Dual-wavelength Laser Research Articles

Dual-wavelength dye laser combined with betamethasone injection for treatment of keloids: protocol of a randomised controlled trial

IntroductionKeloids, benign fibroproliferative tumours characterised by excessive fibroblast proliferation and over-deposition of extracellular matrix, pose a therapeutic challenge with high recurrence rates. Betamethasone (diprospan) injection (BI) is one of the...

Dual-wavelength erbium-doped mode-locked fiber laser based on CoPS3 saturable absorber

An erbium-doped mode-locked fiber laser based on CoPS3 saturable absorber was successfully constructed and ultrashort pulsed light was obtained. The CoPS3 nanosheets solution was prepared using the liquid-phase exfoliation technique, and then drop-coated onto a tapered fiber as a saturable absorber. The fiber laser based on CoPS3 saturable absorber could output conventional solitons at the central wavelengths of 1557.46 nm or 1532.12 nm, respectively, as well as simultaneously output conventional solitons at dual wavelengths of 1531.56 nm and 1557.32 nm, with the ability to switch between the three operational states. The achieved minimum pulse width was 1.59 ps. In addition to conventional solitons, the laser demonstrated the capability to generate bound-state solitons. This study highlights the effectiveness of CoPS3 as a reliable optical modulator for fiber lasers and illustrates its potential for applications in ultrafast optics.

Switchable emissions of an Erbium-doped fiber laser using cascaded MZIs based on CHCF

In this work, a single and dual-wavelength erbium-doped fiber laser (EDFL) based on two Mach-Zehnder interferometers (MZIs) in cascade structure was experimentally validated. MZIs were assembled by joining a capillary hollow-core fiber (CHCF) piece between two multimode fibers (MMFs) sections. The switchable operation is reached by moving the spectrum of one MZI when the temperature is increased. The maximum measured signal noise to ratio (SNR) was more than 50 dB for the single and dual-wavelength laser lines. Besides, stable output is shown since no power and wavelength variations were noticed. It is important to mention that emissions are obtained at precise wavelength positions and not arbitrarily as described by other investigations. This EDFL can be used in applications of optical fiber communications systems and fiber sensing.

Dual-wavelength mid-infrared laser operation at 2.8 μm and 3.6 μm in Er3+ doped fluoride fiber

This study presents a pioneering experimental demonstration of dual-wavelength laser operation at 2.8 μm and 3.6 μm in an Er3+-doped ZrF4-BaF2-YF3-AlF3 double-cladding fluoride glass fiber, fabricated in-house. The achievement is realized through the implementation of a novel dual-wavelength pumping scheme utilizing 980 nm and 1150 nm lasers. This innovative scheme enables the excitation of the lower energy level of the 2.8 μm laser transition (4I11/2) to the upper energy level of the 3.6 μm transition (4F9/2) via an excited state absorption process, resulting in simultaneous emission at 2.8 μm and 3.6 μm. The maximum laser output powers at 2.8 μm and 3.6 μm are measured at 0.96 W and 0.32 W, respectively. This groundbreaking work marks the first experimental realization of dual-wavelength laser operation at 2.8 + 3.6 μm in Er3+-doped fluoride fiber, contributing significantly to the advancement of laser technology in this spectral range.

Switchable Dual-Wavelength Q-Switched Erbium-Doped Fibre Laser using Spider Silk as a Biocompatible and Eco-Friendly Saturable Absorber

Switchable Dual-Wavelength Q-Switched Erbium-Doped Fibre Laser using Spider Silk as a Biocompatible and Eco-Friendly Saturable Absorber

Dual-wavelength distributed feedback laser array based on four-phase-shifted sampled Bragg grating for terahertz generation.

We propose and experimentally demonstrate a dual-wavelength distributed feedback (DFB) laser array utilizing a four-phase-shifted sampled Bragg grating. By using this grating, the coupling coefficient is enhanced by approximately 2.83 times compared to conventional sampled Bragg gratings. The devices exhibit a stable dual-mode lasing achieved by introducing further π-phase shifts at 1/3 and 2/3 positions along the cavity. These devices require only one stage of lithography to define both the ridge waveguide and the gratings, mitigating issues related to misalignment between them. A dual-wavelength laser array has been fabricated with frequency spacings of 320 GHz, 500 GHz, 640 GHz, 800 GHz, and 1 THz. When integrated with semiconductor optical amplifiers, the output power of the device can reach 23.6 mW. Furthermore, the dual-wavelength lasing is maintained across a wide range of injection currents, with a power difference of <3 dB between the two primary modes. A terahertz (THz) signal has been generated through photomixing in a photoconductive antenna, with the measured power reaching 12.8 µW.

Mid-infrared dual-wavelength operation of a diode-pumped Tm:YScO3 laser

A simultaneous continuous-wave (CW) dual-wavelength Tm:YScO3 laser using a single birefringent filter (BF) was experimentally demonstrated. We calculated the wavelength-dependent loss property of the BF. By adjusting the BF plate, the spectral intensity ratio of the generated wavelengths can be maintained to be 1:1. A simultaneous CW dual-wavelength Tm:YScO3 laser at 1948 and 2098 nm is experimentally realized. For a pump power of 15.2 W, mid-infrared dual-wavelength laser radiation at 1948 and 2098 nm and 5.9 W of output power using a 5% output coupler could be generated. A slope efficiency of 42.2% with respect to the absorbed pump power and optical-to-optical efficiency of 38.8% for the highest-incident pump power were obtained. To our knowledge, this is the first study that has realized the dual-wavelength in a Tm:YScO3 laser.

Tunable and switchable dual-wavelength SLM narrow-linewidth fiber laser with Lyot filter cascaded by double-ring cavity

An erbium-doped fiber (EDF) laser with single longitudinal mode (SLM), narrow linewidth, and switchable dual-wavelength based on a Lyot filter cascaded dual-ring cavity structure (DRCs) has been designed and constructed. In the experimental system, an Employed passive DRCs enhances the longitudinal mode spacing, while the Lyot filter effectively mitigates mode competition within the laser cavity. The composite filter structure facilitates stable dual-wavelength output while ensuring a consistent SLM output. Then, experimental results reveal optical signal-to-noise ratios (OSNR) with 62 dB for single-wavelength and 55 dB for dual-wavelength. Additionally, the power and wavelength fluctuations for both single-wavelength and dual-wavelength remained stable throughout monitoring periods of 20 min and 1 h, respectively. Meanwhile, a maximum tuning range of 2 nm is achieved by stretching a polarization-maintaining fiber Bragg grating (PM-FBG) using a fiber displacement stage. The linewidths of each wavelength are 2.8 kHz and 2.6 kHz, respectively. During the process of wavelength tuning, the fluctuations of linewidth do not exceed 0.3 kHz and 0.45 kHz, respectively. Simultaneously, the polarization states of each wavelength are measured, which reveals orthogonal single polarization. The relative intensity noise (RIN) is measured below −133 dB/Hz at frequencies above 1 MHz.

Millimeter-wave generation with a room-temperature nonlinear quantum cascade laser

Millimeter-wave difference frequency generation is reported for a dual-wavelength mid-infrared quantum cascade laser operating at room temperature. To overcome a low mid-infrared-to-terahertz conversion efficiency below 1 THz, a long-wavelength, high-performance mid-infrared quantum cascade laser structure with higher nonlinear susceptivity is adopted. By designing the efficient allocation of mid-infrared pumps to two sections of fabricated distributed feedback grating, a closely separated dual-wavelength (λ1 ∼ 13.53 μm and λ2 ∼ 13.39 μm) laser oscillation was obtained. Consequently, a millimeter-wave emission at a frequency of 231 GHz was successfully observed at room temperature.

High average output power, dual-wavelength synchronously self-mode-locked Ho:LLF laser operating at 2068.5 and 2069.2 nm.

A dual-wavelength synchronously self-mode-locked Ho:LLF laser operating at 2068.5 and 2069.2 nm was demonstrated. The maximum average output power was as high as 2.6 W with a pulse repetition frequency of 3.03 GHz. Meanwhile, the output power ratio of the dual-wavelength lasers can be effectively controlled by varying the incident pump power. To the best of our knowledge, this is the first dual-wavelength synchronously self-mode-locked Ho-doped fluoride solid state laser; moreover, our current experimental results represent the highest average output power from a GHz self-mode-locked oscillator in the 2 µm wave band.

Fluorescent labelling combined with confocal differential Raman spectroscopy to detect microplastics in seawater

As an emerging marine pollutant, microplastics represent a focal point in global monitoring and management efforts. With seawater accounts for 97 % of the total global water resources, scientific assessments of microplastics in seawater are crucial for pollution control and management of marine environments. This study focuses on investigating microplastics in near-shore seawater and proposes a rapid and accurate detection method using a constructed confocal Raman spectroscopy detection system. By optimizing the pretreatment process of seawater microplastic samples, the efficient removal of organic matter interference in microplastic detection is achieved. Employing fluorescent labeling addresses the issues of prolonged detection time and high false positive rates associated with traditional methods, enabling rapid differentiation between microplastics and other substances and significantly enhancing detection efficiency and accuracy. Additionally, the use of differential Raman spectroscopy effectively mitigates fluorescence signal interference, thus improving the signal-to-noise ratio of the spectra. By employing dual-wavelength laser excitation at 784 nm/785 nm, microplastics such as polyethylene (PE), polypropylene (PP), polystyrene (PS) ranging in size from 60 to 500 μm are successfully detected in seawater. The results demonstrate that the proposed pretreatment method for seawater microplastics and novel detection techniques enable rapid screening and comprehensive non-destructive detection of microplastics in seawater, thereby facilitating the characterization of marine microplastics and providing scientific support for enhancing the management of microplastic pollution and ecological risk control.

Orthogonally polarized dual-wavelength Pr:LiGdF4 lasers in the green range

We demonstrate a diode-pumped continuous-wave tunable orthogonally polarized dual-wavelength Pr:LiGdF4 laser in the green range. The excellent mode matching between the pump and green lasers is achieved under the consideration of thermally induced effects. We analyze the condition of gain-to-loss balance via an uncoated glass etalon to achieve the dual-wavelength operation. At an absorbed pump power of 17.9 W, a dual-wavelength laser operating at 546 nm in π-polarization and 538 nm in σ-polarization with 1.72 W of average output power was obtained. Orthogonally polarized dual-wavelength laser operation at shorter- or longer-wavelength pairs with lower average output power could also be realized for other output-coupling transmissions. To the best of our knowledge, this is the first work realizing orthogonally polarized dual-wavelength operation in Pr:LiGdF4 lasers.

Monolithic tunable dual-wavelength laser utilizing erbium-doped lithium niobate on an insulator.

We demonstrate a monolithic tunable dual-wavelength laser fabricated on erbium-doped lithium niobate on an insulator (Er:LNOI). The dual-wavelength laser enables independent tuning with a continuously linear electro-optic (EO)-modulated tuning range of 11.875 GHz at a tuning efficiency of 0.63 pm/V. Tunable microwave generation within 50 GHz with a maximum extinction ratio of 35 dB is experimentally demonstrated by further exploring the charge accumulation effect in LNOI. The monolithic design of this work paves the way for microscale integration of laser devices, presenting significant prospects in photonics research and applications.

Spectroscopy and efficient dual-wavelength laser performances of a Nd:GYSAG crystal.

We reported on the spectral properties and dual-wavelength laser performances of a novel, to the best of our knowledge, Nd:Gd1.8Y1.2ScAl4O12 (Nd:GYSAG) crystal for the first time. The absorption spectra, emission spectra, and fluorescence lifetime were systematically investigated. Further, a continuous-wavelength (CW) laser output power up to 5.02 W was obtained under an absorbed pump power of 9.45 W with slope and optical-to-optical efficiencies of 59.4% and 53.1%, respectively, at 1061.2 and 1063.2 nm. A stable passively Q-switched (PQS) laser employing Cr:YAG as a saturable absorber (SA) was realized. The maximum average output power of 0.756 W with a slope of near 34.4% was obtained with the pulse width, pulse energy, and peak power of 14.0 ns, 128.1 µJ, and 9.15 kW, respectively. The results indicate that the Nd:GYSAG crystal is an excellent laser medium for generating a high-efficiency dual-wavelength laser and has potential in terahertz (THz) laser generation.

Dual wavelength signal generation with four wave mixing based on directly modulated laser

Dual wavelength (DW) lasers are crucial for producing petahertz (PHz) signals, which are higher value terahertz (THz) signals. The infrared and visible light sub-bands are valuable frequency range for a number of applications, including networking, multiple access techniques, next-generation mobile networks (6G), future wireless networks, and new PHz communication systems. The importune need to the high frequency signal such as THz and PHz signal for 5 and 6 next generation wireless cellular mobile networks motivate us to design an optical system to provide these signals rather than an electronic circuits. They are also beneficial for a variety of medical testing. The wavelength spacing ranging from 14 nm to 7 nm is proposed and demonstrated a dual-wavelength generation with FWM based on DML is realized at 1554 and 1548 nm. It is essential to make use of the fiber's non-linearity characteristics to ensure synchronization for continuous wave (CW) laser and directly modulated laser (DML) signals and the creation of the four wave mixing (FWM) components. With the help of OptiSystem version 14.0, the system is designed and investigated then, the desired THz signal is created as pulse amplitude modulation. The position of the FWM components within the frequency range between the spectrums of the two lasers affects the synthesis of the required signal. At the DML frequency equal to or below the CW Laser (1520 nm), neither FWM frequency components nor dual wavelength pulses exist. On the other hand, the FWM frequency components and dual wavelength pulses can only be seen when the DML frequency is greater than 1520 nm. The CW laser frequency is the main controlling factor in the generation THz signal. If the CW laser frequency is set at or below 1520 nm, the dual wavelength and THz signal are accessible. Because these frequencies are so far from the reference fiber frequency, it is impossible to produce dual wavelength pulses at frequencies higher than those mentioned above.

Switchable Dual-Wavelength Thulium-Doped Fiber Laser Based on Polarization-Maintaining Fiber Bragg Grating and Compound Cavity Filter

This paper presents experimental evidence regarding a novel switchable dual-wavelength thulium-doped fiber laser (TDFL). Wavelength switching is achieved by combining a polarization-maintaining fiber Bragg grating (PM-FBG) with a polarization controller (PC). The three-coupler double-ring compound cavity (TC-DRC) structure, acting as a mode-selection filter, is designed to select a single longitudinal mode (SLM) from the dense longitudinal modes. This paper introduces the design and fabrication method of the TC-DRC filter and analyzes, in detail, the mechanism for SLM selection. The experimental results demonstrate that the designed filter exhibits excellent performance. By adjusting the PC, the TDFL achieves stable SLM operation at the wavelengths of 1940.54 nm and 1941.06 nm, respectively. The optical signal-to-noise ratio (OSNR) is superior to 65 dB. When the TDFL is tested at room temperature, there is no significant wavelength drift, and power fluctuations are less than 1.5 dB. The operation of the SLM is verified through the self-heterodyne method, and the laser maintains stable SLM states for both wavelengths after continuous operation for an hour. Furthermore, based on the phase noise demodulation method, the linewidths of both wavelengths are measured to be less than 10 kHz at the integration time of 0.001 s.

Volumetric Modification of Transparent Materials with Two-Color Laser Irradiation: Insight from Numerical Modeling.

Traditionally, single-color laser beams are used for material processing and modifications of optical, mechanical, conductive, and thermal properties of different materials. So far, there are a limited number of studies about the dual-wavelength laser irradiation of materials, which, however, indicate a strong enhancement in laser energy coupling to solid targets. Here, a theoretical study is reported that aimed at exploring the volumetric excitation of fused silica with dual-wavelength (800 nm and 400 nm) ultrashort laser pulses focused on the material's bulk. Numerical simulations are based on Maxwell's equations, accounting for the generation of conduction electrons, their hydrodynamic motion in the laser field, and trapping into an excitonic state. It is shown that, by properly choosing the energies of the two laser harmonics successively coupling with the material, it is possible to strongly enhance the laser energy absorption as compared to the pulses of a single wavelength with the same total energy. Laser energy absorption strongly depends on the sequence of applied wavelengths, so that the shorter wavelength pre-irradiation can yield a dramatic effect on laser excitation by the following longer-wavelength pulse. The predictions of this study can open a new route for enhancing and controlling the highly localized absorption of laser energy inside transparent materials for optoelectronic and photonic applications.

Collision dynamics between soliton molecules and a single soliton: exploding soliton pair and periodic soliton explosions.

Inherent periodic collisions in dual-wavelength mode-locked fiber lasers (MLFLs) stimulate various intra-cavity collision dynamic phenomena. Analogous to the collision of matter particles, collisions between optical soliton molecules (SMs) and single solitons (SSs) have been observed by the real-time spectral measurements. It is demonstrated that the energy accumulation after the collision caused by internal motion within bound pulses leads to soliton pair (SP) explosions, while the periodic soliton explosions with another cavity parameter setting are almost unaffected by the collision. Additionally, the collision between a SP and a SS is reproduced through numerical simulations, and the collision-induced double Hopf-type bifurcation of SP is predicted. These findings provide novel insights, to the best of our knowledge, for further understanding the complex collision dynamics in dual-wavelength MLFLs and will help in the design of high-performance dual-comb sources.

A Study on Accurate Ranging Method of a Dual-Wavelength Orthogonal FMCW Laser Fuze in a Complex Aerosol Environment

A Study on Accurate Ranging Method of a Dual-Wavelength Orthogonal FMCW Laser Fuze in a Complex Aerosol Environment

Wavelength tunable ring cavity erbium-doped fibre laser based on tapered Fabry Perot filter fabricated by hydrofluoric acid corrosion for stretch sensing

In this study, the erbium-doped fiber laser with a ring cavity and a Fabry-Perot (F-P) filter was proposed and experimentally verified. In the design of the laser, hydrofluoric acid was employed for chemical etching to prepare the F-P cavity, and tapering was applied to the F-P cavity to enhance sensitivity. The experimentally prepared F-P filter was placed in the resonant cavity and served as a frequency-selective device for the fiber laser. At a laser threshold of 48 mW, we obtained a single-wavelength laser output at 1565.28 nm, with a 3 dB linewidth of 0.29 nm. To evaluate the stretching sensing performance of the EDFL system, we performed stretching of the F-P filter. The experimental results demonstrated that within a stretching length range of 0 to 3 mm, we could obtain a single-wavelength laser that could be tuned from 1559.57 to 1567.04 nm, corresponding to a tuning range of 7.47 nm. The laser showed a sensitivity of 2.73 nm/mm and a goodness of fit 0.999. Monitoring the stability of a single-wavelength laser within 30 min, the signal-to-noise ratio was greater than 27.212 dB, and the power fluctuation was less than 0.712 dB. Additionally, the polarization controller was adjusted to obtain two different dual-wavelength lasers with a power fluctuation of less than 0.71 dB.