Stable Light Source Research Articles

Exploration of the polarization angle variability of the Crab Nebula with POLARBEAR and its application to the search for axionlike particles

The Crab Nebula, also known as Tau A, is a polarized astronomical source at millimeter wavelengths. It has been used as a stable light source for polarization angle calibration in millimeter-wave astronomy. However, it is known that its intensity and polarization vary as a function of time at a variety of wavelengths. Thus, it is of interest to verify the stability of the millimeter-wave polarization. If detected, polarization variability may be used to better understand the dynamics of Tau A, and for understanding the validity of Tau A as a calibrator. One intriguing application of such observation is to use it for the search of axionlike particles (ALPs). Ultralight ALPs couple to photons through a Chern-Simons term, and induce a temporal oscillation in the polarization angle of linearly polarized sources. After assessing a number of systematic errors and testing for internal consistency, we evaluate the variability of the polarization angle of the Crab Nebula using 2015 and 2016 observations with the 150 GHz P instrument. We place a median 95% upper bound of polarization oscillation amplitude A<0.065° over the oscillation frequencies from 0.75 year−1 to 0.66 hour−1. Assuming that no sources other than ALP are causing Tau A’s polarization angle variation, that the ALP constitutes all the dark matter, and that the ALP field is a stochastic Gaussian field, this bound translates into a median 95% upper bound of ALP-photon coupling gaγγ<2.16×10−12 GeV−1×(ma/10−21 eV) in the mass range from 9.9×10−23 eV to 7.7×10−19 eV. This demonstrates that this type of analysis using bright polarized sources is as competitive as those using the polarization of cosmic microwave background in constraining ALPs. Published by the American Physical Society 2024

Design and characterization of a novel turbidity sensor based on quadrature demodulation

Abstract Turbidity is regarded as a comprehensive indicator in water quality monitoring, and the turbidity sensor deployed in the water supply network can record the dynamic changes of water quality in time. However, the weak photoelectric signal from the photodetector contains a quantity of noise. In order to improve signal-to-noise ratio (SNR), a novel on-line turbidity sensor based on quadrature demodulation principle has been proposed in this paper. A near-infrared light-emitting diode (LED) with a wavelength of 860 nm was selected as a stable monochromatic light source, and a photodiode (PD) with an angle of 90° to the incident light from the LED was selected as the photodetector. Using signal modulation and demodulation technology, the weak photoelectric signal extraction, conversion, amplification and output of the turbidity sensor were realized through the effective integration. A corresponding test apparatus of the turbidity sensor was established and experimental results showed that within a 0~5 NTU measurement range, the turbidity sensor had good linearity and stability, the relative measurement error was within ±1% and the limit of detection could reach as low as 0.0049 NTU. The developed turbidity sensor has good detection performance and can meet the needs of low turbidity detection of drinking water.

Characterizing 1550 nm optical components down to 8 K

Thermal noise sources are relevant for future gravitational wave detectors due to the foreseen increase in sensitivity, especially at frequencies below ▪. As most thermal noise sources scale with the square root of the temperature, cooling critical optical components and their suspension system is essential. This also requires a much wider range of temperature compatibility from all technology deployed in the last suspension stages, including displacement and inertial sensors. We demonstrate and characterize a setup for stable light sources and light intensity sensing for temperatures from 300 to ▪. Commercial collimators and fibers were tested to use light from stabilized laser sources in the cryogenic environment. We also investigated multiple semiconductor compositions of photodiodes and identified a solution with high and stable responsivity at ▪.

Super broadband light source: a promising master oscillator source for high brightness and high-power fiber amplifiers.

Stimulated Raman scattering (SRS) and transverse mode instability (TMI) effects are crucial limitation factors for further power scaling of high-power fiber amplifiers with near-diffraction-limited beam quality. It is an important research direction to carry out laser system optimization from the perspective of seed construction. In this work, we experimentally investigated the impact of utilizing different seed lasers on the SRS and TMI characteristics in high power ytterbium-doped fiber amplifiers. Both the phase modulated single frequency fiber laser (PMSFL), fiber oscillator laser (FOL), and superfluorescent fiber source (SFS) as a typical type of temporally stable broadband light source (SBLS) are employed as seed lasers. The experimental results indicated that the SRS intensity in the fiber amplifier is influenced by the properties of the seed laser source. Notably, the SRS threshold of the SBLS could be comparable to that of a low-noise PMSFL source. There is a significant increase in TMI threshold when employing SBLS as a seed laser in high-power fiber amplifiers, which is 3.86times that of the injected seed laser with a 3dB narrow linewidth of 0.74nm. Considering the combined threshold characteristics of SRS and TMI, it can be found that SBLS is a promising master oscillator source for high brightness and high-power fiber amplifiers. Our work could provide a good reference for the selection of a master oscillator source, and we believe that it is an important direction to go beyond the power limitation of high-power fiber lasers by constructing a light source with broader spectral linewidth and temporal stability.

Photoluminescence measurement of ruby excited by duty ratio-controlled pulse light-emitting diodes (LED) light source.

Photoluminescence (PL) spectra from ruby were obtained using a highly stable LED light source, employing pulse width modulation technique for excitation. The temporal variation in PL intensity caused by the increasing temperature of the LED used for excitation can be mitigated by adjusting the duty ratio (%) of the pulsed LED light to below 10% for cooling the LED. Stable PL spectra measurements were achieved with a duty ratio of less than 10% using a duty ratio-controlled pulsed LED light source, as temperature fluctuations in LED light intensity are minimized at duty ratios less than 10%. Furthermore, fluctuations in the measured PL intensity were diminished by setting the frequency of the pulsed LED light source to greater than 1kHz. This method enables more reliable, cost-effective, and stable PL measurements for material characterization in semiconductors, photonics, and nanotechnology.

Household alternating current electricity plug-and-play quantum-dot light-emitting diodes

As an intrinsically direct current device, quantum-dot LED cannot be directly driven by household alternating current electricity. Thus, a driver circuit is required, which increases the complexity and cost. Here, by using a transparent and conductive indium-zinc-oxide as an intermediate electrode, we develop a tandem quantum-dot LED that can be operated at both negative and positive alternating current cycles with an external quantum efficiency of 20.09% and 21.15%, respectively. Furthermore, by connecting multiple tandem devices in series, the panel can be directly driven by household alternating current electricity without the need for complicated back-end circuits. Under 220 V/50 Hz driving, the red plug-and-play panel demonstrates a power efficiency of 15.70 lm W−1 and a tunable brightness of up to 25,834 cd m−2. The developed plug-and-play quantum-dot LED panel could enable the production of cost-effective, compact, efficient, and stable solid-state light sources that can be directly powered by household alternating current electricity.

High-average-power single-frequency pulse optical parametric oscillator based on pulse-integrated seed-injection automatic locking.

Near-infrared nanosecond (ns) single-longitudinal-mode (SLM) pulse light generated from an optical parametric oscillator (OPO) is an important source in nonlinear optics and high-precision spectral analysis. In this Letter, a stable SLM near-infrared ns pulse light source generated from the OPO is presented, which is achieved by developing a seed-injection automatic locking technique based on a pulse-integrated photodetector (PIPD). Depending on the PIPD, the peak power of the pulse light detected by the photodiode is converted to the average power by integrating several pulses. As a result, the detector saturation is thoroughly eliminated, and the interference signal including the resonance point between seed and pulse lights can easily be attained by scanning the resonator length. On this basis, a microcontroller unit (MCU) is employed to realize automatic locking by looking for the minimum value of the interference signal. Finally, a SLM 824 nm pulse light source with an output power of 20.5 W and a linewidth of 51.42 MHz is obtained. The presented method can pave the way to implement a low-cost and compact high-average-power SLM pulse OPO.

Nighttime visibility classification based on stable light sources

Nighttime visibility classification based on stable light sources

Highly efficient electroluminescence from SnO2 nanocrystals and Er3+ co-doped silica thin film via introducing Ca2.

Efficient and stable near-infrared silicon-based light source is a challenge for future optoelectronic integration and interconnection. In this paper, alkaline earth metal Ca2+ doped SiO2-SnO2: Er3+ films were prepared by sol-gel method. The oxygen vacancies introduced by the doped Ca2+ significantly increase the near-infrared luminescence intensity of Er3+ ions. It was found that the doping concentration of Sn precursors not only modulate the crystallinity of SnO2 nanocrystals but also enhance the luminescence performance of Er3+ ions. The stable electroluminescent devices based on SiO2-SnO2: Er3+/Ca2+ films exhibit the power efficiency as high as 1.04×10-2 with the external quantum efficiency exceeding 10%.

Effects of a variable linewidth laser and variable linewidth shape laser on coherent FMCW LiDAR

To investigate the tolerance of laser linewidth, a stable and variable light source is essential. This study proposes a novel method for generating a variable linewidth and variable light source using a lithium niobite phase modulator, achieved through the application of white Gaussian noise and random walk noise with a limited wall. The proposed approach was thoroughly examined through equations, simulations, and experiments. Further, a practical application was demonstrated while investigating the effects of variable linewidth and shape on FMCW LiDAR performance. The results highlight the importance of optimizing the light source for LiDAR applications to ensure the maximum accuracy and resolution.

Generation of 13.9-mJ Terahertz Radiation from Lithium Niobate Materials.

Extremely strong-field terahertz (THz) radiation in free space has compelling applications in nonequilibrium condensed matter state regulation, all-optical THz electron acceleration and manipulation, THz biological effects, etc. However, these practical applications are constrained by the absence of high-intensity, high-efficiency, high-beam-quality, and stable solid-state THz light sources. Here, the generation of single-cycle 13.9-mJ extreme THz pulses from cryogenically cooled lithium niobate crystals and a 1.2% energy conversion efficiency from 800nm to THz are demonstrated experimentally using the tilted pulse-front technique driven by a home-built 30-fs, 1.2-Joule Ti:sapphire laser amplifier. The focused peak electric field strength is estimated to be 7.5MVcm-1 . A record of 1.1-mJ THz single-pulse energy at a 450 mJ pump at room temperature is produced and observed that the self-phase modulation of the optical pump can induce THz saturation behavior from the crystals in the substantially nonlinear pump regime. This study lays the foundation for the generation of sub-Joule THz radiation from lithium niobate crystals and will inspire more innovations in extreme THz science and applications.

Beat-frequency-resolved two-dimensional electronic spectroscopy: disentangling vibrational coherences in artificial fluorescent proteins with sub-10-fs visible laser pulses.

We perform a beat-frequency-resolved analysis for two-dimensional electronic spectroscopy using a high-speed and stable 2D electronic spectrometer and few-cycle visible laser pulses to disentangle the vibrational coherences in an artificial fluorescent protein. We develop a highly stable ultrashort light source that generates 5.3-fs visible pulses with a pulse energy of 4.7 µJ at a repetition rate of 10 kHz using multi-plate pulse compression and laser filamentation in a gas cell. The above-5.3-fs laser pulses together with a high-speed multichannel detector enable us to measure a series of 2D electronic spectra, which are resolved in terms of beat frequency related to vibrational coherence. We successfully extract the discrete vibrational peaks behind the inhomogeneous broadening in the absorption spectra and the vibrational quantum beats of the excited electronic state behind the strong incoherent population background in the typical 2D electronic spectra.

Resonant electro-optic phase modulator and photodetector for stabilizing laser frequency and quantum optics

Photoelectric functional device with specific optical, electrical and photoelectric conversion effects is one of the most important resources of modern information science and technology. Electro-optic modulator and photodetector are very important photoelectric functional devices, which are key devices in the fields of frequency locking, feedback control, photoelectric information conversion, optical communication, photoelectric information modulation, etc., and play an irreplaceable role in frequency stabilization locking technology of PDH (Pound-Drever-Hall, simply referred to as PDH). The PDH technology is widely used in researches of large scientific devices, quantum optics, optical communication and other fields. Using electro-optical phase modulator to carry out laser phase modulation is the primary process to realize frequency stabilization locking of standard PDH. Photoelectric detection can implement the photoelectric conversion of the carried weak modulation signal and spectral peak signal into electrical signal, and then feedback control through proportional integral and differential circuits, so as to achieve stable locking and frequency stabilization. The resonant electro-optical phase modulation (RPM) with high modulation depth, low power consumption and low half-wave voltage and microwatt resonant photoelectric detection (RPD) functional device with high signal-to-noise (SNR) ratio are invented to meet the demand for extraction and detection of extremely weak signals. The resonant circuit is composed of the single-end wedge-angle lithium niobate crystal, low noise photodiode and low-loss and high-Q electronic components. Low power consumption, high modulation depth electro-optic modulation, and high gain photoelectric detection are realized by the principle of resonant enhancement. When the optimal modulation frequency point is 10 MHz, the bandwidth of RPM is 225 kHz with <i>Q</i> of 44.4, when the modulation depth is 1.435, the RPM requires RF drive voltage of RPM to be 4 V. When the optimal modulation frequency point is 20 MHz, the bandwidth of RPM is 460 kHz with <i>Q</i> of 43.5, the required RF drive voltage of RPM is 6.5 V when the modulation depth is 1.435. The optimal detection frequency point of the self-invent RPD is 20.00 MHz, with a bandwidth of 1 MHz, Q of 20, the gain of 80 dB at 100 μW. With the home-made RPM and RPD in the extraction loop for extremely weak signal, the SNR of error signal is as high as 5.088 at 10 μW, 34.933 at 50 μW and 58.7 at 100 μW. Such a loop improves the performance and stability of the entire feedback control loop by optimizing parameters of proportional integral differential, which provides key devices and technological approaches for preparing a highly stable quantum light source and ultra-stable laser.

Flexible colloidal quantum dot lasers enabled by self-assembly

Colloidal quantum dot (CQD) lasers show promising applications in flexible optoelectronic devices, due to their tunable emission wavelength, narrow spectrum bandwidth and high power intensity. However, fabricating a flexible CQD laser is challenging because of the difficulties in fabricating optical cavities on flexible substrates using traditional microfabrication technologies. Herein, we propose a one-step self-assembly approach to fabricate flexible CQD supraparticle lasers. The whole assembly approach is processed in a liquid environment without surfactants, and the formed spherical CQD supraparticles are featured with smooth surfaces, serving as high-quality-factor whispering-gallery mode cavities to support laser oscillation. A low lasing threshold of 54 µJ/cm2 is observed while exciting a CQD supraparticle with pulsed femtosecond lasers. The calculated cavity quality factor of 963 for CQD supraparticle lasers is twofold larger than that of CQD lasers assembled with surfactants. Moreover, the CQD supraparticles can serve as free-standing lasers, which allows them to be deposited on flexible substrates such as paper and cloth. Furthermore, our CQD lasers show high stability, after being continuously photoexcited above the threshold for 400 min, their lasing intensity remains at 85.7% of the initial value. As bright, free-standing and long-term stable light sources, the assembled CQD lasers proposed in this work show potential applications in wearable devices and medical diagnosis.

Ultrafast light emission at telecom wavelengths from a wafer-scale monolayer graphene enabled by Fabry-Perot interferences.

Ultrafast light emission from monolayer graphene shows attractive potential for developing integrated light sources for next-generation graphene-based electronic-photonic integrated circuits. In particular, graphene light sources operating at the telecom wavelengths are highly desired for the implementation of graphene-based ultrahigh-speed optical communication. Currently, most of the studies on ultrafast light emission from graphene have been performed in the visible spectrum, while studies on ultrafast emission at the telecom wavelengths remain scarce. Here, we present experimental observations of strong ultrafast thermal emission at telecom wavelengths from wafer-scale monolayer graphene. Our results show that the emission spectra can be strongly modified by the presence of the cavity effect to produce an enhanced emission at telecom wavelengths. We corroborate our experimental results with simulations and show that by designing a suitable cavity thickness, one can easily tune the emission profile from visible to telecom wavelength regardless of the pump power. In addition, we demonstrate that the insertion of a monolayer of hexagonal boron nitride between graphene and the substrate helps improve the thermal stability of graphene, thereby providing more than five times enhancement of the ultrafast thermal emission. Our results provide a potential solution for stable on-chip nanoscale light sources with ultrahigh speed modulation.

High-Quality White Laser Diode Fabricated by Laser-Driven Tricolor PiG Film-on-Sapphire

Phosphor-converted white laser diode (WLD) is considered as a promising light source in next-generation high-brightness lighting. However, the WLD suffers from low optical quality in luminous efficacy and color rendering. In this work, we fabricated a high-quality WLD by a blue laser-driven a tricolor phosphor-in-glass (PiG) film-on-sapphire (PIGS). The tricolor PiGS was prepared by sintering a green/yellow/red phosphor glass film on a sapphire substrate. The optical quality of tricolor PiGS-WLDs were optimized by adjusting the phosphor ratio. At the phosphor ratio of 9:6:1, the PiGS-WLD achieves high optical quality with a luminous flux of 362.1 lm, a color rendering index (CRI) of 80.3, and a correlated color temperature (CCT) of 4590 K at a laser power of 2.4 W. The PiGS-WLD has the highest luminous efficacy of 154.5 lm/W at 3.15 W. Furthermore, the PiGS-WLD displays excellent color stability with small CCT and CRI deviation under various laser powers and continuous excitation. The surface temperature of PiGS-WLD is stable at 104 °C due to the high thermal conductivity of sapphire substrate. Therefore, this study provides a stable and high-quality laser-driven white light source for high-brightness lighting and display.

Ultrahigh stable and high power light sources for the gravitational wave detectors

Ultrahigh stable and high power light sources for the gravitational wave detectors

In vitro glucose concentration measurement by a reusable enzymatic glucose sensor and a highly stable circular heterodyne polarimeter

A reliable glucose concentration measurement system was proposed that consisted of a circular heterodyne polarimeter and a reusable enzymatic sensor. The circular heterodyne polarimeter was constructed using a highly stable circular heterodyne light source and a compact alignment-free apparatus that provided phase stability of less than 1° within 20 min. The reusable enzymatic glucose sensor can be reused more than 100 times and retain 90% of its initial performance under optimum storage conditions within a month. The proposed method can be used to determine glucose concentrations in aqueous solutions and human serum. The optimum resolution of the proposed method was approximately 0.88 mg/dl for the glucose solution and 0.68 mg/dl for the serum-based sample.

Increased detector response in optical overfilled measurements due to gas lens formation by nitrogen flow through the entrance aperture

According to our experimental results, a nitrogen flow used to prevent dust and moisture entering a detector may influence measurements performed with trap detectors in overfilled conditions. A stable light source was measured with a wedged trap detector with 4 mm aperture, and the nitrogen flow rate was varied. The nitrogen flow was found to have the largest effect of up to 0.8% on the responsivity of the detector at around 1.0 l min−1 flow rate. The effect of nitrogen flow can be removed down to 0.02% by an added crossflow which removes the nitrogen out of the optical axis. In another experiment, the effect was removed almost completely by changing the flowing gas from nitrogen to synthetic dry air. We also present measurement results that indicate the responsivity changes with nitrogen to be smaller than 0.05% with underfilled beam geometry, even without the added crossflow. Based on simulations, the nitrogen flow through the detector forms a gradient-index type gas lens in front of the detector increasing the effective aperture area and thus the responsivity. In the underfilled measurement geometry there is no light close to the aperture edge which could be refracted inside the detector. Finally, we consider methods to ensure that the responsivity changes due to the gas flow remain below 0.05% in overfilled measurement geometry, without compromising the cleanliness of the detector with too small gas flow rate.

On the Mechanical and Electrical Properties of the Composite Structure of PVC Membrane and Thin-Film Battery under Biaxial Tension

This paper aims to study the mechanical and electrical properties of the composite structure of PVC film and film cell under biaxial tension. The saddle PVC membrane structure with thin-film battery was obtained by biaxial tensile tests carried out on the composite structure along the fiber direction and at an angle of 45 degrees to the fiber, respectively. The deformation of the film cell and PVC membrane materials was tested using digital image technology, and the voltage of the film cell was tested using a multimeter. The results showed that the tensile strain occurred in both membrane batteries and PVC membrane at different loading levels, and the former was always less than the latter. At a tensile load with the ultimate load ratio of 60%, it was only at the film cell’s outer edge that the stripping occurred. Under the illumination of a stable light source, the film cell voltage decreased gradually with the increasing tensile load. No more than 10% of the cell voltage drop occurred when the membrane material, the principal tensile strain of the cell, and the cell’s expansion area ratio were less than 3.1%, 2.8%, and 1.03, respectively. The experimental results show that the film cell can be applied to the saddle membrane structure by controlling the appropriate load.