Spontaneous Emission Source Research Articles

21.8 W acetylene-filled hollow-core anti-resonant fiberamplified spontaneous emission source at 3.1 µm.

We report a 20-W-level acetylene-filled nested hollow-core anti-resonant fiber (nested HC-ARF) amplified spontaneous emission (ASE) source at 3.1 µm. A 1535 nm hundred-watt wavelength tunable single-frequency fiber laser with a high signal-to-noise ratio and narrow linewidth is built for pumping acetylene molecules. Simultaneously, a homemade 120 µm core diameter eight-tube nested HC-ARF is used as a gas chamber to obtain high pump laser coupling efficiency. The mid-infrared (mid-IR) ASE source output power of 21.8 W is achieved at 3.1 µm through the low-pressure acetylene gas-filled nested HC-ARF, and the slope efficiency is 25.1%. In addition, the ASE source features an excellent beam quality of Mx 2 = 1.16 and My 2 = 1.13. To the best of our knowledge, for the first time, it is a record output power for such mid-infrared ASE sources while maintaining excellent beam quality. This work provides a new way to achieve high-power mid-infrared emission.

Arbitrary Time Shaping of Broadband Low-Coherence Light Based on Optical Parametric Amplification

Laser–plasma interactions (LPIs) hinder the interaction of high-energy laser pulses with targets. The use of broadband low-coherence light has been proposed to reduce the impact of LPIs. In this study, to improve the time–frequency characteristics of broadband low-coherence optical seeds, we proposed an arbitrary time-shaping technique scheme based on optical parametric amplification (OPA) that differs from traditional arbitrary time shaping. The shaping process and output characteristics were analyzed in detail. The theoretical and experimental results show that an arbitrary time-shaping pulse output with a large time-shaping contrast, fast-rising edge, and wide spectral width can be obtained. The time shaping contrast of the shaped pulse can be >300:1, and the spectral width is ~40 nm. The output time waveform is smoother than in traditional schemes, and the noise-like modulation is approximately 4% (approximately equal to the unshaped initial amplified spontaneous emission source). The arbitrary time-shaping scheme based on OPA provides a viable solution for the temporal waveform shaping of broadband low-coherence light.

A dual-parameter sensing system for temperature and curvature based on Nano-EYDF and in-line cascaded Mach-Zehnder interferometer

Based on the self-developed erbium ytterbium co-doped fiber, a sensing system consisting of an amplified spontaneous emission (ASE) source and an optical fiber sensor is introduced. The spectrum test results and stability of ASE source are given. A dual-parameter sensor for temperature and curvature based on in-line cascaded Mach-Zehnder interferometer (MZI) is demonstrated theoretically and experimentally. The proposed sensor is mainly composed of single-mode fiber (SMF) and Nano-Erbium-Ytterbium co-doped fiber (Nano-EYDF) to form a symmetrical sensing structure. MZI is formed due to the mode field mismatch between EYDF and SMF. The sensor displays different response to temperature and curvature. By demodulating the wavelength shifts of different peaks or dips, the sensitivity coefficient matrix method can be used to measure the temperature and curvature simultaneously. The experimental results show that, in the range of 25 ∼ 100 °C, the maximum temperature sensitivity is 94.70 pm/ °C and in the curvature range of 0 ∼ 1.03 m−1, the maximum curvature sensitivity is −9.48 nm/m−1. And the power output of ASE source is stable, the spectral unevenness is less than 2.5 dB in the range of 1530 ∼ 1580 nm. The sensor has the advantages of good repeatability, high sensitivity and compact structure. It can be used in 3D reconstruction, robot shape detection, human medicine and other fields.

Experimental free-space continuous-variable quantum key distribution with thermal source.

Passive-state-preparation (PSP) continuous-variable quantum key distribution (CVQKD) protocol explores the intrinsic field fluctuations of a thermal source. Compared with traditional Gaussian-modulated coherent-state CVQKD, it does not need active modulations and has promising applications in chip integration and portable free-space quantum key distribution. In this Letter, we propose and experimentally realize a PSP CVQKD scheme with transmitted local oscillator (LO) through fluctuating transmittance free-space channel using an off-the-shelf amplified spontaneous emission source for the first time. By proposing thermal-state polarization multiplexing transmitted LO, synchronized channel transmittance monitoring and fine-grained phase compensation techniques, secure keys within -15 dB transmittance of simulated free-space channel with turbulence are generated, with a final average secure key rate of 1.015 Mbps asymptotically. Equivalent atmospheric turbulence model analysis shows that the free-space PSP CVQKD scheme provides a promising outlook for high-speed and chip-based CVQKD for kilometer-level atmospheric channel networks.

10 Gb/s physical-layer key distribution in fiber using amplified spontaneous emission.

High-speed physical-layer secure key generation and distribution (SKGD) schemes via channel reciprocity are achieved using external electro-optical modulation or random source distribution via additional fiber links. Here, we propose and demonstrate an SKGD scheme using the fluctuation of polarization states from an amplified spontaneous emission (ASE) source, without any external electro-optical modulation or additional fiber link. Experimentally, an error-free key generation rate (KGR) of 10.1 Gb/s is achieved over a 10-km standard single-mode fiber (SSMF), with true randomness originating from ASE. Moreover, the single fiber channel can be shared for SKGD as well as data transmission, allowing the integration of the proposed SKGD with the deployed fiber infrastructure.

1.73 kW CW Amplification ASE Source Based on Yb3+ Ions-Doped All-Fiber System

The all-fiber ASE source is an intriguing tool in the fields of super-fluorescence detection, coherent measurement and spectrum analysis technology. We experimentally demonstrate a continuous all-fiber amplified spontaneous emission (ASE) source based on amaster-oscillator power amplifier (MOPA) system, which aims at achieving high power and frequency stability. The seed source is homemade ASE low power super-fluorescence source with 200 mW. The system employs large-mode-area Yb3+-doped double-clad fiber (LMA-DCF), and the maximum power can reach 1.73 kW at a center wavelength of 1079.36 nm, and can maintain an optical-to-optical conversion efficiency of 79.13%. During 30 min of real-time monitoring, the ASE source system did not generate a nonlinear effect, and power fluctuation was less than 2%.

Broadband, Continuous-Wave, Mid-Infrared Generation Based on TFBG Spectral Modulation

We demonstrated a tilted fiber Bragg grating (TFBG)-based modulated amplified spontaneous emission (ASE) source, followed by the broadband, continuous-wave (CW) mid-infrared laser generated by intracavity difference-frequency generation (DFG). By flattening the spectrum of the ASE source during its power amplification and injecting another 1018 nm fiber laser in the optical parametric oscillation(OPO) cavity, nonlinear frequency conversion was achieved in the nonlinear crystal. By tuning the polarization period of the crystal, a three-peaked mid-infrared laser with a full width at half maximum (FWHM) of 130 nm and a four-peaked mid-infrared laser with an FWHM of 180 nm was generated.

Open-Path Ghost Spectroscopy Based on Hadamard Modulation

In order to achieve spectral detection in free space, an open-path ghost spectroscopy (GS) based on complementary Hadamard modulation is proposed. In the proposed system, a programmable spectral filter is used to modulate a series of Hadamard patterns to a broadband signal provided by an amplified spontaneous emission (ASE) source, and the spectrum-under-test is recovered by cross correlation between the power measured by an optical power meter and the Hadamard patterns. Both the simulation and experiment are carried out, and the highest spectral resolution up to 0.126 nm is achieved. Furthermore, the detection performance of the GS in a designed strong turbulence path is also demonstrated, which shows that the proposed GS is a promising solution to recover the optical spectrum in the condition of weak light and strong turbulence in the open path.

1030 nm All-Fiber Closed-Loop Fiber Optic Gyroscope with High Sensitivity

Angle random walk (ARW) is a critical noise component of a typical gyroscope alongside with bias instability noise. ARW has dominant effects especially in short-term accuracy. The measurement uncertainty degrades with the deterioration in ARW resulting in the lowered overall gyroscope accuracy. Many inertial navigation applications such as satellite control and gyro-compassing require low ARW. For an interferometric fiber optic gyroscope, lowest detectable rotation is proportional to scale factor of sensor and inversely proportional to optical bandwidth of light source used in the gyroscope. In this study, using a novel pump laser control closed-loop method, gyroscope performance is able to significantly enhance including signal-to-noise ratio (SNR). Fiber optic gyroscope includes an Yb-doped amplified spontaneous emission (ASE) source with broad emission spectra of 15 nm bandwidth used as light source in order to improve gyroscope sensitivity. The final ARW performance is about 0.008°/√hr for a fiber coil of 150 m length.

Model-based end-to-end learning for a self-homodyne coherent system.

We investigate the statistical properties of the inherent intensity fluctuation in a low-cost and low-complexity self-homodyne coherent system employing an amplified spontaneous emission (ASE) source. The noise distribution model of the considered system is established, which is shown to be highly consistent with the experimental results for a 10 GBd 256-ary quadrature amplitude modulation (QAM) signal transmission over a 10 m duplex fiber. With the help of the proposed noise model, we then design advanced mappers and demappers. The optimized system alleviates the need for ASE bandwidth and is evaluated by applying forward error correction codes. Furthermore, we demonstrate an information rate increase of 6.67% with respect to 64-QAM.

Radiation source with enhanced virucide effectiveness based on a mixture of helium and iodine vapor

Subject of study. A source of spontaneous emission (a lamp) in the ultraviolet spectral range excited by a capacitive discharge was investigated. Iodine vapor and mixtures of iodine vapor with inert gases were used as the operating gas medium of the lamp. Conditions for enhancements in specific output parameters of the lamp emission were investigated. Excitation conditions under which the lamp emits predominantly at the iodine atomic line with a wavelength of 206.16 nm were determined. Aim of study. The primary aim of the study was to investigate the spectral and energy characteristics of the lamp based on the iodine vapor, which is promising for the development of a radiation source with enhanced virucidal effectiveness for ultraviolet disinfection of a human environment contaminated with pathogenic microorganisms including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Method. In this study, the composition and pressure of the operating medium were optimized. In addition, the excitation mode of the lamp emission was optimized by changing the repetition rate of voltage pulses. Main results. At a specific excitation power of approximately 1.3mW/cm3 and partial pressures of iodine vapor and helium of approximately 2.5 and 7 Torr, respectively, the line of an iodine atom with a wavelength of 206.16 nm dominates in the output lamp spectrum, and the specific emission power at the outer surface of the lamp tube is approximately 3mW/cm2. Practical significance. The emission of the investigated lamp is in the spectral range of 200–225 nm, which is promising in terms of developing technology for safe ultraviolet inactivation of pathogenic microorganisms including SARS-CoV-2.

Correlation between emission and relative intensity noise spectral profiles of an Er-doped fiber superfluorescent source

The spectral characteristics of the relative intensity noise (RIN) of two amplified spontaneous emission (ASE) sources are experimentally measured. An Er-doped fiber superfluorescent source (EDF-SFS) is investigated and compared with a super-luminescent diode (SLD) source, using a simple tunable fiber Bragg grating filter-based system. Experimental results based on normal ASE operation conditions showed that the RIN distribution of the EDF-SFS is correlated with its emission spectral profile, which is different from the results observed using the SLD source. This finding shows for the first time that an EDF-SFS based ASE has fundamentally different RIN characteristics from other known existing spontaneous emission broadband sources. The amplifying process of the EDF-SFS is discussed and confirmed using a rate equation-based simulation.

Parameters Optimization of ASE Source for the Improvement of Optical Power Stability in Space Radiation Environment

A parameter optimization model of amplified spontaneous emission (ASE) source in space radiation environment has been developed based on the ASE source model and the radiation-induced attenuation (RIA) model of erbium-doped fiber (EDF). The RIA model considers color center generation and annealing process at the same time. Using the radiation attenuation and recovery spectra obtained at the dose rate of 30 Gy/min, the color center generation and recovery parameters in the EDF are obtained. Based on the ASE source model, the parameter optimization model at the high dose rate of 30 Gy/min is established. Then, the model is successfully extrapolated to a small dose rate of 0.06 Gy/min. These effects of the spectral shape, pump power, and fiber length on the output power stability of the ASE source are investigated using this model at the dose of 0.06 Gy/min. Finally, the experiment is performed to evaluate the simulation, and it is suggested that the output power fluctuation of the optimized ASE source is less than 3% within the radiation dose range of 300 Gy.

Research Status of Amplified Spontaneous Emission Sources based on Doped Materials

Amplified spontaneous emission (ASE) was once considered a harmful parasitic effect. This is because ASE will reduce the number of the inverted population in the gain medium, thereby reducing the efficiency of lasers. However, the output characteristics of ASE make it applicable to many studies. Therefore, the experimental settings and beam output characteristics of different doped laser ASE sources are summarized in this review. The summarization begins with the characteristics of ASE, such as threshold condition. Then, two doped fiber lasers are introduced. Based on erbium-doped fiber, an ASE source with high stability is made by measuring the best parameters and selecting a suitable structure. The ytterbium-doped fiber can benefit Q-switch pulses and high-order Stokes generation by suppressing the self-saturation of ASE and offering gain for ASE, respectively. Besides, three different ASE sources based on Nd-doped laser crystals are presented. They are spatially selective ASE sources that achieve high-intensity, narrow-bandwidth output pulses and Q-switching in a cavityless laser. Additionally, the performance of the ASE source can also be improved by doping with gold nanoparticles, Gd3+, and other particles.

Use of SWIR dehydration and OCT to assess the complete arrest of simulated incipient caries lesions.

Previous studies have shown that optical coherence tomography (OCT) can be used to show the formation of a transparent surface zone on caries lesions indicative of remineralization. Studies have also shown that monitoring changes in the diffuse reflectivity of caries lesions during drying with air can be used to assess lesion activity and that the largest changes occur at SWIR wavelengths coincident with high water absorption at 1450 and 1950 nm. The purpose of this study was to determine when remineralization has occurred by monitoring changes in SWIR reflectance measurements and OCT images of simulated lesions over an extended time period during exposure to a remineralization solution. Eight bovine enamel surfaces each with two treatment windows were exposed to a pH cycling regimen to produce simulated lesions 50-100 μm deep. OCT at 1310 nm was used to image the samples at each time point. An extended range tungsten halogen lamp with a 1450 nm band pass filter and a broadband amplified spontaneous emission source centered near the peak of the water-absorption band at 1950 nm were used as light sources. An extended range InGaAs camera (1000-2340 nm) was used to acquire reflected light images as the samples were dried with air. After 32 days of exposure to the remineralization solution there were no further changes to the samples suggesting they had been completely arrested.

Gbit/s secure key generation and distribution based on the phase noise of an amplified spontaneous emission source.

In this paper, a secure key generation and distribution scheme based on the phase noise of an amplified spontaneous emission source is proposed and experimentally verified. A giant key generator that contains two distribution arms is used to generate a specific beat dependent on the path length difference of the arms. Through the method of balanced subtraction of the local signals, the effect of the intensity noise has been mainly excluded, and the two legal users obtain the consistent differential signal that depended on the phase noise. Experiment results show that the correlation coefficient of the key signals reaches to about 0.89, and the bit generation rate of the scheme achieves to 3.06 Gbit/s under a length of 20 km standard single-mode optical fiber route, as the bit error rate stays under 0.02%. Moreover, the converted digital key stream has passed the NIST statistical test suite, which means that the scheme is inherently random in the statistical sense. With the excellent performance mentioned above, the proposed scheme provides a simple and efficient solution for the method of one-time pad.

Broadband ASE source for S + C + L bands using hafnia-bismuth based erbium co-doped fibers

A broadband amplified spontaneous emission (ASE) source is demonstrated experimentally by using hafnia-bismuth based erbium co-doped fibers (HB-EDFs) with a total length of 200-cm as an active medium. Both of parallel and series configurations are used to generate a broadband ASE source, operating at 1.5 µm and that cover S-, C-, and L-bands. The comparison proves that the series configuration provides a relatively larger ASE bandwidth, higher output power, higher efficiency, and lower complexity. At the optimum total pumping power of 280 mW, a broadband ASE source of 57 nm with a power ripple of ± 7.5 dB is achieved. Besides, a total ASE power of 20.8 mW is obtained, which is equivalent to 7% of the pumping efficiency.

Revealing the dynamics of intensity fluctuation transfer in a random Raman fiber laser

Temporal intensity fluctuation is one of the inherent features of fiber lasers. When utilizing the fiber lasers to pump a random Raman fiber laser (RRFL), the intensity fluctuation transfer from the pump to the random lasing could affect the output performance significantly. In this paper, we comprehensively compared the spectral, temporal, and power characteristics of an RRFL pumped by two different fiber lasers—a temporally unstable fiber oscillator and a temporally stable amplified spontaneous emission (ASE) source. Owing to less impact of the intensity fluctuation transfer, the ASE source-pumped RRFL shows ∼ 45.3 % higher maximum output power, higher spectral purity ( > 99.9 % ) and optical signal-to-noise ratio ( > 40 dB ), weaker spectral broadening, and more stable temporal behavior compared to the fiber oscillator-pumped RRFL. Furthermore, based on the temporal-spatial-coupled Raman equations and the generalized nonlinear Schrödinger equations, we numerically revealed the impact of the pump intensity fluctuations on the output characteristics of RRFLs, and found that the temporal walk-off effect played an important role in the dynamics of intensity fluctuation transfer. This work may provide a reference for designing and implementing high-performance RRFLs and promote their practicability in sensing, telecommunications, and high-power applications.

Loss prediction of three-level amplified spontaneous emission sources in radiation environment

A model of three-level amplified spontaneous emission (ASE) sources, considering radiation effect, is proposed to predict radiation induced loss of output power in radiation environment. Radiation absorption parameters of ASE sources model are obtained by the fitting of color centers generation and recovery process of gain loss data at lower dose rate. Gain loss data at higher dose is applied for self-validating. This model takes both the influence of erbium ions absorption and photon bleaching effect into consideration, which makes the prediction of different dose and dose rate more accurate and flexible. The fitness value between ASE model and gain loss data is 99.98%, which also satisfies the extrapolation at the low dose rate. The method and model may serve as a valuable tool to predict ASE performance in harsh environment.

Experimental continuous-variable quantum key distribution using a thermal source

Gaussian-modulated coherent-state (GMCS) continuous-variable quantum key distribution (CVQKD) protocol can allow authenticated users to share secret key with unconditional security. So far, all previous experimental implementations of GMCS CVQKD schemes are based on active modulations, i.e. amplitude and phase modulators and quantum random number generator (QRNG) are required. However, high-speed modulation with high extinction ratio and stability is challenging, which is extremely remarkable in chip-scale silicon photonic realization. While the passive-state-preparation (PSP) CVQKD scheme, which explores the intrinsic field fluctuations of a thermal source, avoids the uses of active modulations and QRNG. In this paper, we experimentally realize the intact PSP CVQKD through a realistic optical fiber channel using off-the-shelf amplified spontaneous emission source. In particular, specially designed frame synchronization method is used to build the correlation between the data measured from the two legitimate parties, and excess noise are synthetically controlled to generate secure secret keys at the metro-area distances when considering the practical and non-negligible finite-size effects under collective Gaussian attacks. Due to the avoidance of modulators and QRNG, the passive state encoding scheme provides a promising direction of applicable high-speed, chip-based and even sunlight-based CVQKD with less cost and complexity.