Multi-wavelength Laser Research Articles

Mach-Zehnder interferometer comb filter for multi-wavelength mode-locked generation from erbium-doped fiber laser.

A picosecond pulse multi-wavelength erbium-doped fiber ring laser based on an optically switchable/tunable Mach-Zehnder interferometer (MZI) filter is proposed and experimentally demonstrated. The MZI configuration is constructed with two 3 dB couplers and two short pieces of endlessly single-mode photonic crystal fiber with different lengths in each arm. The combination of the MZI and a polarization controller (PC) acts as a selective comb filter and a mode-locking device. By adjusting the pump power or the first PC (PC1) state, the laser can emit up to 10 channels with a 20 nm tuning range (1530 to 1550 nm). Furthermore, by changing the PC1 condition, stable picosecond mode-locking generation with a repetition rate of 13.5 MHz is realized. To achieve wavelength spacing tunable multiple-channel laser emissions, the MZI is configured by incorporating a second PC (PC2) in one arm of the conventional MZI. Four channels of picosecond mode-locking pulses with a repetition rate of 11.6 MHz in the range of 1530-1550 nm are realized by carefully controlling the pump power and/or PC2 state. With the manipulation of intracavity birefringence through PCs with comb filtering via MZI, the proposed structure may be a potential tool in various photonics applications.

Tunable and interval-adjustable multiwavelength Erbium-doped fiber laser based on a compound filter

We propose and experimentally demonstrate a multiwavelength erbium-doped fiber laser (EDFL) based on a compound filter. The compound filter is composed of polarization controllers (PCs), polarizers and a piece of home-made polarization-maintaining photonic crystal fiber (PM-PCF). Due to the high birefringence and few-mode properties of the PM-PCF, Lyot filter and multimode interference filter can be realized simultaneously in the compact structure. Hence, the EDFL can achieve flexible lasing output. By adjusting PCs, the lasing can obtain single-, dual-, triple- and quad-wavelength output, respectively. The tuning range of single-wavelength lasing output can exceed 20 nm with side-mode suppression ratio (SMSR) above 40 dB. For dual-wavelength lasing output, the tuning range with fixed interval can reach 16 nm. Besides, the wavelength interval can be adjusted from 2.5 nm to 17.4 nm. The great interval adjustability is also observed in triple-wavelength output. The wavelength interval can be adjusted from 8.2 nm to 14.7 nm. Compact structure, flexible lasing output, and good stability make our proposed EDFL more convenient and practical to the applications such as sensing and wavelength division multiplexing.

Attenuation of the intensities of spectral components of a multiwavelength pulsed laser system by means of the Bragg diffraction of radiation by several acoustic waves

A method for controlling precisely the intensities of several spectral components of radiation generated by a multiwavelength laser system is described. The method is based on the use of simultaneous Bragg diffraction by a set of acoustic waves of corresponding frequencies and adjustment of their amplitudes. The efficiency of the proposed method is demonstrated by the example of a multiwavelength system based on a pulsed Nd:YAG laser (1064 nm) with intracavity parametric generation of a signal wave (1572 nm) and extracavity light conversion into higher harmonics and sum frequencies. An independent control of intensity ratio for four spectral components in the visible range (452, 532, 635, and 786 nm) is obtained by precisely controlled attenuation of acoustic-wave amplitudes using an original 4-channel acousto-optical polychromator.

Multiwavelength laser induced fluorescence spectroscopy for breast cancer diagnostics

Introduction: The 'Getting It Right First Time' report suggests a high rate of re-operative intervention following breast conserving surgery. Intraoperative margin assessment (IMA) tools may reduce re-excision rates. Laser induced fluorescence spectroscopy (LIFS) is a non-invasive optical modality which can be used for real-time discrimination of normal and malignant tissues. This pilot study investigates LIFS signals from varying tissue types, aimed towards IMA tool development.

Tunable multi-wavelength SBS Q-switched random fiber laser based on SMF

Tunable multi-wavelength SBS Q-switched random fiber laser based on SMF

Highly stable multi-wavelength fiber laser based on hybrid enclosed two-armed fiber filter

A compact multi-wavelength fiber laser (MWFL) with high stability based on hybrid enclosed two-armed fiber filter (HETAFF) is demonstrated. The HETAFF composes of an enclosed Mach-Zehnder interferometer with an in-line polarization controller (PC) in one arm of optical couplers #1 (OC1) and a section of polarization maintaining fiber with two PCs in OC2 loop. By using the HETAFF in proposed fiber laser, a lasing state switchable and wavelength-interval adjustable MWFL is obtained. It can be switched in single-, dual-, triple-, quadruple- and quintuple-wavelength states. The wavelength-interval can be adjusted as it operates in dual-, triple- and quadruple-wavelength states. Its optical signal to noise ratio (OSNR) is more than 36.03 dB, and the lasing wavelength shift and power fluctuation are less than 0.08 nm and 0.94 dB, respectively. The output characteristics, such as abundant laser states and high stability, are inseparable from the unique performance of the HETAFF.

Selectable multiwavelength thulium-doped fiber laser based on parallel Lyot filter

This paper demonstrates a selectable wavelength spacing of thulium-doped fiber laser (TDFL) based on a parallel Lyot filter. An intensity-dependent loss (IDL) mechanism acts as an amplitude equalizer to flatten and stabilize the multiwavelength spectrum. The IDL mechanism is obtained at a specific polarization state from the combination of highly nonlinear fiber and polarizer. The wavelength spacing of the TDFL can be selected to either 0.9 nm or 1.8 nm when the polarization controllers (PCs) in each branch of the parallel Lyot filter are adjusted. The wavelength spacing is selected by adjusting PC2 and PC3 to suppress or transmit the light at each branch. Up to 4 and 9 lasing lines are generated based on wavelength spacing of 0.9 nm and 1.8 nm, respectively. Lower pump power has disappeared lasing lines, while different half-wave plate angle of PC has shown variation in the laser performances.

Functional photoacoustic microscopy of hemodynamics: a review.

Functional blood imaging can reflect tissue metabolism and organ viability, which is important for life science and biomedical studies. However, conventional imaging modalities either cannot provide sufficient contrast or cannot support simultaneous multi-functional imaging for hemodynamics. Photoacoustic imaging, as a hybrid imaging modality, can provide sufficient optical contrast and high spatial resolution, making it a powerful tool for in vivo vascular imaging. By using the optical-acoustic confocal alignment, photoacoustic imaging can even provide subcellular insight, referred as optical-resolution photoacoustic microscopy (OR-PAM). Based on a multi-wavelength laser source and developed the calculation methods, OR-PAM can provide multi-functional hemodynamic microscopic imaging of the total hemoglobin concentration (CHb), oxygen saturation (sO2), blood flow (BF), partial oxygen pressure (pO2), oxygen extraction fraction, and metabolic rate of oxygen (MRO2). This concise review aims to systematically introduce the principles and methods to acquire various functional parameters for hemodynamics by photoacoustic microscopy in recent studies, with characteristics and advantages comparison, typical biomedical applications introduction, and future outlook discussion.

Ultralong wavelength operation of a tunable multiwavelength Brillouin-Raman fiber laser in 1.65 μm band

A tunable multiwavelength Brillouin-Raman fiber laser (MW-BRFL) operated at an ultralong wavelength band (U-band) is presented in this work. The MW-BRFL was configured in a full-open linear cavity consisting of 11.2 km long dispersion compensating fiber that functioned as a Brillouin frequency shifter and Raman amplification gain medium. At Raman and Brillouin pump powers of 930 mW and 11.8 dBm, respectively, a stable multiwavelength generation with wavelength spacing of 0.17 nm was generated over a wavelength span of 53 nm. The generated channels covered a spectral range of 1630–1683 nm corresponding to 314 channels. The channels could also be tuned over 10 nm with an average optical signal-to-noise ratio greater than 26 dB. The laser system exhibited power fluctuation of less than 0.25 dB over 3 h. In a nutshell, the proposed MW-BRFL is promising with respect to its performance, simplicity and flexibility.

Six-Wavelength-Switchable SLM Thulium-Doped Fiber Laser Enabled by Sampled FBGs and 3 × 3 Coupler Based Dual-Ring Compound Cavity Filter

A switchable and tunable six-wavelength single-longitudinal mode (SLM) thulium-doped fiber laser in the 2050 nm band is proposed and experimentally demonstrated. Two cascaded sampled fiber Bragg gratings (SFBGs), acted as an integrated six-channel reflector, are to define the lasing wavelength channels in a multi-wavelength switchable fiber laser for the first time. The switchability of the fiber laser was realized by polarization-dependent loss modulation. SLM lasing in each channel was guaranteed by a novel passive dual-ring compound cavity (DRCC), composed of two symmetric 3 × 3 optical couplers (OCs). Six single-wavelength operations are easily obtained and switched, with the high optical signal-to-noise ratios of >71 dB, >72 dB, >62 dB for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> – <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sub> and > 65 dB, >61 dB, >59 dB for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> – <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">23,</sub> respectively. The maximum power and wavelength fluctuations are as low as 0.56 dB and 0.01 nm, respectively. The measured laser linewidths ranged from 7.5 to 9.2 kHz, calculated by the β-separation line method based on the measured frequency noise spectra. Nine switchable dual-wavelength operations with different wavelength intervals and two triple-wavelength operations were also obtained. Our proposed fiber laser has great potential in free-space optical communication.

Dual-wavelength switchable single-mode lasing from a lanthanide-doped resonator

The development of multi-wavelength lasing, particularly with the wavelength tuning in a wide spectral range, is challenging but highly desirable for integrated photonic devices due to its dynamic switching functionality, high spectral purity and contrast. Here, we propose a general strategy, that relies on the simultaneous design on the electronic states and the optical states, to demonstrate dynamically switchable single-mode lasing spanning beyond the record range (300 nm). This is achieved through integrating the reversely designed nanocrystals with two size-mismatched coupled microcavities. We show an experimental validation of a crosstalk-free violet-to-red single-mode behavior through collective control of asymmetric excitation and excitation wavelength. The single-mode action persists for a wide power range, and presents significant enhancement when compared with that in the microdisk laser. These findings enlighten the reverse design of luminescent materials. Given the remarkable doping flexibility, our results may create new opportunities in a variety of frontier applications.

Widely tunable and switchable multiwavelength erbium-doped fiber laser based on a single ring cavity

In this paper, we propose and demonstrate through numerical simulations a novel, to the best of our knowledge, widely tunable and switchable multiwavelength erbium-doped fiber laser (EDFL) operating in the 1524–1650 nm wavelength range covering the C-, L-, and U-bands. The EDFL is based on a single ring cavity and a single forward pump source operating at 980 nm wavelength. The length of the erbium-doped fiber and pumping configuration is optimized, enabling a wide tuning of 126 nm with an average lasing power of 15 dBm. Switchable multiple wavelengths are generated from the EDFL through an intracavity tunable optical filter (TOF) and a specially designed out-of-cavity comb filter (CF). Forty-nine wavelengths having average optical power and linewidth of around −10 dBm and 0.01 nm, respectively, are obtained at the output of the CF. Moreover, the free spectral range among the multiple wavelengths is adjusted easily by simply varying the frequency of sinusoidal radio frequency signal used to modulate the lasing signal obtained by tuning the intracavity TOF at a particular wavelength with the help of a dual-drive Mach–Zehnder modulator. The proposed EDFL is low cost, efficient, and highly stable with an average output power of around 15 dBm for 10% output coupling ratio over a 126 nm wide tuning range covering C-, L- and U-bands.

Coherent optical communications using coherence-cloned Kerr soliton microcombs

Dissipative Kerr soliton microcombs have been recognized as a promising multi-wavelength laser source for fiber optical communications, as their comb lines possess frequency and phase stability far beyond the independent lasers. Especially, for coherent optical communications, a highly beneficial but rarely explored target is to re-generate a Kerr soliton microcomb as the receiver local oscillators that conserve the frequency and phase property of the incoming data carriers, so that to enable coherent detection with minimized optical and electrical compensations. Here, via pump laser conveying and two-point locking, we implement re-generation of a Kerr soliton microcomb that faithfully clones the frequency and phase of another microcomb sent from 50 km away. Moreover, by using the coherence-cloned soliton microcombs as carriers and local oscillators, we demonstrate terabit coherent data interconnect, wherein traditional digital processes for frequency offset estimation are totally dispensed with, and carrier phase estimation is substantially simplified via slowed-down estimation rate per channel and joint estimation among multiple channels. Our work reveals that, in addition to providing a multitude of laser tones, regulating the frequency and phase of Kerr soliton microcombs among transmitters and receivers can significantly improve optical coherent communication in terms of performance, power consumption, and simplicity.

Generation of a multi-wavelength Brillouin erbium fiber laser with low threshold in multiple frequency spacing configurations

Brillouin fiber lasers are a promising optical source technology for industrial and academic purposes that have experienced continuous progress in recent years. Currently, part of this development is focused on proposing laser solutions with low resonator loss, relatively low pump threshold, high efficiency, small linewidth, and multi-wavelength architecture. In this context, we experimentally demonstrate the generation of a cascaded multi-wavelength Brillouin erbium fiber laser source with low threshold at multiple configurations. By employing a laser source of narrow linewidth and a fiber with high nonlinearity, compact all-fiber setups with low loss, single, double, and triple frequency spacing configurations are obtained using a Brillouin pump (BP) power as low as 1 mW. In these proposed configurations, we obtain up to 15, 15, and 11 Stokes channels within a 30 dB range and with frequency spacing between two adjacent lasing lines of 0.08 nm, 0.16 nm, and 0.32 nm, respectively. All laser source configurations investigated exhibit stable temporal behavior without prominent signs of wavelength shifts or power fluctuations. In this way, these multi-wavelength fiber laser sources demonstrated in this paper could be considered experimental and potential source to support dense wavelength division multiplexing systems.

A Multi-Wavelength Thulium-Doped Fiber Laser Using a Photonic Crystal Fiber-Based Sagnac Loop

A multi-wavelength thulium-doped fiber laser incorporating a photonic crystal fiber (PCF) Sagnac loop was presented and experimentally demonstrated. In the laser cavity, the Sagnac loop mirror used a 0.5 m PCF as a comb filter. A nonlinear polarization rotation (NPR)-based 600 m single-mode fiber (SMF) was used to suppress the mode competition. By adjusting the polarization controllers (PCs), up to nine stable wavelength outputs near the 2 μm spectrum were obtained at room temperature with an optical signal-to-noise ratio (OSNR) of up to 30 dB. The channel spacing of this fiber laser is 4.88 nm, and the 10 dB bandwidth encompasses 1950.39 to 1989.43 nm.

Single-, Dual-, Triple, and Quadruple-Wavelength Surface-Emitting Lasing in Blue-Phase Liquid Crystal.

Soft organic lasers with multiwavelength output and high spectral purity are of crucial importance for versatile photonic devices, owing to their monochromaticity, coherence, and high intensity.However, there remain challenges for the achievement ofsurface-emitting multiwavelength lasing in soft photonic crystals, and the relative mechanisms need to be investigated. Herein, single-, dual-, triple-, and quadruple-wavelength lasers are successfully achieved in dye-doped blue-phase liquid crystal (BPLC) film. The number and wavelength of the lasing peaks can be manipulated by tuning the center of the bandgap, the order parameter of the laser dye, the quality of the resonance cavity, and even the pump energy. For single-wavelength lasing, a lasing peak withan ultranarrow linewidth of 0.04nm (Q-factor of 13454) is achieved. Multiwavelength lasing is attained based on the following aspects: i) the narrow bandgaps of the BPLCs withfull width at half maximum of 14-20nm; ii) a laser dye with high gain over a wide wavelength band, having a low-order parameter in the liquid crystal matrix; iii) appropriate relative positions between the reflection and fluorescence peaks; and iv) the highly ordered crystal lattice of BPLC film. The proposed single-to-quadruple-wavelength surface-emitting lasers can be employed as coherent light sources for next-generation optical devices.

Multi-wavelength thulium-doped fiber laser at 2.05 μm incorporating a superimposed polarization-maintaining fiber Bragg grating

A switchable multi-wavelength thulium-doped fiber laser with a high optical signal-to-noise ratio (OSNR) and stability is proposed and experimentally demonstrated at 2.05 μm. For the first time, a superimposed polarization-maintaining fiber Bragg grating (SI-PM-FBG) was utilized as a multi-channel narrow bandwidth filter to select the lasing wavelengths in the laser cavity in the 2-μm band. It also introduced polarization hole burning (PHB) to inhibit the strong wavelength competition induced by homogeneous gain broadening in the thulium-doped fiber. By adjusting the two polarization controllers (PCs), four stable switchable single-wavelength operations were obtained. The OSNR reached 72 dB at a pump power of 2.89 W, and the maximum wavelength and power fluctuations were 0.01 nm and 0.162 dB, respectively. Four combinations of dual-wavelength operations were obtained by adjusting the PCs. The polarization states between each dual-wavelength lasing were orthogonal. The stability of the dual-wavelength operation was investigated in detail. The proposed laser also has the capability for three- or four-wavelength operation. The excellent performance enables this fiber laser to be used in atmospheric sensing and free-space optical communication.

Enzyme-Programmable Microgel Lasers for Information Encoding and Anti-Counterfeiting.

Microscale laser emissions have emerged as a promising approach for information encoding and anti-counterfeiting for their feature-rich spectra and high sensitivity to the surrounding environment. Compared with artificial materials, natural responsive biomaterials enable a higher level of complexity and versatile ways for tailoring optical responses. However, precise control of lasing wavelengths and spatial locations with biomolecules remains a huge challenge. Here, a biologically programmable laser, in which the lasing can be manipulated by biomolecular activities at the nanoscale, is developed. Tunable lasing wavelengths are achieved by exploiting the swelling properties of enzyme-responsive hydrogel droplets in a Fabry-Pérot microcavity. Both experimental and theoretical means demonstrate that inner 3D network structures and external curvature of the hydrogel droplets lead to different lasing thresholds and resonance wavelengths. Finally, inkjet-printed multiwavelength laser encoding and anti-counterfeiting are showcased under different scalabilities and environments. Hyperspectral laser images are utilized as an advanced feature for a higher level of security. The biologically encoded laser will provide a new insight into the development of biosynthetic and bioprogrammable laser devices, offering new opportunities for secure communication and smart sensing.

Tunable Brillouin-erbium fiber laser producing multiwavelength cylindrical vector beams

A multiwavelength Brillouin-erbium fiber laser producing cylindrical vector beams with tunable central wavelength and wavelength spacing is presented and experimentally investigated. Owing to the inhomogeneous broadening characteristic of the Brillouin gain, stable multiwavelength lasing is achieved by combination of the cascaded stimulated Brillouin scattering in the ultra-long single mode fiber and the wavelength selection of the fiber Mach-Zehnder interferometer. Multiwavelength lasing with tunable wavelength spacing of about 0.09, 0.11, 0.17, 0.24 and 0.3 nm is achieved by adjusting the optical delay line in the Mach-Zehnder comb filter. With the sufficient pump power, multiwavelength lasing with more than 10 channels is obtained when the wavelength spacing is tuned to be about 0.09 nm. Through adjusting the flat-top tunable bandpass filter, the central lasing wavelength can be tuned from 1534.37 nm to 1570.06 nm continuously. Cylindrical vector beams with purity higher than 93% are produced through regulating polarization controllers on either side of the two-mode long-period grating serving as the mode convertor. Multiwavelength cylindrical vector beams with the largest number of channels and tuning range are obtained to the best of our knowledge.

Demonstration of a 17 × 25 Gb/s Heterogeneous III-V/Si DWDM Transmitter based on (De-) Interleaved Quantum Dot Optical Frequency Combs

We discuss the design and demonstration of a space and dense wavelength division multiplexed heterogeneous III-V&#x002F;Si transmitter based on a single multi-wavelength quantum dot laser source and ultra-power-efficient metal-oxide-semiconductor capacitor (MOSCAP) (de-)interleaver. This paper begins by introducing a transceiver architecture capable of &gt; 1 Tb&#x002F;s transmission with &lt; 1.5 pJ&#x002F;bit power consumption, followed by a detailed discussion of the heterogeneous laser source and (de-)interleaver. The O-band quantum dot laser, based on a compound cavity design, has a FSR &#x223C; 64 GHz with a 1&#x03C3; variation of &#x223C; 1.08 GHz and a measured relative intensity noise (RIN) of &#x223C; -144 dB&#x002F;Hz for the largest comb peak. The single-ring-assisted asymmetric Mach-Zehnder interferometer (1-RAMZI) MOSCAP (de-)interleaver exhibit cross-talk (XT) levels down to -27 dB for tuning powers of 10.0 nW. Finally, to the best of our knowledge, we have demonstrated for the first time, a simultaneous wavelength and space division multiplexed transmitter fabricated on a heterogeneous III-V-on-silicon platform. Experiments show (de-)interleaved 17 optical comb lines, each modulated at 25 Gb&#x002F;s non-return-to-zero (NRZ) for an aggregate bandwidth of 425 Gb&#x002F;s.