Low cost and highly efficient THz waves using chaotic supremacy

The digital communication in a system of two multi-mode solid state chaotic lasers is investigated theoretically. If the usual method working well in a single-mode laser system is applied to a multi-mode laser system, the memory effect of the two nearest digits can cause high rate of mistakes when the digits are decoded through the subtraction of receiver output from the transmittal. By introducing the deviations of two nearest maximum and minimum fluctuations of the signal to decode the digit, the message can be decoded correctly. Also, this communication method does not critically depend on the quality of the chaotic synchronization of the two multi-mode lasers.

The introductory remarks show that the properties of light sources and discs require the use of objectives similar to those used in microscopes. Conventional lasers and semiconductor lasers have a Gaussian intensity distribution. Bearing this in mind the ideal intensity distribution is calculated and the results are shown as "light mountains". Finally, the influence of aberrations and tolerances is discussed.

Pulsed laser, single-color, (2 + 1) multiphoton ionization is used to achieve elemental selectivity while concurrently eliminating isobaric interferences for lead (Pb) and bismuth (Bi) mixtures detected via resonance ionization mass spectrometry. Experimental results are compared with theoretical calculations by using a simple rate equation formalism. The following oscillator strengths were determined: Pb, 6p7p /sup 3/P/sub 0/ reverse arrow 6p7s /sup 3/P/sub 1//sup 0/, f = 0.4 +/- 0.1; Bi, 6p/sup 2/ (/sup 3/P/sub 0/) 7p J = /sup 3///sub 2//sup 0/ reverse arrow 6p/sup 2/7s /sup 4/P/sub 1/2/, f = 0.07 +/- 0.02. In addition, the Bi ionization cross section at 64,412 cm/sup -1/ was estimated to be (5 +/- 2) x 10/sup -18/ cm/sup 2/. Relative efficiencies of the ionization processes for these elements and a comparison between pulsed and continuous laser excitation are discussed.

The nonequilibrium quasi-Fermi-levels of electrons and holes in quantum wells are calculated during photoluminescence. It is assumed the electrons and holes are created by continuous laser excitation. Various recombination processes are included: electron radiative recombination with holes bound at neutral acceptors, electron radiative recombination with free holes, hole trapping at ionized acceptors, and Auger decay. A numerical example is presented for acceptors in GaAs/${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Al}}_{\mathit{x}}$As quantum wells.

An efficient method to investigate the microstructure and spatial distribution of nitrogen and nitrogen-vacancy (N-V) defects in detonation nanodiamond (DND) with primary particle sizes ranging from approximately 3 to 50 nm is presented. Detailed analysis reveals atomic nitrogen concentrations as high as 3 at% in 50% of diamond primary particles with sizes smaller than 6 nm. A non-uniform distribution of nitrogen within larger primary DND particles is also presented, indicating a preference for location within the defective central part or at twin boundaries. A photoluminescence (PL) spectrum with well-pronounced zero-phonon lines related to the N-V centers is demonstrated for the first time for electron-irradiated and annealed DND particles at continuous laser excitation. Combined Raman and PL analysis of DND crystallites dispersed on a Si substrate leads to the conclusion that the observed N-V luminescence originates from primary particles with sizes exceeding 30 nm. These findings demonstrate that by manipulation of the size/nitrogen content in DND there are prospects for mass production of nanodiamond photoemitters based on bright and stable luminescence from nitrogen-related defects.

Biosynthesis of Ag@Au bimetallic nanoparticles from Hymenaea courbaril extract (Jatobá) and nonlinear optics properties

Conventional tunable semiconductor lasers tuned by the carrier induced effect suffer from intrinsically nonuniform optical frequency modulation (FM) response due to the associated thermal effect. Electric field effect tuned lasers involving no current injection, offer intrinsically uniform FM response. We report here the first quantum-confined Stark effect tuned two-section ridge waveguide laser fabricated by postgrowth band gap engineering techniques. An highly uniform FM response, within /spl plusmn/3 dB from 30 kHz to 6 GHz, is achieved, independent of laser output power, the widest and most uniform response yet reported for a field effect tuned laser. The residual intensity modulation is less than 5% for 4.5-GHz peak frequency deviation.

Wide bandgap semiconductors (e.g. GaN) and semiconductor heterostructures (e.g. AlxGa1−xN/GaN) are the key wide bandgap semiconductor technologies in the twenty-first century. The one-dimensional photonic structures (OPSs) play increasingly important roles in the design and fabrication of light-emitting diodes (LEDs), lasers, and semiconductor detectors. Conventional LEDs and semiconductor lasers based on planar designs, however, suffer light extraction inefficiency in LEDs and spatial hole burning (SHB) and “hard” thermal fold catastrophes in lasers. These limitations can be overcome effectively with the use of OPSs which are formed by building the semiconductor heterostructures or directly integration with the photonic crystal design. This chapter presents the state-of-the-art designs and fabrication techniques of OPSs based on oriented growth of group III-nitride semiconductors for LED and laser applications (Amuru et al., 2022; Jouppi et al., 2023; Ning et al., 2024).

Metallic nanostructures supporting surface plasmon modes can concentrate optical fields and enhance luminescence processes from the metal surface at plasmonic hotspots. Such nanoplasmonic metal luminescence contributes to the spectral background in surface-enhanced Raman spectroscopy (SERS) measurements and is helpful in bioimaging, nanothermometry and chemical reaction monitoring applications. Although there is growing interest in nanoplasmonic metal luminescence, its dependence on voltage modulation has received limited attention in research investigations. Also, the hyphenated electrochemical surface-enhanced Raman spectroscopy (EC-SERS) technique typically ignores voltage-dependent spectral background information associated with nanoplasmonic metal luminescence due to limited mechanistic understanding and poor measurement reproducibility. Here, we report a combined experiment and theory study on dynamic voltage-modulated nanoplasmonic metal luminescence from hotspots at the electrode-electrolyte interface using multiresonant nanolaminate nano-optoelectrode arrays. Our EC-SERS measurements under 785 nm continuous wavelength laser excitation demonstrate that short-wavenumber nanoplasmonic metal luminescence associated with plasmon-enhanced electronic Raman scattering (PE-ERS) exhibits a negative voltage modulation slope (up to ≈30% V-1) in physiological ionic solutions. Furthermore, we have developed a phenomenological model to intuitively capture the plasmonic, electronic, and ionic characteristics at the metal-electrolyte interface to understand the observed dependence of the PE-ERS voltage modulation slope on voltage polarization and ionic strength. The current work represents a critical step toward the general application of nanoplasmonic metal luminescence signals in optical voltage biosensing, hybrid optical-electrical signal transduction, and interfacial electrochemical monitoring.

The impact of pulsed versus continuous wave (cw) laser excitation on the photophysical properties of single quantum dots (QDs) has been investigated in an experiment in which all macroscopic variables are identical except the nature of laser excitation. Pulsed excitation exaggerates the effects of photobleaching, results in a lower probability of long ON fluorescence blinking events, and leads to shorter fluorescence lifetimes with respect to cw excitation at the same wavelength and average intensity. Spectral wandering, biexciton quantum yields, and power law exponents that describe fluorescence blinking are largely insensitive to the nature of laser excitation. These results explicitly illustrate important similarities and differences in fluorescence dynamics between pulsed and cw excitation, enabling more meaningful comparisons between literature reports and aiding in the design of new experiments to mitigate possible influences of high photon flux on QDs.

Laser Spectroscopy Theory

Multimode interference (MMI) structure is introduced in semiconductor laser to realize higher power and shorter device length. We use BPM simulation in the device design. MMI-LD was fabricated and realized in InGaAsP/InP based material and output power of up to 2.296 mW was achieved. The implemented MMI-LD exhibits stable single-mode output operating at a wavelength of 1.52 mum at 10degC. As a comparison, conventional semiconductor laser using straight waveguide is also fabricated in the same wafer and the output power is 0.534 mW. MMI-LD also shows better temperature tolerance due to the MMI wavelength selecting function.

A novel surface‐emitting laser design that utilizes leaky mode emission is proposed. Power is coupled out of the active layer in a narrow beam by monolithically integrating a prism‐like structure with a conventional semiconductor laser. Threshold current densities and external efficiencies approximately 1 kA / cm2 and 0.3, respectively, are estimated.

Though a variety of lasers have been used for holography over the years, a data storage system that is commercially viable requires a compact, efficient and ultimately low-cost source. The main requirements are coherence and wavelength compatibility with the material. Conventional semiconductor lasers, though compact and efficient, generally lack the coherence length required for holography. Similarly, gas lasers such as argon ion can be used in the laboratory to characterize materials, but the need for external cooling, the large size, and the immense power requirements preclude their use in real systems. In this section we first examine the general requirements for a laser suitable for practical holographic data storage, and then concentrate on two particular laser systems that meet our criteria: diode-pumped solid-state lasers and wavelength-stabilized semiconductor lasers. The two lasers that are particularly relevant are the diode-pumped frequency-doubled Nd:YAG, and the InGaP DFB lasers.KeywordsSemiconductor LaserDistribute Bragg ReflectorMaster Oscillator Power AmplifierData PageHolographic Data StorageThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Strained quantum-well lasers have been demonstrated to show superior performance over conventional semiconductor lasers in many aspects of the laser characteristics. In this talk, theoretical modeling of the strained quantum-well lasers including the electronic properties such as band structures with valence band-mixing effects and the optical properties such as polarization-dependent gain and lasing characteristics will be illustrated. Important issues including the Auger recombination rates and many-body effects on the laser performance will be discussed.