Dual-wavelength Oscillation Research Articles

A highly stable and switchable dual-wavelength laser using coupled microfiber Mach-Zehnder interferometer as an optical filter

The generation and switching of dual-wavelength laser based on compact coupled microfiber Mach-Zehnder interferometer (CM-MZI) is reported. The CM-MZI is constructed by overlapping two portions of a single tapered optical fiber which has a diameter of 9μm as to create multi-mode interference and also to produce spatial mode beating as to suppress mode competition in the homogeneous gain medium. The system is able to generate a dual-wavelength laser output that can be switched with the aid of the polarization rotation technique. Four dual-wavelength oscillation pairs are obtained from the interference fringe peaks of the CM-MZI comb filter with a switched channel spacing of 1.5nm, 3.0nm, and 6.0nm. The wavelength spacing is stable at different pump powers. The lasing wavelength has a 3-dB linewidth of about 30pm and peak-to-floor ration of about 55dB at a pump power of 38mW.

A stable wavelength-spacing-tunable dual-wavelength single-longitudinal-mode fiber ring laser based on a DMD filter

A stable single-longitudinal-mode dual-wavelength( SLM-DW) multiple ring fiber laser with a tunable wavelength spacing was proposed and demonstrated. In the multiple ring cavities,the mode selection is made by the tunable digital micro-mirror device( DMD) filter and two different length passive sub-ring cavities. The DMD filter can select and couple any two wavelengths from the gain spectrum of the erbium-doped fiber( EDF). The SLM lasing is guaranteed by the two sub-ring cavities which serve as a mode filter. The stable and uniform dualwavelength oscillation is obtained by the highly-nonlinear photonic crystal fiber( HN-PCF),which can generate the four-wave-mixing( FWM) effective. By loading different gratings on the DMD filter without any mechanically shift,the tunable wavelength spacing from appropriately 0. 165 nm to 1. 08 nm within a tuning accuracy of 0. 055 nm is achieved at room temperature.

Tunable dual-wavelength single-longitudinal-mode fiber laser based on spectral narrowing effect in a nonlinear semiconductor optical amplifier

A tunable dual-wavelength single-longitudinal-mode (SLM) fiber laser based on a nonlinear semiconductor optical amplifier (NL-SOA) and an optical comb filter is proposed and demonstrated successfully. The SLM operation principle is based on the spectral narrowing effect resulting from the inverse four-wave mixing (FWM) in a NL-SOA. By inserting the NL-SOA inside the fiber laser cavity, SLM lasing can be possibly achieved when stable laser oscillation is established after many roundtrips through the NL-SOA. Further, tunable dual-wavelength SLM output can be obtained by incorporating a tunable optical filter (TOF) and a comb filter inside the laser cavity to perform dual-wavelength selection function. As a result, tunable dual-wavelength SLM oscillation with a wavelength spacing of 0.4nm and a wavelength tuning range of about 56nm has been achieved. Each wavelength has a linewidth less than 8kHz and a side-mode suppression ratio (SMSR) larger than 40dB.

Spectroscopic properties and laser operation of Yb3+ : SGYB crystal

A Sr3Yb0.1Gd0.2Y0.7(BO3)3 single crystal was grown by the Czochralski method. The crystal was evaluated by absorption, emission, and luminescence decay measurements. The relevant absorption and emission cross-sections as well as fluorescence lifetimes were calculated and compared. Studies showed that the existence of Gd3+ can lead to greater structural disorder and broaden the spectra of the crystal. Diode-pumped laser action of this crystal is demonstrated for the first time, and the best output power of 1.8 W with a slope efficiency of 75.8% was obtained. Dual-wavelength and three-wavelength oscillations were observed. Thus, this crystal is suitable for use as tunable or ultrashort laser mediums.

Passively Q-switched dual-wavelength green laser with an Yb:YAG/Cr4+:YAG/YAG composite crystal.

A compact dual-wavelength passively Q-switched green laser by intra-cavity frequency doubling of a Yb:YAG/Cr4+:YAG/YAG composite crystal was demonstrated for the first time to our best knowledge. The maximum green laser output power of 1.0 W was obtained under the pump power of 9.7 W, and the corresponding slope efficiency is 15.2%. The shortest pulse width, largest pulse energy, and highest peak power were achieved to be 5.54 ns, 246.1μJ, and 40.76 KW, respectively. Dual-wavelength laser oscillation simultaneously at 515 nm and 524.5 nm has been achieved. This passively Q-switched dual-wavelength green laser can be used as a laser source for Terahertz generation.

Orthogonally polarized dual-wavelength Yb:KGW laser induced by thermal lensing

Simultaneous dual-wavelength laser oscillation with orthogonal polarizations has been observed and analyzed in a continuous wave N g-cut Yb:KGW oscillator. Without inserting any optical elements for polarization control, the N m- and N p-polarized modes, each of which possessed a distinct wavelength, coexisted and switched twice in two power regimes as the pump power was varied. The two wavelengths and their separation slightly depended on output coupling level. The wavelength switching and coexistence was studied and explained by considering the thermal and spectral anisotropy of the Yb:KGW crystals, which led to polarization-dependent reabsorption loss in the unpumped regions of the crystal. The maximum average output power obtained in the dual-wavelength regime was 4.6 W.

Studies on output characteristics of stable dual-wavelength ytterbium-doped photonic crystal fiber laser

A stable dual-wavelength ytterbium-doped photonic crystal fiber laser pumped by a 976 nm laser diode has been demonstrated at room temperature. Single-wavelength, dual-wavelength laser oscillations are observed when the fiber laser operates under different pump power by using different length of fibers. Stable dual-wavelength radiation around 1045 nm and 1075 nm has been generated simultaneously at a high pump power directly from an ytterbium-doped fiber laser without using any spectral control mechanism. A small core ytterbium-doped PCF fabricated by the powder sinter direction drawn rod technology is used as gain medium. The pump power and fiber length which can affect the output characteristics of dual-wavelength fiber laser are analyzed in the experiment. Experiments confirm that higher pump power and longer fiber length favors 1075 nm output; lower pump power and shorter fiber length favors 1045 nm output. Those results have a good reference in multi-wavelength fiber laser.

Topological Insulator-Assisted Dual-Wavelength Fiber Laser Delivering Versatile Pulse Patterns

We report on the generation of dual-wavelength mode-locked pulses in an erbium-doped fiber laser incorporating a topological insulator (TI): Bi2Se3/Polyvinyl Alcohol (PVA) film which could operate as both an excellent saturable absorber (SA) for mode-locking and a high-nonlinear medium for mitigating the mode competition of erbium-doped fiber and stabilizing the dual-wavelength oscillation. The TI: Bi2Se3/PVA film is prepared through a liquid-phase exfoliation/spin-coating method. Its saturating intensity and modulation depth are measured to be about 31.5 MW/cm2 and 3.4%, respectively. Taking advantage of the high nonlinearity and saturable absorption of the TI: Bi2Se3, three dual-wavelength pulse patterns, namely bright pulse, bright-dark soliton pair, and hybrid step-like and dark pulse, could be achieved under different lengths of single mode fiber by properly adjusting the pump power and the polarization state. For the bright pulse operation, we obtain its fundamental repetition rate of 9.75 MHz. For the bright-dark soliton pair operation, we find that it contains two distinct parts in the whole optical spectrum: one is at shorter wavelength corresponds to bright soliton and the other one is at longer wavelength corresponds to dual-wavelength dark soliton. In addition, we also achieved the harmonic mode-locking (HML) of the bright-dark soliton pair. The highest obtained repetition rate is about 433.8 MHz, which corresponds to the 280th harmonic of the fundamental repetition rate. For the hybrid step-like and dark pulse operation, we achieve its fundamental repetition rate of 8.805 MHz. Our findings suggest that TI: Bi2Se3 can operate as both an excellent SA for short pulse generation and a promising highly nonlinear photonic material for the related nonlinear optics applications.

Dual-wavelength waveguide lasers at 1064 and 1079 nm in Nd:YAP crystal by direct femtosecond laser writing.

Low-loss depressed cladding waveguides have been produced in Nd:YAP laser crystal by using direct femtosecond laser writing. Under optical pump at 812 nm at room temperature, continuous-wave simultaneous dual-wavelength laser oscillations at 1064 and 1079 nm, both along TM polarization, have been realized in the waveguiding structures. It has been found that, with the variation of pump polarization, the intensity ratio of 1064 and 1079 nm emissions varies periodically, while the polarization of output dual-wavelength laser remains unchanged. The maximum output power achieved for the Nd:YAP waveguide lasers is ∼200 mW with a slope efficiency of 33.4%.

A tunable dual-wavelength fiber Bragg grating laser using an external-injected DFB laser

A tunable dual-wavelength fiber Bragg grating (FBG) laser based on a distributed feedback (DFB) laser injection is proposed and experimentally demonstrated. The wavelength spacing can be tuned by adjusting the operation temperature of the DFB laser. When the DFB works at 25 °C, a dual-wavelength simultaneous oscillation at 1 549.67 nm and 1 553.44 nm with wavelength spacing of 3.77 nm is achieved. Our experimental results demonstrate the new concept of dual-wavelength lasing with a DFB laser injection and the technical feasibility.

Single-Longitudinal-Mode Dual Wavelength-Switchable Fiber Laser Based on Superposed Fiber Bragg Gratings

In this work, a simple switchable dual-wavelength short-cavity fiber laser operating in a single-longitudinal-mode regime at room temperature and based on superposed fiber Bragg gratings is proposed and experimentally demonstrated. Only by introducing stress into one of the overwritten FBGs, single- or dual-wavelength laser oscillations can be attained. Either single- or multimode operation of the laser can be easily achieved. Single-longitudinal-mode emission has been verified in two different ways: the first corroboration has been conducted by the heterodyne detection of the output signal, and the second one has been carried out by using a high-resolution optical spectrum analyzer.

Dual-Wavelength Passively Q-Switched Nd,Mg:LiTaO3 Laser With a Monolayer Graphene as Saturable Absorber

Compact LD pumped, CW, and passively Q-switched Nd,Mg:LiTaO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> lasers with a stable, synchronous dual-wavelength operation near 1082 and 1092 nm were demonstrated for the first time. Under an incident pump power of 7.69 W, a maximum CW output power of 464 mW was obtained, corresponding to a slope efficiency of 7.6%. By using a monolayer graphene as saturable absorber, the steadily Q-switched Nd,Mg:LiTaO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> laser with dual-wavelength oscillation was achieved. The maximum output power of the Q-switched laser was 365 mW with a repetition rate of 133 kHz. The minimum pulse duration was measured to be 176 ns. The corresponding maximum pulse energy and peak power were 2.75 μJ and 15.7 W, respectively.

Three-channel dual-wavelength fiber laser based on a digital micromirror-device processor and photonic crystal fiber

A stable three-channel dual-wavelength fiber ring laser is proposed and experimentally demonstrated. The digital micromirror-device (DMD) processor can select and recirculate any dual waveband from the gain spectrum of the erbium-doped fiber at each channel. The uniform and stable dual-wavelength oscillation is obtained by a highly nonlinear photonic crystal fiber, which causes two degenerate the four-wave-mixing processes. By loading different reproducibility diffraction gratings on the optoelectronic DMD processor, the laser can be operated stably in a three-channel dual-wavelength scheme at room temperature. The power fluctuation of each laser channel is less than -0.02 dB.

Modulated dual-wavelength Er-doped fiber laser based on a semiconductor saturable absorber mirror

A modulated dual-wavelength Er-doped fiber laser based on a semiconductor saturable absorber mirror (SESAM) is proposed and experimentally demonstrated. The proof of concept device consists of two cascaded fiber Bragg gratings and a semiconductor saturable absorber mirror. By changing the operation temperature of the fiber Bragg grating and adjusting the polarization controller, stable dual-wavelength modulated pulses are obtained. Results demonstrate that dual-wavelength simultaneous oscillation at 1549.69nm and 1550.5nm (1548.2nm and 1549.69nm) is achieved with the pump threshold power of ∼110mW, pulse repetition rate is a function of the operation temperature of fiber Bragg grating. Our experimental results demonstrate the new concept of SESAM based modulated dual-wavelength fiber laser and the technical feasibility.

Dual-wavelength erbium-doped fiber laser with tunable wavelength spacing using a twin core fiber-based filter

A dual-wavelength erbium-doped fiber laser with tunable wavelength spacing was proposed and experimentally demonstrated by using a twin core fiber (TCF)–based filter. Benefiting from the polarization dependence of the TCF-based filter, the laser operated in dual-wavelength oscillation with two orthogonal polarization states. By adjusting the polarization controller, the wavelength spacing was tuned from 0.1 nm to 1.2 nm without shifting the centre position of the two wavelengths. By stretching the TCF, the two wavelengths were simultaneously tuned with fixed wavelength spacing. Such a dual-wavelength fiber laser could find applications in optical fiber sensors and microwave photonics generation.

Tunable microwave signal generation based on an Opto-DMD processor and a photonic crystal fiber

Frequency-tunable microwave signal generation is proposed and experimentally demonstrated with a dual-wavelength single-longitudinal-mode (SLM) erbium-doped fiber ring laser based on a digital Opto-DMD processor and four-wave mixing (FWM) in a high-nonlinear photonic crystal fiber (PCF). The high-nonlinear PCF is employed for the generation of the FWM to obtain stable and uniform dual-wavelength oscillation. Two different short passive sub-ring cavities in the main ring cavity serve as mode filters to make SLM lasing. The two lasing wavelengths are electronically selected by loading different gratings on the Opto-DMD processor controlled with a computer. The wavelength spacing can be smartly adjusted from 0.165 nm to 1.08 nm within a tuning accuracy of 0.055 nm. Two microwave signals at 17.23 GHz and 27.47 GHz are achieved. The stability of the microwave signal is discussed. The system has the ability to generate a 137.36-GHz photonic millimeter signal at room temperature.

Intracavity Cr3+:LiCAF + PPSLT optical parametric oscillator with self-injection-locked pump wave

In this letter we present an intracavity pumped continuous wave (CW) doubly resonant optical parametric oscillator (OPO) based on Cr3+:LiCaAlF6 (Cr:LiCAF) as the material generating the OPO pump wave and periodically poled stoichiometric lithium tantalate (PPSLT) as the nonlinear material. The OPO pump wave is spectrally narrowed and tuned by means of an external cavity, thus allowing self-injection locking of the OPO pump wavelength. When operated near degeneracy, the constructed OPO enables a fast tuning of the parametrically generated wavelengths in response to small perturbations of the phase-matching condition. The Cr:LiCAF emission band is especially well suited to provide dual-wavelength oscillation in the optical communications 1550 nm band as a result of the parametric oscillation in PPSLT.

A dual-reflected-structure switchable multi-wavelength erbium-doped fiber laser using the multi-mode fiber as the wavelength selector

A simple and effective dual-reflected-structure switchable multi-wavelength polarization-maintaining erbium-doped fiber laser is proposed and demonstrated. Using the structure of single-mode fiber (SMF)-multi-mode fiber (MMF)-SMF as the wavelength selective filter and reflector simultaneously the polarization-maintaining erbium-doped fiber as the gain medium and an optical circulator as the all-reflecting mirror, the laser realizes stable single-wavelength, dual-wavelength and triple-wavelength oscillations based on polarization hole burning of a multi-mode fiber by means of adjusting the polarization controller. The 3 dB bandwidth is about 0.01 nm. The side-mode suppression ratios (SMSRs) are over 50 dB. The power fluctuation and wavelength shifts are measured to be less than 1.5 dB and 0.01 nm over an hour at room temperature.

Photonic generation of microwave signal by beating a dual-wavelength single longitudinal mode erbium-doped fiber ring laser based on the polarization maintaining fiber bragg grating

A single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber (EDF) ring laser based on one polarization maintaining fiber Bragg grating (PMFBG) is demonstrated.Due to the polarization hole burning enhanced by the PMFBG, the laser can be designed to operate in stable dual-wavelength oscillation with a wavelength spacing of 0.182 nm at room temperature by adjusting a polarization controller. A section of unpumped EDF acting as a saturable absorber and a feedback fiber loop is used to ensure SLM operation in each of the two lasing lines. A microwave signal at 22.807 GHz is obtained by beating the dual-wavelength fiber laser at a photodetector. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:347–351, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27280

A new mechanism to suppress the homogeneous gain broadening for stable multi-wavelength erbium-doped fiber laser

A suppressant effect of wavelength competition for multi-wavelength lasing oscillations is experimentally demonstrated in an ordinary erbium-doped fiber laser (EDFL). The polarization hole burning is exploited by a segment of erbium-doped fiber (EDF) coiled round the plates of the three-loop polarization controller. The mechanism to suppress the wavelength competition is discussed in detail. Results show that the mechanism is helpful to obtain stable multi-wavelength lasing oscillations at room temperature in the EDFL. By properly adjusting the comb filter, three-wavelength and tunable dual-wavelength lasing oscillations have been achieved. The power fluctuation is measured to be less than 0.75dB over 30min for all the multi-wavelength lasing oscillations obtained in the experiment. The 3dB bandwidth of each lasing oscillation is 0.01nm and the 30dB bandwidth is 0.10nm. The side mode suppression ratio (SMSR) of the three-wavelength lasing oscillation is more than 45dB and that of the dual-wavelength lasing oscillations is more than 50dB.