Broadband Laser Research Articles

Concentration-dependent photothermal conversion efficiency of gold nanoparticles under near-infrared laser and broadband irradiation.

The photothermal conversion efficiency of gold different nanoparticles (GNPs) in different concentrations (1.25-20 µg/mL) and at different irradiation intensities of near-infrared (NIR) broadband and NIR laser irradiation is evaluated. Results show that for a concentration of 20.0 µg/mL, 40 nm gold nanospheres, 25 × 47 nm gold nanorods (GNRs), and 10 × 41 nm GNRs show a 4-110% higher photothermal conversion efficiency under NIR broadband irradiation than under NIR laser irradiation. Broadband irradiation seems suitable to attain higher efficiencies for the nanoparticles whose absorption wavelength is different from the irradiation wavelength. Lower concentrations (1.25-5 µg/mL) of such nanoparticles show 2-3 times higher efficiency under NIR broadband irradiation. For GNRs of sizes 10 × 38 nm and 10 × 41 nm, the different concentrations show almost equal efficiencies for NIR laser and broadband irradiation. On increasing the irradiation power from 0.3 to 0.5 W, for 10 × 41 nm GNRs in the concentration range of 2.5-20.0 µg/mL, NIR laser irradiation results in 5-32% higher efficiencies, while NIR broadband irradiation leads to a 6-11% increase in efficiency. Under NIR laser irradiation, the photothermal conversion efficiency increases with an increase in optical power. The findings will facilitate the selection of nanoparticle concentrations, irradiation source, and irradiation power for a variety of plasmonic photothermal applications.

Spectral properties and high-efficiency broadband laser operation of Tm:CaY0.9Gd0.1AlO4 crystal

We report on spectral properties and a high-efficiency broadband laser operation of Tm:CaY0.9Gd0.1AlO4 (Tm:CYGA) crystal. The polarized absorption and emission spectra, gain cross sections and fluorescence lifetime are systematically studied, presenting a broad absorption and emission spectra and thus a smooth gain band. Furthermore, under an absorbed pump power of 4.35 W, a maximum continuous-wave (CW) laser output power of 1.43 W at 1967.8 nm is obtained, corresponding to a slope efficiency of 42.2 %. The beam quality factors (M2) in X-axis and Y-axis are measured to be 1.011 and 1.027, respectively. A tunable Tm:CYGA laser with a tuning range of 284.7 nm from 1837.5 to 2122.2 nm is achieved employing a birefringent filter (BF). The results indicate that the Tm:CYGA crystal is an excellent laser medium for generating high-efficiency broadband CW laser, indicating its potential for ultrashort pulse generation in the 2-μm spectral range.

Photoelectron circular dichroism in fenchone by short coherent broadband laser pulses

Photoelectron circular dichroism (PECD) of fenchone induced by short coherent broadband laser pulses is studied theoretically using the time-dependent single-center method. In particular, we investigate the chiral response to circularly polarized pulses with a sine-squared energy spectrum between 1 and 3 eV. We consider nonchirped and differently chirped pulses of a moderate peak intensity of $3\ifmmode\times\else\texttimes\fi{}{10}^{12}\phantom{\rule{3.33333pt}{0ex}}\mathrm{W}/{\mathrm{cm}}^{2}$ and a nonchirped pulse of a higher peak intensity of $1\ifmmode\times\else\texttimes\fi{}{10}^{14}\phantom{\rule{3.33333pt}{0ex}}\mathrm{W}/{\mathrm{cm}}^{2}$ leading to a strong-field ionization. Thereby, effects of the frequency ordering and pulse intensity are investigated in some detail. The present theoretical study predicts a substantial multiphoton PECD of fenchone, which can be manipulated by tailoring a spectral phase and intensity profile of a single coherent broadband laser pulse.

Two-qubit gate in neutral atoms using transitionless quantum driving

A neutral-atom system serves as a promising platform for realizing gate-based quantum computing because of its capability to trap and control several atomic qubits in different geometries and the ability to perform strong, long-range interactions between qubits; however, the two-qubit entangling gate fidelity lags behind competing platforms such as superconducting systems and trapped ions. The aim of our work is to design a fast, robust, high-fidelity controlled-Z (CZ) gate, based on the Rydberg-blockade mechanism, for neutral atoms. We propose a gate procedure that relies on simultaneous and transitionless quantum driving of a pair of atoms using broadband lasers. By simulating a system of two interacting Caesium atoms, including spontaneous emission from excited levels and parameter fluctuations, we yield a Rydberg-blockade CZ gate with fidelity 0.9985 over an operation time of $0.12~\mu$s. Our gate procedure delivers CZ gates that are superior than the state-of-the-art experimental CZ gate and the simulated CZ gates based on adiabatic driving of atoms. Our results show that our gate procedure carries significant potential for achieving scalable quantum computing using neutral atoms.

Covalent functionalization of Sb2S3 with poly(N-vinylcarbazole) for solid-state broadband laser protection.

An optimized complex multi-component nanomaterial system would help greatly enhance the optical limiting performance and applicability of 2D nanomaterials. By using antimony sulfide-[S-1-dodecyl-S'-(α,α'-dimethyl-α''-acetic acid)trithiocarbonate] (Sb2S3-DDAT) as a reversible addition fragmentation chain transfer (RAFT) agent, a highly soluble poly(N-vinylcarbazole)-covalently modified Sb2S3 (Sb2S3-PVK) was synthesized in situ and embedded into a non-optically active poly(methylmethacrylate) (PMMA) matrix producing a PMMA-based film with good optical quality. In contrast to both the Sb2S3/PMMA and Sb2S3:PVK blends/PMMA films, the Sb2S3-PVK/PMMA film exhibits more superior optical limiting performance. After annealing in N2 at 200 °C for 30 minutes, the achieved nonlinear absorption coefficient and limiting threshold are changed from 411.79 cm GW-1 and 1.93 J cm-2 at 532 nm and 242.79 cm GW-1 and 4.17 J cm-2 at 1064 nm before annealing to 478.04 cm GW-1 and 1.70 J cm-2 at 532 nm and 520.92 cm GW-1 and 1.40 J cm-2 at 1064 nm after annealing, respectively. These advantages make Sb2S3-PVK one of the potential promising candidates for a broadband laser protector in both the visible and near-infrared ranges.

PHOTOBIOMODULATION IN DENTISTRY: A REVIEW OF THE LITERATURE

Photobiomodulation therapy (PBMT), is the ability to modulate cell growth, survival, and differentiation processes of cells using optimal amount of energy ,not causing phototoxicity . It includes a wide range of electromagnetic wavelengths such as broadband lights, LEDs, and lasers that may have both photo stimulation and photo inhibitory effects on the target tissues, each of which can be used in therapeutic applications. Some of the benets of using PBMTin dentistry include reducing dentin sensitivity to tactile and thermal stimulations, improving dentin formation from dental pulp, reducing inammation of oral mucosa, accelerating bone formation, reducing pain after all types of dental treatments, and improving wound healing processes. In this review of literature, we emphasize that PBMT itself or as an adjunct can have a crucial role in decreasing postoperative dental pain, increasing depth of anesthesia during cavity preparation, decreasing tooth hypersensitivity, reducing inammation of the tissues, and healing of denture stomatiti

Broad-band self-injection organic laser amplifier based on a DBR microcavity

A self-injected regenerative laser amplifier is achieved on a periodic array of DBR microcavities, where an Al coating on the back of the substrate supplies high-reflection of the output of the oscillator and facilitates injection of the amplifier.

Pulse-shaped broadband multiphoton excitation for single-molecule fluorescence detection in the far field

Multiphoton excitation of fluorescence has many potential advantages over resonant (one-photon) excitation, but the method has not found widespread use for ultrasensitive applications. We recently described an approach to the multiphoton excitation of single molecules that uses a pulse shaper to compress and tailor pulses from an ultrafast broadband laser in order to optimise the brightness and signal-to-background ratio following non-linear excitation. Here we provide a detailed description of the setup and illustrate its use and potential by optimising two-photon fluorescence of a common fluorophore, rhodamine 110, at the single-molecule level. We also show that a DNA oligonucleotide labelled with a fluorescent nucleobase analogue, tC, can be detected using two-photon FCS, whereas one-photon excitation causes rapid photobleaching. The ability to improve the signal-to-background ratio and to reduce the incident power required to attain a given brightness can be applied to the multiphoton excitation of any fluorescent species, from small molecules with low multiphoton cross sections to the brightest nanoparticles.

Instantaneous Beam Smoothing Technique Based on Beat Frequency of Broadband Laser

Instantaneous Beam Smoothing Technique Based on Beat Frequency of Broadband Laser

Research on Optical Path and Phase Simultaneous Control in Coherent Beam Combining of Broadband Laser Based on Spectral Filtering

Research on Optical Path and Phase Simultaneous Control in Coherent Beam Combining of Broadband Laser Based on Spectral Filtering

Ultra-broadband all-optical sampling of optical waveforms.

Optical-field sampling techniques provide direct access to the electric field of visible and near-infrared light. The existing methods achieve the necessary bandwidth using highly nonlinear light-matter interaction that involves ionization of atoms or generation of charge carriers in solids. We demonstrate an alternative, all-optical approach for measuring electric fields of broadband laser pulses, which offers an advantage in terms of sensitivity and signal-to-noise ratio and extends the detection bandwidth of optical methods to the petahertzdomain.

Features of noncollinear second harmonic generation by infrared laser pulses with opposite frequency chirps

The features of noncollinear second harmonic generation during the interaction of broadband laser pulses with opposite frequency chirps are considered. The impact of spectral phase mismatch of the interacting pulses on spectrum width and the efficiency of conversion to the noncollinear second harmonic is analyzed on an example of lithium triborate and beta-barium borate crystals.

Effect of absorption oscillation of resonant radiation observed in a compact installation for hyper-polarization of 129Xe

This work presents the discovery and study of a new, to the best of our knowledge, effect of oscillation of resonant radiation absorption in optical cells with rubidium vapor in the presence of xenon and nitrogen inside an installation for xenon polarization by spin-exchange optical pumping. This effect was observed at temperatures of 100°C–130°C, partial xenon pressure exceeding 100 kPa, total gas mix pressure of 400 kPa, and power of broad-band ( Δ λ = ∼ 2 n m ) laser radiation over 2 W. The highest registered magnitude of power oscillations of the transmitted radiation exceeded 20%, the oscillation period depending on the temperature and lying in the range of 4.8–7 s. The conducted measurements of the parameters of the transmitted radiation lead to the conclusion that the discovered effect is related to concentration oscillations of the atomic rubidium vapor, which probably arises due to cyclic dimerization of rubidium or an oscillating continuous chemical reaction of rubidium and the optical cell contents.

Performance of different correction maps in the extended phase-space method for spinning compact binaries

ABSTRACT Since the first detection of gravitational waves by the LIGO/VIRGO team, the related research field has attracted more attention. The spinning compact binaries system, as one of the gravitational-wave sources for broad-band laser interferometers, has been widely studied by related researchers. In order to analyse the gravitational wave signals using matched filtering techniques, reliable numerical algorithms are needed. Spinning compact binaries systems in post-Newtonian (PN) celestial mechanics have an inseparable Hamiltonian. The extended phase-space algorithm is an effective solution for the problem of this system. We have developed correction maps for the extended phase-space method in our previous work, which significantly improves the accuracy and stability of the method with only a momentum scale factor. In this paper, we will add more scale factors to modify the numerical solution in order to minimize the errors in the constants of motion. However, we find that these correction maps will result in a large energy bias in the subterms of the Hamiltonian in chaotic orbits, whose potential and kinetic energy, etc. are calculated inaccurately. We develop a new correction map to reduce the energy bias of the subterms of the Hamiltonian, which can instead improve the accuracy of the numerical solution and also provides a new idea for the application of the manifold correction in other algorithms.

Theoretical and experimental study of ultraviolet broadband laser amplification using Ce:LiCAF crystal

Trivalent cerium ion-doped lithium calcium aluminum fluoride (Ce:LiCAF) crystals have been demonstrated as efficient amplification gain media in the ultraviolet (UV) wavelength region. However, spectral characteristics in the multipass amplification process have not yet been studied theoretically and experimentally. This work investigates the spectral effects, including gain narrowing and spectral shifting using the chromatic Frantz–Nodvik model to simulate the amplification of broadband nanosecond UV pulses from a Ce:LiCAF crystal. From the simulation results, 5.5 mJ amplified pulses can be obtained using a 4-pass amplifier with seed pulses having 0.7 mJ pulse energy, 3 ns pulse duration and 288.5 nm peak wavelength. These values are in good agreement with experimental results. Seed pulses with peak wavelength of 290.0 nm and linewidth of 2.0 nm could be shifted to 289.8 nm peak wavelength and narrowed to 1.9 nm linewidth after 4-pass amplification. Accounting for the spectral effects will enable a more accurate prediction of the amplified pulses’ characteristics, thereby aiding the applications of high-power UV lasers.

Broadband chaos generation utilizing a wavelength-tunable monolithically integrated chaotic semiconductor laser subject to optical feedback.

We demonstrate a broadband and wavelength-tunable chaotic laser by using a monolithically integrated wavelength-tunable chaotic semiconductor laser subject to optical feedback. The chip consists of a gain section, a distributed Bragg reflection grating section, a semiconductor optical amplifier section, and a phase section. By applying an optical feedback loop to the chaotic semiconductor laser chip, a nonlinear frequency mixing is stimulated in the laser cavity, and the chaos bandwidth is expanded to 33.6 GHz, which is 4.4 times larger than the bandwidth without optical feedback. Furthermore, the effect of feedback optical power on the bandwidth is investigated. The results show that the wide power spectrum of chaotic laser is available in a large wavelength range from 1556.44 nm to 1566.42 nm. This work explores a broadband and wavelength-tunable chaotic semiconductor laser for the wavelength division multiplexing to enlarge the capacity in chaotic secure optical communications.

High laser performance of an Al3+ and Nd3+-codoping in sodium-borotellurite glass for NIR broadband laser application

The main spectroscopic properties of Nd3+ ions immersed in an oxide glass with composition 59B2O3–10TeO2–30Na2O–1Al2O3:1Nd2O3 (in mol%) has been studied by X-ray diffraction, EDS, SEM, luminescence, transmission, FTIR and Raman spectroscopies. Very high values of the main spectroscopic parameters of Nd3+ ions were determined from the Ωt intensity parameters according to Judd-Ofelt formalism. The 4F3/2 → 4I11/2 NIR transition at 1060 nm of Nd3+ ions is evaluated from the relevant laser parameters reporting a very high quantum efficiency (95%), large effective bandwidth (36 nm), high laser performance quality (9.19 × 10−24 cm2·s) and low saturation intensity (2.04 × 108 W/m2). The excellent non-linear properties of Nd3+ ions are attributed to a microcrystallization inside the glass induced by Al3+ and Nd3+-codoping and a high sodium concentration which intensified the ligand field strengths around Nd3+ ions. Such microcristallization is verified by the presence of several crystalline peaks observed in the FTIR and Raman spectra and identified as Al–O and Te–O linkage vibrations in α-Al2O3 and α-TeO2 phases. As a consequence, a significant reduction of free hydroxyls is appreciated at the midinfrared region in both spectra. Whereas the presence of graphite was detected in the Raman spectrum at 2450 and 2889 cm−1. The great centrosymmetric loss of the Nd3+-sites is indicated by a high value of the Ω2 parameter (36.98 × 10−20 cm2) and confirmed by matched vibrational modes displayed in the deconvoluted Raman and FTIR spectra from 370 to 1750 cm−1 according to the Mutual Exclusion Rule for non-centrosymmetric point groups. The X-ray pattern of the Nd3+-doped oxide glass shows three different amorphous phases generated by delocalized and localized 4f-electrons indicating coexistence of ionic and covalent oxide-metal bonds as characteristic of the invert glasses. However, the compositional parameters confirmed a preferentially covalent domain of oxide-metal bonds as well as presence of crystalline phase, being both structural characteristics consistent with the Judd-Ofelt, transmission, FTIR and Raman results. Finally, the radiative properties are compared with those reported for other Nd3+-activated aluminate glasses suggesting that Al3+ and Nd3+-codoped sodium-borotellurite glass has a great potential for NIR broadband laser application.

High-gain broadband laser amplification of mid-IR pulses in Fe:CdSe crystal at 5 μm with millijoule output energy and multigigawatt peak power.

We report on a first of its kind, to our knowledge broadband amplification in a Fe:CdSe single crystal in the mid-IR beyond 5 µm. The experimentally measured gain properties demonstrate saturation fluence close to 13 mJ/cm2 and support the bandwidth up to 320 nm (full width at half maximum). Such properties allow the energy of the seeding mid-IR laser pulse, generated by an optical parametric amplifier, to be pushed up to more than 1 mJ. Dispersion management with bulk stretcher and prism compressor enables 5-µm laser pulses of 134-fs duration, providing access to multigigawatt peak power. Ultrafast laser amplifiers based on a family of Fe-doped chalcogenides open the route for wavelength tuning together with energy scaling of mid-IR laser pulses that are strongly demanded for the areas of spectroscopy, laser-matter interaction, and attoscience.

Optical-parametric oscillation in photonic-crystal ring resonators

By-design access to laser wavelength, especially with integrated photonics, is critical to advance quantum sensors, such as optical clocks and quantum-information systems, and open opportunities in optical communication. Semiconductor-laser gain provides exemplary efficiency and integration but merely in developed wavelength bands. Alternatively, nonlinear optics requires control of phase matching, but the principle of nonlinear conversion of a pump laser to a designed wavelength is extensible. We report on laser-wavelength access by versatile customization of optical-parametric oscillation (OPO) with a photonic-crystal ring resonator (PhCR). Leveraging the exquisite control of laser propagation provided by a photonic crystal in a traveling-wave ring resonator, we enable OPO generation across a wavelength range of 1234–2093 nm with a 1550-nm pump and 1016–1110 nm with a 1064-nm pump. Moreover, our platform offers pump-to-sideband conversion efficiency of > 10 % and negligible additive optical-frequency noise across the output range. From laser design to simulation of nonlinear dynamics, we use a Lugiato–Lefever framework that predicts the system characteristics, including bidirectional OPO generation in the PhCR and conversion efficiency in agreement with our observations. Our experiments introduce broadband lasers by design with PhCR OPOs, providing critical functionalities in integrated photonics.

Laser induced white emission of diamond.

Laser-induced white emission of diamond was investigated under irradiation with a focused beam of an infrared laser diode. It is a surface-related coherent emission, characterized by an excitation threshold and an exponential dependence on pumping laser power. The mechanism of white emission is discussed in terms of multiphoton ionization of carbon atoms in an irradiated spot. The excitation power dependence of white emission intensity has demonstrated hysteresis loop behavior. This phenomenon could be useful in new broadband laser sources and optical information storage.