric-field-dependent variation in the energy band gap by employing a gradient quantum system. In this system, the energy band edges are inclined due to the action of the indium (In)-segregation effect. This special design can effectively weaken the changes in the band profile associated with the electric field effect and counteract the electric-field-dependent band gap variations within the active region to a certain extent. Experimental studies indicate that the energy band gap of this gradient quantum system remains almost unchanged (<18.9 μeV cm /A) even under a relatively strong applied electric field. Meanwhile, compared with the traditional GaAs quantum well, the efficiency improvement in the band gap stability of our nanowire–well gradient system is 64.1 % and 70.6 % for the TE and TM polarization modes, respectively, which suggests that our proposed gradient quantum structure can significantly mitigate the electric-field-induced change in the energy band gap. This achievement is of great significance for advancing the development of high-performance frequency-stable laser devices in some advanced fields, such as quantum sensing systems and optical communications.