Tunable Dual-wavelength Laser Research Articles

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.

Fiber laser with intracavity parallel Mach-Zehnder interferometers towards Vernier refractive index sensing.

In this paper, dual-wavelength laser emission of an erbium-doped fiber laser (EDFL) with a tunable distinct wavelength selection of the simultaneously produced laser lines was achieved by applying a parallel comb filter configuration based on the optical Vernier effect. The intracavity inserted proposed comb filter consists of two parallel branches to generate the Vernier effect. Each branch is an in-line Mach-Zehnder interferometer (MZI) filter, which is composed of a polarization-maintaining fiber fusion spliced between single-mode fibers with sphere shapes at both ends. The tunability of the selected laser wavelength was realized by submerging the proposed filter in different sodium chloride/water mixtures. The proposed comb filter-based Vernier effect was used to independently achieve the selection of the dual-wavelength EDFL lines and for refractive index (RI) sensing applications. The in-line M Z I 1 and M Z I 2 structures show a wavelength shift sensitivity to RI variations of -88 and 79nm/RIU, respectively. Our proposed MZI structure presents a reliable, straightforward, and low-cost spectral comb filter for separate tunable dual-wavelength laser generation in the c-band region. Furthermore, the proposed filter structure-based Vernier effect presents a new perspective and method in the RI sensing application.

Photonic-assisted 2-D terahertz beam steering enabled by a LWA array monolithically integrated with a BFN.

A novel photonic-assisted 2-D Terahertz beam steering chip using only two tuning elements is presented. The chip is based on an array of three leaky wave antennas (LWAs) with a monolithically integrated beamforming network (BFN) on a 50 µm-thick indium phosphide substrate. The THz beam angle in elevation (E-plane) is controlled via optical frequency tuning using a tunable dual-wavelength laser. An optical delay line is used for azimuth (H-plane) beam control. The simulated beam scanning range is 92° in elevation for a frequency sweep from 0.23 THz to 0.33 THz and 69.18° in azimuth for a time delay of 3.6 ps. For the frequency range from 0.26 THz to 0.32 THz, it is confirmed experimentally that the THz beam scans from -12° to +33°, which is in good agreement with the numerical simulations. The beam direction in azimuth scans with a total angle of 39° when applying a delay difference of 1.68 ps. A good agreement is found between theoretically predicted and experimentally determined THz beam angles with a maximum angle deviation below 5°. The experimental scanning angles are limited due to the mechanical constraints of the on-wafer probes, the on-chip integrated transition and the bandwidth of the THz receiver LNA. The mechanical limitation will be overcome when using a packaged chip.

High-power tunable dual-wavelength diode laser with a composite external cavity

A high-power tunable dual-wavelength composite external cavity architecture obtained by means of a holographic grating and a volume Bragg grating is proposed and demonstrated. The tunable frequency difference of the dual-wavelength output is from 0.41 THz to 3.89 THz. We obtain an output power of 2.1 W when the frequency difference is 1.86 THz. The side-mode suppression ratio of more than 29 dB is suppressed over the entire tunable dual-wavelength output range. The two corresponding wavelengths of the dual-wavelength output basically maintain the same intensity with the smallest power difference of only 0.10%.

Robust and low cost in-fiber acousto-optic Mach-Zehnder interferometer and its application in a dual-wavelength laser.

A robust in-fiber tunable acousto-optic Mach-Zehnder interferometer with a taper-shaped sandwich-like fiber structure is proposed and characterized experimentally, based on which tunable dual-wavelength lasers are demonstrated. The fiber structure was prepared by two-step etching methods, which could be used to fabricate either a symmetric structure for a continuous tuning dual-wavelength laser or an asymmetric structure for a switchable one. The proposed structure has advantages of low cost, low driving power, and robustness. The method for preparing the fiber structure is agile, which paves the way for its applications.

Tunable Narrow-Linewidth Ring Laser Based on the Polarization Conversion in a Tapered Fiber-Coupled Whispering Gallery Mode Resonator

Based on the polarization conversion in a tapered fiber-coupled whispering gallery mode (WGM) system, a simple-structured narrow linewidth band-pass filter was fabricated and a narrow linewidth ring laser was demonstrated. With a fiber Bragg grating (FBG) to further select the resonant mode, the ring laser could be in the single-longitudinal-mode with the linewidth about 6 kHz and its wavelength could be tuned from 1540.10 nm to 1570.01 nm. Benefit from the dense modes in the WGM resonator, high conversion efficiency, and better stability of the structure, a tunable dual-wavelength laser could be achieved based on two FBGs with different resonant wavelengths. The configuration of the proposed laser is simple and stable, which will benefit its applications in the future.

Theory and experiments of a power-ratio tunable dual-wavelength Nd:YVO4/Nd:GdVO4 laser by varying the pump wavelength

We demonstrate the theory and experiments of a power-ratio tunable dual-wavelength laser with coaxial diode end-pumping configuration by varying the pump wavelength, which is realized by controlling the working temperature of the pump laser diode (LD). Composite laser gain media containing an Nd : YVO4 crystal and an Nd : GdVO4 crystal was used for example. The dynamics of the dual-wavelength laser generation based on practical input operating parameters were simulated, and in the experiment, a total power of 3.72 W was obtained under the maximum LD pump power of 8 W, corresponding to the optical–optical conversion efficiency of 46.5%. The characteristics of the power-ratio tuning and output power agreed well with the theoretical predictions.

Laser properties of Nd3+/Yb3+ co-doped glass fiber around 1 µm

The interest in N d 3 + / Y b 3 + co-doping was initially motivated by the discovery of N d 3 + → Y b 3 + energy transfer in 1964, which profoundly influenced the motivation for subsequent research. Here, however, we propose a new mechanism based on an 808 nm and 975 nm dual-pumping scheme, in which the effect of N d 3 + → Y b 3 + energy transfer process is negligible. Gain spectrum modulation and its application in tunable dual-wavelength lasers around 1 µm were demonstrated in a 30-cm-long N d 3 + / Y b 3 + co-doped silica glass fiber. In addition, interesting laser efficiency improvements, thermal performance improvements, and even photodarkening resistance behavior were observed. This work broadens the knowledge of N d 3 + / Y b 3 + co-doping and may provide useful insights for exploring co-doping with rare-earth ions.

Tunable continuous-wave dual-wavelength laser operation of Pr3+:LiYF4 around 900 nm

We present here the first tunable continuous-wave (CW) simultaneous dual-wavelength laser operation of a Pr3+:LiYF4 crystal in the 900 nm spectral range using a single birefringent filter (BF) under excitation with a frequency doubled optically pumped semiconductor laser. By adjusting the rotation angle of the BF, the CW simultaneous dual-wavelength lasers operating at 869 and 915 nm, 894 and 915 nm, 915 and 923 nm, were obtained respectively.

Dual-wavelength fiber-laser-based transmission of millimeter waves for 5G-supported Radio-over-Fiber (RoF) links

This work utilizes an experimentally designed erbium-doped fiber-based tunable dual-wavelength laser (EDFL) to generate phase-stable millimeter waves over a wide-band of ≈ 12–110 GHz and their transmission over the radio-over-fiber (RoF) link. The generated fiber-laser-based millimeter waves are transmitted over aRoFlink, including an optical link of 20 km and a wireless link of 50 m, which is carried out via a co-simulation ofOptisystem™andMATLAB™software. The successful transmission of the proposed fiber-laser-based millimeter waves show the possibilities of realizingdiverse 5G-supported microwave-photonic systems.

Tunable dual wavelength and narrow linewidth laser using a single solid-state gain medium in a double Littman resonator

We propose a scheme for generating two continuously tunable laser wavelengths with picometer linewidths using only one solid-state laser gain medium, two end mirrors, one output coupler, and one grating in a double Littman resonator. Each laser wavelength emission can be tuned independently while maintaining the very narrow linewidth. We demonstrate our scheme in the ultraviolet region by simulating the ultraviolet laser emission from a cerium-doped lithium calcium aluminum fluoride crystal, where we obtained a linewidth of about 2 pm and continuous tunability in the wavelength range from 278 nm to 315 nm. This wavelength region has important applications in monitoring the concentration of sulfur dioxide and ozone in the atmosphere using differential absorption lidar, which require two closely spaced wavelengths with linewidths of 100 pm or less. The proposed scheme can be extended to other wavelength regions using an appropriate laser gain medium, enabling other applications requiring a tunable dual wavelength and narrow linewidth laser.

Experimental investigation on the Y-type cavity tunable dual-wavelength laser based on neodymium-doped vanadate crystals

The Y-type cavity tunable dual-wavelength laser (DWL) based on the Nd:GdVO4 and Nd:YVO4 crystals is demonstrated. The DWL consists of two end-pumped structures being joined by a polarizer and sharing one same output coupler. The two end-pumped structures generate the DWL beams at 1063 nm and 1064 nm with orthogonal polarizations, as well the two optical cavity lengths are 33 and 26 mm, respectively. The output powers of 1063 nm and 1064 nm laser linearly increase with the incident pump powers increasing, reach 598.73 mW and 601.04 mW with the corresponding slope efficiencies at 18.9% and 13.1%, where the incident pump powers are 7.11 and 6.86 W, respectively. The long term stability of output powers are measured less than 2.0% in 2 h. By independently adjusting the incident pump powers, the frequency separation of the DWL is tuned from 259.60 to 373.50 GHz, with the output power ratio from 0.08 to 13.77. Such a stable, tunable DWL is potential for optical terahertz waves generation.

Compact Dynamic In-Fiber Acoustically-Induced Mach-Zehnder Interferometer Based on Phase Mismatch and Its Application in a Tunable and Switchable Dual-Wavelength Laser

A compact and robust in-fiber acoustically-induced Mach-Zehnder interferometer (AI-MZI) was demonstrated based on the phase mismatch in an acoustic wave driving fiber Bragg grating (FBG). The fiber structure of the AI-MZI was easy to fabricate and of a uniform diameter with larger refractive index difference in its arm part, which helped to reduce the length of the arm. In the experiment, the total length of the AI-MZI was less than 7 cm and the response time was about 120 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> s. The bandpass isolation and resonant center wavelength could be optimized by changing the power and frequency of the radio frequency source, respectively. As its application, a tunable and individually switchable dual-wavelength fiber ring laser was realized and characterized. The proposed structure gains advantages of robustness, easy fabrication, compact size and fast tuning speed accordingly. At the same time, it provides another practical way to use an FBG to introduce phase mismatch into an acousto-optic fiber grating.

A Tunable Synchronous Pulsed Dual-Wavelength Laser Based on the Nd:YVO4/Nd:GdVO4 Combined Crystals Pair

A tunable pulsed dual-wavelength laser is presented based on an Nd:YVO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /Nd:GdVO <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> combined crystals pair as amplifying medium. By employing pulse width adjustment of an 808 nm laser diode pumping, and a Cr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> :YAG crystal for Q-switching, synchronized dual-wavelength laser pulses were obtained at 1063 nm and 1064 nm. Time jitter between the two wavelength pulses is reduced to about 10% of the laser pulse duration. Adjusting the pump beam operation parameters and tuning the crystals pair steady-state temperature between 10 °C and 50 °C, the frequency separation between the dual-wavelength laser pulses gradually decreases from 344.11 GHz to 305.99 GHz. The relative peak powers and the pulses time synchronization remain stable during their frequency separation tuning.

Multi- and dual-wavelength Thulium-doped fluoride fiber laser assisted by four-wave mixing in S-band region

In this work, multi-wavelength lasing in the S-band region using a Sagnac loop filter in a thulium-doped fluoride fiber laser (TDFFL) was demonstrated for the first time. The Sagnac loop served as a comb-like wavelength filter, while a 10-km long dispersion compensating fiber (DCF) was utilized to induce the four-wave mixing (FWM) effect in the cavity. The FWM effect was used to suppress mode competition in the TDFFL as well as to enhance the number of lasing lines. At its optimum polarization state, 17 stable lasing lines at peak powers of less than 10 dB from the highest peak power were observed, with these lasing lines having a uniform wavelength spacing of 0.23 nm. The multi-wavelength operation exhibited minimal wavelength drifts and power fluctuations of less than 0.01 nm and 1.2 dB respectively. A tunable dual-wavelength laser output was also demonstrated, with a constant wavelength spacing throughout the tuning range.

Double-wavelength nanolaser based on strong coupling of localized and propagating surface plasmon

We theoretically demonstrate a kind of plasmon coupled cavity to achieve a nanolaser with high intensity and low threshold. The plasmon cavity is composed of the gold film substrate and gold disk array, which supports two strong coupled resonance modes (i.e. surface plasmon polariton (SPP) and localized surface plasmon (LSP)). Compared with the nanolaser with the LSP resonance structure, the scattering cross-section of the LSP-SPP coupled laser is 80 times higher. The coupled cavity nanolaser with different wavelengths can be excited with different plasmon resonance modes by selecting the appropriate gain medium. In addition, a compact tunable dual-wavelength laser can be developed using this coupled structure.

Simulation and design of a compact GaAs based tunable dual-wavelength diode laser system

We present our design of a compact, integrated and tunable dual-wavelength diode laser system emitting around 785 nm, which is of interest for several applications like Raman spectroscopy and the generation of THz radiation. To achieve a more compact device compared to previous GaAs based designs two etch depths are realized, leading to shallowly etched ridge waveguides in regions were optical gain is applied and deeply etched waveguides used to enable compact integrated waveguide components. The device parameters are optimized using a numerically efficient simulation tool for passive waveguides. Subsequently, the entire laser system is further analyzed applying a sophisticated traveling-wave equation based model for active devices giving access to internal intensity and carrier density distributions. It is shown that active laser simulations are crucial to deduce critical and performance limiting design aspects not accessible via an all-passive simulation.

Electrically tunable dual-wavelength organic laser based on holographic polymer dispersed liquid crystal grating

Abstract An organic dual-wavelength surface-emitting distributed feedback (DFB) laser with low threshold and high conversion efficiency based on holographic polymer dispersed liquid crystal (HPDLC) grating is reported. In such a laser configuration, the dye blend 4-(dicyanomethylene)-2-methyl-6-( p -dimethylaminostyryl)-4H-pyran (DCM)/1,3,5,7,8-pen- tamethyl-2,6-diethylpyrromethene-difluoroborate (PM567) -doped HPDLC grating is formed on the top of an organic semiconductor poly(2-methoxy-5-(20 -ethyl-hexyloxy)-p- phenylenevinylene) (MEH-PPV) layer. The dual-wavelength laser located at 605.2 nm and 629.8 nm are obtained in a single beam. The dual-wavelength laser performance under an external electric field are investigated and illustrated for the first time. This study provides some new ideas for the improvement of tunable dual-wavelength laser and extends more applications in laser displays and integrated photonic circuits.

Tunable dual-wavelength laser based on Nd:YVO4/Nd:GdVO4 combined crystal.

A tunable dual-wavelength laser (DWL) based on Nd:YVO4/Nd:GdVO4 combined crystal is presented. The frequency separation tuning characteristics of the DWL are investigated experimentally. In the experiments, the DWL with tunable frequency separation is obtained with fixed pumping power and controlled heat sink temperature (Tc) of the combined crystal. The frequency separations are measured at 351.11-316.15 GHz by varying Tc from 5.0 °C to 40.0 °C, with a slope of -0.95 GHz/°C. When Tc is kept at 32.3 °C, a 435-mW power-balanced DWL signal is achieved with frequency separation at 324.29 GHz. By analyzing the experimental results from the perspective of thermal-induced emission cross section (ECS) spectra evolution of the combined crystal, it is found the frequency separation tuning of the DWL is caused by the different ECS spectral wavelength shifting rates of the Nd:YVO4 and Nd:GdVO4 crystals with Tc varying. The analysis results are in good agreement with the experimental results.

基于液晶/聚合物光栅的可调谐双波长有机激光器

基于液晶/聚合物光栅的可调谐双波长有机激光器