Generation Light Sources Research Articles

Octave-spanning frequency comb generation based on a dual-mode microcavity laser

Octave-spanning optical frequency comb (OFC) generation has achieved great breakthroughs and enabled significant applications in many fields, such as optical clocks and spectroscopy. Here, we demonstrate octave-spanning OFC generation with a repetition rate of tens of GHz via a four-wave mixing (FWM) effect seeded by a dual-mode microcavity laser for the first time, to our knowledge. A 120-m Brillouin nonlinear fiber loop is first utilized to generate wideband OFCs using the FWM effect. Subsequently, a time-domain optical pulse is shaped by appropriate optical filtering via fiber Bragg gratings. The high-repetition-rate pulse train is further boosted to 11 pJ through optimal optical amplification and dispersion compensation. Finally, an octave optical comb spanning from 1100 to 2200 nm is successfully realized through the self-phase modulation effect and dispersion wave generation in a commercial nonlinear optical fiber. Using dual-mode microcavity lasers with different mode intervals, we achieve frequency combs with octave bandwidths and repetition rates of 29–65 GHz, and demonstrate the dual-mode lasing microcavity laser as an ideal seeding light source for octave-spanning OFC generation.

On-the-fly investigation of XUV excited large molecular ions using a high harmonic generation light source

We present experiments where extreme ultraviolet femtosecond light pulses are used to photoexcite large molecular ions at high internal energy. This is done by combining an electrospray ionization source and a mass spectrometer with a pulsed light source based on high harmonic generation. This allows one to study the interaction between high energy photons and mass selected ions in conditions that are accessible on large-scale facilities. We show that even without an ion trapping device, systems as large as a protein can be studied. We observe light induced dissociative ionization and proton migration in model systems such as reserpine, insulin and cytochrome c. These results offer new perspectives to perform time-resolved experiments with ultrashort pulses at the heart of the emerging field of attosecond chemistry.

Efficient near-infrared broadband garnet phosphor for pc-LED and its application to vascular visualization and night vision.

Ultra-broadband near-infrared (NIR) spectroscopy has unparalleled application prospects in intelligent detection and phosphor-converted light-emitting diodes (pc-LED), which are most likely to become the next generation of NIR light sources, has become a hot spot for research nowadays. To cope with the demand for more NIR spectroscopy applications, more efficient NIR phosphors need to be developed. Here, by screening the subject with a smaller band gap and by screening the suitable ion electronegativity of the lattice position where the Cr3+ is located, and then through the energy transfer, a series of Gd3Zn2GaGe2O12:xCr3+, yYb3+ (GZGG:Cr3+/Yb3+) NIR broadband garnet phosphors were found for the first time. By controlling the energy transfer process, the internal quantum yield (IQY) (54.9%), external quantum yield (EQY) (24.65%), bandwidth (260 nm), and thermal stability (60% at 150 °C) of NIR emission were substantially improved. The obtained phosphors are packaged with blue light chips into pc-LED, which can be applied in different fields such as vascular visualization and night vision.

Far-red-emitting Mn4+-doped Ca2GdZr2Al3O12 phosphors for growing indoor plants

Pc-LEDs (phosphor-converted light-emitting diodes) are a relatively new generation of light sources frequently used for room lighting, backlighting, and plant development on account of numerous advantages, such as compactness, good stability, low energy consumption, and environmental friendliness. However, the absence of red-light emission limits the practical application of pc-LEDs. For example, pc-LEDs have a high correlated color temperature and a low rendering index. Here, a group of far-red emitting Mn4+-doped Ca2GdZr2Al3O12 (CGZA: Mn4+) phosphors was effectively synthesized using a solid-state reaction technique at 1450 °C. The phase purity, morphology, and fluorescence properties of prepared phosphors were investigated using XRD, SEM, PL/PLE, and fluorescence decay analysis, respectively. Under a 344-nm excitation, CGZA: Mn4+ emitted high-purity far-red light with a peak at approximately 702 nm. Phosphor quenching was observed once the Mn4+ concentration reached 0.3 mol%. The concentration quenching mechanism of Mn4+in the CGZA matrix resulted from electric dipole-dipole interactions. An important result was that the PL band was well superposed on the absorption bands of phytochromes Pr and Pfr. The PL intensity was 50% of the initial value at 373 K. These experimental results demonstrated the board application potential of the prepared phosphors for plant breeding.

Special Section Guest Editorial: Next Generation Light Source, Materials, and Metrology/Inspection Equipment

The <i>Journal of Micro/Nanopatterning, Materials, and Metrology</i> (JM3) publishes peer-reviewed papers on the core enabling technologies that address the patterning needs of the electronics industry.

Broadband NIR-emitting Te cluster-doped glass for smart light source towards night-vision and NIR spectroscopy applications

Broadband near-infrared (NIR)-emitting materials are crucial components of the next generation of smart NIR light sources based on blue light-emitting diodes (LEDs). Here, we report a Te cluster-doped borate glass, which exhibits ultra-broadband emission around 980 nm with a full-width at half-maximum (FWHM) of 306 nm under blue light excitation. We propose adjustments of glass chemistry and processing condition as a means for topo-chemical tailoring of the NIR photoemission characteristics in such materials. Through implementing strongly reducing conditions during glass melting, Te clusters with broad NIR photoluminescence can be generated and stabilized once the melt is vitrified to the glassy state. Tunability of the NIR emission peak over the wavelength range of 904 to 1026 nm is possible in this way, allowing for fine adjustments of spectral properties relative to the stretching vibrations of common chemical bonds, for example, in water, proteins, and fats. This potentially enables high sensitivity in NIR spectroscopy. We further demonstrate potential application of glass-converted LEDs in night vision.

Iron lamination and interlaminar insulation for high-frequency pulsed magnets.

In high-frequency pulsed magnets, such as kickers in particle accelerators, it is essential to reduce eddy currents that could be induced in the magnet core during excitation not to distort and attenuate the magnetic field pulse. A novel iron lamination scheme with additional interlaminar insulation is proposed for the magnet core of such pulsed magnets. A laminated steel sheet core is formed by alternately stacking thin steel and insulation sheets. For application to matched kicker magnets for accelerators, test magnets with the new and conventional iron lamination were designed, assembled, and extensively evaluated. The pulsed magnetic field waveforms of two test magnets with the new lamination successfully matched to below 0.1% over the entire pulse duration, which was significantly better than those with the conventional lamination. Among the applications of the developed high-frequency pulsed magnets, beam injection kickers for the coming next generation light sources and future colliders, where suppression of the transient stored-beam oscillation during beam injection is crucial, are considered to be promising.

Enhancing Thermal Stability of Laser-Driven Phosphor Converter by Utilizing Copper Powder Sintering Framework/Paraffin

Laser-driven white light illumination is considered as the next generation of high brightness white light source. The most common way to achieve laser-based white light is using a blue laser to excite phosphor/ silicone converter (reference converter). However, the relatively low thermal conductivity of phosphor limits most of the heat to its surface and cannot be dissipated effectively. In this work, a converter with copper sintering powder framework/paraffin (CPSF/P) embedded into the phosphor/silicone is proposed. As an internal heat transfer channel, copper powder sintering framework (CPSF) transfers heat to paraffin coated in porous skeleton, and then paraffin absorbs the generated heat through solid–liquid phase transition, which effectively dissipates the heat concentrated on the phosphor surface and improves its thermal stability. Under high-power laser excitation of 7.74 W, the surface temperature of the reference converter is up to 660 °C, while the maximum temperature of the CPSF/P converter is only 139 °C, which is reduced by 521 °C (78.9%). The results show that the proposed CPSF/P converter can withstand higher excitation power and show better thermal stability than the reference converter, which is helpful to obtain higher color stability. This provides an efficient heat dissipation scheme for high-power laser-driven lighting.

A scalable light-diffusing photochemical reactor for continuous processing of photoredox reactions

In the last decade, photoredox catalysis has received a remarkable attention for its unique reactivity for synthesizing fine chemicals and active pharmaceutical ingredients. However, the coupled photon and heat generation of light sources create challenges for achieving a proper heat management of photochemical reactors, thus inhibiting large-scale applications. In this work, we proposed a strategy to decouple photon and heat using light guide plate (LGP) technology, and accordingly designed a continuous light-diffusing photochemical reactor (LDPR). In LDPR, the photons emitted from the edge light source are distributed uniformly on the top surface of LGP where the fluidic channels are located. This configuration isolates heat generation location from where photons are utilized, benefiting the heat management of the reaction zone. The photon flux of LDPR was characterized with a chemical actinometry method. Two important photocatalytic bond-forming reactions, α-amino arylation and C(sp2)–N cross-coupling, were demonstrated in LDPR with high efficiency. To show the scalability of LDPR, we increased the throughput via a hybrid strategy of scaling-up and scaling-out, achieving a continuous 10-gram synthesis of an α-amino arylation product.

Generation of high-order single harmonics by using chirp waveform control

We present a method to generate the high-order single harmonics on the harmonic spectra. It is shown that by properly choosing the chirp parameters, the laser intensities and the pulse durations of two-color chirped pulse, the high-order single and even double harmonics can be enhanced and generated on the harmonic spectra. The reason behind the single and double harmonic generation is because the nonlinear electron acceleration in the chirp region caused by the reversed sub-peak structure. The results are beneficial to the generation of single and double harmonic light sources.

Externally Driven Nonlinear Time-Variant Metasurfaces

Resonant photonic nanostructures exhibiting enhanced nonlinear responses and efficient frequency conversion are an emergent platform in nonlinear optics. High-index semiconductor metasurfaces with rapidly tuned high-Q resonances enable a novel class of time-variant metasurfaces, which expands the toolbox of color management at the nanoscale. Here, we report on the dynamic control of the nonlinear optical response in time-variant semiconductor metasurfaces supporting high-quality factor resonances in the near-infrared spectral range. Pump-probe measurements of germanium metasurfaces at negative pump-probe time delays reveals frequency conversion in the fundamental beam and a blue-shift of 10~nm (3.05$\omega$) and 40% broadening in the third harmonic signal due to the photoinduced time-variant refractive index. A time-dependent coupled-mode theory, in excellent agreement with the experimental data, validated the time-variant nature of the system. Our findings expand the scope of time-variant metasurfaces and may serve as base for the next generation of nanoscale pulse shapers, optical switches and light sources.

Stacked metasurfaces for enhancing the emission and extraction rate of single nitrogen-vacancy centers in nanodiamond

Dielectric metasurfaces with unique possibilities of manipulating light–matter interaction lead to new insights in exploring spontaneous emission control using single quantum emitters. Here, we study the stacked metasurfaces in one- (1D) and two-dimensions (2D) to enhance the emission rate of a single quantum emitter using the associated optical resonances. The 1D structures with stacked bilayers are investigated to exhibit Tamm plasmon resonance optimized at the zero phonon line (ZPL) of the negative nitrogen-vacancy (NV−) center. The 2D stacked metasurface comprising of two-slots silicon nano-disks is studied for the Kerker condition at ZPL wavelength. The far-field radiation plots for the 1D and 2D stacked metasurfaces show an increased extraction efficiency rate for the NV− center at ZPL wavelength that reciprocates the localized electric field intensity. The modified local density of optical states results in large Purcell enhancement of 3.8 times and 25 times for the single NV− center integrated with 1D and 2D stacked metasurface, respectively. These results have implications in exploring stacked metasurfaces for applications such as single photon generation and CMOS compatible light sources for on-demand chip integration.

Relationship between anti-blue hazard mode and color gamut of display devices

Display devices based on new generation of light source have become the mainstream of the market due to the advantages of large color gamut, high brightness, and high resolution. Blue light, as one of the three primary colors, is an indispensable part of the display system. Its parameters, such as wavelength, spectral width, brightness affect the color gamut of the display system from different aspects. Strong blue light can damage the retinal cells of the human eye and affect the biological rhythm. Therefore, it is needed to consider how to reduce the blue light hazard when designing the display system. Display devices, represented by mobile phones and TV are an important part for human-computer interaction. In order to reduce the blue light hazard, anti-blue hazard mode is usually used and this mode will affect the color gamut of display device. To measure the color gamut and blue light hazards in a display system with the blue light protection mode is necessary. We propose a theory of measuring the characteristic points of display devices to obtain the stereoscopic color gamut. Several mainstream mobile phones currently on the market are used as experimental samples to measure the stereoscopic color gamut and blue light hazard value. Based on the results, we propose the measurement standard of the conversion ratio between the color gamut and the blue light hazard to evaluate the quality of the anti-blue hazard mode.

Concept of circular-linear energy recovery accelerator to probe the energy frontier

Energy-frontier accelerators provide powerful tools performing high precision measurements confirming the fundamentals of the physics and broadening new research horizons. Such machines are either driven by circular or linear accelerators. The circular machines, having the centre-of-mass (CM) energy values reaching 200 GeV (for leptons) and above, experience beam energy loss and quality dilution, for example, due to synchrotron radiation, limiting the overall CM energy achievable and requiring a constant energy top-up to compensate the loss and the beam quality dilution. Linear colliders overcome these limitations, while the finite capabilities of generating high average current beams limits the luminosity. This is partially compensated by the quality of the colliding beams. In this work, we suggest a novel design of circular-linear accelerator based on the merging of the “non-emitting”, low-energy storage rings and energy recovery linear accelerators. We suggest using the recently considered dual-axis asymmetric cavities to enable the operation of such a system, and in particular the energy recovery from spent, high-intensity beams. The machine considered, under the scope of the SNOWMASS-2021 initiative, can be potentially used to reach ultimate energy frontiers in high-energy physics as well as to drive next generation light sources. The merging of circular and linear systems, and applications of dual axes cavities, should allow the maintaining of high beam quality, high luminosity, and high energy efficiency, while offering a flexible energy management and opening clear opportunity for reducing the running cost. We note that the numbers shown in the paper are for illustration purpose and can be improved further.

QED effects on high-order harmonic generation from ultraintense laser-irradiated solid-plasmas

High-order harmonic generation (HHG) from relativistically intense laser irradiation of solid-density plasmas provides novel coherent light sources in the extreme-ultraviolet (XUV) to x-ray spectral region with attosecond duration and high intensity even toward the Schwinger limit. However, whether the HHG process and mechanism are effective at extremely high laser intensities in the QED-plasma regime remains unclear, since QED processes, such as discrete synchrotron radiation, quantum radiation reaction, and pair creation, would change the energy partition and particle dynamics. In this work, through particle-in-cell simulations, we numerically demonstrate that the HHG process with the relativistically oscillating mirror mechanism can be scaled to an ultrahigh intensity level of 1024 W/cm2. The high harmonic spectrum, attosecond pulses, and conversion efficiency are not significantly affected by the QED processes. This result is of great benefit to the generation of coherent XUV and x-ray light sources with higher intensity, higher cutoff frequency, and shorter duration.

Self-compression of a high-intensity laser pulse in a double-ionizing gas

The self-compression and spatiotemporal evolution of a Gaussian laser pulse propagating in a double-ionized helium gas are investigated. The numerical model is formulated by solving the nonlinear Schrödinger equation using the paraxial like approach. The beam width parameter and pulse width parameter are estimated to investigate the laser pulse advancement in a tunnel ionizing gas. Transverse focusing and longitudinal compression are examined by characterizing the beam spot size in space and time, incorporating the gas ionization processes, relativistic mass variation, and ponderomotive effects. The results show that the inclusion of laser-induced double ionization of helium gas modifies the plasma density, which significantly affects the laser pulse evolution. For intense laser pulse, relativistic-ponderomotive nonlinearity enhances the pulse compression and consequently the self-focusing of the laser pulse. The compression mechanism and the localization of the pulse intensity both are boosted by the modified electron density via a dielectric function. At a helium gas pressure of 1.4 bar, we observed that 100 fs long laser pulse with intensity I0=8.5×1016 W/cm2 is compressed to 20 fs and the initial laser spot size 10 μm focused to 2 μm. These results promise to be a method for the generation of table-top light sources for ultrafast high-field physics and advanced optics.

Ternary type BaY2ZnO5: Eu3+ deep-red phosphor for possible latent fingerprint, security ink and WLED applications

Pc-WLEDs are considered to play a spectacular role in future generation light sources in view of their outstanding energy efficiency. In this regard, Eu 3+ activated BaY 2 ZnO 5 phosphor was prepared and investigated by XRD, PL and SEM analyses. Rietveld refinement analysis was carried out to confirm the structure of the synthesized phosphor. The prepared phosphor shows an intense red emission around 627 nm under excitation by near UV light. The 5 D 0 - 7 F 2 transition intensity of the prepared phosphor is three times higher compared to the commercial (Y,Gd)BO 3 :Eu 3+ red phosphor. The CIE colour coordinates of BaY 2 ZnO 5 :Eu 3+ (9mol%) phosphor corresponds to be (0.6169, 0.3742) and it has a high 97.9 % colour purity. The obtained results reveal the utility of BaY 2 ZnO 5 :Eu 3+ phosphor as an efficient red component in WLEDs, anti-counterfeiting and fingerprint detection applications. • Eu 3+ activated BaY 2 ZnO 5 deep-red emitting phosphor was synthesized at low temperature for possible applications in Latent fingerprint, Security ink & WLEDs. • The prepared phosphor absorbs near-UV and the intense emission lies in the deep-red region. • The BaY 2 ZnO 5 :Eu 3+ red phosphor shows three fold higher intensity ( 5 D 0 - 7 F 2 ) and high colour purity compared to the commercial (Y,Gd)BO 3 :Eu 3+ red phosphor.

Observation of quasi-monochromatic resonant Cherenkov diffraction radiation

The first observation and investigation of a new mechanism of resonant Cherenkov diffraction radiation appearing when relativistic 6 MeV electrons move alongside a periodically shaped Teflon target have been presented and analysed. Numerical simulations performed using computer code KARAT are in good agreement with the experimental results. This new mechanism is a promising technique for generation and monochromatisation of THz and sub-THz radiation beams that could be integrated into any short bunch linear accelerator facility including 4th generation light sources providing new opportunities for user community.

New Spectral Range Generations from Laser-plasma Interaction

High-intensity laser-produced plasma has been extensively investigated in many studies. In this demonstration, a new spectral range was observed in the resulted spectra from the laser-plasma interaction, which opens up new discussions for new light source generation. Moreover, the characterizations of plasma have been improved through the interaction process of laser-plasma. Three types of laser were incorporated in the measurements, continuous-wave CW He-Ne laser, CW diode green laser, pulse Nd: YAG laser. As the plasma system, DC glow discharge plasma under the vacuum chamber was considered in this research. The plasma spectral peaks were evaluated, where they refer to Nitrogen gas. The results indicated that the plasma intensity increased from several thousands to several tens of thousands through the process of interaction of the Nd: YAG laser with the plasma. This increase in the intensity of the plasma as laser intensity increased occurs regardless of laser wavelength involved in the interaction or not. According to laser-plasma interaction, the so-called full width at half maximum FWHM of the highest peak in the plasma spectrum was broadened from 1.43 to 2.73. Considering the equation of plasma density computing, the plasma density was increased from 1.07× 1018 to 2.05× 1018 cm-3 with increasing FWHM. As a result of the interaction, the electron temperature of plasma was increased from 0.176 to 0.782 eV. It was also noticed that the position of the highest peak in the plasma spectrum depends on the interacted laser wavelength.

Simultaneous correction of high order geometrical driving terms with octupoles in synchrotron light sources

As the next generation of light sources is pushing toward high-brightness storage rings with ultralow emittance, the control of the beam nonlinear dynamics becomes increasingly challenging. Nonlinear perturbations, arising from sextupole cross talks, set the limit to the achievable dynamic performance of the machine. Octupoles can be an efficient mean to tackle the remaining resonant driving terms generated to the second order by the lattice sextupoles. However, they have been used sparingly in light sources because of a lack of control on higher order effects. In this paper, we discuss the optimal positioning of octupoles, with respect to the sextupoles present in the lattice, for a local and simultaneous compensation of all fourth order on-momentum phase and amplitude dependent driving terms, using only three families of octupoles. In addition, higher order geometrical terms are also minimized, including among others, second-order tune shift with amplitude. This study is a continuation of past research made on the optimal use of octupoles for the operation of future light sources. The correction method was built on observations made on a simple model, then applied to a realistic low-emittance lattice, designed in the framework of the upgrade of the National Synchrotron Light Source II, to demonstrate its potential.